Engine Controls Tests W/codes - Diesel GMC Savana I

MODEL IDENTIFICATION

Vehicle model is identified by fifth character of Vehicle Identification Number (VIN). VIN is stamped on metal pad on top of left end of instrument panel, near windshield. See MODEL IDENTIFICATION table.

MODEL IDENTIFICATION

INTRODUCTION

The Powertrain Control Module (PCM) controls EGR system operation, Torque Converter Clutch (TCC) engagement, transmission, fuel control and fuel injection timing. The PCM also monitors a number of transmission functions and uses the data to control shift solenoids, TCC, and pressure control solenoid to regulate upshift pattern, downshift pattern and line pressure (shift quality).

Most engine/transmission control problems are not computer related, but result from mechanical breakdowns, poor electrical connections, or damaged vacuum hoses. Before condemning the computer system, carefully perform visual and mechanical inspections covered in appropriate BASIC DIAGNOSTIC PROCEDURES article. Failure to perform these inspections can result in lost diagnostic time.

If no faults were found while performing visual and mechanical inspections in appropriate BASIC DIAGNOSTIC PROCEDURES article, proceed with DIAGNOSTIC PROCEDURE under SELF-DIAGNOSTIC SYSTEM. If no Diagnostic Trouble Codes (DTCs) are present and driveability problems exist, proceed to appropriate TROUBLE SHOOTING - NO CODES article for diagnosis by symptom (i.e., ROUGH IDLE, NO START, etc.). If only intermittent codes are present, see INTERMITTENTS in appropriate TROUBLE SHOOTING - NO CODES article.

DESCRIPTION

PCM is equipped with a self-diagnostic system, which detects system failures or abnormalities. When a malfunction occurs, PCM will store a Diagnostic Trouble Code (DTC) and, in most cases, illuminate the Malfunction Indicator Light (MIL) located on instrument cluster. OBD-II requires that PCM illuminate MIL when a malfunction is detected that affects vehicle emissions. Malfunctions are recorded as hard failures or as intermittent failures.

Hard Failures

Most hard failures cause MIL to illuminate and remain on until malfunction is repaired. If MIL illuminates and remains on (light may flash) during vehicle operation, cause of malfunction must be determined. See DIAGNOSTIC PROCEDURE . If a sensor fails, PCM will use a substitute value in its calculations to continue engine operation. In this condition, vehicle is functional, but it will most likely display degraded driveability.

Intermittent Failures

Intermittent failures cause MIL to flash, or illuminate and turn off about 10 seconds after intermittent fault goes away. Corresponding DTC, however, will be retained in PCM memory. If related fault does not reoccur within 40 engine starts, DTC will be erased from PCM memory. Intermittent failures may be caused by sensor, connector or wiring related problems. See INTERMITTENTS in appropriate TROUBLE SHOOTING - NO CODES article.

DTC Types

DTCs are divided into 4 categories: type "A", type "B", type "C" and type "C*". Each DTC is directly related to a specific diagnostic test. PCM sets a DTC based on failure of tests during trip(s). A trip is defined as a KEY ON/RUN/KEY OFF cycle which satisfies certain enable criteria for a given diagnostic test. Certain tests must fail 2 consecutive trips before a DTC is set. The following are the 4 different types (categories) of DTCs and their description

Type "A"

1. Emissions related.
2. Requests illumination of MIL on first trip with a fail.
3. Stores a history DTC on first trip with a fail.
4. Stores a freeze frame record on first trip with a fail (if empty).

Type "B"

1. Emissions related.
2. Requests illumination of MIL on second consecutive trip with a fail.
3. Stores a history DTC on second consecutive trip with a fail.
4. Stores a freeze frame record on second consecutive trip with a fail (if empty).

Type "C"

1. Non-emissions related.
2. Requests illumination of service throttle soon light only when more than one DTC (type "C") is stored.

Type "C*"

1. Non-emissions related.
2. Does not request illumination of any light.
3. Stores a history DTC on first trip with a fail.
4. Does not store a freeze frame record.

Type "D"

1. Non-emissions related.
2. Does not request illumination of any light.

FREEZE FRAME DATA

Engine operating conditions are required to be captured and stored in PCM memory whenever MIL is illuminated. Data captured is called FREEZE FRAME data. Freeze frame data is similar to a single record of operating conditions. Whenever MIL is illuminated, corresponding record of operating conditions is recorded to freeze frame buffer.

Freeze frame data can only be overwritten with data associated with a misfire or fuel trim malfunction. Misfire data takes priority over all other data because of its related part-damaging effects (oxygen sensors, catalytic converters, etc.). Freeze frame data will not be erased unless associated DTC is cleared from PCM memory.

During an intermittent fault, MIL may illuminate, and then turn off after 3 trips. However, corresponding DTC will be stored in PCM memory. Check for an intermittent malfunction when an unexpected DTC appears. If an intermittent DTC can not be resolved by following test procedures related to DTC, or if no DTC is set, see INTERMITTENTS in appropriate TROUBLE SHOOTING - NO CODES article.

DIAGNOSTIC PROCEDURE

Diagnosis of computerized engine control system should be performed in the following order

1. Ensure all engine systems not related to computer are operating properly. Check for any Technical Service Bulletins (TSBs) that may apply. DO NOT proceed with testing unless all other problems have been repaired. Perform «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel__on-board-diagnostic-obd-system-check) before diagnosing Diagnostic Trouble Codes (DTCs).
2. If DTC(s) were displayed, determine whether codes are hard or intermittent trouble codes. Hard codes will cause MIL to illuminate continuously while engine is running. See «HARD OR INTERMITTENT TROUBLE CODE DETERMINATION»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel__hard-or-intermittent-trouble-code-determination) . For diagnosing hard codes, proceed to appropriate DTC test. See «DIAGNOSTIC TESTS»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel__diagnostic-tests) . For diagnosing intermittent codes, proceed to INTERMITTENTS in appropriate TROUBLE SHOOTING - NO CODES article.
3. If no DTCs are present and a driveability problem exists, refer to SYMPTOMS in appropriate TROUBLE SHOOTING - NO CODES article. Doing so will help identify proper system or component to check. See appropriate SYSTEM & COMPONENT TESTING article for diagnosis of faulty component.
4. After necessary repairs are made, clear DTCs, verify vehicle will enter "closed loop" operation, and ensure no DTCs set.

RETRIEVING DTCS

DTCs are retrieved using a Tech 1 or 2 scan tool, or other OBD-II compatible scan tool connected to OBD-II 16-pin Data Link Connector (DLC). (Scheme 1) DLC is located below instrument panel, on driver's side of vehicle.

Scheme 1

ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK

Note. Do not perform this check if a driveability complaint is not present.

On-Board Diagnostic (OBD) system check is an organized approach in identifying a problem created by an electronic engine system malfunction. It must be the starting point for any driveability complaint diagnosis, because it directs service technician to the next logical step in diagnosing a complaint. Understanding and using it correctly will reduce diagnostic time and prevent unnecessary replacement of good parts.

1. Check for one or more of the following conditions: Malfunction Indicator Light (MIL) illuminated with engine running. Confirmed customer driveability concern. Suspected fault in computerized engine control system. If any conditions are present, go to next step. If specified conditions are not present, system is okay at this time. Check for an intermittent problem. See INTERMITTENTS in appropriate TROUBLE SHOOTING - NO CODES article.
2. Turn ignition on with engine off. Observe MIL. If MIL illuminates, go to next step. If MIL does not illuminate, go to «NO MALFUNCTION INDICATOR LIGHT (MIL)»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel__no-malfunction-indicator-light-mil) under CIRCUIT TESTS.
3. Turn ignition off. Install scan tool according to manufacturer's instructions. Turn ignition on with engine off. If scan tool displays PCM data, go to next step. If scan tool does not display PCM data, go to «DATA LINK CONNECTOR (DLC) DIAGNOSIS»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel__data-link-connector-dlc-diagnosis) under CIRCUIT TESTS.
4. Attempt to start engine. If engine starts and runs, go to next step. If engine will not run, go to appropriate NO START-ENGINE CRANKS OKAY under NO START DIAGNOSIS in appropriate BASIC DIAGNOSTIC PROCEDURES article.
5. Observe DTC data. If no DTCs are set, go to next step. If any DTCs are set, save freeze frame data using scan tool, and go to appropriate Diagnostic Trouble Code (DTC). See «DIAGNOSTIC TESTS»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel__diagnostic-tests) .
6. If MIL is illuminated and no DTCs are set, diagnose using DTC P1641. See «DIAGNOSTIC TESTS»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel__diagnostic-tests) . If MIL is off and no DTCs are set, go to next step.
7. Compare scan tool data with values shown in «SCAN TOOL DATA VALUES»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel) table under SCAN TOOL DATA. If displayed values are within specified ranges, suspect an intermittent fault. See INTERMITTENTS in appropriate TROUBLE SHOOTING - NO CODES article. If displayed values are not within specified ranges, diagnose suspect component. See appropriate SYSTEM & COMPONENT TESTING article.

DTC DEFINITIONS

Note. Diagnostic Trouble Codes (DTCs) retrieved from PCM may be either engine or transmission related. Only engine related DTCs are covered in this article. For transmission related DTCs, see appropriate ELECTRONIC CONTROLS article in AUTOMATIC TRANSMISSIONS. See DTC IDENTIFICATION table to determine if DTC is engine or transmission related.

1. The DTCs indicate failure of a specific sensor and/or circuit. Sensor/circuit diagnosis may indicate replacement of PCM.
2. If PCM is replaced at any point during diagnostic testing and if condition is still not corrected after replacing PCM, the following may be the cause: An incorrect PCM may cause a malfunction, which may or may not set a DTC. The PCM connector may be the problem. Connector terminals may have to be removed from connector to be properly checked. Replacement PCM may be faulty. Intermittent problem. Make a careful physical inspection of affected sensor/circuit. A shorted solenoid, coil relay, or harness may be the cause of PCM failure. Use Short Circuit Tester (J-34636) to check for short circuits.

DTC IDENTIFICATION

HARD OR INTERMITTENT TROUBLE CODE DETERMINATION

Note. DTCs will be recorded at various operating times. Some codes require operation of related sensor or switch for 5 seconds; others require operation for 5 minutes or longer at normal operating temperature, vehicle speed and load. Therefore, some DTCs may not set in a service bay operational mode and may require road testing vehicle in order to duplicate conditions under which code will set.

During any diagnostic procedure, determine if DTC(s) are hard failure codes or intermittent failure codes. Diagnostic procedures will not always help analyze intermittent codes. To determine hard codes and intermittent codes

1. Enter diagnostic mode. Read and record all stored DTCs. Exit diagnostic mode, and clear DTCs. See «CLEARING DTCS»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel__clearing-dtcs) .
2. Apply parking brake, and place transmission in Neutral or Park. Block drive wheels, and start engine. MIL should turn off. Operate warm engine at specified RPM for 2 minutes and note MIL.
3. If MIL illuminates, enter diagnostic mode. Read and record DTCs. This will reveal hard failure codes. Oxygen sensor related codes may require a road test to reset hard failure after DTCs were cleared.
4. If MIL does not illuminate, all stored DTCs were intermittent failures, except as noted above.

CLEARING DTCS

Note. Do not clear DTCs until directed by diagnostic procedure. Before clearing DTCs, record FREEZE FRAME and FAILURE RECORDS for reference during testing. When DTCs are cleared, freeze frame data which could be used for intermittent fault diagnosis, will also be erased from memory.

To clear DTCs using scan tool, select CLEAR DTCs or CLEAR INFORMATION function. Follow scan tool manufacturer's instructions.

If a scan tool is not available, DTCs can be cleared by disconnecting one of the following power sources for at least 30 seconds

1. Power source to PCM (such as battery pigtail, PCM connectors, fuse, etc.).
2. Negative battery cable (loss of radio presets and/or clock settings will result).

PCM will clear stored DTC if fault that caused DTC to set is not detected for 40 consecutive warm-up cycles.

PCM LOCATION

On "C" and "K" Series, PCM is located behind right side of instrument panel, above blower motor. On "G" Series, PCM is located behind center of instrument panel. On "P" Series, PCM is located behind left side of instrument panel.

Diagnostic Aids

Diagnostic aids (located in many circuit tests) are provided as additional tips to help with diagnosis when inspected circuit is okay.

SPECIAL TOOLS (DIAGNOSTIC)

Note. Diagnosis of computerized engine control system requires using a scan tool. Use of a scan tool saves a great deal of diagnostic time and prevents replacement of good parts. Computer related diagnosis without a scan tool is NOT recommended.

Computerized engine control system is diagnosed using a Tech 1 or 2 scan tool, or other OBD-II compatible scan tool. However, other tools are needed to aid in diagnosing problems. These tools include a tachometer (inductive pickup), a non-powered test light, digital multimeter with 10-megohm input impedance (minimum), vacuum pump and vacuum gauge, High Energy Ignition (HEI) spark tester, fuel pressure gauge, fuel injector test light (noid-light), and fused jumper wires. A test light, rather than a voltmeter, must be used when indicated by a circuit or diagnostic test procedure.

SCAN TOOL USAGE

Note. Before connecting scan tool to vehicle, diagnostic system should be checked to determine if system is operating properly, and if information received will be accurate. This is done by performing ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK . If vehicle does not pass OBD system check, information received may be invalid.

Note. Information obtained by a scan tool is only as accurate as the scan tool itself. A scan tool that displays faulty data should not be used. If faulty data readings are suspected, verify scan tool information using a digital multimeter and wiring schematic.

Scan tool is a specialized tester which, when plugged into DLC, can diagnose on-board computer control systems by providing almost instant access to circuit data without crawling under instrument panel or hood to backprobe sensors and connectors. Scan tools reduce diagnostic time by furnishing input data (sensor values) which can be compared to specification parameters. See SCAN TOOL DATA .

Scan tools also furnish status data of output devices (solenoids and motors). However, status parameters are only an indication that output signals have been sent to devices by PCM. They do not indicate whether devices respond properly to that signal. This must be verified at output device using a voltmeter or test light.

If DTCs are not present, a problem may still exist. Driveability-related problems with DTCs displayed occur about 20 percent of the time, while driveability problems without DTCs occur about 80 percent of the time. Out-of-calibration sensors may NOT set a DTC, but WILL cause driveability problems. A scan tool is the easiest method of checking sensor specifications and other data parameters. A scan tool is also useful in finding intermittent wiring problems by wiggling wiring harnesses and connections (key on, engine off) while observing data parameters.

SCAN TOOL DATA

Note. Information contained in the following table is typical of readings taken on vehicle with engine idling, upper radiator hose hot, throttle closed, transmission in Park or Neutral, closed loop status achieved and all accessories off (except as noted in tables). Not all devices and systems are used on all models. Refer to scan tool manufacturer's instructions.

SCAN TOOL DATA VALUES

SUMMARY

If no hard fault codes are present, driveability symptoms exist or intermittent DTC(s) exist, proceed to appropriate TROUBLE SHOOTING - NO CODES article for diagnosis by symptom (i.e., ROUGH IDLE, NO START, etc.) or intermittent diagnostic procedures.

CIRCUIT TESTS

Note. Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK under SELF-DIAGNOSTIC SYSTEM before proceeding with CIRCUIT TESTS.

NO MALFUNCTION INDICATOR LIGHT (MIL)

1. Perform «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel__on-board-diagnostic-obd-system-check) . After performing OBD system check, go to next step.
2. Attempt to start engine. If engine starts, go to next step. If engine does not start, go to step 6 .
3. Check fuse No. 4 (Gauges). If fuse if faulty, go to step 14 . If fuse is okay, go to next step.
4. Turn ignition on. Using test light connected to ground, probe ignition feed terminal at instrument cluster connector. See WIRING DIAGRAMS article. If test light illuminates, go to next step. If test light does not illuminate, go to step 11 .
5. Turn ignition off. Disconnect Blue PCM harness connector. Turn ignition on. Connect a fused jumper wire between ground and MIL control circuit of PCM harness connector. See WIRING DIAGRAMS article. If MIL illuminates, go to step 9 . If MIL does not illuminate, go to step 10 .
6. Check fuses to PCM ignition and battery feed circuit. If fuses are okay, go to next step. If fuse(s) are faulty, go to step 13 .
7. Turn ignition off. Disconnect PCM harness connectors. Turn ignition on. Using test light connected to ground, probe PCM harness connector ignition and battery feed circuits. See WIRING DIAGRAMS article. If test light illuminates on both circuits, go to next step. If test light does not illuminate on both circuits, go to step 12 .
8. Check for faulty or poor PCM ground connections. Repair as necessary. After repairs, go to step 20 . If ground connections are okay, go to next step.
9. Check for poor connection at PCM harness connector. Repair as necessary. After repairs, go to step 20 . If connector is okay, go to step 15 .
10. Check for open in MIL control circuit. Repair as necessary. After repairs, go to step 20 . If circuit is okay, go to step 16 .
11. Repair open in ignition feed circuit to instrument cluster. After repairs, go to step 20 .
12. Locate and repair open in PCM battery feed or ignition circuit. Repair as necessary. After repairs, go to step 20 .
13. Locate and repair short to ground in PCM ignition feed circuit or PCM battery feed circuit. Repair as necessary. After repairs, go to step 20 .
14. Locate and repair short to ground in instrument cluster ignition feed circuit. After repairs, go to step 20 .
15. Replace PCM. Program PCM using required equipment. After repairs, go to step 20 .
16. Check for poor connection at MIL control circuit to instrument cluster connector. Repair as necessary. After repairs, go to step 20 . If circuit is okay, go to next step.
17. Remove instrument cluster assembly. Inspect MIL bulb. If bulb is okay, go to step 19 . If bulb is faulty, go to next step.
18. Replace MIL bulb. After replacing bulb, go to step 20 .
19. Replace instrument cluster. After repairs, go to next step.
20. Start engine and operate vehicle under conditions which original symptom was noted. If system does not operate properly, go to step 2 . If system operates properly, go to «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel__on-board-diagnostic-obd-system-check) .

DATA LINK CONNECTOR (DLC) DIAGNOSIS

1. Perform «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel__on-board-diagnostic-obd-system-check) . After performing OBD system check, go to next step.
2. Disconnect scan tool. Install scan tool to another vehicle of the same year and same systems. Turn ignition on with engine off. If scan tool communicates with PCM, go to next step. If scan tool does not communicate with PCM, go to step 4 .
3. Reconnect scan tool to original vehicle. Turn ignition on with engine off. If scan tool communicates with PCM, go to step 11 . If scan tool does not communicate with PCM, go to next step.
4. Scan tool may be faulty. Refer to scan tool instruction manual. After repairs, go to step 17 .
5. Turn ignition off. Disconnect PCM harness connectors. Using DVOM, measure resistance between DLC terminals No. 4 (ground circuit) and No. 2 (serial data class II circuit). See WIRING DIAGRAMS article. If resistance is less than 10 ohms, go to next step. If resistance is 10 ohms or greater, go to step 7 .
6. Disconnect Electronic Brake Control Module (EBCM) harness connector. Using DVOM, measure resistance between DLC terminals No. 4 (ground circuit) and No. 2 (serial data class II circuit). Disconnect other control modules connected to serial data class II circuit one at a time and re-measure resistance with each module disconnected. If resistance is greater than 10 ohms with any module disconnected, go to step 15 . If resistance 10 ohms or less with any module disconnected, go to step 14 .
7. Turn ignition on with engine off. Using DVOM, measure voltage between DLC terminals No. 4 (ground circuit) and No. 2 (serial data class II circuit). See WIRING DIAGRAMS article. If voltage is less than one volt, go to next step. If voltage is one volt or greater, go to step 12 .
8. Turn ignition off. Using DVOM, measure resistance between DLC terminal No. 2 (serial data class II circuit) and PCM harness connector terminal C8 (serial data class II circuit). See WIRING DIAGRAMS article. If resistance is less than 10 ohms, go to next step. If resistance is 10 ohms or greater, go to step 13 .
9. Check for opens or shorts to ground in all power and ground circuits to PCM. Repair as necessary. After repairs, go to step 17 . If all power and ground circuits are okay, go to next step.
10. Check for poor connections at PCM. Repair as necessary. After repairs, go to step 17 . If connections are okay, go to next step.
11. Repair intermittent short or open in serial data class II circuit. After repairs, go to step 17 .
12. Repair short to voltage in serial data class II circuit. After repairs, go to step 17 .
13. Repair open in serial data class II circuit. After repairs, go to step 17 .
14. Repair short to ground in serial data class II circuit. After repairs, go to step 17 .
15. Replace control module that caused resistance to increase. After repairs, go to step 17 .
16. Replace PCM. Program PCM using required equipment. After replacing PCM, go to next step.
17. Start engine and operate vehicle under conditions which original symptom was noted. If system does not operate properly, go to step 2 . If system operates properly, go to «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel__on-board-diagnostic-obd-system-check) .

DIAGNOSTIC TESTS

Note. Before clearing DTCs, record FREEZE FRAME and FAILURE RECORDS for reference during testing. Data will be erased when DTCs are cleared.

Note. If PCM is replaced, NEW PCM must be programmed using special equipment.

Note. Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK under SELF-DIAGNOSTIC SYSTEM before proceeding with DIAGNOSTIC TESTS.

Scheme 2

Circuit Description

The Mass Airflow (MAF) sensor measures the amount of air entering the engine during a given time. PCM uses MAF sensor information to monitor EGR flow rates. A large quantity of air entering the engine indicates acceleration, high load situation or no EGR flow, while a small quantity of air entering the engine indicates deceleration, idle or full EGR operation.

MAF sensor produces a frequency signal. DTC P0101 will set if the signal from the MAF sensor does not match a predicted value based on engine coolant temperature, throttle angle and engine speed. DTC will also set when the following conditions are present

1. Engine is running.
2. Engine speed is 506-806 RPM.
3. Throttle angle is zero degrees.
4. The change in MAF sensor is less than a calculated value.
5. The listed conditions are met for more than 3 seconds.

Diagnostic Procedures

1. If OBD system check has been performed, go to next step. If OBD system check has not been performed, go to «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel__on-board-diagnostic-obd-system-check) under SELF-DIAGNOSTIC SYSTEM.
2. Turn ignition on, with engine off. Review and record scan tool FAILURE RECORDS data. Operate vehicle within the FAILURE RECORDS conditions. Using scan tool, monitor Specific DTC info for DTC P0101. If scan tool indicates that DTC P0101 failed this ignition cycle, go to next step. If scan tool does not indicate that DTC P0101 failed, see «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel) .
3. Check for plugged intake air duct, dirty air filter, intake manifold vacuum leaks or EGR leak. Repair or replace as necessary. After repairs, go to step 17 . If no problems are found, go to next step.
4. Turn ignition on, with engine off. Ensure throttle is closed. Observe APP angle display on scan tool. APP angle should be zero percent. If APP angle is as specified or close to zero percent, go to next step. If APP angle is not as specified, see DTC P0121 for diagnosis.
5. Turn ignition off. Disconnect MAF sensor harness connector. Turn ignition on, with engine off. Using DVOM, measure voltage between MAF sensor harness connector terminal "A" (signal circuit) and chassis ground. DVOM should read 5 volts. If voltage is as specified, go to next step. If voltage is not as specified, go to step 7 .
6. Connect test light between MAF sensor harness connector terminals "C" (ignition feed circuit) and "B" (ground circuit). If test light illuminates, go to step 10 . If test does not illuminate, go to step 9 .
7. If voltage is less than 4.5 volts, go to step 11 . If voltage is 4.5 volts or greater, go to next step.
8. Turn ignition off. Disconnect PCM harness connector. Turn ignition on, with engine off. Using DVOM, measure voltage between ground and MAF sensor harness connector terminal "A". If voltage is zero volts, go to step 15 . If voltage is not zero volts, go to step 14 .
9. Connect test light between MAF sensor harness connector terminal "C" and chassis ground. If test light illuminates, go to step 12 . If test light does not illuminate, go to step 13 .
10. Check for poor connection at MAF sensor. Repair or replace terminals as necessary. After repairs, go to step 17 . If terminals are okay, go to step 15 .
11. Check MAF signal circuit between PCM and MAF sensor for an open, short to ground, or short to MAF sensor ground circuit. Repair as necessary. After repairs, go to step 17 . If circuits are okay, go to step 16 .
12. Locate and repair open in ground circuit to MAF sensor. After repairs, go to step 17 .
13. Locate and repair open in ignition feed circuit to MAF sensor. After repairs, go to step 17 .
14. Locate and repair short to voltage in MAF sensor signal circuit. After repairs, go to step 17 .
15. Replace MAF sensor. After replacing sensor, go to step 17 .
16. Replace PCM. Program PCM using required equipment. After replacing PCM, go to next step.
17. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, and then enter DTC P0101. Operate vehicle within the conditions for setting this DTC. If scan tool indicates that this test ran and passed, go to next step. If scan tool does not indicate that this test ran and passed, repeat step 2 .
18. Using scan tool, select CAPTURE INFO, REVIEW INFO. If any undiagnosed DTC(s) are displayed, go to applicable DTC test.

Check wiring harness for damage. If harness appears to be okay, observe scan tool while moving connectors and wiring harnesses related to the MAF sensor. A change in the display will indicate location of fault.

Check for plugged intake air duct or dirty air filter. A wide-open throttle acceleration from a stop should cause the mass airflow displayed on scan tool to increase. If not, check for restrictions. If DTC P0101 cannot be duplicated, the information included in the FAILURE RECORDS data can be useful in determining vehicle mileage since the DTC was last set and how often the DTC sets.

DTC P0102: MAF SENSOR CIRCUIT LOW FREQUENCY ("C" & "K" SERIES)

Note. For circuit reference, refer to DTC P0101 schematic. (Scheme 2)

The Mass Airflow (MAF) sensor measures the amount of air entering the engine during a given time. PCM uses MAF sensor information to monitor EGR flow rates. A large quantity of air entering the engine indicates acceleration, high load situation or no EGR flow, while a small quantity of air entering the engine indicates deceleration, idle, or full EGR operation.

MAF sensor produces a frequency signal. DTC P0102 will set if the signal from the MAF sensor does not match a predicted value based on engine coolant temperature, throttle angle, engine speed or MAF sensor is below the possible range of a normally operating MAF sensor. DTC will also set when the following conditions are present

1. Engine is running.
2. Engine run time is greater than 2 seconds.
3. Ignition on for 2 seconds.
4. MAF sensor is less than 1280 Hz.

1. If OBD system check has been performed, go to next step. If OBD system check has not been performed, go to «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel__on-board-diagnostic-obd-system-check) under SELF-DIAGNOSTIC SYSTEM.
2. Start and idle engine. Monitor MAF display on scan tool. If MAF reading is less than 1280 Hz, go to step 4 . If MAF reading is greater than 1280 Hz, go to next step.
3. Turn engine off. Turn ignition on, with engine off. Review and record FAILURE RECORDS data on scan tool. Operate vehicle within the FAILURE RECORDS conditions as noted. Using scan tool, monitor SPECIFIC DTC information for DTC P0102. If scan tool indicates that DTC P0102 failed in this ignition cycle, go to next step. If DTC P0102 did not fail in this ignition cycle, see «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel) .
4. Check for blocked MAF sensor inlet, large intake manifold or EGR leaks, or large leaks downstream of MAF sensor. Repair as necessary. After repairs, go to step 14 . If no problems are found, go to next step.
5. Turn ignition off. Disconnect MAF sensor harness connector. Turn ignition on, with engine off. Using DVOM, measure voltage between ground and MAF sensor harness connector terminal "A" (signal circuit). If voltage is 5 volts, go to next step. If voltage is not 5 volts, go to step 9 .
6. Connect test light between MAF sensor harness connector terminal "C" (ignition feed) and ground. If test light illuminates, go to step 8 . If test light does not illuminate, go to next step.
7. Connect test light between MAF sensor harness connector terminal "C" and battery negative terminal. If test light illuminates, go to step 10 . If test light does not illuminate, go to step 11 .
8. Check for poor connection at MAF sensor. Repair as necessary. After repairs, go to step 14 . If connections are okay, go to step 12 .
9. Check signal circuit between MAF sensor and PCM for an open, short to ground, short to MAF sensor ground circuit, or short to voltage. Repair as necessary. After repairs, go to step 14 . If circuits are okay, go to step 13 .
10. Locate and repair open in ground circuit to MAF sensor. After repairs, go to step 14 .
11. Locate and repair open in ignition feed circuit to MAF sensor. After repairs, go to step 14 .
12. Replace MAF sensor. After replacing MAF sensor, go to step 14 .
13. Replace PCM. Program PCM using required equipment. After replacing PCM, go to next step.
14. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, and then enter DTC P0102. Operate vehicle within the conditions for setting this DTC. If scan tool indicates that this test ran and passed, go to next step. If scan tool does not indicate that this test ran and passed, repeat step 2 .
15. Using scan tool, select CAPTURE INFO, REVIEW INFO. If any undiagnosed DTC(s) are displayed, go to applicable DTC test.

Check wiring harness for damage. If harness appears to be okay, observe scan tool while moving connectors and wiring harnesses related to the MAF sensor. A change in the display will indicate location of fault.

Check for plugged intake air duct or dirty air filter. A wide-open throttle acceleration from a stop should cause the mass airflow displayed on scan tool to increase. If not, check for restrictions. If DTC P0102 cannot be duplicated, the information included in the FAILURE RECORDS data can be useful in determining vehicle mileage since the DTC was last set and how often the DTC sets.

DTC P0103: MAF SENSOR CIRCUIT HIGH FREQUENCY ("C" & "K" SERIES)

Note. For circuit reference, refer to DTC P0101 schematic. (Scheme 2)

The Mass Airflow (MAF) sensor measures the amount of air entering the engine during a given time. PCM uses MAF sensor information to monitor EGR flow rates. A large quantity of air entering the engine indicates acceleration, high load situation or no EGR flow, while a small quantity of air entering the engine indicates deceleration, idle, or full EGR operation.

MAF sensor produces a frequency signal. DTC P0103 will set if signal from MAF sensor does not match a predicted value based on engine coolant temperature, throttle angle, engine speed or MAF sensor is above the possible range of a normally operating MAF sensor. DTC will also set when the following conditions are present

1. Engine is running.
2. Engine run time is greater than 2 seconds.
3. Engine speed greater than zero RPM.
4. MAF signal frequency is greater than 10,496 Hz.
5. Listed conditions present for more than 2 seconds.

1. If OBD system check has been performed, go to next step. If OBD system check has not been performed, go to «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel__on-board-diagnostic-obd-system-check) under SELF-DIAGNOSTIC SYSTEM.
2. Start and idle engine. Monitor MAF display on scan tool. If MAF reading is greater than 10,496 Hz, go to step 4 . If MAF reading is 10,496 Hz or less, go to next step.
3. Turn engine off. Turn ignition on, with engine off. Review and record FAILURE RECORDS data on scan tool. Operate vehicle within the FAILURE RECORDS conditions as noted. Using scan tool, monitor SPECIFIC DTC information for DTC P0103. If scan tool indicates that DTC P0103 failed in this ignition cycle, go to next step. If DTC P0103 did not fail in this ignition cycle, see «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel) .
4. Turn ignition off. Disconnect MAF sensor harness connector. Start and idle engine. Using scan tool, monitor MAF display. If MAF value is 00 Hz, go to next step. If MAF value is not 00 Hz, go to step 7 .
5. Check for poor connection at MAF harness connector terminals. Repair as necessary. After repairs, go to step 10 . If terminals or connection is okay, go to next step.
6. Replace MAF sensor. After replacing MAF sensor, go to step 10 .
7. Check MAF sensor harness for incorrect routing. Ensure there are no aftermarket add-ons near harness. Correct harness routing as necessary. After repairs, go to step 10 . If no problems are found, go to next step.
8. Check MAF sensor signal circuit terminal connections at PCM. Repair as necessary. After repairs, go to step 10 . If no problems are found, go to next step.
9. Replace PCM. Program PCM using required equipment. After replacing PCM, go to next step.
10. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, and then enter DTC P0103. Operate vehicle within the conditions for setting this DTC. If scan tool indicates that this test ran and passed, go to next step. If scan tool does not indicate that this test ran and passed, repeat step 2 .
11. Using scan tool, select CAPTURE INFO, REVIEW INFO. If any undiagnosed DTC(s) are displayed, go to applicable DTC test.

Check wiring harness or terminals for damage. If harness or terminals appears to be okay, observe scan tool while moving connectors and wiring harnesses related to the MAF sensor. A change in the display will indicate the location of fault.

Scheme 3

Intake Air Temperature (IAT) sensor is a thermistor that controls a monitored signal voltage to PCM. When air is cool, sensor resistance will be high and PCM will sense a high voltage signal. When air is warm, sensor resistance will be low and PCM will sense a low voltage signal.

DTC will set when the following conditions are present

1. Engine coolant temperature is less than 109°F (42.5°C).
2. Intake air temperature is greater than or equal to 304°F (151°C).
3. Conditions are met for 2 seconds.

1. If OBD system check has been performed, go to next step. If OBD system check has not been performed, go to «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel__on-board-diagnostic-obd-system-check) under SELF-DIAGNOSTIC SYSTEM.
2. Install scan tool. Start engine. Using scan tool, monitor IAT display on scan tool. If IAT display is greater than or equal to 304°F (151°C), go to next step. If IAT display is less than 304°F (151°C), go to step 5 .
3. Turn engine off. Disconnect IAT sensor connector. Turn ignition on. Monitor IAT display on scan tool. If IAT is less than or equal to -30°F (-22°C), go to step 7 . If IAT is greater than -30°F (-22°C), go to next step.
4. Turn ignition off. Using DVOM, check resistance between IAT sensor connector terminals. If resistance is infinite, go to step 8 . If resistance is not infinite, go to step 6 .
5. DTC is intermittent. If no additional DTCs are set, see «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel) . If any additional DTCs are set, go to applicable DTC test.
6. Repair short to ground in IAT signal circuit. After repairs, go to step 9 .
7. Replace IAT sensor. After replacing sensor, go to step 9 .
8. Replace PCM. Program PCM using required equipment. After replacing PCM, go to next step.
9. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, and then enter DTC P0112. Operate vehicle within the conditions for setting this DTC. If scan tool indicates that this test ran and passed, go to next step. If scan tool does not indicate that this test ran and passed, repeat step 2 .
10. Using scan tool, select CAPTURE INFO, REVIEW INFO. If any undiagnosed DTC(s) are displayed, go to applicable DTC test.

Check harness routing for a potential short to ground in signal circuit. Scan tool displays intake air temperature in degrees centigrade. See appropriate TROUBLE SHOOTING - NO CODES article. A skewed sensor could result in poor driveability complaints.

DTC P0113: INTAKE AIR TEMPERATURE (IAT) SENSOR CIRCUIT HIGH VOLTAGE ("C", "G", "K" & "P" SERIES)

Note. For circuit reference, refer to DTC P0112 schematic. (Scheme 3)

Intake Air Temperature (IAT) sensor is a thermistor that controls a monitored signal voltage to PCM. When air is cool, sensor resistance will be high and PCM will sense a high voltage signal. When air is warm, sensor resistance will be low and PCM will sense a low voltage signal.

DTC will set when the following conditions are present

1. Engine is operating for 8 minutes.
2. IAT is less than or equal to -40°F (-40°C).
3. Conditions are met for 2 seconds.

1. If OBD system check has been performed, go to next step. If OBD system check has not been performed, go to «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel__on-board-diagnostic-obd-system-check) under SELF-DIAGNOSTIC SYSTEM.
2. Install scan tool. Start engine. Monitor IAT display on scan tool. If IAT is less than or equal to -22°F (-30°C), go to next step. If IAT is greater than -22°F (-30°C), go to step 5 .
3. Turn engine off. Disconnect IAT sensor harness connector. Turn ignition on. Connect a jumper wire between IAT sensor connector terminals. Monitor IAT display on scan tool. If reading is greater than or equal to 304°F (151°C), go to step 6 . If IAT is less than 304°F (151°C), go to next step.
4. Connect a jumper wire between IAT signal circuit of IAT sensor connector and ground. Monitor IAT display on scan tool. If reading is greater than or equal to 304°F (151°C), go to step 7 . If IAT is less than 304°F (151°C), go to step 8 .
5. DTC is intermittent. If no additional DTCs are set, see «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel) . If any additional DTCs are set, go to applicable DTC test.
6. Check for poor connections at IAT sensor and PCM. If a problem is found, go to step 14 . If no problems are found, go to step 9 .
7. Check for open in IAT ground circuit between IAT sensor and PCM. If IAT ground circuit is open, go to step 14 . If IAT ground circuit is not open, go to step 11 .
8. Check for open in IAT signal circuit between IAT sensor and PCM. If IAT signal circuit is open, go to step 14 . If IAT signal circuit is not open, go to step 11 .
9. Using DVOM in mA (milliamp) scale, measure current at IAT harness connector terminals. If reading is less than 48 mA, go to step 12 . If reading is 48 mA or greater, go to next step.
10. Repair short to voltage in IAT signal circuit. After repairs, go to step 14 .
11. Check PCM connectors for poor connections. Repair as necessary. After repairs, go to step 14 . If connectors are okay, go to step 13 .
12. Replace IAT sensor. After replacing sensor, go to step 14 .
13. Replace PCM. Program PCM using required equipment. After replacing PCM, go to next step.
14. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, and then enter DTC P0113. Operate vehicle within the conditions for setting this DTC. If scan tool indicates that this test ran and passed, go to next step. If scan tool does not indicate that this test ran and passed, repeat step 2 .
15. Using scan tool, select CAPTURE INFO, REVIEW INFO. If any undiagnosed DTC(s) are displayed, go to applicable DTC test.

Scan tool displays intake air temperature in degrees centigrade. See appropriate TROUBLE SHOOTING - NO CODES article. A skewed sensor could result in poor driveability complaints.

DTC P0117: ENGINE COOLANT TEMPERATURE (ECT) SENSOR CIRCUIT LOW VOLTAGE ("C", "G", "K" & "P" SERIES)

Note. For circuit reference, refer to DTC P0112 schematic. (Scheme 3)

Engine Coolant Temperature (ECT) sensor is a thermistor that controls a monitored signal voltage to PCM. When engine coolant is cool, sensor resistance will be high and PCM will sense a high voltage signal. When engine coolant is warm, sensor resistance will be low and PCM will sense a low voltage signal. Voltage measured across thermistor is interpreted as a temperature.

DTC will set when engine coolant temperature is greater than or equal to 304°F (151°C) for 2 seconds.

1. If OBD system check has been performed, go to next step. If OBD system check has not been performed, go to «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel__on-board-diagnostic-obd-system-check) under SELF-DIAGNOSTIC SYSTEM.
2. Install scan tool. Start engine. Monitor ECT display on scan tool. If ECT is greater than or equal to 304°F (151°C), go to next step. If ECT is less than 304°F (151°C), go to step 5 .
3. Turn engine off. Disconnect ECT sensor connector. Turn ignition on. Monitor ECT display on scan tool. If ECT is less than or equal to -22°F (-30°C), go to step 7 . If ECT is greater than -22°F (-30°C), go to next step.
4. Turn ignition off. Using DVOM, check resistance between ECT sensor connector terminals. If resistance is infinite, go to step 8 . If resistance is not infinite, go to step 6 .
5. DTC is intermittent. If no additional DTCs are set, see «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel) . If any additional DTCs are set, go to applicable DTC test.
6. Repair short to ground in ECT signal circuit. After repairs, go to step 9 .
7. Replace ECT sensor. After replacing sensor, go to step 9 .
8. Replace PCM. Program PCM using required equipment. After replacing PCM, go to next step.
9. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, and then enter DTC P0117. Operate vehicle within the conditions for setting this DTC. If scan tool indicates that this test ran and passed, go to next step. If scan tool does not indicate that this test ran and passed, repeat step 2 .
10. Using scan tool, select CAPTURE INFO, REVIEW INFO. If any undiagnosed DTC(s) are displayed, go to applicable DTC test.

Check harness routing for a potential short to ground. After engine is started, coolant temperature should rise steadily to about 185°F (85°C). See appropriate TROUBLE SHOOTING - NO CODES article. A skewed sensor could result in poor driveability complaints.

DTC P0118: ENGINE COOLANT TEMPERATURE (ECT) SENSOR CIRCUIT HIGH VOLTAGE ("C", "G", "K" & "P" SERIES)

Note. For circuit reference, refer to DTC P0112 schematic. (Scheme 3)

Engine Coolant Temperature (ECT) sensor is a thermistor that controls a monitored signal voltage to PCM. When engine coolant is cool, sensor resistance will be high and PCM will sense a high voltage signal. When engine coolant is warm, sensor resistance will be low and PCM will sense a low voltage signal. Voltage measured across thermistor is interpreted as a temperature.

DTC will set when the following conditions are present

1. Engine running for at least 8 minutes.
2. ECT is less than -40°F (-40°C).
3. Conditions are met for 2 seconds.

1. If OBD system check has been performed, go to next step. If OBD system check has not been performed, go to «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel__on-board-diagnostic-obd-system-check) under SELF-DIAGNOSTIC SYSTEM.
2. Install scan tool. Start engine. Monitor ECT display on scan tool. If ECT is less than or equal to -22°F (-30°C), go to next step. If ECT is greater than -22°F (-30°C), go to step 5 .
3. Turn engine off. Disconnect ECT sensor harness connector. Turn ignition on. Connect a jumper wire between ECT sensor connector terminals. Monitor ECT display on scan tool. If ECT is greater than or equal to 304°F (151°C), go to step 6 . If ECT is less than 304°F (151°C), go to next step.
4. Connect a jumper wire between ECT sensor harness connector terminal "B" (signal circuit) and ground. Monitor ECT display on scan tool. If ECT is greater than or equal to 304°F (151°C), go to step 7 . If ECT is less than 304°F (151°C), go to step 8 .
5. DTC is intermittent. If no additional DTCs are set, see «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel) . If any additional DTCs are set, go to applicable DTC test.
6. Check for poor connections at ECT sensor and PCM. If a problem is found, go to step 14 . If no problems are found, go to step 9 .
7. Check for open in ECT ground circuit between ECT sensor and PCM. If ECT ground circuit is open, go to step 14 . If ECT ground circuit is not open, go to step 11 .
8. Check for open in ECT signal circuit between ECT sensor and PCM. If circuit is open, repair as necessary. After repairs, go to step 14 . If circuit is not open, go to step 11 .
9. Using DVOM in mA (milliamp) scale, measure current at ECT harness connector terminals. If reading is less than 48 mA, go to step 12 . If reading is 48 mA or greater, go to next step.
10. Repair short to voltage in ECT signal circuit. After repairs, go to step 14 .
11. Check PCM connectors for poor connections. Repair or replace terminals as necessary. After repairs, go to step 14 . If terminals are okay, go to step 13 .
12. Replace ECT sensor. After replacing sensor, go to step 14 .
13. Replace PCM. Program PCM using required equipment. After replacing PCM, go to next step.
14. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, and then enter DTC P0118. Operate vehicle within the conditions for setting this DTC. If scan tool indicates that this test ran and passed, go to next step. If scan tool does not indicate that this test ran and passed, repeat step 2 .
15. Using scan tool, select CAPTURE INFO, REVIEW INFO. If any undiagnosed DTC(s) are displayed, go to applicable DTC test.

Check harness routing for a potential short to ground. After engine is started, coolant temperature should rise steadily to about 185°F (85°C). See appropriate TROUBLE SHOOTING - NO CODES article. A skewed sensor could result in poor driveability complaints.

Scheme 4

Accelerator Pedal Position (APP) module provides a voltage signal that changes relative to accelerator pedal position. Three sensors are located within APP module and are scaled differently.

DTC will set when the following conditions are present

1. Ignition voltage is greater than 6.4 volts.
2. Engine speed is greater than 300 RPM.
3. Difference between APP 1 and APP 2 is greater than .23 volt (PCM compares pre-scaled voltage - internal to PCM).
4. Difference between APP 1 and APP 3 is greater than .50 volt (PCM compares pre-scaled voltage - internal to PCM).
5. No in range faults for APP 2 or APP 3 (PCM checks for high and low voltage faults).
6. Conditions are met for 2 seconds.

1. If OBD system check has been performed, go to next step. If OBD system check has not been performed, go to «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel__on-board-diagnostic-obd-system-check) under SELF-DIAGNOSTIC SYSTEM.
2. Install scan tool. Turn ignition on, with engine off. Using scan tool, with throttle closed, observe APP voltages. APP 1 voltage should be .45-.95 volt. APP 2 voltage should be 4.0-4.5 volts. APP 3 voltage should be 3.6-4.1 volts. If voltages are as specified, go to next step. If voltages are not as specified, go to step 4 .
3. DTC is intermittent. If no additional DTCs are set, see «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel) . If any additional DTCs are set, go to applicable DTC test.
4. Turn ignition off. Disconnect APP sensor connector. Turn ignition on, with engine off. Using DVOM, probe 5-volt reference circuits (terminals "D", "E" and "G") of APP sensor connectors to ground. If voltage on all circuits is greater than or equal to 4.75 volts, go to next step. If voltage on all circuits is less than 4.75 volts, go to step 6 .
5. Turn ignition on, with engine off. Using test light, probe ground circuits (terminals "A", "B" and "J") of APP sensor connectors to battery voltage. If test light illuminates on all circuits, go to step 9 . If test light does not illuminate on all circuits, go to step 8 .
6. Turn ignition off. Disconnect PCM harness connector. Check for open or short to ground in 5-volt reference circuits. Repair as necessary. If open or short to ground was present in 5-volt reference circuits, go to step 11 . If open or short to ground was not present in 5-volt reference circuits, go to next step.
7. Check for poor connections at 5-volt reference terminals of PCM. Repair as necessary. After repairs, go to step 11 . If connections are okay, go to step 10 .
8. Turn ignition off. Disconnect PCM harness connector. Check for open in ground circuits. Repair as necessary. If open was present in ground circuits, go to step 11 . If open was not present in ground circuits, go to step 10 .
9. Replace APP module. After replacing module, go to step 11 .
10. Replace PCM. Program PCM using required equipment. After replacing PCM, go to next step.
11. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, and then enter DTC P0121. Operate vehicle within the conditions for setting this DTC. If scan tool indicates that this test ran and passed, go to next step. If scan tool does not indicate that this test ran and passed, repeat step 2 .
12. Using scan tool, select CAPTURE INFO, REVIEW INFO. If any undiagnosed DTC(s) are displayed, go to applicable DTC test.

Scan tool reads APP 1 position in volts. With throttle closed and ignition on or at idle, voltage should be .45-.95 volt. Voltage should increase at a steady rate as throttle is moved toward Wide Open Throttle (WOT). Ninety percent pedal travel is acceptable for correct APP operation. Scan APP 1 sensor while depressing accelerator pedal with engine off and ignition on. Display should vary from about .74 volt with throttle closed to greater than 3.7 volts with throttle held at WOT.

Diagnostic procedures checks if all APP circuit voltages fall within normal ranges. PCM compares pre-scaled voltages (voltages scan tool can not read). Scan tool reads only output voltages.

DTC P0122: ACCELERATOR PEDAL POSITION (APP) SENSOR 1 CIRCUIT LOW VOLTAGE ("C", "G", "K" & "P" SERIES)

Note. For circuit reference, refer to DTC P0121 schematic. (Scheme 4)

Accelerator Pedal Position (APP) module provides a voltage signal that changes relative to accelerator pedal position. Three sensors are located within APP module and are scaled differently.

DTC will set when voltage on APP 1 is less than .25 volt for 2 seconds.

1. If OBD system check has been performed, go to next step. If OBD system check has not been performed, go to «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel__on-board-diagnostic-obd-system-check) under SELF-DIAGNOSTIC SYSTEM.
2. Install scan tool. Turn ignition on, with engine off. Using scan tool, with throttle closed, observe APP 1 voltage. If APP 1 voltage is less than or equal to .25 volt, go to step 4 . If APP 1 voltage is greater than .25 volt, go to next step.
3. DTC is intermittent. If no additional DTCs are set, see «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel) . If any additional DTCs are set, go to applicable DTC test.
4. Turn ignition off. Disconnect APP sensor connector. Connect a jumper wire between 5-volt reference circuit and signal circuit of APP 1 sensor connector. Using scan tool, observe APP 1 voltage. If APP 1 voltage is greater than 4.75 volts, go to step 10 . If APP 1 voltage is less than 4.75 volts, go to next step.
5. Connect test light between signal circuit of APP 1 sensor connector and battery voltage. Using scan tool, observe APP 1 voltage. If APP 1 voltage is greater than 4.75 volts, go to next step. If APP 1 voltage is less than 4.75 volts, go to step 8 .
6. Turn ignition off. Disconnect PCM harness connector. Check for open or short to ground in 5-volt reference circuit. Repair as necessary. If 5-volt reference circuit is open or shorted to ground, go to step 12 . If 5-volt reference circuit is okay, go to next step.
7. Check for poor connection at 5-volt reference circuit terminal to PCM. Repair or replace terminals as necessary. After repairs, go to step 13 . If terminals are okay, go to step 12 .
8. Turn ignition off. Disconnect PCM harness connector. Check for open or short to ground in APP 1 signal circuit. Repair as necessary. If APP 1 signal circuit is open or shorted to ground, go to step 13 . If APP 1 signal circuit is okay, go to next step.
9. Check for poor connections at APP 1 signal terminal to PCM. Repair or replace terminal as necessary. After repairs, go to step 13 . If terminal was okay, go to step 12 .
10. Check for poor connection at APP module. Repair as necessary. After repairs, go to step 13 . If connections are okay, go to next step.
11. Replace APP module. After replacing module, go to step 13 .
12. Replace PCM. Program PCM using required equipment. After replacing PCM, go to next step.
13. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, and then enter DTC P0122. Operate vehicle within the conditions for setting this DTC. If scan tool indicates that this test ran and passed, go to next step. If scan tool does not indicate that this test ran and passed, repeat step 2 .
14. Using scan tool, select CAPTURE INFO, REVIEW INFO. If any undiagnosed DTC(s) are displayed, go to applicable DTC test.

Scan tool reads APP 1 position in volts. With throttle closed and ignition on or at idle, reading should be .45-.95 volt. Voltage should increase at a steady rate as throttle is moved toward Wide Open Throttle (WOT). Ninety percent pedal travel is acceptable for correct APP operation. Scan APP 1 sensor while depressing accelerator pedal with engine off and ignition on. Display should vary from about .74 volt with throttle closed to greater than 3.7 volts with throttle held at WOT. DTC will set if signal or 5-volt reference circuits are open.

DTC P0123: ACCELERATOR PEDAL POSITION (APP) SENSOR 1 CIRCUIT HIGH VOLTAGE ("C", "G", "K" & "P" SERIES)

Note. For circuit reference, refer to DTC P0121 schematic. (Scheme 4)

Accelerator Pedal Position (APP) module provides a voltage signal that changes relative to accelerator pedal position. Three sensors are located within APP module and are scaled differently.

DTC will set when voltage on APP 1 is greater than 4.75 volts for 2 seconds.

1. Perform «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel__on-board-diagnostic-obd-system-check) . After performing OBD system check, go to next step.
2. Install scan tool. Turn ignition on, with engine off. Using scan tool, with throttle closed, observe APP 1 voltage. If APP 1 voltage is greater than 4.75 volts, go to step 4 . If APP 1 voltage is less than 4.75 volts, go to next step.
3. DTC is intermittent. If no additional DTCs are set, see «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel) . If any additional DTCs are set, go to applicable DTC test.
4. Disconnect APP sensor harness connector. Using scan tool, observe APP 1 voltage. If APP 1 voltage is less than .25 volt, go to next step. If APP 1 voltage is greater than .25 volt, go to step 6 .
5. Using test light connected to battery voltage, probe APP 1 sensor harness connector ground circuit. If test light illuminates, go to step 7 . If test light does not illuminate, go to step 8 .
6. Check for short to voltage in APP 1 signal circuit. If circuit is shorted to voltage, repair as necessary. After repairs, go to step 12 . If circuit is okay, go to step 11 .
7. Repair APP 1 5-volt reference circuit for short to battery voltage. After repairs, go to step 12 .
8. Check for poor connections at APP sensor. Repair as necessary. After repairs, go to step 12 . If circuit is okay, go to next step.
9. Check for an open in sensor ground circuit. Repair as necessary. After repairs, go to step 12 . If ground circuit is okay, go to next step.
10. Replace APP module. After replacing module, go to step 12 .
11. Replace PCM. Program PCM using required equipment. After replacing PCM, go to next step.
12. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, and then enter DTC P0123. Operate vehicle within the conditions for setting this DTC. If scan tool indicates that this test ran and passed, go to next step. If scan tool does not indicate that this test ran and passed, repeat step 2 .
13. Using scan tool, select CAPTURE INFO, REVIEW INFO. If any undiagnosed DTC(s) are displayed, go to applicable DTC test.

Scan tool reads APP 1 position in volts. With throttle closed and ignition on or at idle, voltage should be .45-.95 volt. Voltage should increase at a steady rate as throttle is moved toward Wide Open Throttle (WOT). Ninety percent pedal travel is acceptable for correct APP operation. Scan APP 1 sensor while depressing accelerator pedal with engine off and ignition on. Display should vary from about .74 volt with throttle closed to greater than 3.7 volts with throttle held at WOT. DTC will set if ground circuit is open or signal circuit is shorted to voltage.

DTC P0126: INSUFFICIENT ECT FOR STABLE OPERATION ("C", "G" & "K" SERIES)

Note. For circuit reference, refer to DTC P0112 schematic. (Scheme 3)

While engine is warming, PCM monitors the ECT sensor to determine how long it takes engine to reach the coolant temperature required for a closed loop operation. DTC P0126 will set if PCM determines that the engine does not reach closed loop operation in a specified amount of time. This test will run if either the IAT or ECT is too low at start up. PCM will only run this DTC on a cold start and only once per cold start.

DTC will set when the following conditions are present

1. Engine run time is greater than 600 seconds.
2. DTCs P0112, P0113, P0117 or P0118 are not set.
3. Engine coolant temperature at less than 133°F (56°C).
4. Intake air temperature is greater than 20°F (-7°C).
5. Fuel burned since start is greater than 1,000,000 cu. mm.
6. Total idle time since start is less than 450 seconds.

Or

1. Engine run time is greater than 300 seconds.
2. DTCs P0112, P0113, P0117 or P0118 are not set.
3. Engine coolant temperature is less than 133°F (56°C).
4. Intake air temperature is greater than 20°F (-7°C).
5. Fuel burned since start is greater than 468,120 cu. mm.
6. Total idle time since start is less than 225 seconds.

1. If OBD system check has been performed, go to next step. If OBD system check has not been performed, go to «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel__on-board-diagnostic-obd-system-check) under SELF-DIAGNOSTIC SYSTEM.
2. Check if any engine coolant temperature DTC(s) are present. If other DTC(s) are present, diagnose using affected DTC test. If no other DTC(s) are present, go to next step.
3. Turn ignition on, with engine off. Disconnect ECT harness connector. Using scan tool, check ECT sensor value. If ECT sensor value is less than -31°F (-35°C), go to next step. If ECT sensor value is greater than -31°F (-35°C), diagnose using DTC P0117 test.
4. Using a jumper wire, jumper ECT sensor harness connector terminals. If scan tool indicates ECT value is greater than 302°F (150°C), go to next step. If ECT value is less than 302°F (150°C), diagnose using DTC P0118 test.
5. Reconnect ECT sensor harness connector. Start and warm engine to normal operating temperature. Select ENGINE 1 DATA LIST on scan tool and observe ECT sensor display. If scan tool display reads that engine coolant temperature reached 140°F (60°C), recheck system on a cold start and refer to «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel) . If scan tool display does not indicate that engine coolant temperature has reached 140°F (60°C), go to next step.
6. Using DVOM, check ECT sensor resistance. See appropriate SYSTEM & COMPONENT TESTING article. If resistance is not as specified, go to next step. If resistance is as specified, go to step 8 .
7. Check thermostat operation, coolant level, coolant mixture ratio and cooling fan operation. Repair as necessary. After checking cooling system, go to step 9 .
8. Replace ECT sensor. After replacing sensor, go to next step.
9. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, and then enter DTC P0126. Operate vehicle within the conditions for setting this DTC. If scan tool indicates that this test ran and passed, go to next step. If scan tool does not indicate that this test ran and passed, repeat step 2 .
10. Using scan tool, select CAPTURE INFO, REVIEW INFO. If any undiagnosed DTC(s) are displayed, go to applicable DTC test.

Using FREEZE FRAME and/or FAILURE RECORDS data may aid in locating an intermittent condition. If DTC cannot be duplicated, this information can be useful in determining how many times since the DTC set. The Fail Counter and Pass Counter can also be used to determine how many ignition cycles the diagnostic reported a pass and/or a fail. Operate vehicle with the same FREEZE FRAME conditions (RPM, load, vehicle speed, temperature, etc.) that were noted.

If other DTC(s) are set that share the same ground and/or 5-volt reference circuit, check for faulty connections or wiring. If engine has been allowed to sit overnight, ECT sensor and IAT sensor values should display within a few degrees of each other.

If engine coolant temperature exceeds 140°F (60°C), this indicates that the engine is capable of reaching proper temperature, but not necessarily in the correct amount of time. This test must be repeated on a cold engine, engine coolant and intake air temperature at less than 122°F (50°C) and within 5°F (3°C) of each other, and the time required to reach the temperature threshold must be measured.

The engine should reach the specified temperature within 8 minutes. If specified temperature is not reached within the specified time, check the cooling system.

Scheme 5

Fuel temperature sensor is a thermistor that controls signal voltage to PCM. When fuel is cool, sensor resistance will be high and PCM will sense a high voltage signal. When fuel is warm, sensor resistance will be low and PCM will sense a low voltage signal. Fuel temperature sensor is integrated within optical sensor.

DTC will set when fuel temperature is greater than 215°F (102°C) for 2 seconds.

1. If OBD system check has been performed, go to next step. If OBD system check has not been performed, go to «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel__on-board-diagnostic-obd-system-check) under SELF-DIAGNOSTIC SYSTEM.
2. Install scan tool. Start engine. Monitor fuel temperature display on scan tool. If fuel temperature is greater than 215°F (102°C), go to next step. If fuel temperature is less than 215°F (102°C), go to step 5 .
3. Turn engine off. Disconnect optical/fuel temperature sensor connector. Turn ignition on. Monitor fuel temperature display on scan tool. If fuel temperature is less than or equal to 63°F (17°C), go to step 7 . If fuel temperature is greater than 63°F (17°C), go to next step.
4. Turn ignition off. Using DVOM, check resistance between fuel temperature sensor connector terminals. If resistance is infinite, go to step 8 . If resistance is not infinite, go to step 6 .
5. DTC is intermittent. If no additional DTCs are set, see «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel) . If any additional DTCs are set, go to applicable DTC test.
6. Repair short to ground in fuel temperature signal circuit. After repairs go to step 9 .
7. Replace fuel injection pump. If fuel injection pump is replaced, new pump must be timed. See appropriate ON-VEHICLE ADJUSTMENTS article. After repairs, go to step 9 .
8. Replace PCM. Program PCM using required equipment. After replacing PCM, go to next step.
9. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, and then enter DTC P0182. Operate vehicle within the conditions for setting this DTC. If scan tool indicates that this test ran and passed, go to next step. If scan tool does not indicate that this test ran and passed, repeat step 2 .
10. Using scan tool, select CAPTURE INFO, REVIEW INFO. If any undiagnosed DTC(s) are displayed, go to applicable DTC test.

Scan tool displays fuel temperature in degrees centigrade. After engine is started, fuel temperature should rise steadily.

DTC P0183: FUEL TEMPERATURE SENSOR CIRCUIT HIGH VOLTAGE ("C", "G", "K" & "P" SERIES)

Note. For circuit reference, refer to DTC P0182 schematic. (Scheme 5)

Fuel temperature sensor is a thermistor that controls signal voltage to PCM. When fuel is cool, sensor resistance will be high and PCM will sense a high voltage signal. When fuel is warm, sensor resistance will be low and PCM will sense a low voltage signal. Fuel temperature sensor is integrated within optical sensor.

DTC will set when the following conditions are present

1. Engine running for at least 8 minutes.
2. Fuel temperature is less than or equal to 63°F (17°C).
3. Conditions are met for 2 seconds.

1. If OBD system check has been performed, go to next step. If OBD system check has not been performed, go to «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel__on-board-diagnostic-obd-system-check) under SELF-DIAGNOSTIC SYSTEM.
2. Install scan tool. Start engine. Monitor fuel temperature display on scan tool. If fuel temperature is less to 63°F (17°C), go to next step. If fuel temperature is 63°F (17°C) or greater, go to step 5 .
3. Turn engine off. Disconnect optical/fuel temperature sensor connector. Turn ignition on. Connect a jumper wire between fuel temperature sensor connector terminals. Monitor fuel temperature on scan tool. If fuel temperature is greater than 221°F (105°C), go to step 6 . If fuel temperature is 221°F (105°C) or less, go to next step.
4. Connect a jumper wire between fuel temperature sensor connector signal circuit and ground. Monitor fuel temperature on scan tool. If fuel temperature is greater than 221°F (105°C), go to step 7 . If fuel temperature is 221°F (105°C) or less, go to step 8 .
5. DTC is intermittent. If no additional DTCs are set, see «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel) . If any additional DTCs are set, go to applicable DTC test.
6. Check for poor connections at fuel temperature sensor harness connector. Repair as necessary. After repairs, go to step 14 . If connections are okay, go to step 9 .
7. Check for open in fuel temperature ground circuit between fuel temperature sensor and PCM. Repair as necessary. After repairs, go to step 14 . If circuit is okay, go to step 11 .
8. Check for open in fuel temperature signal circuit between fuel temperature sensor and PCM. Repair as necessary. After repairs, go to step 14 . If fuel temperature signal circuit is okay, go to step 11 .
9. Using DVOM in mA (milliamp) scale, measure current at fuel temperature sensor harness connector terminals. If reading is less than 50 mA, go to step 12 . If reading is 50 mA or greater, go to next step.
10. Repair short to voltage in fuel temperature sensor signal circuit. After repairs, go to step 14 .
11. Check PCM harness connectors for poor connections. Repair or replace terminals as necessary. After repairs, go to step 14 . If connectors are okay, go to step 13 .
12. Replace fuel injection pump. If fuel injection pump is replaced, new pump must be timed. See appropriate ON-VEHICLE ADJUSTMENTS article. After repairs, go to step 14 .
13. Replace PCM. Program PCM using required equipment. After replacing PCM, go to next step.
14. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, and then enter DTC P0183. Operate vehicle within the conditions for setting this DTC. If scan tool indicates that this test ran and passed, go to next step. If scan tool does not indicate that this test ran and passed, repeat step 2 .
15. Using scan tool, select CAPTURE INFO, REVIEW INFO. If any undiagnosed DTC(s) are displayed, go to applicable DTC test.

Scan tool displays fuel temperature in degrees centigrade. After engine is started, fuel temperature should rise steadily. DTC will set if a faulty connection is present or signal circuit is open.

Scheme 6

Scheme 7

Scheme 8

Injection pump fuel supply line has a solenoid controlled shutoff located in injection pump. When solenoid is energized, valve is open and fuel is supplied to injection pump. PCM energizes solenoid by providing a ground path.

DTC will set when the following conditions are present

1. PCM requested engine shutoff solenoid on.
2. Control circuit voltage at PCM is less than 8 volts.
3. Conditions are met for 2 seconds.

Or

1. PCM requested engine shutoff solenoid off.
2. Control circuit voltage at PCM is greater than 8 volts.
3. Conditions are met for 2 seconds.

1. If OBD system check has been performed, go to next step. If OBD system check has not been performed, go to «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel__on-board-diagnostic-obd-system-check) under SELF-DIAGNOSTIC SYSTEM.
2. Turn ignition off. Disconnect Engine Shutoff (ESO) harness connector. Turn ignition on, with engine off. Using test light connected to ground, probe ESO harness connector terminal "B" (ignition feed). If test light illuminates, go to next step. If test light does not illuminate, go to step 6 .
3. Turn ignition off. Using test light, jumper ESO harness connector terminals together. Turn ignition on, with engine off. If test light illuminates, go to next step. If test light does not illuminate, go to step 7 .
4. Using test light connected to battery voltage, probe ESO terminal "A" (control circuit). Turn ignition on, with engine off. Using scan tool, command ESO solenoid on and off. If test light turns on and off with each command, go to next step. If test light does not turn on and off with each command, go to step 8 .
5. Check ESO harness connector for poor connections. Repair or replace terminals as necessary. After repairs, go to step 13 . If connectors and terminals are okay, go to step 11 .
6. Check ESO ignition feed circuit for open or faulty fuse. Repair as necessary. After repairs, go to step 13 .
7. Using test light connected to ground, probe ESO harness connector terminal "A" (control circuit). Turn ignition on, with engine off. If test light illuminates, go to step 10 . If test light does not illuminate, go to step 9 .
8. Repair short to ground in ESO control circuit. After repairs, go to step 13 .
9. Check ESO control circuit for open or poor connection at PCM. Repair as necessary. After repairs, go to step 13 . If circuit and connections are okay, go to step 12 .
10. Check ESO control circuit for short to voltage. Repair as necessary. After repairs, go to step 13 . If circuit is okay, go to step 12 .
11. Replace ESO solenoid. After replacing solenoid, go to step 13 .
12. Replace PCM. Program PCM using required equipment. After replacing PCM, go to next step.
13. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, and then enter DTC P0215. Operate vehicle within the conditions for setting this DTC. If scan tool indicates that this test ran and passed, go to next step. If scan tool does not indicate that this test ran and passed, repeat step 2 .
14. Using scan tool, select CAPTURE INFO, REVIEW INFO. If any undiagnosed DTC(s) are displayed, go to applicable DTC test.

DTC will set if control circuit or ignition feed circuit is open. A no start condition will also exist. Scan tool has capability to turn ESO solenoid on and off. This can be a quick operational check of solenoid.

Scheme 9

Timing of combustion is accomplished by delivering a pulse of fuel into combustion chamber at a desired degree of cylinder travel. This desired degree (desired timing) defines current position of cylinder in relationship to top dead center. This test compares retard injection timing, PCM extends stepper motor. To advance injection timing, PCM retracts stepper motor.

DTC will set when the following conditions are present

1. Engine speed has not changed more than 56 RPM for 5 seconds.
2. A 5 degree difference between actual injection time and desired injection time exists.

1. If OBD system check has been performed, go to next step. If OBD system check has not been performed, go to «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel__on-board-diagnostic-obd-system-check) under SELF-DIAGNOSTIC SYSTEM.
2. Install scan tool. Start and warm engine to normal operating temperature. Scan injection timing at idle and at 1500 RPM using scan tool. If scan tool displays a difference of 5 degrees between actual and desired injection time at idle and at 1500 RPM, go to step 4 . If scan tool does not indicate a difference of 5 degrees between actual and desired injection time at idle and at 1500 RPM, go to next step.
3. DTC is intermittent. If no additional DTCs are set, see «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel) . If any additional DTCs are set, go to applicable DTC test.
4. Turn ignition off. Disconnect PCM harness connector. Using DVOM, measure resistance between coil 1 low and coil 1 high circuits of PCM harness connector. If resistance is 10-60 ohms, go to next step. If resistance is not 10-60 ohms, go to step 9 .
5. Using DVOM, measure resistance between coil 2 low and coil 2 high circuits of PCM harness connector. If resistance is 10-60 ohms, go to next step. If resistance is not 10-60 ohms, go to step 10 .
6. Reconnect PCM harness connector. Disconnect injection timing stepper motor harness connector. Start and idle engine. Using scan tool, command time set on. Using DVOM, check for a varying voltage between ground and each terminal of injection timing stepper motor connector. If voltage varies, go to next step. If voltage does not vary, go to step 12 .
7. Disconnect crankshaft position sensor harness connector. Using DVOM, measure resistance between crankshaft position sensor signal circuit and 5-volt reference circuit of crankshaft position sensor pigtail. If resistance is 950-1050 ohms, go to next step. If resistance is not 950-1050 ohms, go to step 13 .
8. Reconnect sensor harness connector. Check if injection timing is set correctly. Check for a sheared camshaft driven key. Repair as necessary. After repairs, go to step 17 . If no problems are found, go to step 15 .
9. Turn ignition off. Disconnect stepper motor harness connector. Check for open in coil 1 low and coil 1 high circuits. Repair as necessary. After repairs, go to step 17 . If circuits are okay, go to step 11 .
10. Turn ignition off. Disconnect stepper motor harness connector. Check for open in coil 2 low and coil 2 high circuits. Repair as necessary. After repairs, go to step 17 . If circuits are okay, go to step 11 .
11. Check for poor connections at injection timing stepper motor. Repair terminals as necessary. After repairs, go to step 17 . If terminals are okay, go to step 15 .
12. Check non-varying injection timing stepper motor circuit for short to ground, short to voltage or for poor connections at PCM. Repair as necessary. After repairs, go to step 17 . If circuit and connection is okay, go to step 16 .
13. Check for short to ground in crankshaft position sensor pigtail. Repair as necessary. After repairs, go to step 17 . If circuit is okay, go to next step.
14. Replace crankshaft position sensor. Program PCM with new offset. See appropriate ON-VEHICLE ADJUSTMENTS article. After replacing sensor, go to step 17 .
15. Replace fuel injection pump. If fuel injection pump is replaced, new pump must be timed. See appropriate ON-VEHICLE ADJUSTMENTS article. After replacing pump, go to step 17 .
16. Replace PCM. Program PCM using required equipment. After replacing PCM, go to next step.
17. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, and then enter DTC P0216. Operate vehicle within the conditions for setting this DTC. If scan tool indicates that this test ran and passed, go to next step. If scan tool does not indicate that this test ran and passed, repeat step 2 .
18. Using scan tool, select CAPTURE INFO, REVIEW INFO. If any undiagnosed DTC(s) are displayed, go to applicable DTC test.

An intermittent may be caused by poor connections, rubbed through wire insulation or broken wire inside insulation. A hard start and possible poor performance may exist. Actual injection time will freeze at point of fault. DTC could set if injection timing is not correctly set. See appropriate ON-VEHICLE ADJUSTMENTS article.

DTC P0219: ENGINE OVERSPEED CONDITION ("C", "G", "K" & "P" SERIES)

Note. For circuit reference, refer to DTC P0215 schematics. (Scheme 6), (Scheme 7) or (Scheme 8).

PCM has ability to place vehicle in engine shutoff controlled idle if an engine overspeed condition has been detected.

DTC will set when 5 engine shutoff cycles with an RPM drop are present.

1. If OBD system check has been performed, go to next step. If OBD system check has not been performed, go to «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel__on-board-diagnostic-obd-system-check) under SELF-DIAGNOSTIC SYSTEM.
2. Replace fuel injection pump. If fuel injection pump is replaced, new pump must be timed. See appropriate ON-VEHICLE ADJUSTMENTS article. After replacing fuel injection pump, go to next step.
3. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, and then enter DTC P0219. Operate vehicle within the conditions for setting this DTC. If scan tool indicates that this test ran and passed, go to next step. If scan tool does not indicate that this test ran and passed, repeat step 2 .
4. Using scan tool, select CAPTURE INFO, REVIEW INFO. If any undiagnosed DTC(s) are displayed, go to applicable DTC test.

DTC will not set if an external fuel source is causing an overspeed condition. DTC P1216 will also set if DTC P0219 is set.

DTC P0220: ACCELERATOR PEDAL POSITION (APP) SENSOR 2 CIRCUIT ("C", "G", "K" & "P" SERIES)

Note. For circuit reference, refer to DTC P0121 schematic. (Scheme 4)

Accelerator Pedal Position (APP) module provides a voltage signal that changes relative to accelerator pedal position. Three sensors are located within APP module and are scaled differently.

DTC will set when reference voltage on APP 2 is less than 4.8 volts for 2 seconds.

1. If OBD system check has been performed, go to next step. If OBD system check has not been performed, go to «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel__on-board-diagnostic-obd-system-check) under SELF-DIAGNOSTIC SYSTEM.
2. Turn ignition off. Disconnect APP sensor connector. Turn ignition on, with engine off. Using DVOM, measure voltage between ground and 5-volt reference circuits (terminals "D", "E" and "G") of APP sensor connectors. If voltage on all circuits is less than 4.8 volts, go to step 4 . If voltage on all circuits is not less than 4.8 volts, go to next step.
3. DTC is intermittent. If no additional DTCs are set, see «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel) . If any additional DTCs are set, go to applicable DTC test.
4. Turn ignition off. Disconnect PCM harness connector. Check for short to ground in 5-volt reference circuits. Repair as necessary. If short to ground was present in 5-volt reference circuits, go to step 6 . If short to ground was not present in 5-volt reference circuits, go to next step.
5. Replace PCM. Program PCM using required equipment. After replacing PCM, go to next step.
6. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, and then enter DTC P0220. Operate vehicle within the conditions for setting this DTC. If scan tool indicates that this test ran and passed, go to next step. If scan tool does not indicate that this test ran and passed, repeat step 2 .
7. Using scan tool, select CAPTURE INFO, REVIEW INFO. If any undiagnosed DTC(s) are displayed, go to applicable DTC test.

Most likely cause of DTC is loose connectors or terminals. All 5-volt reference circuits must be checked for proper reference voltage.

DTC P0221: ACCELERATOR PEDAL POSITION (APP) SENSOR 2 CIRCUIT PERFORMANCE ("C", "G", "K" & "P" SERIES)

Note. For circuit reference, refer to DTC P0121 schematic. (Scheme 4)

Accelerator Pedal Position (APP) module provides a voltage signal that changes relative to accelerator pedal position. Three sensors are located within APP module and are scaled differently.

DTC will set when the following conditions are present

1. Ignition voltage is greater than 6.4 volts.
2. Engine speed is greater than 300 RPM.
3. Difference between APP 2 and APP 1 is greater than .23 volt (PCM compares pre-scaled voltage - internal to PCM).
4. Difference between APP 2 and APP 3 is greater than .50 volt (PCM compares pre-scaled voltage - internal to PCM).
5. No in-range faults for APP 1 or APP 3 (PCM checks for high and low voltage faults).
6. Conditions are met for 2 seconds.

1. If OBD system check has been performed, go to next step. If OBD system check has not been performed, go to «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel__on-board-diagnostic-obd-system-check) under SELF-DIAGNOSTIC SYSTEM.
2. Install scan tool. Turn ignition on, with engine off. Using scan tool, with throttle closed, observe APP voltages. APP 1 voltage should be .45-.95 volt. APP 2 voltage should be 4.0-4.5 volts. APP 3 voltage should be 3.6-4.0 volts. If voltages are as specified, go to next step. If voltages are not as specified, go to step 4 .
3. DTC is intermittent. If no additional DTCs are set, see «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel) . If any additional DTCs are set, go to applicable DTC test.
4. Turn ignition off. Disconnect APP sensor harness connector. Turn ignition on, with engine off. Using DVOM, probe 5-volt reference circuits (terminals "D", "E" and "G") of APP sensor connectors to ground. If voltage on all circuits is 4.75 volts, go to next step. If voltage on all circuits is not 4.75 volts, go to step 6 .
5. Turn ignition on, with engine off. Using test light, probe ground circuits (terminals "A", "B" and "J") of APP sensor connectors to battery voltage. If test light illuminates on all circuits, go to step 9 . If test light does not illuminate on all circuits, go to step 8 .
6. Turn ignition off. Disconnect PCM harness connector. Check for open or short to ground in 5-volt reference circuits. Repair as necessary. If circuit is open or shorted to ground, repair as necessary and go to step 11 . If circuit is okay, go to next step.
7. Check for poor connections at 5-volt reference terminals of PCM. Repair terminals as necessary. After repairs, go to step 11 . If connections are okay, go to step 10 .
8. Turn ignition off. Disconnect PCM harness connector. Check for open in ground circuits. Repair as necessary. After repairs, go to step 11 . If circuits are okay, go to step 10 .
9. Replace APP module. After replacing module, go to step 11 .
10. Replace PCM. Program PCM using required equipment. After replacing PCM, go to next step.
11. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, and then enter DTC P0221. Operate vehicle within the conditions for setting this DTC. If scan tool indicates that this test ran and passed, go to next step. If scan tool does not indicate that this test ran and passed, repeat step 2 .
12. Using scan tool, select CAPTURE INFO, REVIEW INFO. If any undiagnosed DTC(s) are displayed, go to applicable DTC test.

Scan tool reads APP 2 position in volts. With throttle closed and ignition on or at idle, voltage should be 4.5 volts. Voltage should decrease at a steady rate as throttle is moved toward Wide Open Throttle (WOT). Ninety percent pedal travel is acceptable for correct APP operation. See appropriate TROUBLE SHOOTING - NO CODES article. Scan APP 2 sensor while depressing accelerator pedal with engine off and ignition on. Display should vary from about 4.5 volts with throttle closed to about 1.5 volts with throttle held at WOT.

DTC P0222: ACCELERATOR PEDAL POSITION (APP) SENSOR 2 CIRCUIT LOW VOLTAGE ("C", "G", "K" & "P" SERIES)

Note. For circuit reference, refer to DTC P0121 schematic. (Scheme 4)

Accelerator Pedal Position (APP) module provides a voltage signal that changes relative to accelerator pedal position. Three sensors are located within APP module and are scaled differently.

DTC will set when voltage on APP 2 is less than .25 volt for 2 seconds.

1. If OBD system check has been performed, go to next step. If OBD system check has not been performed, go to «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel__on-board-diagnostic-obd-system-check) under SELF-DIAGNOSTIC SYSTEM.
2. Install scan tool. Turn ignition on, with engine off. Using scan tool, with throttle closed, observe APP 2 voltage. If APP 2 voltage is less than or equal to .25 volt, go to step 4 . If APP 2 voltage is greater than .25 volt, go to next step.
3. DTC is intermittent. If no additional DTCs are set, see «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel) . If any additional DTCs are set, go to applicable DTC test.
4. Turn ignition off. Disconnect APP sensor harness connector. Using DVOM, measure voltage at 5-volt reference circuit of APP 2 sensor harness connector. If voltage is greater than 5 volts, go to next step. If voltage is less than 5 volts, go to step 6 .
5. Using DVOM, measure voltage at APP 2 sensor signal circuit of APP 2 sensor harness connector. If voltage is greater than 4.8 volts, go to step 10 . If voltage is less than or equal to 4.8 volts, go to step 8 .
6. Turn ignition off. Disconnect PCM harness connector. Check for open or short to ground in 5-volt reference circuits. Repair as necessary. After repairs, go to step 13 . If circuits are okay, go to next step.
7. Check for poor connections at 5-volt reference terminals of PCM. Repair terminals as necessary. After repairs, go to step 13 . If connections are okay, go to step 12 .
8. Turn ignition off. Disconnect PCM harness connector. Check for open or short to ground in APP 2 signal circuit. Repair as necessary. After repairs, go to step 13 . If circuits are okay, go to next step.
9. Check for poor connections at APP 2 signal terminal at PCM. Repair terminal as necessary. After repairs, go to step 13 . If terminal connection is okay, go to step 12 .
10. Check for poor connections at APP sensor. Repair terminal as necessary. After repairs, go to step 13 . If terminal connections are okay, go to next step.
11. Replace APP module. After replacing module, go to step 13 .
12. Replace PCM. Program PCM using required equipment. After replacing PCM, go to next step.
13. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, and then enter DTC P0222. Operate vehicle within the conditions for setting this DTC. If scan tool indicates that this test ran and passed, go to next step. If scan tool does not indicate that this test ran and passed, repeat step 2 .
14. Using scan tool, select CAPTURE INFO, REVIEW INFO. If any undiagnosed DTC(s) are displayed, go to applicable DTC test.

Scan tool reads APP 2 position in volts. With throttle closed and ignition on or at idle, voltage should be 4.5 volts. Voltage should decrease at a steady rate as throttle is moved toward Wide Open Throttle (WOT). See appropriate TROUBLE SHOOTING - NO CODES article. Scan APP 2 sensor while depressing accelerator pedal with engine off and ignition on. Display should vary from about 4.5 volts with throttle closed to about 1.5 volts with throttle held at WOT.

DTC P0223: ACCELERATOR PEDAL POSITION (APP) SENSOR 2 CIRCUIT HIGH VOLTAGE ("C", "G", "K" & "P" SERIES)

Note. For circuit reference, refer to DTC P0121 schematic. (Scheme 4)

Accelerator Pedal Position (APP) module provides a voltage signal that changes relative to accelerator pedal position. Three sensors are located within APP module and are scaled differently.

DTC will set when APP 2 voltage is greater than 4.75 volts for 2 seconds.

1. If OBD system check has been performed, go to next step. If OBD system check has not been performed, go to «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel__on-board-diagnostic-obd-system-check) under SELF-DIAGNOSTIC SYSTEM.
2. Install scan tool. Turn ignition on, with engine off. Using scan tool and with throttle closed, observe APP 2 voltage. If voltage is greater than or equal to 4.75 volts, go to step 4 . If voltage is less than 4.75 volts, go to next step.
3. DTC is intermittent. If no additional DTCs are set, see «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel) . If any additional DTCs are set, go to applicable DTC test.
4. Disconnect APP sensor harness connector. Using test light connected to battery voltage, probe APP 2 ground circuit at APP 2 sensor harness connector. If test light illuminates, go to next step. If test light does not illuminate, go to step 7 .
5. Connect a fused jumper wire between APP 2 signal circuit and APP 2 ground circuit of APP sensor harness connector. Using scan tool, observe APP 2 voltage. If voltage is less than .25 volt, go to step 8 . If voltage is greater than or equal to .25 volt, go to next step.
6. Check for an open in APP 2 signal circuit. Repair as necessary. After repairs, go to step 13 . If circuit is okay, go to step 12 .
7. Check for open in APP 2 sensor ground circuit. Repair as necessary. After repairs, go to step 13 . If circuit is okay, go to step 12 .
8. Turn ignition on, with engine off. Ensure APP harness connector is disconnected. Using DVOM in mA (milliamp) scale, measure current between APP 2 signal circuit and ground circuit at APP 2 sensor harness connector. If reading is less than 50 mA, go to step 10 . If reading is 50 mA or greater, go to next step.
9. Repair short to voltage in APP 2 signal circuit. After repairs, go to step 13 .
10. Check for poor connection at APP sensor. Repair as necessary. After repairs, go to step 13 . If connection is okay, go to next step.
11. Replace APP module. After replacing module, go to step 13 .
12. Replace PCM. Program PCM using required equipment. After replacing PCM, go to next step.
13. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, and then enter DTC P0223. Operate vehicle within the conditions for setting this DTC. If scan tool indicates that this test ran and passed, go to next step. If scan tool does not indicate that this test ran and passed, repeat step 2 .
14. Using scan tool, select CAPTURE INFO, REVIEW INFO. If any undiagnosed DTC(s) are displayed, go to applicable DTC test.

Scan tool reads APP 2 position in volts. With throttle closed and ignition on or at idle, voltage should be 4.5 volts. Voltage should decrease at a steady rate as throttle is moved toward Wide Open Throttle (WOT). Ninety percent pedal travel is acceptable for correct APP operation. See appropriate TROUBLE SHOOTING - NO CODES article. Scan APP 2 sensor while depressing accelerator pedal with engine off and ignition on. Display should vary from about 4.5 volts with throttle closed to about 1.5 volts with throttle held at WOT. If signal circuit is open, P1125 could also be set when P0223 sets.

DTC P0225: ACCELERATOR PEDAL POSITION (APP) SENSOR 3 CIRCUIT ("C", "G", "K" & "P" SERIES)

Note. For circuit reference, refer to DTC P0121 schematic. (Scheme 4)

Accelerator Pedal Position (APP) module provides a voltage signal that changes relative to accelerator pedal position. Three sensors are located within APP module and are scaled differently.

DTC will set when reference voltage on APP 3 is less than 4.8 volts for 2 seconds.

1. If OBD system check has been performed, go to next step. If OBD system check has not been performed, go to «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel__on-board-diagnostic-obd-system-check) under SELF-DIAGNOSTIC SYSTEM.
2. Turn ignition off. Disconnect APP sensor harness connector. Turn ignition on, with engine off. Using DVOM, measure voltage between ground and 5-volt reference circuits (terminals "D", "E" and "G") of APP sensor harness connectors. If voltage on all circuits is less than 4.8 volts, go to step 5 . If voltage on all circuits is 4.8 volts or greater, go to next step.
3. If any other APP DTCs are set, diagnose affected DTC. If other DTCs are not present, go to next step.
4. DTC is intermittent. If no additional DTCs are set, see «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel) . If any additional DTCs are set, go to applicable DTC test.
5. Turn ignition off. Disconnect PCM harness connector. Check for short to ground in 5-volt reference circuits. Repair as necessary. After repairs, go to step 7 . If circuits are okay, go to next step.
6. Replace PCM. Program PCM using required equipment. After replacing PCM, go to next step.
7. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, and then enter DTC P0225. Operate vehicle within the conditions for setting this DTC. If scan tool indicates that this test ran and passed, go to next step. If scan tool does not indicate that this test ran and passed, repeat step 2 .
8. Using scan tool, select CAPTURE INFO, REVIEW INFO. If any undiagnosed DTC(s) are displayed, go to applicable DTC test.

All 5-volt reference circuits must be checked for proper reference voltage.

DTC P0226: ACCELERATOR PEDAL POSITION (APP) SENSOR 3 CIRCUIT PERFORMANCE ("C", "G", "K" & "P" SERIES)

Note. For circuit reference, refer to DTC P0121 schematic. (Scheme 4)

Accelerator Pedal Position (APP) module provides a voltage signal that changes relative to accelerator pedal position. Three sensors are located within APP module and are scaled differently.

DTC will set when the following conditions are present

1. Ignition voltage is greater than 6.4 volts.
2. Engine speed is greater than 300 RPM.
3. Difference between APP 3 and APP 1 is greater than .23 volt (PCM compares pre-scaled voltage - internal to PCM).
4. Difference between APP 3 and APP 2 is greater than .50 volt (PCM compares pre-scaled voltage - internal to PCM).
5. No in-range faults for APP 1 or APP 2 (PCM checks for high and low voltage faults).
6. Conditions are met for 2 seconds.

1. If OBD system check has been performed, go to next step. If OBD system check has not been performed, go to «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel__on-board-diagnostic-obd-system-check) under SELF-DIAGNOSTIC SYSTEM.
2. Install scan tool. Turn ignition on, with engine off. Using scan tool, with throttle closed, observe APP voltages. APP 1 voltage should be .45-.95 volt. APP 2 voltage should be 4.0-4.5 volts. APP 3 voltage should be 3.6-4.0 volts. If voltages are as specified, go to next step. If voltages are not as specified, go to step 4 .
3. DTC is intermittent. If no additional DTCs are set, see «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel) . If any additional DTCs are set, go to applicable DTC test.
4. Turn ignition off. Disconnect APP sensor harness connector. Turn ignition on, with engine off. Using DVOM, probe 5-volt reference circuits (terminals "D", "E" and "G") of APP sensor connectors to ground. If voltage on all circuits is 4.75 volts, go to next step. If voltage on all circuits is not 4.75 volts, go to step 6 .
5. Turn ignition on, with engine off. Using test light, probe ground circuits (terminals "A", "B" and "J") of APP sensor connectors to battery voltage. If test light illuminates on all circuits, go to step 9 . If test light does not illuminate on all circuits, go to step 8 .
6. Turn ignition off. Disconnect PCM harness connector. Check for open or short to ground in 5-volt reference circuits. Repair as necessary. After repairs, go to step 11 . If circuits are okay, go to next step.
7. Check for poor connections at 5-volt reference terminals of PCM. Repair terminals as necessary. After repairs, go to step 11 . If connections are okay, go to step 10 .
8. Turn ignition off. Disconnect PCM harness connector. Check for open in ground circuits. Repair as necessary. After repairs, go to step 11 . If circuits are okay, go to step 10 .
9. Replace APP module. After replacing module, go to step 11 .
10. Replace PCM. Program PCM using required equipment. After replacing PCM, go to next step.
11. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, and then enter DTC P0226. Operate vehicle within the conditions for setting this DTC. If scan tool indicates that this test ran and passed, go to next step. If scan tool does not indicate that this test ran and passed, repeat step 2 .
12. Using scan tool, select CAPTURE INFO, REVIEW INFO. If any undiagnosed DTC(s) are displayed, go to applicable DTC test.

Scan tool reads APP 3 position in volts. With throttle closed and ignition on or at idle, voltage should be 4 volts. Voltage should decrease at a steady rate as throttle is moved toward Wide Open Throttle (WOT). Ninety percent pedal travel is acceptable for correct APP operation. Scan APP 3 sensor while depressing accelerator pedal with engine off and ignition on. Display should vary from about 4 volts with throttle closed to about 2 volts with throttle held at WOT.

DTC P0227: ACCELERATOR PEDAL POSITION (APP) SENSOR 3 CIRCUIT LOW VOLTAGE ("C", "G", "K" & "P" SERIES)

Note. For circuit reference, refer to DTC P0121 schematic. (Scheme 4)

Accelerator Pedal Position (APP) module provides a voltage signal that changes relative to accelerator pedal position. Three sensors are located within APP module and are scaled differently.

DTC will set when voltage on APP 3 is less than .25 volt for 2 seconds.

1. If OBD system check has been performed, go to next step. If OBD system check has not been performed, go to «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel__on-board-diagnostic-obd-system-check) under SELF-DIAGNOSTIC SYSTEM.
2. Install scan tool. Turn ignition on, with engine off. Using scan tool, with throttle closed, observe APP 3 voltage. If APP 3 voltage is less than or equal to .25 volt, go to step 4 . If APP 3 voltage is greater than .25 volt, go to next step.
3. DTC is intermittent. If no additional DTCs are set, see «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel) . If any additional DTCs are set, go to applicable DTC test.
4. Turn ignition off. Disconnect APP sensor harness connector. Connect a jumper wire between 5-volt reference circuit and signal circuit of APP 3 sensor connector. Using scan tool, observe APP 3 voltage. If APP 3 voltage is about 5 volts, go to next step. If voltage is not about 5 volts, go to step 6 .
5. Using DVOM, probe APP 3 sensor harness signal circuit terminal. If voltage is about 5 volts, go to step 10 . If voltage is not about 5 volts, go to step 8 .
6. Turn ignition off. Disconnect PCM harness connector. Check for open or short to ground in 5-volt reference circuits. Repair as necessary. After repairs, go to step 13 . If circuits are okay, go to next step.
7. Check for poor connections at 5-volt reference terminals of PCM. Repair terminals as necessary. After repairs, go to step 13 . If connections are okay, go to step 12 .
8. Turn ignition off. Disconnect PCM harness connector. Check for open or short to ground in APP 3 signal circuit. Repair as necessary. After repairs, go to step 13 . If circuits are okay, go to next step.
9. Check for poor connections at APP 3 signal terminal at PCM. Repair terminal as necessary. After repairs, go to step 13 . If terminal is okay, go to step 12 .
10. Check for poor connection at APP sensor. Repair as necessary. After repairs, go to step 13 . If connection is okay, go to next step.
11. Replace APP module. After replacing module, go to step 13 .
12. Replace PCM. Program PCM using required equipment. After replacing PCM, go to next step.
13. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, and then enter DTC P0227. Operate vehicle within the conditions for setting this DTC. If scan tool indicates that this test ran and passed, go to next step. If scan tool does not indicate that this test ran and passed, repeat step 2 .
14. Using scan tool, select CAPTURE INFO, REVIEW INFO. If any undiagnosed DTC(s) are displayed, go to applicable DTC test.

Scan tool reads APP 3 position in volts. With throttle closed and ignition on or at idle, voltage should be 4 volts. Voltage should decrease at a steady rate as throttle is moved toward Wide Open Throttle (WOT). Ninety percent pedal travel is acceptable for correct APP operation. See appropriate TROUBLE SHOOTING - NO CODES article. Scan APP 3 sensor while depressing accelerator pedal with engine off and ignition on. Display should vary from about 4 volts with throttle closed to about 2 volts with throttle held at WOT.

DTC P0228: ACCELERATOR PEDAL POSITION (APP) SENSOR 3 CIRCUIT HIGH VOLTAGE ("C", "G", "K" & "P" SERIES)

Note. For circuit reference, refer to DTC P0121 schematic. (Scheme 4)

Accelerator Pedal Position (APP) module provides a voltage signal that changes relative to accelerator pedal position. Three sensors are located within APP module and are scaled differently.

DTC will set when voltage on APP 3 is greater than 4.75 volts for 2 seconds.

1. If OBD system check has been performed, go to next step. If OBD system check has not been performed, go to «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel__on-board-diagnostic-obd-system-check) under SELF-DIAGNOSTIC SYSTEM.
2. Install scan tool. Turn ignition on, with engine off. Using scan tool, with throttle closed, observe APP 3 voltage. If APP 3 voltage is greater than 4.75 volts, go to step 4 . If APP 3 voltage is 4.75 volts or less, go to next step.
3. DTC is intermittent. If no additional DTCs are set, see «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel) . If any additional DTCs are set, go to applicable DTC test.
4. Disconnect APP 3 sensor harness connector. Using test light connected to battery voltage, probe APP 3 sensor harness connector ground circuit. If test light illuminates, go to next step. If test light does not illuminate, go to step 7 .
5. Connect a fused jumper wire between APP 3 sensor signal circuit and APP 3 ground circuit of APP 3 sensor harness connector. Using scan tool, observe APP 3 voltage. If APP 3 voltage is less than .25 volt, go to step 8 . If APP 3 voltage is greater than or equal to .25 volt, go to next step.
6. Check for open in APP 3 sensor signal circuit. Repair as necessary. After repairs, go to step 13 . If circuit is okay, go to step 12 .
7. Check for open in APP 3 sensor ground circuit. Repair as necessary. After repairs, go to step 13 . If circuit is okay, go to step 12 .
8. Turn ignition on, with engine off. Ensure APP harness connector is disconnected. Using DVOM in mA (milliamp) scale, measure current between APP 3 signal circuit and ground circuit at APP 2 sensor harness connector. If reading is less than 50 mA, go to step 10 . If reading is 50 mA or greater, go to next step.
9. Repair short to voltage in APP 3 signal circuit. After repairs, go to step 13 .
10. Check for poor connection at APP sensor harness connector. Repair or replace terminals as necessary. After repairs, go to step 13 . If connections are okay, go to next step.
11. Replace APP module. After replacing module, go to step 13 .
12. Replace PCM. Program PCM using required equipment. After replacing PCM, go to next step.
13. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, and then enter DTC P0228. Operate vehicle within the conditions for setting this DTC. If scan tool indicates that this test ran and passed, go to next step. If scan tool does not indicate that this test ran and passed, repeat step 2 .
14. Using scan tool, select CAPTURE INFO, REVIEW INFO. If any undiagnosed DTC(s) are displayed, go to applicable DTC test.

Scan tool reads APP 3 position in volts. With throttle closed and ignition on or at idle, voltage should be 4 volts. Voltage should decrease at a steady rate as throttle is moved toward Wide Open Throttle (WOT). Ninety percent pedal travel is acceptable for correct APP operation. Scan APP 3 sensor while depressing accelerator pedal with engine off and ignition on. Display should vary from about 4 volts with throttle closed to about 2 volts with throttle held at WOT.

PCM monitors status of lift pump. Signal is also used store a DTC if fuel pump relay is defective or fuel pump voltage is lost while engine is running. About 12 volts should be present on fuel pump signal circuit during glow plug cycle.

DTC will set when the following conditions are present

1. Fuel lift pump is commanded on.
2. Difference between ignition voltage and fuel pump voltage is greater than 4 volts.
3. Conditions are met for 2 seconds.

1. If OBD system check has been performed, go to next step. If OBD system check has not been performed, go to «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel__on-board-diagnostic-obd-system-check) under SELF-DIAGNOSTIC SYSTEM.
2. Install scan tool. Turn ignition on, with engine off. Using scan tool, command fuel pump on. If fuel pump operates, see «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel) . If fuel pump does not operate, go to next step.
3. Turn ignition off. Using DVOM connected to ground, backprobe fuel lift pump signal circuit at PCM harness connector. Connect a fused jumper wire between battery voltage and fuel pump test terminal. If DVOM reads battery voltage, go to step 8 . If DVOM does not read battery voltage, go to next step.
4. Remove fuel pump relay. Connect a fused jumper wire between battery voltage and fuel pump relay terminal A3 from underneath fuse/relay block. If DVOM reads battery voltage, go to next step. If DVOM does not read battery voltage, go to step 6 .
5. Check for poor connection at fuse/relay block to fuel pump relay. Repair as necessary. After repairs, go to step 19 . If connection is okay, go to step 18 .
6. Check for open or short to ground in fuel pump signal circuit. Repair as necessary. After repairs, go to step 19 . If circuit is okay, go to next step.
7. Check for poor connection at PCM and fuse/relay block. Repair as necessary. After repairs, go to step 19 . If connections are okay, go to step 16 .
8. Remove fuel pump relay. Turn ignition on. Using test light connected to ground, probe fuel pump relay harness connector terminal B1. If test light illuminates, go to step 10 . If test light does not illuminate, go to next step.
9. Repair open in battery feed circuit to fuel pump relay. After repairs, go to step 19 .
10. Connect test light between fuel pump harness connector terminals A1 and B1. If test light illuminates, go to step 12 . If test light does not illuminate, go to next step.
11. Repair open in fuel pump relay ground circuit. After repairs, go to step 19 .
12. Turn ignition off. Connect test light between fuel pump relay harness connector terminal B3 and ground. Turn ignition on. If test light illuminates during the glow plug cycle, and then turns off, go to next step. If test light does not illuminate during the glow plug cycle, go to step 14 .
13. Turn ignition off. Connect test light between ground and fuel lift pump signal circuit of PCM harness connector. Turn ignition on. If test light illuminates during the glow plug cycle, and then turns off, go to step 16 . If test light does not illuminate during the glow plug cycle, go to step 17 .
14. Check for open or short to ground in fuel pump relay harness connector terminal B3 and PCM. Repair as necessary. After repairs, go to next step. If circuit is okay, go to step 16 .
15. Repair open or short to ground in fuel pump control circuit. After repairs, go to step 19 .
16. Replace PCM. Program PCM using required equipment. After replacing PCM, go to step 19 .
17. Check for poor connection at control circuit of fuel pump relay. Repair as necessary. After repairs, go to step 19 . If circuit is okay, go to next step.
18. Replace fuel pump relay. After replacing relay, go to next step.
19. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, and then enter DTC P0231. Operate vehicle within the conditions for setting this DTC. If scan tool indicates that this test ran and passed, go to next step. If scan tool does not indicate that this test ran and passed, repeat step 2 .
20. Using scan tool, select CAPTURE INFO, REVIEW INFO. If any undiagnosed DTC(s) are displayed, go to applicable DTC test.

This DTC will not check for fuel pump operation.

Scheme 10

Scheme 11

Scheme 12

PCM operates a normally open solenoid to control boost. PCM energizes solenoid by providing a ground path which then allows vacuum to pass to wastegate valve. During normal operation, PCM compares wastegate duty cycle signal with boost signal and corrects duty cycle accordingly.

DTC will set when the following conditions are present

1. Engine speed is greater than 2400 RPM.
2. Fuel rate is greater than 20 cu. mm.
3. Boost pressure is less than or equal to 20 kPa from desired (internal to PCM).
4. Conditions are met for 10 seconds.

Or

1. Engine speed is greater than 1800 RPM but less than 2400 RPM.
2. Fuel rate is greater than 20 cu. mm.
3. Boost pressure is less than, greater than or equal to 20 kPa from desired (internal to PCM).
4. Conditions are met for 10 seconds.

1. If OBD system check has been performed, go to next step. If OBD system check has not been performed, go to «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel__on-board-diagnostic-obd-system-check) under SELF-DIAGNOSTIC SYSTEM.
2. Check if DTC P1656 is also set. If DTC P1656 is set, diagnose DTC P1656 first. If DTC P1656 is not set, go to next step.
3. Disconnect vacuum hose from turbocharger wastegate actuator. Install vacuum gauge to vacuum hose. Start and idle engine. Observe vacuum reading. If vacuum is greater than or equal to 15 in. Hg, go to next step. If vacuum is less than 15 in. Hg, go to step 6 .
4. Disconnect wastegate solenoid harness connector. With engine running, check vacuum gauge reading. If vacuum reading is greater than one in. Hg, go to step 12 . If vacuum reading is one in. Hg or less, go to next step.
5. Turn engine off. Connect a hand-held vacuum pump to wastegate actuator. Apply 5 in. Hg of vacuum to actuator. If actuator holds vacuum, go to step 7 . If actuator does not hold vacuum, go to step 14 .
6. Check all vacuum lines from vacuum pump to wastegate actuator for leaks, deformities or pinches. Repair as necessary. After repairs, go to step 15 . If vacuum hoses are okay, go to step 8 .
7. Ensure engine is off. Disconnect vacuum lines to wastegate actuator. Using a pair of pliers, grip wastegate actuator rod. Move actuator rod back and forth. If actuator rod moves freely, go to next step. If actuator rod does not move freely, go to step 14 .
8. Check vacuum pump for proper output. Repair as necessary. After repairs, go to step 15 . If vacuum pump output is okay, go to next step.
9. Install scan tool. Start and idle engine. Observe boost pressure on scan tool display. Increase engine speed to 1500 RPM, and then return to idle. If scan tool displays a change in boost pressure, go to next step. If scan tool does not display a change in boost pressure, go to step 11 .
10. DTC is intermittent. If no additional DTC(s) are present, see «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel) . If additional DTC(s) are present, diagnose affected DTC(s).
11. Replace boost sensor. After replacing sensor, go to step 16 .
12. Check for plugged wastegate solenoid filter. Repair or replace as necessary. After repairs, go to step 16 . If filter is okay, go to next step.
13. Replace wastegate solenoid. After replacing solenoid, go to step 16 .
14. Replace turbocharger actuator. After replacing actuator, go to step 16 .
15. Replace vacuum pump. After replacing pump, go to step 16 .
16. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, and then enter DTC P0236. Operate vehicle within the conditions for setting this DTC. If scan tool indicates that this test ran and passed, go to next step. If scan tool does not indicate that this test ran and passed, repeat step 2 .
17. Using scan tool, select CAPTURE INFO, REVIEW INFO. If any undiagnosed DTC(s) are displayed, go to applicable DTC test.

A vacuum leak or pinched vacuum line could cause DTC P0236 to set. Check all vacuum lines and components connected to hoses for leaks or sharp bends. Check vacuum source. A possible EGR DTC will set if problem is present with vacuum source. Check for proper vacuum line routing.

The turbocharger wastegate actuator uses a pulse width modulated vacuum solenoid that causes vacuum to fluctuate under normal conditions. A steady vacuum reading indicates a restricted or plugged solenoid vent filter or solenoid vent orifice.

DTC P0237: TURBOCHARGER BOOST SENSOR CIRCUIT LOW VOLTAGE ("C", "G", "K" & "P" SERIES)

Note. For circuit reference, refer to DTC P0236 schematics. (Scheme 10), (Scheme 11) or (Scheme 12).

PCM operates a normally open solenoid to control boost. PCM energizes solenoid by providing a ground path which then allows vacuum to pass to wastegate valve. During normal operation, PCM compares wastegate duty cycle signal with boost signal and corrects duty cycle accordingly.

DTC will set when boost pressure is less than 40 kPa for 2 seconds.

1. If OBD system check has been performed, go to next step. If OBD system check has not been performed, go to «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel__on-board-diagnostic-obd-system-check) under SELF-DIAGNOSTIC SYSTEM.
2. Install scan tool. Start and idle engine. Observe boost pressure on scan tool display. If scan tool displays a boost pressure less than or equal to 40 kPa, go to next step. If scan tool displays a boost pressure greater than 40 kPa, go to step 5 .
3. Turn ignition off. Disconnect boost sensor harness connector. Connect a jumper wire between 5-volt reference and boost signal circuits of boost sensor connector. Turn ignition on. If scan tool displays a boost pressure greater than or equal to 202 kPa, go to step 6 . If scan tool displays a boost pressure less than 202 kPa, go to next step.
4. Turn ignition off. Ensure boost sensor connector is still disconnected. Remove jumper wire. Connect test light between boost signal circuit of boost sensor connector and battery voltage. Turn ignition on. If scan tool displays a boost pressure greater than or equal to 202 kPa, go to step 8 . If scan tool displays a boost pressure less than 202 kPa, go to step 7 .
5. DTC is intermittent. If no additional DTCs are set, see «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel) . If any additional DTCs are set, diagnose affected DTC(s).
6. Check for poor connection at boost sensor. Repair as necessary. After repairs, go to step 13 . If connection is okay, go to step 10 .
7. Check for open or short to ground in boost sensor signal circuit. Repair as necessary. After repairs, go to step 13 . If circuit is okay, go to step 11 .
8. Check for open in boost sensor 5-volt reference circuit. Repair as necessary. After repairs, go to step 13 . If circuit is okay, go to next step.
9. Check for short to ground in boost sensor 5-volt reference circuit. Repair as necessary. After repairs, go to step 13 . If circuit is okay, go to step 12 .
10. Replace boost sensor. After replacing sensor, go to step 13 .
11. Check for poor terminal connections at PCM. Repair as necessary. After repairs, go to step 13 . If connections are okay, go to next step.
12. Replace PCM. Program PCM using required equipment. After replacing PCM, go to next step.
13. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, and then enter DTC P0237. Operate vehicle within the conditions for setting this DTC. If scan tool indicates that this test ran and passed, go to next step. If scan tool does not indicate that this test ran and passed, repeat step 2 .
14. Using scan tool, select CAPTURE INFO, REVIEW INFO. If any undiagnosed DTC(s) are displayed, go to applicable DTC test.

Very little boost can be attained by revving engine in Neutral. Boost solenoid will show zero duty cycle if boost sensor signal circuit is open or shorted to ground. An intermittent can be caused by poor connections, rubbed through wire insulation or broken wire inside the insulation.

DTC P0238: TURBOCHARGER BOOST SENSOR CIRCUIT HIGH VOLTAGE ("C", "G", "K" & "P" SERIES)

Note. For circuit reference, refer to DTC P0236 schematics. (Scheme 10), (Scheme 11) or (Scheme 12).

PCM operates a normally open solenoid to control boost. PCM energizes solenoid by providing a ground path which then allows vacuum to pass to wastegate valve. During normal operation, PCM compares wastegate duty cycle signal with boost signal and corrects duty cycle accordingly.

DTC will set when boost pressure is greater than or equals to 202 kPa and engine speed less than 3506 RPM.

1. If OBD system check has been performed, go to next step. If OBD system check has not been performed, go to «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel__on-board-diagnostic-obd-system-check) under SELF-DIAGNOSTIC SYSTEM.
2. Install scan tool. Start and idle engine. Observe boost pressure on scan tool display. If scan tool displays a boost pressure greater than or equal to 202 kPa, go to next step. If scan tool displays a boost pressure less than 202 kPa, go to step 5 .
3. Turn ignition off. Disconnect boost sensor harness connector. Connect a fused jumper wire between ground and boost sensor signal circuit of boost sensor harness connector. Turn ignition on. If scan tool displays a boost pressure less than or equal to 10 kPa, go to step 6 . If scan tool displays a boost pressure greater than 10 kPa, go to next step.
4. Ensure boost sensor connector is still disconnected. Turn ignition on. Using DVOM in mA (milliamp) scale, measure current between boost sensor signal circuit and ground circuit of boost sensor harness connector. If reading is less than 10 mA, go to step 6 . If reading is 10 mA or greater, go to step 11 .
5. DTC is intermittent. If no additional DTCs are set, see «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel) . If any additional DTCs are set, go to applicable DTC test.
6. Turn ignition on, with engine off. Using DVOM connected to ground, probe 5-volt reference circuit terminal at boost sensor harness connector. If voltage is greater than 5.2 volts, go to step 12 . If voltage is 5.2 volts or less, go to next step.
7. Ensure boost sensor connector is still disconnected. Using DVOM, measure voltage between 5-volt reference circuit and ground circuit of boost sensor harness connector. If voltage is 4.8-5.2 volts, go to next step. If voltage is not 4.8-5.2 volts, go to next step 13 .
8. Check for open or poor connection in boost sensor signal circuit at PCM. Repair as necessary. After repairs, go to step 15 . If circuit is okay, go to next step.
9. Check boost sensor for restriction. Repair as necessary. After repairs, go to step 15 . If sensor is okay, go to next step.
10. Replace boost sensor. After replacing sensor, go to step 15 .
11. Check for short to voltage in boost sensor signal circuit. Repair as necessary. After repairs, go to step 15 . If circuit is okay, go to step 14 .
12. Check for short to voltage in 5-volt reference circuit. Repair as necessary. After repairs, go to step 15 . If circuit is okay, go to step 14 .
13. Check for open or poor connection in boost sensor ground circuit at PCM. Repair as necessary. After repairs, go to step 15 . If circuit is okay, go to next step.
14. Replace PCM. Program PCM using required equipment. After replacing PCM, go to next step.
15. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, and then enter DTC P0238. Operate vehicle within the conditions for setting this DTC. If scan tool indicates that this test ran and passed, go to next step. If scan tool does not indicate that this test ran and passed, repeat step 2 .
16. Using scan tool, select CAPTURE INFO, REVIEW INFO. If any undiagnosed DTC(s) are displayed, go to applicable DTC test.

Very little boost can be attained by revving engine in Neutral. An intermittent can be caused by poor connections, rubbed through wire insulation or broken wire inside the insulation.

DTC P0251: INJECTION PUMP CAM SYSTEM ("C", "G", "K" & "P" SERIES)

Note. For circuit reference, refer to DTC P0182 schematic. (Scheme 5)

Optical sensor provides a pump cam signal to PCM by counting pulses on sensor disk located in injection pump. Pump cam is an important input by PCM for fuel control and timing. Test monitors number of crankshaft position pulses that have occurred since last cam pulse. Physical one-to-one correspondence between pump cam and crankshaft implies that if more crank pulses are detected than cam pulses, the cam pulses have been missed.

DTC will set when 8 consecutive cam pulses are missing, or an average of 8 cam pulses are missing.

1. If OBD system check has been performed, go to next step. If OBD system check has not been performed, go to «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel__on-board-diagnostic-obd-system-check) under SELF-DIAGNOSTIC SYSTEM.
2. Check if DTC P0370 is also set. If DTC P0370 is set, diagnose DTC P0370 first. If DTC P0370 is not set, go to next step.
3. Start and idle engine. Using scan tool, with throttle closed, observe CAM REF MISSED display. If scan tool displays "8", go to step 5 . If scan tool does not display "8", go to next step.
4. DTC is intermittent. If no additional DTCs are set, see «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel) . If any additional DTCs are set, go to applicable DTC test.
5. Turn ignition off. Disconnect optical/fuel temperature sensor harness connector. Turn ignition on, with engine off. Using DVOM, measure voltage between ground and 5-volt reference circuit of optical/fuel temperature sensor harness connector. If voltage is 4.8-5.2 volts, go to next step. If voltage is not 4.8-5.2 volts, go to step 8 .
6. Using test light connected to battery voltage, probe ground circuit at optical/fuel temperature sensor harness connector. If test light illuminates, go to next step. If test light does not illuminate, go to step 9 .
7. Reconnect optical/fuel temperature sensor harness connector. Start and idle engine. Using scan tool, command engine speed to 900 RPM. Using DVOM on Hz scale, backprobe cam signal circuit at PCM harness connector. If DVOM reading is 57-63 Hz, go to step 15 . If DVOM reading is not 57-63 Hz, go to step 11 .
8. Turn ignition off. Disconnect PCM harness connector. Check 5-volt reference circuit for open, short to ground, or short to sensor ground circuit. Repair as necessary. After repairs, go to step 21 . If circuit is okay, go to step 10 .
9. Check for open or poor sensor ground terminal connection at PCM. Repair as necessary. After repairs, go to step 21 . If connection is okay, go to step 20 .
10. Check optical/fuel temperature 5-volt reference circuit for poor connection at PCM. Repair as necessary. After repairs, go to step 21 . If connection is okay, go to step 20 .
11. Turn ignition on, with engine off. Disconnect optical/fuel temperature sensor harness connector. Using DVOM, measure voltage between ground and CAM signal circuit of optical/fuel temperature sensor harness connector. If voltage is 4.8-5.2 volts, go to step 16 . If voltage is not 4.8-5.2 volts, go to next step.
12. If voltage is greater than 4.8-5.2 volts, go to next step. If voltage is 4.8-5.2 volts or less, go to step 14 .
13. Repair short to battery/ignition voltage in CAM signal circuit. After repairs, go to step 21 .
14. Turn ignition off. Check for an open or short to ground in CAM signal circuit. Repair as necessary. After repairs, go to step 21 . If circuit is okay, go to next step.
15. Check for poor connection at PCM harness connector. Repair or replace terminals as necessary. After repairs, go to step 21 . If connection is okay, go to step 20 .
16. Using DVOM in mA (milliamp) scale, measure current between CAM signal circuit and ground circuit of optical/fuel temperature sensor harness connector. If reading is less than 50 mA, go to step 18 . If reading is 50 mA or greater, go to next step.
17. Repair short to reference voltage in CAM signal circuit. After repairs, go to step 21 .
18. Check for poor connection at injection pump. Repair as necessary. After repairs, go to step 21 . If connection is okay, go to next step.
19. Replace injection pump. If fuel injection pump is replaced, new pump must be timed. See appropriate ON-VEHICLE ADJUSTMENTS article. After replacing injection pump, go to step 21 .
20. Replace PCM. Program PCM using required equipment. After replacing PCM, go to next step.
21. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, and then enter DTC P0251. Operate vehicle within the conditions for setting this DTC. If scan tool indicates that this test ran and passed, go to next step. If scan tool does not indicate that this test ran and passed, repeat step 2 .
22. Using scan tool, select CAPTURE INFO, REVIEW INFO. If any undiagnosed DTC(s) are displayed, go to applicable DTC test.

Intermittent DTCs P0251, P0370 and P1216 may be caused by air entering fuel system when fuel level is less than 1/8 tank while performing hard acceleration or turning maneuvers. If vehicle runs out of fuel, DTCs P0251, P0370 and P1216 will set. If vehicle has been operating under these conditions, bleed air from fuel system and test drive vehicle. Fast idle and poor performance will exist when PCM is in back-up fuel (less than 1/8 tank). An intermittent can be caused by poor connections, rubbed through wire insulation or broken wire inside the insulation.

Scheme 13

PCM has ability to increase and decrease amount of fuel to each cylinder to provide smooth idle operation. DTC will set if fuel correction amount exceeds defined limits.

DTC will set when the following conditions are present

1. Engine at idle.
2. All engine misfire DTCs ran and passed.
3. Engine coolant at normal temperatures.
4. Cylinder fault must be constant.
5. Fuel correction amount exceeds limits (internal to PCM).
6. Conditions are met for 2 seconds.

1. If OBD system check has been performed, go to next step. If OBD system check has not been performed, go to «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel__on-board-diagnostic-obd-system-check) under SELF-DIAGNOSTIC SYSTEM.
2. Install scan tool. Start and idle engine. Operate engine at normal operating temperature. Ensure all DTCs are cleared. Using scan tool, cut out (injector balance) the suspected cylinder. If RPM drops in suspected cylinder, go to next step. If RPM does not drop in suspected cylinder, go to step 4 .
3. DTC is intermittent. If no additional DTCs are set, see «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel) . If any additional DTCs are set, go to applicable DTC test.
4. Check for basic engine mechanical or fuel delivery problem (i.e., injection nozzle malfunction, intake manifold restriction) in suspected cylinder. Repair as necessary. After repairs, go to step 6 . If repairs were not necessary, go to next step.
5. Replace fuel injection pump. If fuel injection pump is replaced, new pump must be timed. See appropriate ON-VEHICLE ADJUSTMENTS article. After replacing injection pump, go to next step.
6. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, and then enter DTC P0263. Operate vehicle within the conditions for setting this DTC. If scan tool indicates that this test ran and passed, go to next step. If scan tool does not indicate that this test ran and passed, repeat step 2 .
7. Using scan tool, select CAPTURE INFO, REVIEW INFO. If any undiagnosed DTC(s) are displayed, go to applicable DTC test.

Injector balance test on scan tool should be used to confirm faulty cylinder. Scan tool will cut out specific cylinder requested. If a cylinder balance fault has been detected and engine has been running for a long time, PCM may try to increase or decrease fuel in other cylinders to compensate for rough idle which will cause multiple cylinder balance DTCs to set.

Scan tool snapshot mode can be used to properly identify suspected cylinder. Most likely cause of cylinder balance DTCs are faulty nozzles or engine mechanical (low compression) problems.

DTC P0266: CYLINDER NO. 2 BALANCE SYSTEM ("C", "G", "K" & "P" SERIES)

Note. For circuit reference, refer to DTC P0263 schematic. (Scheme 13)

PCM has ability to increase and decrease amount of fuel to each cylinder to provide smooth idle operation. DTC will set if fuel correction amount exceeds defined limits.

DTC will set when the following conditions are present

1. Engine at idle.
2. All engine misfire DTCs ran and passed.
3. Engine coolant at normal temperatures.
4. Cylinder fault must be constant.
5. Fuel correction amount exceeds limits (internal to PCM).
6. Conditions are met for 2 seconds.

1. If OBD system check has been performed, go to next step. If OBD system check has not been performed, go to «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel__on-board-diagnostic-obd-system-check) under SELF-DIAGNOSTIC SYSTEM.
2. Install scan tool. Start and idle engine. Operate engine at normal operating temperature. Ensure all DTCs are cleared. Using scan tool, cut out (injector balance) the suspected cylinder. If RPM drops in suspected cylinder, go to next step. If RPM does not drop in suspected cylinder, go to step 4 .
3. DTC is intermittent. If no additional DTCs are set, see «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel) . If any additional DTCs are set, go to applicable DTC test.
4. Check for basic engine mechanical or fuel delivery problem (i.e., injection nozzle malfunction, intake manifold restriction) in suspected cylinder. Repair as necessary. After repairs, go to step 6 . If repairs were not necessary, go to next step.
5. Replace fuel injection pump. If fuel injection pump is replaced, new pump must be timed. See appropriate ON-VEHICLE ADJUSTMENTS article. After replacing injection pump, go to next step.
6. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, and then enter DTC P0266. Operate vehicle within the conditions for setting this DTC. If scan tool indicates that this test ran and passed, go to next step. If scan tool does not indicate that this test ran and passed, repeat step 2 .
7. Using scan tool, select CAPTURE INFO, REVIEW INFO. If any undiagnosed DTC(s) are displayed, go to applicable DTC test.

Injector balance test on scan tool should be used to confirm faulty cylinder. Scan tool will cut out specific cylinder requested. If a cylinder balance fault has been detected and engine has been running for a long time, PCM may try to increase or decrease fuel in other cylinders to compensate for rough idle which will cause multiple cylinder balance DTCs to set.

Scan tool snapshot mode can be used to properly identify suspected cylinder. Most likely cause of cylinder balance DTCs are faulty nozzles or engine mechanical (low compression) problems.

DTC P0269: CYLINDER NO. 3 BALANCE SYSTEM ("C", "G", "K" & "P" SERIES)

Note. For circuit reference, refer to DTC P0263 schematic. (Scheme 13)

PCM has ability to increase and decrease amount of fuel to each cylinder to provide smooth idle operation. DTC will set if fuel correction amount exceeds defined limits.

DTC will set when the following conditions are present

1. Engine at idle.
2. All engine misfire DTCs ran and passed.
3. Engine coolant at normal temperatures.
4. Cylinder fault must be constant.
5. Fuel correction amount exceeds limits (internal to PCM).
6. Conditions are met for 2 seconds.

1. If OBD system check has been performed, go to next step. If OBD system check has not been performed, go to «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel__on-board-diagnostic-obd-system-check) under SELF-DIAGNOSTIC SYSTEM.
2. Install scan tool. Start and idle engine. Operate engine at normal operating temperature. Ensure all DTCs are cleared. Using scan tool, cut out (injector balance) the suspected cylinder. If RPM drops in suspected cylinder, go to next step. If RPM does not drop in suspected cylinder, go to step 4 .
3. DTC is intermittent. If no additional DTCs are set, see «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel) . If any additional DTCs are set, go to applicable DTC test.
4. Check for basic engine mechanical or fuel delivery problem (i.e., injection nozzle malfunction, intake manifold restriction) in suspected cylinder. Repair as necessary. After repairs, go to step 6 . If repairs were not necessary, go to next step.
5. Replace fuel injection pump. If fuel injection pump is replaced, new pump must be timed. See appropriate ON-VEHICLE ADJUSTMENTS article. After replacing injection pump, go to next step.
6. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, and then enter DTC P0269. Operate vehicle within the conditions for setting this DTC. If scan tool indicates that this test ran and passed, go to next step. If scan tool does not indicate that this test ran and passed, repeat step 2 .
7. Using scan tool, select CAPTURE INFO, REVIEW INFO. If any undiagnosed DTC(s) are displayed, go to applicable DTC test.

Injector balance test on scan tool should be used to confirm faulty cylinder. Scan tool will cut out specific cylinder requested. If a cylinder balance fault has been detected and engine has been running for a long time, PCM may try to increase or decrease fuel in other cylinders to compensate for rough idle which will cause multiple cylinder balance DTCs to set.

Scan tool snapshot mode can be used to properly identify suspected cylinder. Most likely cause of cylinder balance DTCs are faulty nozzles or engine mechanical (low compression) problems.

DTC P0272: CYLINDER NO. 4 BALANCE SYSTEM ("C", "G", "K" & "P" SERIES)

Note. For circuit reference, refer to DTC P0263 schematic. (Scheme 13)

PCM has ability to increase and decrease amount of fuel to each cylinder to provide smooth idle operation. DTC will set if fuel correction amount exceeds defined limits.

DTC will set when the following conditions are present

1. Engine at idle.
2. All engine misfire DTCs ran and passed.
3. Engine coolant at normal temperatures.
4. Cylinder fault must be constant.
5. Fuel correction amount exceeds limits (internal to PCM).
6. Conditions are met for 2 seconds.

1. If OBD system check has been performed, go to next step. If OBD system check has not been performed, go to «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel__on-board-diagnostic-obd-system-check) under SELF-DIAGNOSTIC SYSTEM.
2. Install scan tool. Start and idle engine. Operate engine at normal operating temperature. Ensure all DTCs are cleared. Using scan tool, cut out (injector balance) the suspected cylinder. If RPM drops in suspected cylinder, go to next step. If RPM does not drop in suspected cylinder, go to step 4 .
3. DTC is intermittent. If no additional DTCs are set, see «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel) . If any additional DTCs are set, go to applicable DTC test.
4. Check for basic engine mechanical or fuel delivery problem (i.e., injection nozzle malfunction, intake manifold restriction) in suspected cylinder. Repair as necessary. After repairs, go to step 6 . If repairs were not necessary, go to next step.
5. Replace fuel injection pump. If fuel injection pump is replaced, new pump must be timed. See appropriate ON-VEHICLE ADJUSTMENTS article. After replacing injection pump, go to next step.
6. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, and then enter DTC P0272. Operate vehicle within the conditions for setting this DTC. If scan tool indicates that this test ran and passed, go to next step. If scan tool does not indicate that this test ran and passed, repeat step 2 .
7. Using scan tool, select CAPTURE INFO, REVIEW INFO. If any undiagnosed DTC(s) are displayed, go to applicable DTC test.

Injector balance test on scan tool should be used to confirm faulty cylinder. Scan tool will cut out specific cylinder requested. If a cylinder balance fault has been detected and engine has been running for a long time, PCM may try to increase or decrease fuel in other cylinders to compensate for rough idle which will cause multiple cylinder balance DTCs to set.

Scan tool snapshot mode can be used to properly identify suspected cylinder. Most likely cause of cylinder balance DTCs are faulty nozzles or engine mechanical (low compression) problems.

DTC P0275: CYLINDER NO. 5 BALANCE SYSTEM ("C", "G", "K" & "P" SERIES)

Note. For circuit reference, refer to DTC P0263 schematic. (Scheme 13)

PCM has ability to increase and decrease amount of fuel to each cylinder to provide smooth idle operation. DTC will set if fuel correction amount exceeds defined limits.

DTC will set when the following conditions are present

1. Engine at idle.
2. All engine misfire DTCs ran and passed.
3. Engine coolant at normal temperatures.
4. Cylinder fault must be constant.
5. Fuel correction amount exceeds limits (internal to PCM).
6. Conditions are met for 2 seconds.

1. If OBD system check has been performed, go to next step. If OBD system check has not been performed, go to «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel__on-board-diagnostic-obd-system-check) under SELF-DIAGNOSTIC SYSTEM.
2. Install scan tool. Start and idle engine. Operate engine at normal operating temperature. Ensure all DTCs are cleared. Using scan tool, cut out (injector balance) the suspected cylinder. If RPM drops in suspected cylinder, go to next step. If RPM does not drop in suspected cylinder, go to step 4 .
3. DTC is intermittent. If no additional DTCs are set, see «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel) . If any additional DTCs are set, go to applicable DTC test.
4. Check for basic engine mechanical or fuel delivery problem (i.e., injection nozzle malfunction, intake manifold restriction) in suspected cylinder. Repair as necessary. After repairs, go to step 6 . If repairs were not necessary, go to next step.
5. Replace fuel injection pump. If fuel injection pump is replaced, new pump must be timed. See appropriate ON-VEHICLE ADJUSTMENTS article. After replacing injection pump, go to next step.
6. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, and then enter DTC P0275. Operate vehicle within the conditions for setting this DTC. If scan tool indicates that this test ran and passed, go to next step. If scan tool does not indicate that this test ran and passed, repeat step 2 .
7. Using scan tool, select CAPTURE INFO, REVIEW INFO. If any undiagnosed DTC(s) are displayed, go to applicable DTC test.

Injector balance test on scan tool should be used to confirm faulty cylinder. Scan tool will cut out specific cylinder requested. If a cylinder balance fault has been detected and engine has been running for a long time, PCM may try to increase or decrease fuel in other cylinders to compensate for rough idle which will cause multiple cylinder balance DTCs to set.

Scan tool snapshot mode can be used to properly identify suspected cylinder. Most likely cause of cylinder balance DTCs are faulty nozzles or engine mechanical (low compression) problems.

DTC P0278: CYLINDER NO. 6 BALANCE SYSTEM ("C", "G", "K" & "P" SERIES)

Note. For circuit reference, refer to DTC P0263 schematic. (Scheme 13)

PCM has ability to increase and decrease amount of fuel to each cylinder to provide smooth idle operation. DTC will set if fuel correction amount exceeds defined limits.

DTC will set when the following conditions are present

1. Engine at idle.
2. All engine misfire DTCs ran and passed.
3. Engine coolant at normal temperatures.
4. Cylinder fault must be constant.
5. Fuel correction amount exceeds limits (internal to PCM).
6. Conditions are met for 2 seconds.

1. If OBD system check has been performed, go to next step. If OBD system check has not been performed, go to «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel__on-board-diagnostic-obd-system-check) under SELF-DIAGNOSTIC SYSTEM.
2. Install scan tool. Start and idle engine. Operate engine at normal operating temperature. Ensure all DTCs are cleared. Using scan tool, cut out (injector balance) the suspected cylinder. If RPM drops in suspected cylinder, go to next step. If RPM does not drop in suspected cylinder, go to step 4 .
3. DTC is intermittent. If no additional DTCs are set, see «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel) . If any additional DTCs are set, go to applicable DTC test.
4. Check for basic engine mechanical or fuel delivery problem (i.e., injection nozzle malfunction, intake manifold restriction) in suspected cylinder. Repair as necessary. After repairs, go to step 6 . If repairs were not necessary, go to next step.
5. Replace fuel injection pump. If fuel injection pump is replaced, new pump must be timed. See appropriate ON-VEHICLE ADJUSTMENTS article. After replacing injection pump, go to next step.
6. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, and then enter DTC P0278. Operate vehicle within the conditions for setting this DTC. If scan tool indicates that this test ran and passed, go to next step. If scan tool does not indicate that this test ran and passed, repeat step 2 .
7. Using scan tool, select CAPTURE INFO, REVIEW INFO. If any undiagnosed DTC(s) are displayed, go to applicable DTC test.

Injector balance test on scan tool should be used to confirm faulty cylinder. Scan tool will cut out specific cylinder requested. If a cylinder balance fault has been detected and engine has been running for a long time, PCM may try to increase or decrease fuel in other cylinders to compensate for rough idle which will cause multiple cylinder balance DTCs to set.

Scan tool snapshot mode can be used to properly identify suspected cylinder. Most likely cause of cylinder balance DTCs are faulty nozzles or engine mechanical (low compression) problems.

DTC P0281: CYLINDER NO. 7 BALANCE SYSTEM ("C", "G", "K" & "P" SERIES)

Note. For circuit reference, refer to DTC P0263 schematic. (Scheme 13)

PCM has ability to increase and decrease amount of fuel to each cylinder to provide smooth idle operation. DTC will set if fuel correction amount exceeds defined limits.

DTC will set when the following conditions are present

1. Engine at idle.
2. All engine misfire DTCs ran and passed.
3. Engine coolant at normal temperatures.
4. Cylinder fault must be constant.
5. Fuel correction amount exceeds limits (internal to PCM).
6. Conditions are met for 2 seconds.

1. If OBD system check has been performed, go to next step. If OBD system check has not been performed, go to «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel__on-board-diagnostic-obd-system-check) under SELF-DIAGNOSTIC SYSTEM.
2. Install scan tool. Start and idle engine. Operate engine at normal operating temperature. Ensure all DTCs are cleared. Using scan tool, cut out (injector balance) the suspected cylinder. If RPM drops in suspected cylinder, go to next step. If RPM does not drop in suspected cylinder, go to step 4 .
3. DTC is intermittent. If no additional DTCs are set, see «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel) . If any additional DTCs are set, go to applicable DTC test.
4. Check for basic engine mechanical or fuel delivery problem (i.e., injection nozzle malfunction, intake manifold restriction) in suspected cylinder. Repair as necessary. After repairs, go to step 6 . If repairs were not necessary, go to next step.
5. Replace fuel injection pump. If fuel injection pump is replaced, new pump must be timed. See appropriate ON-VEHICLE ADJUSTMENTS article. After replacing injection pump, go to next step.
6. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, and then enter DTC P0281. Operate vehicle within the conditions for setting this DTC. If scan tool indicates that this test ran and passed, go to next step. If scan tool does not indicate that this test ran and passed, repeat step 2 .
7. Using scan tool, select CAPTURE INFO, REVIEW INFO. If any undiagnosed DTC(s) are displayed, go to applicable DTC test.

Injector balance test on scan tool should be used to confirm faulty cylinder. Scan tool will cut out specific cylinder requested. If a cylinder balance fault has been detected and engine has been running for a long time, PCM may try to increase or decrease fuel in other cylinders to compensate for rough idle which will cause multiple cylinder balance DTCs to set.

Scan tool snapshot mode can be used to properly identify suspected cylinder. Most likely cause of cylinder balance DTCs are faulty nozzles or engine mechanical (low compression) problems.

DTC P0284: CYLINDER NO. 8 BALANCE SYSTEM ("C", "G", "K" & "P" SERIES)

Note. For circuit reference, refer to DTC P0263 schematic. (Scheme 13)

PCM has ability to increase and decrease amount of fuel to each cylinder to provide smooth idle operation. DTC will set if fuel correction amount exceeds defined limits.

DTC will set when the following conditions are present

1. Engine at idle.
2. All engine misfire DTCs ran and passed.
3. Engine coolant at normal temperatures.
4. Cylinder fault must be constant.
5. Fuel correction amount exceeds limits (internal to PCM).
6. Conditions are met for 2 seconds.

1. If OBD system check has been performed, go to next step. If OBD system check has not been performed, go to «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel__on-board-diagnostic-obd-system-check) under SELF-DIAGNOSTIC SYSTEM.
2. Install scan tool. Start and idle engine. Operate engine at normal operating temperature. Ensure all DTCs are cleared. Using scan tool, cut out (injector balance) the suspected cylinder. If RPM drops in suspected cylinder, go to next step. If RPM does not drop in suspected cylinder, go to step 4 .
3. DTC is intermittent. If no additional DTCs are set, see «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel) . If any additional DTCs are set, go to applicable DTC test.
4. Check for basic engine mechanical or fuel delivery problem (i.e., injection nozzle malfunction, intake manifold restriction) in suspected cylinder. Repair as necessary. After repairs, go to step 6 . If repairs were not necessary, go to next step.
5. Replace fuel injection pump. If fuel injection pump is replaced, new pump must be timed. See appropriate ON-VEHICLE ADJUSTMENTS article. After replacing injection pump, go to next step.
6. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, and then enter DTC P0284. Operate vehicle within the conditions for setting this DTC. If scan tool indicates that this test ran and passed, go to next step. If scan tool does not indicate that this test ran and passed, repeat step 2 .
7. Using scan tool, select CAPTURE INFO, REVIEW INFO. If any undiagnosed DTC(s) are displayed, go to applicable DTC test.

Injector balance test on scan tool should be used to confirm faulty cylinder. Scan tool will cut out specific cylinder requested. If a cylinder balance fault has been detected and engine has been running for a long time, PCM may try to increase or decrease fuel in other cylinders to compensate for rough idle which will cause multiple cylinder balance DTCs to set.

Scan tool snapshot mode can be used to properly identify suspected cylinder. Most likely cause of cylinder balance DTCs are faulty nozzles or engine mechanical (low compression) problems.

DTC P0300: ENGINE MISFIRE DETECTED ("C", "G", "K" & "P" SERIES)

Note. For circuit reference, refer to DTC P0263 schematic. (Scheme 13)

PCM times the interval between each pulse of the CKP sensor and compares each time interval with the other 8 to determine when an excessive change in crankshaft speed has occurred.

This pulse is generated from a 4X reluctor wheel located on front of crankshaft. If crankshaft speed is less than an expected amount, PCM will increase amount of fuel needed to correct misfire. If amount of fuel exceeds the calibrated value, PCM will interpret this as a misfire and set the DTC. This misfire diagnostic is used only to identify a weak cylinder needing additional fuel.

DTC will set when the following conditions are present

1. ECT greater 132°F (56°C).
2. Engine idling for total of 90 seconds.
3. Fuel adjustment is greater than calibrated value (internal to PCM).
4. Multiple engine misfires detected.

1. If OBD system check has been performed, go to next step. If OBD system check has not been performed, go to «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel__on-board-diagnostic-obd-system-check) under SELF-DIAGNOSTIC SYSTEM.
2. Install scan tool. Start and idle engine. Operate engine at normal operating temperature. Using scan tool, cut out (injector balance) the suspected cylinder. If RPM drops in suspected cylinder, go to next step. If RPM does not drop in suspected cylinder, go to step 4 .
3. DTC is intermittent. If no additional DTCs are set, see «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel) . If any additional DTCs are set, go to applicable DTC test.
4. Check for basic engine mechanical or fuel delivery problem (i.e., injection nozzle malfunction, intake manifold restriction) in suspected cylinder. Repair as necessary. After repairs, go to step 6 . If repairs were not necessary, go to next step.
5. Replace fuel injection pump. If fuel injection pump is replaced, new pump must be timed. See appropriate ON-VEHICLE ADJUSTMENTS article. After replacing injection pump, go to next step.
6. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, and then enter DTC P0300. Operate vehicle within the conditions for setting this DTC. If scan tool indicates that this test ran and passed, go to next step. If scan tool does not indicate that this test ran and passed, repeat step 2 .
7. Using scan tool, select CAPTURE INFO, REVIEW INFO. If any undiagnosed DTC(s) are displayed, go to applicable DTC test.

Scan tool can be used to control suspected cylinder (cylinder balance test). DTC will set when there is a mechanical failure that will cause low cylinder compression in more than one cylinder, fuel leak at high pressure fuel injection lines or nozzle, or a stuck closed fuel injector nozzle.

DTC P0301: CYLINDER NO. 1 MISFIRE DETECTED ("C", "G", "K" & "P" SERIES)

Note. For circuit reference, refer to DTC P0263 schematic. (Scheme 13)

PCM times the interval between each pulse of the CKP sensor and compares each time interval with the other 8 to determine when an excessive change in crankshaft speed has occurred.

This pulse is generated from a 4X reluctor wheel located on front of crankshaft. If crankshaft speed is less than an expected amount, PCM will increase amount of fuel needed to correct misfire. If amount of fuel exceeds the calibrated value, PCM will interpret this as a misfire and set the DTC. This misfire diagnostic is used only to identify a weak cylinder needing additional fuel.

DTC will set when the following conditions are present

1. ECT greater 132°F (56°C).
2. Engine idling for total of 90 seconds.
3. Amount of fuel added is greater than calibrated value (internal to PCM).

1. If OBD system check has been performed, go to next step. If OBD system check has not been performed, go to «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel__on-board-diagnostic-obd-system-check) under SELF-DIAGNOSTIC SYSTEM.
2. Install scan tool. Start and idle engine. Operate engine at normal operating temperature. Using scan tool, cut out (injector balance) the suspected cylinder. If RPM drops in suspected cylinder, go to next step. If RPM does not drop in suspected cylinder, go to step 4 .
3. DTC is intermittent. If no additional DTCs are set, see «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel) . If any additional DTCs are set, go to applicable DTC test.
4. Check for basic engine mechanical or fuel delivery problem (i.e., injection nozzle malfunction, intake manifold restriction) in suspected cylinder. Repair as necessary. After repairs, go to step 6 . If repairs were not necessary, go to next step.
5. Replace fuel injection pump. If fuel injection pump is replaced, new pump must be timed. See appropriate ON-VEHICLE ADJUSTMENTS article. After replacing injection pump, go to next step.
6. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, and then enter DTC P0301. Operate vehicle within the conditions for setting this DTC. If scan tool indicates that this test ran and passed, go to next step. If scan tool does not indicate that this test ran and passed, repeat step 2 .
7. Using scan tool, select CAPTURE INFO, REVIEW INFO. If any undiagnosed DTC(s) are displayed, go to applicable DTC test.

The following can cause this DTC to set: mechanical problem, injector leak or stuck injector nozzle. If an injector is suspected, move affected injector to another cylinder. If problem follows injector, injector is faulty. Replace injector. After repairs, engine might take about 30 seconds to return to stable idle.

DTC P0302: CYLINDER NO. 2 MISFIRE DETECTED ("C", "G", "K" & "P" SERIES)

Note. For circuit reference, refer to DTC P0263 schematic. (Scheme 13)

PCM times the interval between each pulse of the CKP sensor and compares each time interval with the other 8 to determine when an excessive change in crankshaft speed has occurred.

This pulse is generated from a 4X reluctor wheel located on front of crankshaft. If crankshaft speed is less than an expected amount, PCM will increase amount of fuel needed to correct misfire. If amount of fuel exceeds the calibrated value, PCM will interpret this as a misfire and set the DTC. This misfire diagnostic is used only to identify a weak cylinder needing additional fuel.

DTC will set when the following conditions are present

1. ECT greater 132°F (56°C).
2. Engine idling for total of 90 seconds.
3. Amount of fuel added is greater than calibrated value (internal to PCM).

1. If OBD system check has been performed, go to next step. If OBD system check has not been performed, go to «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel__on-board-diagnostic-obd-system-check) under SELF-DIAGNOSTIC SYSTEM.
2. Install scan tool. Start and idle engine. Operate engine at normal operating temperature. Using scan tool, cut out (injector balance) the suspected cylinder. If RPM drops in suspected cylinder, go to next step. If RPM does not drop in suspected cylinder, go to step 4 .
3. DTC is intermittent. If no additional DTCs are set, see «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel) . If any additional DTCs are set, go to applicable DTC test.
4. Check for basic engine mechanical or fuel delivery problem (i.e., injection nozzle malfunction, intake manifold restriction) in suspected cylinder. Repair as necessary. After repairs, go to step 6 . If repairs were not necessary, go to next step.
5. Replace fuel injection pump. If fuel injection pump is replaced, new pump must be timed. See appropriate ON-VEHICLE ADJUSTMENTS article. After replacing injection pump, go to next step.
6. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, and then enter DTC P0302. Operate vehicle within the conditions for setting this DTC. If scan tool indicates that this test ran and passed, go to next step. If scan tool does not indicate that this test ran and passed, repeat step 2 .
7. Using scan tool, select CAPTURE INFO, REVIEW INFO. If any undiagnosed DTC(s) are displayed, go to applicable DTC test.

The following can cause this DTC to set: mechanical problem, injector leak or stuck injector nozzle. If an injector is suspected, move affected injector to another cylinder. If problem follows injector, injector is faulty. Replace injector. After repairs, engine might take about 30 seconds to return to stable idle.

DTC P0303: CYLINDER NO. 3 MISFIRE DETECTED ("C", "G", "K" & "P" SERIES)

Note. For circuit reference, refer to DTC P0263 schematic. (Scheme 13)

PCM times the interval between each pulse of the CKP sensor and compares each time interval with the other 8 to determine when an excessive change in crankshaft speed has occurred.

This pulse is generated from a 4X reluctor wheel located on front of crankshaft. If crankshaft speed is less than an expected amount, PCM will increase amount of fuel needed to correct misfire. If amount of fuel exceeds the calibrated value, PCM will interpret this as a misfire and set the DTC. This misfire diagnostic is used only to identify a weak cylinder needing additional fuel.

DTC will set when the following conditions are present

1. ECT greater 132°F (56°C).
2. Engine idling for total of 90 seconds.
3. Amount of fuel added is greater than calibrated value (internal to PCM).

1. If OBD system check has been performed, go to next step. If OBD system check has not been performed, go to «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel__on-board-diagnostic-obd-system-check) under SELF-DIAGNOSTIC SYSTEM.
2. Install scan tool. Start and idle engine. Operate engine at normal operating temperature. Using scan tool, cut out (injector balance) the suspected cylinder. If RPM drops in suspected cylinder, go to next step. If RPM does not drop in suspected cylinder, go to step 4 .
3. DTC is intermittent. If no additional DTCs are set, see «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel) . If any additional DTCs are set, go to applicable DTC test.
4. Check for basic engine mechanical or fuel delivery problem (i.e., injection nozzle malfunction, intake manifold restriction) in suspected cylinder. Repair as necessary. After repairs, go to step 6 . If repairs were not necessary, go to next step.
5. Replace fuel injection pump. If fuel injection pump is replaced, new pump must be timed. See appropriate ON-VEHICLE ADJUSTMENTS article. After replacing injection pump, go to next step.
6. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, and then enter DTC P0303. Operate vehicle within the conditions for setting this DTC. If scan tool indicates that this test ran and passed, go to next step. If scan tool does not indicate that this test ran and passed, repeat step 2 .
7. Using scan tool, select CAPTURE INFO, REVIEW INFO. If any undiagnosed DTC(s) are displayed, go to applicable DTC test.

The following can cause this DTC to set: mechanical problem, injector leak or stuck injector nozzle. If an injector is suspected, move affected injector to another cylinder. If problem follows injector, injector is faulty. Replace injector. After repairs, engine might take about 30 seconds to return to stable idle.

DTC P0304: CYLINDER NO. 4 MISFIRE DETECTED ("C", "G", "K" & "P" SERIES)

Note. For circuit reference, refer to DTC P0263 schematic. (Scheme 13)

PCM times the interval between each pulse of the CKP sensor and compares each time interval with the other 8 to determine when an excessive change in crankshaft speed has occurred.

This pulse is generated from a 4X reluctor wheel located on front of crankshaft. If crankshaft speed is less than an expected amount, PCM will increase amount of fuel needed to correct misfire. If amount of fuel exceeds the calibrated value, PCM will interpret this as a misfire and set the DTC. This misfire diagnostic is used only to identify a weak cylinder needing additional fuel.

DTC will set when the following conditions are present

1. ECT greater 132°F (56°C).
2. Engine idling for total of 90 seconds.
3. Amount of fuel added is greater than calibrated value (internal to PCM).

1. If OBD system check has been performed, go to next step. If OBD system check has not been performed, go to «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel__on-board-diagnostic-obd-system-check) under SELF-DIAGNOSTIC SYSTEM.
2. Install scan tool. Start and idle engine. Operate engine at normal operating temperature. Using scan tool, cut out (injector balance) the suspected cylinder. If RPM drops in suspected cylinder, go to next step. If RPM does not drop in suspected cylinder, go to step 4 .
3. DTC is intermittent. If no additional DTCs are set, see «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel) . If any additional DTCs are set, go to applicable DTC test.
4. Check for basic engine mechanical or fuel delivery problem (i.e., injection nozzle malfunction, intake manifold restriction) in suspected cylinder. Repair as necessary. After repairs, go to step 6 . If repairs were not necessary, go to next step.
5. Replace fuel injection pump. If fuel injection pump is replaced, new pump must be timed. See appropriate ON-VEHICLE ADJUSTMENTS article. After replacing injection pump, go to next step.
6. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, and then enter DTC P0304. Operate vehicle within the conditions for setting this DTC. If scan tool indicates that this test ran and passed, go to next step. If scan tool does not indicate that this test ran and passed, repeat step 2 .
7. Using scan tool, select CAPTURE INFO, REVIEW INFO. If any undiagnosed DTC(s) are displayed, go to applicable DTC test.

The following can cause this DTC to set: mechanical problem, injector leak or stuck injector nozzle. If an injector is suspected, move affected injector to another cylinder. If problem follows injector, injector is faulty. Replace injector. After repairs, engine might take about 30 seconds to return to stable idle.

DTC P0305: CYLINDER NO. 5 MISFIRE DETECTED ("C", "G", "K" & "P" SERIES)

Note. For circuit reference, refer to DTC P0263 schematic. (Scheme 13)

PCM times the interval between each pulse of the CKP sensor and compares each time interval with the other 8 to determine when an excessive change in crankshaft speed has occurred.

This pulse is generated from a 4X reluctor wheel located on front of crankshaft. If crankshaft speed is less than an expected amount, PCM will increase amount of fuel needed to correct misfire. If amount of fuel exceeds the calibrated value, PCM will interpret this as a misfire and set the DTC. This misfire diagnostic is used only to identify a weak cylinder needing additional fuel.

DTC will set when the following conditions are present

1. ECT greater 132°F (56°C).
2. Engine idling for total of 90 seconds.
3. Amount of fuel added is greater than calibrated value (internal to PCM).

1. If OBD system check has been performed, go to next step. If OBD system check has not been performed, go to «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel__on-board-diagnostic-obd-system-check) under SELF-DIAGNOSTIC SYSTEM.
2. Install scan tool. Start and idle engine. Operate engine at normal operating temperature. Using scan tool, cut out (injector balance) the suspected cylinder. If RPM drops in suspected cylinder, go to next step. If RPM does not drop in suspected cylinder, go to step 4 .
3. DTC is intermittent. If no additional DTCs are set, see «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel) . If any additional DTCs are set, go to applicable DTC test.
4. Check for basic engine mechanical or fuel delivery problem (i.e., injection nozzle malfunction, intake manifold restriction) in suspected cylinder. Repair as necessary. After repairs, go to step 6 . If repairs were not necessary, go to next step.
5. Replace fuel injection pump. If fuel injection pump is replaced, new pump must be timed. See appropriate ON-VEHICLE ADJUSTMENTS article. After replacing injection pump, go to next step.
6. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, and then enter DTC P0305. Operate vehicle within the conditions for setting this DTC. If scan tool indicates that this test ran and passed, go to next step. If scan tool does not indicate that this test ran and passed, repeat step 2 .
7. Using scan tool, select CAPTURE INFO, REVIEW INFO. If any undiagnosed DTC(s) are displayed, go to applicable DTC test.

The following can cause this DTC to set: mechanical problem, injector leak or stuck injector nozzle. If an injector is suspected, move affected injector to another cylinder. If problem follows injector, injector is faulty. Replace injector. After repairs, engine might take about 30 seconds to return to stable idle.

DTC P0306: CYLINDER NO. 6 MISFIRE DETECTED ("C", "G", "K" & "P" SERIES)

Note. For circuit reference, refer to DTC P0263 schematic. (Scheme 13)

PCM times the interval between each pulse of the CKP sensor and compares each time interval with the other 8 to determine when an excessive change in crankshaft speed has occurred.

This pulse is generated from a 4X reluctor wheel located on front of crankshaft. If crankshaft speed is less than an expected amount, PCM will increase amount of fuel needed to correct misfire. If amount of fuel exceeds the calibrated value, PCM will interpret this as a misfire and set the DTC. This misfire diagnostic is used only to identify a weak cylinder needing additional fuel.

DTC will set when the following conditions are present

1. ECT greater 132°F (56°C).
2. Engine idling for total of 90 seconds.
3. Amount of fuel added is greater than calibrated value (internal to PCM).

1. If OBD system check has been performed, go to next step. If OBD system check has not been performed, go to «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel__on-board-diagnostic-obd-system-check) under SELF-DIAGNOSTIC SYSTEM.
2. Install scan tool. Start and idle engine. Operate engine at normal operating temperature. Using scan tool, cut out (injector balance) the suspected cylinder. If RPM drops in suspected cylinder, go to next step. If RPM does not drop in suspected cylinder, go to step 4 .
3. DTC is intermittent. If no additional DTCs are set, see «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel) . If any additional DTCs are set, go to applicable DTC test.
4. Check for basic engine mechanical or fuel delivery problem (i.e., injection nozzle malfunction, intake manifold restriction) in suspected cylinder. Repair as necessary. After repairs, go to step 6 . If repairs were not necessary, go to next step.
5. Replace fuel injection pump. If fuel injection pump is replaced, new pump must be timed. See appropriate ON-VEHICLE ADJUSTMENTS article. After replacing injection pump, go to next step.
6. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, and then enter DTC P0306. Operate vehicle within the conditions for setting this DTC. If scan tool indicates that this test ran and passed, go to next step. If scan tool does not indicate that this test ran and passed, repeat step 2 .
7. Using scan tool, select CAPTURE INFO, REVIEW INFO. If any undiagnosed DTC(s) are displayed, go to applicable DTC test.

The following can cause this DTC to set: mechanical problem, injector leak or stuck injector nozzle. If an injector is suspected, move affected injector to another cylinder. If problem follows injector, injector is faulty. Replace injector. After repairs, engine might take about 30 seconds to return to stable idle.

DTC P0307: CYLINDER NO. 7 MISFIRE DETECTED ("C", "G", "K" & "P" SERIES)

Note. For circuit reference, refer to DTC P0263 schematic. (Scheme 13)

PCM times the interval between each pulse of the CKP sensor and compares each time interval with the other 8 to determine when an excessive change in crankshaft speed has occurred.

This pulse is generated from a 4X reluctor wheel located on front of crankshaft. If crankshaft speed is less than an expected amount, PCM will increase amount of fuel needed to correct misfire. If amount of fuel exceeds the calibrated value, PCM will interpret this as a misfire and set the DTC. This misfire diagnostic is used only to identify a weak cylinder needing additional fuel.

DTC will set when the following conditions are present

1. ECT greater 132°F (56°C).
2. Engine idling for total of 90 seconds.
3. Amount of fuel added is greater than calibrated value (internal to PCM).

1. If OBD system check has been performed, go to next step. If OBD system check has not been performed, go to «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel__on-board-diagnostic-obd-system-check) under SELF-DIAGNOSTIC SYSTEM.
2. Install scan tool. Start and idle engine. Operate engine at normal operating temperature. Using scan tool, cut out (injector balance) the suspected cylinder. If RPM drops in suspected cylinder, go to next step. If RPM does not drop in suspected cylinder, go to step 4 .
3. DTC is intermittent. If no additional DTCs are set, see «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel) . If any additional DTCs are set, go to applicable DTC test.
4. Check for basic engine mechanical or fuel delivery problem (i.e., injection nozzle malfunction, intake manifold restriction) in suspected cylinder. Repair as necessary. After repairs, go to step 6 . If repairs were not necessary, go to next step.
5. Replace fuel injection pump. If fuel injection pump is replaced, new pump must be timed. See appropriate ON-VEHICLE ADJUSTMENTS article. After replacing injection pump, go to next step.
6. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, and then enter DTC P0307. Operate vehicle within the conditions for setting this DTC. If scan tool indicates that this test ran and passed, go to next step. If scan tool does not indicate that this test ran and passed, repeat step 2 .
7. Using scan tool, select CAPTURE INFO, REVIEW INFO. If any undiagnosed DTC(s) are displayed, go to applicable DTC test.

The following can cause this DTC to set: mechanical problem, injector leak or stuck injector nozzle. If an injector is suspected, move affected injector to another cylinder. If problem follows injector, injector is faulty. Replace injector. After repairs, engine might take about 30 seconds to return to stable idle.

DTC P0308: CYLINDER NO. 8 MISFIRE DETECTED ("C", "G", "K" & "P" SERIES)

Note. For circuit reference, refer to DTC P0263 schematic. (Scheme 13)

PCM times the interval between each pulse of the CKP sensor and compares each time interval with the other 8 to determine when an excessive change in crankshaft speed has occurred.

This pulse is generated from a 4X reluctor wheel located on front of crankshaft. If crankshaft speed is less than an expected amount, PCM will increase amount of fuel needed to correct misfire. If amount of fuel exceeds the calibrated value, PCM will interpret this as a misfire and set the DTC. This misfire diagnostic is used only to identify a weak cylinder needing additional fuel.

DTC will set when the following conditions are present

1. ECT greater 132°F (56°C).
2. Engine idling for total of 90 seconds.
3. Amount of fuel added is greater than calibrated value (internal to PCM).

1. If OBD system check has been performed, go to next step. If OBD system check has not been performed, go to «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel__on-board-diagnostic-obd-system-check) under SELF-DIAGNOSTIC SYSTEM.
2. Install scan tool. Start and idle engine. Operate engine at normal operating temperature. Using scan tool, cut out (injector balance) the suspected cylinder. If RPM drops in suspected cylinder, go to next step. If RPM does not drop in suspected cylinder, go to step 4 .
3. DTC is intermittent. If no additional DTCs are set, see «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel) . If any additional DTCs are set, go to applicable DTC test.
4. Check for basic engine mechanical or fuel delivery problem (i.e., injection nozzle malfunction, intake manifold restriction) in suspected cylinder. Repair as necessary. After repairs, go to step 6 . If repairs were not necessary, go to next step.
5. Replace fuel injection pump. If fuel injection pump is replaced, new pump must be timed. See appropriate ON-VEHICLE ADJUSTMENTS article. After replacing injection pump, go to next step.
6. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, and then enter DTC P0308. Operate vehicle within the conditions for setting this DTC. If scan tool indicates that this test ran and passed, go to next step. If scan tool does not indicate that this test ran and passed, repeat step 2 .
7. Using scan tool, select CAPTURE INFO, REVIEW INFO. If any undiagnosed DTC(s) are displayed, go to applicable DTC test.

The following can cause this DTC to set: mechanical problem, injector leak or stuck injector nozzle. If an injector is suspected, move affected injector to another cylinder. If problem follows injector, injector is faulty. Replace injector. After repairs, engine might take about 30 seconds to return to stable idle.

DTC P0335: CRANKSHAFT POSITION (CKP) SENSOR CIRCUIT PERFORMANCE ("C", "G", "K" & "P" SERIES)

Note. For circuit reference, see appropriate wiring diagram in WIRING DIAGRAMS article.

Crankshaft Position (CKP) sensor is a Hall Effect sensor that monitors crankshaft position and speed. CKP sensor is equipped with 4 teeth, 90 degrees apart that generate a signal which is then transmitted to PCM. Physical one-to-one correspondence exists between pump cam and crankshaft.

DTC will set when 8 consecutive crank pulses are missing, or an average of 8 consecutive crank pulses are missing.

1. If OBD system check has been performed, go to next step. If OBD system check has not been performed, go to «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel__on-board-diagnostic-obd-system-check) under SELF-DIAGNOSTIC SYSTEM.
2. Install scan tool. Start and idle engine. Using scan tool, with throttle closed, observe CRANK REF MISSED display. If scan tool displays "8", go to step 4 . If scan tool does not display "8", go to next step.
3. DTC is intermittent. If no additional DTCs are set, see «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel) . If any additional DTCs are set, go to applicable DTC test.
4. Turn ignition off. Disconnect CKP sensor harness connector. Turn ignition on, with engine off. Using DVOM, measure voltage between ground and 5-volt reference circuit of CKP sensor harness connector. If voltage is 4.8-5.2 volts, go to next step. If voltage is not 4.8-5.2 volts, go to step 8 .
5. Using test light connected to battery voltage, probe ground circuit of CKP sensor harness connector. If test light illuminates, go to next step. If test light does not illuminate, go to step 9 .
6. Reconnect CKP sensor harness connector. Using DVOM connected to ground, backprobe CKP sensor signal circuit at PCM harness connector. Crank engine. If voltage is 4.2-4.5 volts, go to step 14 . If voltage is not 4.2-4.5 volts, go to next step.
7. If voltage is greater than 4.2-4.5 volts, go to step 12 . If voltage is 4.2-4.5 volts or less, go to step 11 .
8. Turn ignition off. Disconnect PCM harness connector. Check 5-volt reference circuit for open, short to ground, or short to sensor ground circuit. Repair as necessary. After repairs, go to step 17 . If circuits are okay, go to step 10 .
9. Check for open or poor connection at sensor ground circuit of PCM. Repair as necessary. After repairs, go to step 17 . If circuit and connection are okay, go to step 16 .
10. Check for poor connection at 5-volt reference circuit of PCM. Repair as necessary. After repairs, go to step 17 . If connection is okay, go to step 16 .
11. Turn ignition off. Disconnect PCM harness connector. Check CKP sensor signal circuit for open, short to ground, or short to sensor ground circuit. Check for poor connection at CKP sensor. Repair as necessary. After repairs, go to step 17 . If circuit and connections are okay, go to step 15 .
12. Disconnect CKP sensor harness connector. Turn ignition on, with engine off. Using DVOM connected to ground, probe CKP signal circuit at engine harness connector. If voltage is present, go to next step. If voltage is not present, go to step 14 .
13. Repair short to voltage in CKP signal circuit. After repairs, go to step 17 .
14. Check for poor connection at CKP signal circuit of PCM. Repair as necessary. After repairs, go to step 17 . If connection is okay, go to step 16 .
15. Replace CKP sensor. If CKP sensor is replaced, PCM must be programmed with new TDC offset. See appropriate ON-VEHICLE ADJUSTMENTS article. After replacing sensor, go to step 17 .
16. Replace PCM. Program PCM using required equipment. After replacing PCM, go to next step.
17. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, and then enter DTC P0335. Operate vehicle within the conditions for setting this DTC. If scan tool indicates that this test ran and passed, go to next step. If scan tool does not indicate that this test ran and passed, repeat step 2 .
18. Using scan tool, select CAPTURE INFO, REVIEW INFO. If any undiagnosed DTC(s) are displayed, go to applicable DTC test.

When PCM is in back-up fuel, long crank times, fast idle and poor performance conditions will exist. Check for poor connections at crankshaft position sensor and PCM. Intermittents could be caused by poor connections or wiring. When diagnosing intermittents, reproduce conditions under which failure occurs. Operate engine at a higher temperature and near RPM when problem occurs. Since heat and vibration often cause intermittents, operating engine at a higher temperature and near RPM when problem occurs could cause intermittent condition.

DTC P0370: TIMING REFERENCE HIGH RESOLUTION ("C", "G", "K" & "P" SERIES)

Note. For circuit reference, refer to DTC P0182 schematic. (Scheme 5)

Optical sensor provides a high resolution signal to PCM by counting pulses on sensor disk located in injection pump. High resolution is an important input by PCM for fuel control and timing. Test monitors number of high resolution pulses that have been missed (not detected). Number of pulses detected since last pump cam pulse is compared to number of pulses that should have occurred.

DTC will set when a number of high resolution pulses (internal to PCM) are missing per every 8 cam reference pulses.

1. If OBD system check has been performed, go to next step. If OBD system check has not been performed, go to «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel__on-board-diagnostic-obd-system-check) under SELF-DIAGNOSTIC SYSTEM.
2. Turn ignition off. Disconnect optical/fuel temperature sensor harness connector. Turn ignition on, with engine off. Using DVOM, measure voltage between ground and 5-volt reference circuit of optical/fuel temperature sensor harness connector. If voltage is 4.8-5.2 volts, go to next step. If voltage is not 4.8-5.2 volts, go to step 6 .
3. Leave optical/fuel temperature sensor harness connector disconnected. Using test light connected to battery voltage, probe ground circuit at optical/fuel temperature sensor harness connector. If test light illuminates, go to next step. If test light does not illuminate, go to step 7 .
4. Reconnect optical/fuel temperature sensor harness connector. Start and operate engine as close to conditions saved in scan tool FREEZE FRAME/FAILURE RECORDS. Using scan tool, select DTC, SPECIFIC, and then enter DTC P0370. If scan tool displays "Last Test Failed" message, go to next step. If "Last Test Failed" message is not displayed, go to «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel) .
5. Maintain engine speed at point of failure as indicated in step 4) . Using DVOM on Hz scale, backprobe high resolution signal circuit at PCM harness connector. See «HIGH RESOLUTION SIGNAL SPECIFICATIONS»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel) table. If DVOM reading is within 100 Hz of specified value relating to RPM, go to step 16 . If DVOM reading is not within 100 Hz of specified value relating to RPM, go to step 9 .
6. Turn ignition off. Disconnect PCM harness connector. Check 5-volt reference circuit for open, short to ground, or short to sensor ground circuit. Repair as necessary. After repairs, go to step 19 . If circuit is okay, go to step 8 .
7. Check sensor ground circuit for open or poor connection at PCM. Repair as necessary. After repairs, go to step 19 . If circuit and connection are okay, go to step 18 .
8. Check 5-volt reference circuit for poor connection at PCM. Repair as necessary. After repairs, go to step 19 . If connection is okay, go to step 18 .
9. Disconnect optical/fuel temperature sensor harness connector. Turn ignition, with engine off. Using DVOM connected to ground, probe high resolution signal circuit at optical/fuel temperature sensor harness connector. If voltage is 4.8-5.2 volts, go to step 13 . If voltage is not 4.8-5.2 volts, go to next step.
10. If voltage is greater than 4.8-5.2 volts, go to next step. If voltage is 4.8-5.2 volts or less, go to step 12 .
11. Repair short to battery/ignition voltage in high resolution signal circuit. After repairs, go to step 17 .
12. Turn ignition off. Disconnect PCM harness connector. Check high resolution signal circuit for an open, short to ground, or short to sensor ground circuit. Repair as necessary. After repairs, go to step 19 . If circuit is okay, go to step 16 .
13. Using DVOM in mA (milliamp) scale, measure current between high resolution signal circuit and ground circuit of optical/fuel temperature sensor harness connector. If reading is less than 50 mA, go to step 15 . If reading is 50 mA or greater, go to next step.
14. Repair short to reference voltage on high resolution signal circuit. After repairs, go to step 19 .
15. Check high resolution signal circuit for poor connection at injection pump. Repair as necessary. After repairs, go to step 19 . If connection is okay, go to step 17 .
16. Turn ignition off. Disconnect PCM harness connector. Check high resolution signal circuit for poor connection at PCM. Repair as necessary. After repairs, go to step 19 . If connection is okay, go to step 18 .
17. Replace injection pump. If fuel injection pump is replaced, new pump must be timed. See appropriate ON-VEHICLE ADJUSTMENTS article. After replacing injection pump, go to step 19 .
18. Replace PCM. Program PCM using required equipment. After replacing PCM, go to next step.
19. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, and then enter DTC P0370. Operate vehicle within the conditions for setting this DTC. If scan tool indicates that this test ran and passed, go to next step. If scan tool does not indicate that this test ran and passed, repeat step 2 .
20. Using scan tool, select CAPTURE INFO, REVIEW INFO. If any undiagnosed DTC(s) are displayed, go to applicable DTC test.

HIGH RESOLUTION SIGNAL SPECIFICATIONS

Intermittent DTCs P0251, P0370 and P1216 may be caused by air entering fuel system when fuel level is less than 1/8 tank while performing hard acceleration or turning maneuvers. If vehicle runs out of fuel, DTCs P0251, P0370 and P1216 will set. If vehicle has been operating under these conditions, bleed air from fuel system and test drive vehicle. Fast idle and poor performance will exist when PCM is in back-up fuel (less than 1/8 tank). If DTC P0251 is also set, use scan tool on snapshot mode to properly identify fault. DTCs P0335, P1216 and P1217 may also set with DTC P0370. PCM is the least likely cause of failure.

Glow plug system assists in providing heat required to begin combustion during engine starting at cold ambient temperatures. Glow plugs are heated before and during cranking as well as initial engine operation. PCM controls glow plug on-time by monitoring coolant temperatures and glow plug voltage.

DTC will set when PCM has commanded glow plugs on and voltage at glow plugs is less than 4 volts, or PCM has commanded glow plugs off and voltage at glow plugs is greater than 4 volts, or PCM has commanded glow plugs on and a greater than 2 volt difference exists between glow plug voltage and ignition voltage.

1. If OBD system check has been performed, go to next step. If OBD system check has not been performed, go to «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel__on-board-diagnostic-obd-system-check) under SELF-DIAGNOSTIC SYSTEM.
2. Turn ignition on, with engine off. Using scan tool, command glow plugs on. Observe GLOW PLUG display on scan tool. If scan tool displays that glow plug system is enabled, go to next step. If glow plug system is not enabled, go to step 8 .
3. Command glow plugs on again. Observe GLOW PLUG display on scan tool. If scan tool displays battery voltage, go to next step. If battery voltage is not displayed, go to step 6 .
4. If glow plug voltage is present all the time, go to step 16 . If glow plug voltage is not present all the time, go to next step.
5. DTC is intermittent. If no additional DTCs are set, see «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel) . If additional DTCs are set, go to applicable DTC test.
6. Turn ignition off. Disconnect glow plug relay harness connector. Turn ignition on, with engine off. Connect test light between ignition feed circuit and ground circuit of glow plug relay harness connector. If test light illuminates, go to next step. If test light does not illuminate, go to step 10 .
7. Turn ignition on, with engine off. Connect test light between ignition feed circuit and ground circuit of glow plug relay harness connector. If test light illuminates, go to next step. If test light does not illuminate, go to step 11 .
8. Turn ignition on, with engine off. Leave glow plug relay harness connector disconnected. Using DVOM connected to ground, probe control circuit at glow plug relay harness connector. Using scan tool, command glow plugs on. If battery voltage is present, go to next step. If battery voltage is not present, go to step 12 .
9. Reconnect glow plug relay harness connector. Turn ignition on, with engine off. Using test light connected to ground, probe glow plug side of glow plug relay connector. Using scan tool, command glow plugs on. If test light illuminates when glow plugs are commanded on, go to step 14 . If test light does not illuminate when glow plugs are commanded on, go to step 18 .
10. Repair open or short to ground in glow plug relay ignition feed circuit. After repairs, go to step 20 .
11. Repair open or poor connections in glow plug relay ground circuit. After repairs, go to step 20 .
12. Check for open or short to ground in glow plug relay control circuit. Repair as necessary. After repairs, go to step 20 . If circuit is okay, go to next step.
13. Check glow plug relay control circuit for poor connection at PCM. Repair as necessary. After repairs, go to step 20 . If connection is okay, go to step 19 .
14. Check for open or short to ground in glow plug relay signal circuit. Repair as necessary. After repairs, go to step 20 . If circuit is okay, go to next step.
15. Check glow plug relay signal circuit for poor connection at PCM. Repair as necessary. After repairs, go to step 20 . If connection is okay, go to step 19 .
16. Disconnect glow plug relay connector. Turn ignition on, with engine off. Using test light connected to ground, probe glow plug relay control circuit. If test light stays on all the time, go to next step. If test light does not stay on all the time, go to step 18 .
17. Repair short to voltage on glow plug relay control circuit. After repairs, go to step 20 .
18. Replace glow plug relay. After replacing relay, go to step 20 .
19. Replace PCM. Program PCM using required equipment. After replacing PCM, go to next step.
20. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, and then enter DTC P0380. Operate vehicle within the conditions for setting this DTC. If scan tool indicates that this test ran and passed, go to next step. If scan tool does not indicate that this test ran and passed, repeat step 2 .
21. Using scan tool, select CAPTURE INFO, REVIEW INFO. If any undiagnosed DTC(s) are displayed, go to applicable DTC test.

Check for proper operation of glow plugs if glow plug relay is stuck on. When glow plugs are commanded on by scan tool, an internal PCM timer protects glow plugs from damage by cycling them on for 3 seconds, and then off for 12 seconds. Ensure glow plug output feed wire nut and battery feed wire nut are tightened to 44 INCH lbs.( 5 N.m). An intermittent can be caused by poor connections, rubbed through wire insulation or broken wire inside insulation.

DTC P0400: EGR FLOW MALFUNCTION ("C" & "K" SERIES)

Note. For circuit reference, refer to DTC P0101 schematic. (Scheme 2)

PCM operates a Pulse Width Modulated (PWM) solenoid to control EGR valve. This is a normally open solenoid. During normal operation, PCM compares desired MAF signal with the measured MAF signal and makes corrections in the duty cycle accordingly.

DTC will set when the following conditions are present

1. BARO reading is greater than or equal to 75 kPa.
2. DTCs P0405, P0406, P0102 and P0103 are not set.
3. Lowest achieved EGR pressure at full EGR is less than look-up table value (internal to PCM).
4. MAF value is greater than or equal to 0.1484 g/cyl.
5. Conditions are met for 2 seconds.

1. If OBD system check has been performed, go to next step. If OBD system check has not been performed, go to «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel__on-board-diagnostic-obd-system-check) under SELF-DIAGNOSTIC SYSTEM.
2. Install vacuum gauge in place of EGR valve. Start and idle engine. Apply parking brakes and block drive wheels. Place transmission in Drive. Using scan tool, command EGR solenoid to 100 percent duty cycle. Observe vacuum gauge. If vacuum is greater than 15 in. Hg, go to next step. If vacuum is less than 15 in. Hg, to step 5 .
3. Turn ignition off. Install a hand-held vacuum pump to EGR valve. Start and idle engine. Place transmission in Park. Using scan tool, observe cylinder air display while applying 15 in. Hg to EGR valve. If scan tool displays a decrease of greater than or equal to .10 g/cyl., go to next step. If scan tool displays a decrease of less than .10 g/cyl., go to step 7 .
4. DTC is intermittent. If no additional DTCs are set, see «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel) . If any additional DTCs are set, go to applicable DTC test.
5. Check vacuum source at solenoid assembly. If vacuum is 15 in. Hg, go to next step. If vacuum is not 15 in. Hg, go to step 8 .
6. Repair restricted or leaky vacuum hose from solenoid to EGR valve. After repairs, go to step 9 .
7. Replace EGR valve. After replacing valve, go to step 9 .
8. Repair vacuum pump. After repairs, go to next step.
9. After repairs, reset EGR Adaptive Learn Matrix (ALM) cells using scan tool. After resetting EGR ALM cells, go to next step.
10. Using scan tool, select CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, and then enter DTC P0400. Operate vehicle within the conditions for setting this DTC. If scan tool indicates that this test ran and passed, go to next step. If scan tool does not indicate that this test ran and passed, repeat step 2 .
11. Using scan tool, select CAPTURE INFO, REVIEW INFO. If any undiagnosed DTC(s) are displayed, go to applicable DTC test.

The most likely cause of failure is a restricted vacuum line from the EGR valve to the vacuum "T" fitting.

DTC P0402: EGR SYSTEM FLOW EXCESSIVE ("C" & "K" SERIES)

Note. For circuit reference, refer to DTC P0101 schematic. (Scheme 2)

The Mass Airflow (MAF) sensor measures the amount of air entering the engine during a given time. PCM uses MAF sensor information to monitor EGR flow rates. A large quantity of air entering the engine indicates acceleration, high load situation or no EGR flow, while a small quantity of air entering the engine indicates deceleration, idle or full EGR operation. PCM will monitor MAF and EGR pressure at different ranges to determine correct EGR flow rates.

DTC will set when the following conditions are present

1. BARO reading is greater than or equal to 75 kPa.
2. DTCs P0405, P0406, P0102 and P0103 are not set.
3. DTC will set when the 5 ALM cells are less than 0.5.
4. Conditions are met for 2 seconds.

1. If OBD system check has been performed, go to next step. If OBD system check has not been performed, go to «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel__on-board-diagnostic-obd-system-check) under SELF-DIAGNOSTIC SYSTEM.
2. Check if other EGR related DTCs are set. If other DTC(s) are present, diagnose affected DTC(s). If no other DTC(s) are present, go to next step.
3. Check for malfunctioning EGR valve (valve not remaining closed), or restriction in exhaust system (high back pressure). Repair as necessary. After repairs, go to next step.
4. After repairs, reset EGR Adaptive Learn Matrix (ALM) using scan tool. After resetting EGR ALM, go to next step.
5. Using scan tool, select CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, and then enter DTC P0402. Operate vehicle within the conditions for setting this DTC. If scan tool indicates that this test ran and passed, go to next step. If scan tool does not indicate that this test ran and passed, repeat step 2 .
6. Using scan tool, select CAPTURE INFO, REVIEW INFO. If any undiagnosed DTC(s) are displayed, go to applicable DTC test.

The most likely cause of failure is a mechanical malfunction in EGR valve not allowing it to close.

DTC P0404: EGR SYSTEM PERFORMANCE ("C" & "K" SERIES)

Note. For circuit reference, refer to DTC P0101 schematic. (Scheme 2)

PCM operates a normally open solenoid to control EGR valve. PCM energizes solenoid by providing a ground path which then allows vacuum to pass to EGR. During normal operation, PCM compares desired EGR signal with EGR pressure signal and corrects duty cycle accordingly. PCM will make minor adjustments to correct any difference in PCM command and what is sensed at EGR valve by EGR control pressure/BARO sensor.

DTC will set when the following conditions are present

1. DTCs P0405, P0406, P0102 and P0103 are not set.
2. EGR vent solenoid on.
3. Difference between ambient air pressure and EGR pressure is less than 15 kPa.
4. Conditions are met for 2 seconds.

1. If OBD system check has been performed, go to next step. If OBD system check has not been performed, go to «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel__on-board-diagnostic-obd-system-check) under SELF-DIAGNOSTIC SYSTEM.
2. Install vacuum gauge in place of EGR control pressure/BARO sensor. Start and warm engine to normal operating temperature. Operate engine at idle. Apply parking brakes and block drive wheels. Place transmission in Drive. Using scan tool, command EGR solenoid to 100 percent duty cycle. Observe vacuum gauge. If vacuum is greater than 15 in. Hg, go to step 4 . If vacuum is 15 in. Hg or less, go to next step.
3. Repair restriction between EGR control pressure/BARO sensor and vacuum "T" fitting. After repairs, go to step 5 .
4. Replace EGR control pressure/BARO sensor. After replacing sensor, go to next step.
5. After repairs, reset EGR Adaptive Learn Matrix (ALM) cells using scan tool. After resetting EGR ALM cells, go to next step.
6. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, and then enter DTC P0404. Operate vehicle within the conditions for setting this DTC. If scan tool indicates that this test ran and passed, go to next step. If scan tool does not indicate that this test ran and passed, repeat step 2 .
7. Using scan tool, select CAPTURE INFO, REVIEW INFO. If any undiagnosed DTC(s) are displayed, go to applicable DTC test.

A vacuum leak or pinched vacuum line will cause DTC P0404 to set. Check all vacuum lines and components connected to vacuum lines for leaks, sharp bends or deformities. Check vacuum source to EGR solenoid assembly. Check for leak in EGR valve and for proper vacuum line routing.

DTC P0405: EGR SENSOR CIRCUIT LOW VOLTAGE ("C" & "K" SERIES)

Note. For circuit reference, refer to DTC P0101 schematic. (Scheme 2)

EGR control pressure/BARO sensor is used to monitor amount of vacuum in EGR circuit. Sensor senses actual vacuum in EGR vacuum line and sends a signal back to PCM. Signal is used to control EGR duty cycle calculated by PCM. DTC will set when ignition is on and actual EGR is less than or equal to .24 volt (15 kPa) for 2 seconds.

1. If OBD system check has been performed, go to next step. If OBD system check has not been performed, go to «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel__on-board-diagnostic-obd-system-check) under SELF-DIAGNOSTIC SYSTEM.
2. Install scan tool. With engine idling, observe EGR sensor voltage display on scan tool. If scan tool displays EGR sensor voltage at less than or equal to .24 volt, go to next step. If scan tool displays EGR sensor voltage at greater than .24 volt, go to step 5 .
3. Turn ignition off. Disconnect EGR control pressure/BARO sensor harness connector. Connect a jumper wire between 5-volt reference circuit and signal circuit of EGR control pressure/BARO sensor harness connector. Turn ignition on, with engine off. If scan tool displays EGR sensor voltage at greater than 4 volts, go to step 6 . If scan tool displays EGR sensor voltage 4 volts or less, go to next step.
4. Turn ignition off. Remove jumper wire. Using test light connected to battery voltage, probe signal circuit at EGR control pressure/BARO sensor harness connector. Turn ignition on, with engine off. If scan tool displays EGR sensor voltage at greater than 4 volts, go to step 9 . If scan tool displays EGR sensor voltage at 4 volts or less, go to step 7 .
5. DTC is intermittent. If no additional DTCs are set, see «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel) . If any additional DTCs are set, go to applicable DTC test.
6. Check for poor connection at EGR control pressure/BARO sensor. Repair as necessary. After repairs, go to step 12 . If connection is okay, go to step 11 .
7. Check for open in EGR control pressure/BARO sensor signal circuit. Repair as necessary. After repairs, go to step 12 . If circuit is okay, go to next step.
8. Check for short to ground in EGR control pressure/BARO sensor signal circuit. Repair as necessary. After repairs, go to step 12 . If circuit is okay, go to step 13 .
9. Check for open in EGR control pressure/BARO sensor 5-volt reference circuit. Repair as necessary. After repairs, go to step 12 . If circuit is okay, go to next step.
10. Check for short to ground in EGR pressure control/BARO sensor 5-volt reference circuit. Repair circuit as necessary. After repairs, go to step 12 . If circuit is okay, go to step 13 .
11. Replace EGR control pressure/BARO sensor. After replacing sensor, go to step 14 .
12. Repair circuit as necessary. After repairs, go to step 14 .
13. Replace PCM. Program PCM using required equipment. After replacing PCM, go to next step.
14. After repairs, reset EGR Adaptive Learn Matrix (ALM) cells using scan tool. After resetting EGR ALM cells, go to next step.
15. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, and then enter DTC P0405. Operate vehicle within the conditions for setting this DTC. If scan tool indicates that this test ran and passed, go to next step. If scan tool does not indicate that this test ran and passed, repeat step 2 .
16. Using scan tool, select CAPTURE INFO, REVIEW INFO. If any undiagnosed DTC(s) are displayed, go to applicable DTC test.

With ignition on and engine off, EGR pressure is equal to atmospheric pressure with signal voltage being high.

DTC P0406: EGR SENSOR CIRCUIT HIGH VOLTAGE ("C" & "K" SERIES)

Note. For circuit reference, refer to DTC P0101 schematic. (Scheme 2)

EGR control pressure/BARO sensor is used to monitor amount of vacuum in EGR circuit. Sensor senses actual vacuum in EGR vacuum line and sends a signal back to PCM. Signal is used to control EGR duty cycle calculated by PCM. DTC will set when ignition is on and EGR control pressure signal is greater than 3.96 volts (85 kPa) for 2 seconds.

1. If OBD system check has been performed, go to next step. If OBD system check has not been performed, go to «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel__on-board-diagnostic-obd-system-check) under SELF-DIAGNOSTIC SYSTEM.
2. Check if DTC P1653 is also set. If DTC P1653 is set, go to DTC P1653 test. If DTC P1653 is not set, go to next step.
3. Install scan tool. With engine idling, observe EGR control pressure/BARO sensor voltage display on scan tool. If scan tool displays EGR control pressure/BARO sensor voltage at greater than 4 volts, go to next step. If scan tool displays EGR control pressure/BARO sensor voltage at 4 volts or less, go to step 5 .
4. Turn ignition off. Disconnect EGR control pressure/BARO sensor harness connector. Turn ignition on. If scan tool displays actual EGR voltage at less than one volt, go to step 6 . If scan tool displays actual EGR voltage at one volt or greater, go to step 10 .
5. DTC is intermittent. If no additional DTCs are set, see «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel) . If any additional DTCs are set, go to applicable DTC test.
6. Turn ignition on, with engine off. With DVOM connected to ground, probe 5-volt reference circuit at EGR control pressure/BARO sensor harness connector. If voltage is greater than 5.2 volts, go to step 11 . If voltage is 5.2 volts or less, go to next step.
7. Using test light connected to battery voltage, probe ground circuit of EGR control pressure/BARO sensor harness connector. If test light illuminates, go to next step. If test light does not illuminate, go to step 12 .
8. Check for restriction in EGR vacuum source. If a problem is found, go to step 13 . If no problems are found, go to next step.
9. Replace EGR control pressure/BARO sensor. After replacing sensor, go to step 15 .
10. Check for short to voltage in EGR control pressure/BARO sensor signal circuit. Repair as necessary. After repairs, go to step 13 . If circuit is okay, go to step 14 .
11. Check for short to voltage in EGR control pressure/BARO sensor 5-volt reference circuit. Repair as necessary. After repairs, go to step 15 . If circuit is okay, go to step 14 .
12. Repair open in sensor ground circuit. After repairs, go to step 15 .
13. Repair as necessary. After repairs, go to step 15 .
14. Replace PCM. Program PCM using required equipment. After replacing PCM, go to next step.
15. After repairs, reset EGR Adaptive Learn Matrix (ALM) using scan tool. After resetting EGR ALM, go to next step.
16. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, and then enter DTC P0406. Operate vehicle within the conditions for setting this DTC. If scan tool indicates that this test ran and passed, go to next step. If scan tool does not indicate that this test ran and passed, repeat step 2 .
17. Using scan tool, select CAPTURE INFO, REVIEW INFO. If any undiagnosed DTC(s) are displayed, go to applicable DTC test.

With ignition on and engine off, EGR pressure is equal to atmospheric pressure with signal voltage being high. Information is used by PCM as an indication of vehicle altitude. If DTC is intermittent, see appropriate TROUBLE SHOOTING - NO CODES article.

Vehicle speed sensor circuit consists of a magnetic, induction-type sensor, vehicle speed sensor buffer/module and wiring. Gear teeth pressed on output shaft induce an alternating current in sensor. Signal is transmitted to buffer. Buffer compensates for various axle ratios and converts signal into a square wave for use by speedometer, cruise control, anti-lock brakes and PCM. Buffer sends 2 different signals to PCM.

DTC will set when the following conditions are present

1. Vehicle speed is greater than 20 MPH.
2. Four wheel low is not selected.
3. VSS buffer calculated speed is greater than transmission calculated speed by 20 MPH.
4. Conditions are met for 2 seconds.

1. If OBD system check has been performed, go to next step. If OBD system check has not been performed, go to «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel__on-board-diagnostic-obd-system-check) under SELF-DIAGNOSTIC SYSTEM.
2. Install scan tool. Raise drive wheels. With engine running, place transmission in any drive range. With drive wheels rotating, if vehicle speed increases when drive wheel speed increases, go to step 7 . If vehicle speed does not increase when drive wheel speed increases, go to next step.
3. Place transmission in Park. Using test light connected to ground, backprobe ignition feed circuit at VSS buffer/module harness connector. If test light illuminates, go to next step. If test light does not illuminate, go to step 8 .
4. Using test light connected to ground, backprobe ignition feed circuit at VSS buffer/module harness connector. If test light illuminates, go to next step. If test light does not illuminate, go to step 9 .
5. Using DVOM on AC scale, backprobe both VSS input circuits at VSS buffer/module harness connector to each other. Place transmission in any drive range with drive wheels rotating. If voltage increases as drive wheel speed increases, go to next step. If voltage does not increase as drive wheel speed increases, go to step 10 .
6. If scan tool displays a trans output speed (MPH) increase with drive wheel speed increase, go to step 13 . If trans output speed (MPH) reading does not change, go to step 12 .
7. DTC is intermittent. If no additional DTCs are set, see «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel) . If any additional DTCs are set, go to applicable DTC test.
8. Repair open in VSS ignition feed circuit. After repairs, go to step 18 .
9. Repair open in VSS ground circuit. After repairs, go to step 18 .
10. Check for open or short to ground in VSS input circuit. After repairs, go to step 18 . If circuit is okay, go to next step.
11. Check for poor connection at VSS. Repair as necessary. After repairs, go to step 18 . If connection is okay, go to step 15 .
12. Using DVOM connected to ground, backprobe VSS output circuit at VSS buffer/module harness connector. Place transmission in any drive range with drive wheels rotating. If voltage is present, go to next step. If voltage is not present, go to step 16 .
13. Check for open or short to ground in VSS output circuit. Repair as necessary. After repairs, go to step 18 . If circuit is okay, go to next step.
14. Check VSS output circuit for poor connection at PCM. Repair as necessary. After repairs, go to step 18 . If connection is okay, go to step 17 .
15. Replace VSS sensor. After replacing sensor, go to step 18 .
16. Replace VSS buffer/module. After replacing module, go to step 18 .
17. Replace PCM. Program PCM using required equipment. After replacing PCM, go to next step.
18. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, and then enter DTC P0501. Operate vehicle within the conditions for setting this DTC. If scan tool indicates that this test ran and passed, go to next step. If scan tool does not indicate that this test ran and passed, repeat step 2 .
19. Using scan tool, select CAPTURE INFO, REVIEW INFO. If any undiagnosed DTC(s) are displayed, go to applicable DTC test.

Check connections at VSS buffer/module and PCM. If DTC P0722 or DTC P0723 is also set, see appropriate ELECTRONIC CONTROLS article in AUTOMATIC TRANSMISSIONS.

Scheme 14

Cruise resume/accel switch is an input to fuel control portion of PCM. Inputs allow PCM to control and hold requested speed. Cruise resume/accel switch sends ignition voltage to PCM when switch is on.

DTC will set when cruise switch is off and ignition voltage is present on resume switch signal circuit, or cruise switch is on and resume switch is on for longer than 25.5 seconds.

1. If OBD system check has been performed, go to next step. If OBD system check has not been performed, go to «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel__on-board-diagnostic-obd-system-check) under SELF-DIAGNOSTIC SYSTEM.
2. Install scan tool. Turn ignition on, with engine off. Turn cruise switch off. If scan tool displays resume switch is on, go to next step. If scan tool does not display that resume switch is on, go to step 4 .
3. Turn ignition off. Disconnect PCM harness connector containing resume switch signal circuit. Turn ignition on, with engine off. Using test light connected to ground, probe resume switch signal circuit at PCM harness connector. If test light illuminates, go to step 5 . If test light does not illuminate, go to step 6 .
4. DTC is intermittent. If no additional DTCs are set, see «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel) . If any additional DTCs are set, go to applicable DTC test.
5. Check for short to voltage in resume switch signal circuit or resume switch stuck in ON position. Repair as necessary. After repairs, go to step 8 .
6. Replace PCM. Program PCM using required equipment. After replacing PCM, go to next step.
7. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, and then enter DTC P0567. Operate vehicle within the conditions for setting this DTC. If scan tool indicates that this test ran and passed, go to next step. If scan tool does not indicate that this test ran and passed, repeat step 2 .
8. Using scan tool, select CAPTURE INFO, REVIEW INFO. If any undiagnosed DTC(s) are displayed, go to applicable DTC test.

Check for resume/accel switch stuck in engage position or signal circuit shorted to voltage.

DTC P0568: CRUISE SET CIRCUIT ("C", "G", "K" & "P" SERIES)

Note. For circuit reference, refer to DTC P0567 schematic. (Scheme 14)

Cruise set/coast switch is an input to fuel control portion of PCM. Inputs allow PCM to control and hold requested speed. Cruise set/coast switch sends ignition voltage to PCM when set/coast switch is on.

DTC will set when cruise switch is off and ignition voltage is present on set switch signal circuit, or cruise switch is on and set switch is on for more than 25.5 seconds.

1. If OBD system check has been performed, go to next step. If OBD system check has not been performed, go to «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel__on-board-diagnostic-obd-system-check) under SELF-DIAGNOSTIC SYSTEM.
2. Install scan tool. Turn ignition on, with engine off. Turn cruise switch off. If scan tool displays set switch is on, go to next step. If scan tool does not display that set switch is on, go to step 4 .
3. Turn ignition off. Disconnect PCM harness connector containing set switch signal circuit. Turn ignition on, with engine off. Using test light connected to ground, probe set switch signal circuit at PCM harness connector. If test light illuminates, go to step 5 . If test light does not illuminate, go to step 6 .
4. DTC is intermittent. If no additional DTCs are set, see «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel) . If any additional DTCs are set, go to applicable DTC test.
5. Check for short to voltage in set switch signal circuit or set switch stuck in ON position. Repair as necessary. After repairs, go to step 8 .
6. Replace PCM. Program PCM using required equipment. After replacing PCM, go to next step.
7. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, and then enter DTC P0568. Operate vehicle within the conditions for setting this DTC. If scan tool indicates that this test ran and passed, go to next step. If scan tool does not indicate that this test ran and passed, repeat step 2 .
8. Using scan tool, select CAPTURE INFO, REVIEW INFO. If any undiagnosed DTC(s) are displayed, go to applicable DTC test.

Check for set/coast switch stuck in engage position or signal circuit shorted to voltage.

DTC P0571: CRUISE BRAKE SWITCH CIRCUIT ("C", "G", "K" & "P" SERIES)

Note. For circuit reference, refer to DTC P0567 schematic. (Scheme 14)

TCC normally closed brake switch supplies battery voltage signal on TCC/brake switch signal circuit to PCM. Circuit is opened when brakes are applied. Brakelight/cruise control normally open brake switch supplies battery voltage signal on cruise control brake switch signal circuit to PCM when brakes are applied.

DTC will set when switches disagree for 10 consecutive minutes, or TCC and cruise control brake switches are not toggling open and closed during 6 brake applications on same ignition cycle.

1. If OBD system check has been performed, go to next step. If OBD system check has not been performed, go to «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel__on-board-diagnostic-obd-system-check) under SELF-DIAGNOSTIC SYSTEM.
2. Install scan tool. Turn ignition on, with engine off. Apply brakes. If scan tool displays cruise brake switch closed, and then open when brakes are applied, go to next step. If scan tool does not display cruise brake switch closed, and then open when brakes are applied, go to step 7 .
3. Apply brakes again. If scan tool displays cruise brake switch open, and then closed when brakes are applied, go to step 9 . If scan tool does not display cruise brake switch open, and then closed when brakes are applied, go to next step.
4. Turn ignition off. Disconnect brakelight switch harness connector. Turn ignition on, with engine off. Using test light connected to ground, probe normally open feed circuit (terminal "B") at brakelight switch harness connector. If test light illuminates, go to next step. If test light does not illuminate, go to step 10 .
5. Leave brakelight switch harness connector disconnected. Turn ignition on, with engine off. Turn headlights on. Using test light connected to ground, probe normally open signal circuit (terminal "A") at brakelight switch harness connector. If test light illuminates, go to step 11 . If test light does not illuminate, go to next step.
6. Leave brakelight switch harness connector disconnected. Connect a jumper wire between normally open feed circuit (terminal "A") and normally open signal circuit (terminal "B") of brakelight switch harness connector. If scan tool displays cruise brake switch closed, go to step 17 . If scan tool does not display cruise brake switch closed, go to step 12 .
7. Leave brakelight switch harness connector disconnected. Turn ignition on, with engine off. Using test light connected to ground, probe normally closed feed circuit (terminal "F") at brakelight switch harness connector. If test light illuminates, go to next step. If test light does not illuminate, go to step 14 .
8. Leave brakelight switch harness connector disconnected. Connect a jumper wire between normally closed feed circuit (terminal "F") and normally closed signal circuit (terminal "E") of brakelight switch harness connector. If scan tool displays cruise brake switch closed, go to step 17 . If scan tool does not display cruise brake switch closed, go to step 15 .
9. DTC is intermittent. If no additional DTCs are set, see «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel) . If any additional DTCs are set, go to applicable DTC test.
10. Check for open or short to ground in normally open feed circuit. Repair as necessary. After repairs, go to step 19 .
11. Check for short to voltage in normally open signal circuit. Repair as necessary. After repairs, go to step 19 . If circuit is okay, go to step 18 .
12. Check for open or short to ground in normally open signal circuit. Repair as necessary. After repairs, go to step 19 . If circuit is okay, go to next step.
13. Check normally open signal circuit for poor connection at PCM. Repair as necessary. After repairs, go to step 19 . If connection is okay, go to step 18 .
14. Check for open or short to ground in normally closed feed circuit. Repair as necessary. After repairs, go to step 19 .
15. Check for open or short to ground in normally closed signal circuit. Repair as necessary. After repairs, go to step 19 . If circuit is okay, go to next step.
16. Check normally closed signal circuit for poor connection at PCM. Repair as necessary. After repairs, go to step 19 . If connection is okay, go to step 18 .
17. Replace brakelight switch. After replacing switch, go to step 19 .
18. Replace PCM. Program PCM using required equipment. After replacing PCM, go to next step.
19. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, and then enter DTC P0571. Operate vehicle within the conditions for setting this DTC. If scan tool indicates that this test ran and passed, go to next step. If scan tool does not indicate that this test ran and passed, repeat step 2 .
20. Using scan tool, select CAPTURE INFO, REVIEW INFO. If any undiagnosed DTC(s) are displayed, go to applicable DTC test.

See appropriate TROUBLE SHOOTING - NO CODES article. Check customer driving habits and/or unusual traffic conditions (i.e., stop and go, expressway traffic).

1. If OBD system check has been performed, go to next step. If OBD system check has not been performed, go to «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel__on-board-diagnostic-obd-system-check) under SELF-DIAGNOSTIC SYSTEM.
2. Replace PCM. Program PCM using required equipment. After replacing PCM, go to next step.
3. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, and then enter DTC P0601. Operate vehicle within the conditions for setting this DTC. If scan tool indicates that this test ran and passed, go to next step. If scan tool does not indicate that this test ran and passed, repeat step 2 .
4. Using scan tool, select CAPTURE INFO, REVIEW INFO. If any undiagnosed DTC(s) are displayed, go to applicable DTC test.

1. If OBD system check has been performed, go to next step. If OBD system check has not been performed, go to «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel__on-board-diagnostic-obd-system-check) under SELF-DIAGNOSTIC SYSTEM.
2. Replace PCM. Program PCM using required equipment. After replacing PCM, go to next step.
3. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, and then enter DTC P0602. Operate vehicle within the conditions for setting this DTC. If scan tool indicates that this test ran and passed, go to next step. If scan tool does not indicate that this test ran and passed, repeat step 2 .
4. Using scan tool, select CAPTURE INFO, REVIEW INFO. If any undiagnosed DTC(s) are displayed, go to applicable DTC test.

1. If OBD system check has been performed, go to next step. If OBD system check has not been performed, go to «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel__on-board-diagnostic-obd-system-check) under SELF-DIAGNOSTIC SYSTEM.
2. Replace PCM. Program PCM using required equipment. After replacing PCM, go to next step.
3. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, and then enter DTC P0604. Operate vehicle within the conditions for setting this DTC. If scan tool indicates that this test ran and passed, go to next step. If scan tool does not indicate that this test ran and passed, repeat step 2 .
4. Using scan tool, select CAPTURE INFO, REVIEW INFO. If any undiagnosed DTC(s) are displayed, go to applicable DTC test.

1. If OBD system check has been performed, go to next step. If OBD system check has not been performed, go to «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel__on-board-diagnostic-obd-system-check) under SELF-DIAGNOSTIC SYSTEM.
2. Check if any other DTC(s) are set. If other DTC(s) are set, diagnose using applicable DTC. If no other DTC(s) are set, go to next step.
3. Replace PCM. Program PCM using required equipment. After replacing PCM, go to next step.
4. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, and then enter DTC P0606. Operate vehicle within the conditions for setting this DTC. If scan tool indicates that this test ran and passed, go to next step. If scan tool does not indicate that this test ran and passed, repeat step 2 .
5. Using scan tool, select CAPTURE INFO, REVIEW INFO. If any undiagnosed DTC(s) are displayed, go to applicable DTC test.

DTC P1125: ACCELERATOR PEDAL POSITION (APP) SYSTEM ("C", "G", "K" & "P" SERIES)

Note. For circuit reference, refer to DTC P0121 schematic. (Scheme 4)

Accelerator pedal position (APP) module provides a voltage signal that changes relative to accelerator position. Three sensors are located within APP module and are scaled differently.

DTC will set when ignition is on, and PCM has recognized an intermittent APP fault and no other current APP faults are stored.

1. If OBD system check has been performed, go to next step. If OBD system check has not been performed, go to «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel__on-board-diagnostic-obd-system-check) under SELF-DIAGNOSTIC SYSTEM.
2. Turn ignition off. Disconnect APP sensor harness connector. Turn ignition on, with engine off. Using DVOM connected to ground, measure voltage on all 5-volt reference circuits at APP sensor harness connector. If voltage is less than 4.8 volts, go to step 4 . If voltage is 4.8 volts or greater, go to next step.
3. DTC is intermittent. If no additional DTCs are set, see «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel) . If any additional DTCs are set, go to applicable DTC test.
4. Turn ignition off. Disconnect PCM harness connector. Check for short to ground in 5-volt reference circuit. Repair as necessary. After repairs, go to step 6 . If circuit is okay, go to next step.
5. Replace PCM. Program PCM using required equipment. After replacing PCM, go to next step.
6. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, and then enter DTC P1125. Operate vehicle within the conditions for setting this DTC. If scan tool indicates that this test ran and passed, go to next step. If scan tool does not indicate that this test ran and passed, repeat step 2 .
7. Using scan tool, select CAPTURE INFO, REVIEW INFO. If any undiagnosed DTC(s) are displayed, go to applicable DTC test.

There are no driveability issues associated with APP module unless a DTC is set. Most likely causes of DTC P1125 are poor connections or the sensor itself. Least likely cause is a PCM problem. DTC P1125 will set along with multiple APP DTCs. Diagnose all other APP DTCs first.

DTC P1191: INTAKE AIR DUCT LEAK ("C" & "K" SERIES)

Note. For circuit reference, refer to DTC P0101 schematic. (Scheme 2)

The Mass Airflow (MAF) sensor measures the amount of air entering the engine during a given time. PCM uses MAF sensor information to monitor EGR flow rates. A large quantity of air entering the engine indicates acceleration, high load situation or no EGR flow, while a small quantity of air entering the engine indicates deceleration, idle or full EGR operation. PCM uses MAF sensor and EGR control pressure/BARO sensor to determine an intake leak.

DTC will set when the following conditions are present

1. BARO reading at greater than or equal to 75 kPa.
2. DTCs P0405, P0406, P0102 and P0103 are not set.
3. All EGR tests have been completed (internal to PCM).
4. Intake leak greater than calibrated value (internal to PCM).
5. Conditions are met for 2 seconds.

1. If OBD system check has been performed, go to next step. If OBD system check has not been performed, go to «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel__on-board-diagnostic-obd-system-check) under SELF-DIAGNOSTIC SYSTEM.
2. Check if any other EGR DTC(s) are set. If other EGR DTC(s) are set, diagnose using applicable DTC. If no other EGR DTC(s) are set, go to next step.
3. Check for air inlet duct leaks (after MAF sensor), missing EGR tower gasket or intake manifold gasket leak. Repair as necessary. After repairs, go to next step.
4. After repairs, reset EGR Adaptive Learn Matrix (ALM) cells using scan tool. After resetting EGR ALM cells, go to next step.
5. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, and then enter DTC P1191. Operate vehicle within the conditions for setting this DTC. If scan tool indicates that this test ran and passed, go to next step. If scan tool does not indicate that this test ran and passed, repeat step 2 .
6. Using scan tool, select CAPTURE INFO, REVIEW INFO. If any undiagnosed DTC(s) are displayed, go to applicable DTC test.

Failure is most likely caused by a leaky intake duct after the MAF sensor.

PCM has the ability to determine the amount of offset needed to bring the engine to TDC. PCM uses this to determine proper injection time. DTC will set when engine is operating and TDC offset is greater than 2.46 degrees, or TDC offset is less than -2.46 degrees.

1. If OBD system check has been performed, go to next step. If OBD system check has not been performed, go to «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel__on-board-diagnostic-obd-system-check) under SELF-DIAGNOSTIC SYSTEM.
2. Check if any other DTC(s) are set. If other DTC(s) are set, diagnose using applicable DTC. If no other DTC(s) are set, go to next step.
3. Clear all DTCs and reset injection timing until TDC offset is -0.25 to -0.75. See appropriate ON-VEHICLE ADJUSTMENTS article. If timing is as specified, go to step 6 . If timing is not as specified, go to next step.
4. Check crankshaft position sensor for proper installation, or loose or broken sensor mounting tab. Repair as necessary. After repairs, go to step 6 . If no problems are found, go to next step.
5. Replace fuel injection pump. If fuel injection pump is replaced, new pump must be timed. See appropriate ON-VEHICLE ADJUSTMENTS article. After replacing injection pump, go to next step.
6. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, and then enter DTC P1214. Operate vehicle within the conditions for setting this DTC. If scan tool indicates that this test ran and passed, go to next step. If scan tool does not indicate that this test ran and passed, repeat step 2 .
7. Using scan tool, select CAPTURE INFO, REVIEW INFO. If any undiagnosed DTC(s) are displayed, go to applicable DTC test.

PCM will only run diagnostic test when a time set procedure has been activated. This DTC is highly unlikely to be set.

DTC P1216: FUEL SOLENOID RESPONSE TIME TOO SHORT ("C", "G", "K" & "P" SERIES)

Note. For circuit reference, refer to DTC P0215 schematics. (Scheme 6), (Scheme 7) or (Scheme 8).

Injection pump delivers fuel to individual cylinders by opening and closing a solenoid control fuel valve. PCM monitors amount of time fuel solenoid valve physically takes to close after being commanded to close. Fault will occur if closure time is out of range. Response time is measured in milliseconds.

DTC will set when the following conditions are present

1. Battery voltage is greater than 11 volts but less than 15 volts.
2. Engine coolant temperature is greater than 34°F (-1°C).
3. Engine speed is greater than 506 RPM.
4. Requested fuel rate is greater than 0.0 mm.
5. Injection pump closure time is less than .75 milliseconds.

1. If OBD system check has been performed, go to next step. If OBD system check has not been performed, go to «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel__on-board-diagnostic-obd-system-check) under SELF-DIAGNOSTIC SYSTEM.
2. Check if DTC P0219 is set. If DTC P0219 is set, go to DTC P0219 test. If DTC P0219 is not set, go to next step.
3. Check if engine starts. If engine starts, go to next step. If engine does not start, go to step 7 .
4. Start and warm engine to normal operating temperature. Using scan tool, observe injection pump closure time. If scan tool displays injection pump closure time less than or equal to .75 millisecond, go to next step. If scan tool displays injection pump closure time greater than .75 millisecond, go to step 6 .
5. With engine running, observe injection pump closure time on scan tool. If scan tool displays injection pump closure time less than or equal to 0.1 millisecond, go to step 8 . If scan tool displays injection pump closure time greater than 0.1 millisecond, go to step 10 .
6. DTC is intermittent. If no additional DTCs are set, see «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel) . If any additional DTCs are set, go to applicable DTC test.
7. Check for open in closure ground circuit. Repair as necessary. After repairs, go to step 12 . If circuit is okay, go to step 10 .
8. Check for open or short to ground in closure signal circuit. Check for poor connection at driver. Repair as necessary. After repairs, go to step 12 . If circuit and connection are okay, go to next step.
9. Check closure signal circuit for poor connection at PCM. Repair as necessary. After repairs, go to step 12 . If connection is okay, go to step 11 .
10. Replace fuel injection pump. If fuel injection pump is replaced, new pump must be timed. See appropriate ON-VEHICLE ADJUSTMENTS article. After replacing fuel injection pump, go to step 12 .
11. Replace PCM. Program PCM using required equipment. After replacing PCM, go to next step.
12. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, and then enter DTC P1216. Operate vehicle within the conditions for setting this DTC. If scan tool indicates that this test ran and passed, go to next step. If scan tool does not indicate that this test ran and passed, repeat step 2 .
13. Using scan tool, select CAPTURE INFO, REVIEW INFO. If any undiagnosed DTC(s) are displayed, go to applicable DTC test.

Intermittent DTCs P0251, P0370 and P1216 may be caused by air entering fuel system when fuel level is less than 1/8 tank while performing hard acceleration or turning maneuvers. If vehicle runs out of fuel, DTCs P0251, P0370 and P1216 will set. If vehicle has been operating under these conditions, bleed air from fuel system and test drive vehicle. If any other DTCs are set with DTC P1216, diagnose other DTCs first. If vehicle is running close to DTC setting closure time, vehicle should be checked during cold start-ups and during hot conditions.

DTC P1217: FUEL SOLENOID RESPONSE TIME TOO LONG ("C", "G", "K" & "P" SERIES)

Note. For circuit reference, refer to DTC P0215 schematics. (Scheme 6), (Scheme 7) or (Scheme 8).

Injection pump delivers fuel to individual cylinders by opening and closing a solenoid control fuel valve. PCM monitors amount of time fuel solenoid valve physically takes to close after being commanded to close. Fault will occur if closure time is out of range. Response time is measured in milliseconds.

DTC will set when the following conditions are present

1. Battery voltage is greater than 10 volts but less than 16 volts.
2. Engine coolant temperature is greater than 34°F (-1°C).
3. Engine speed is greater than 506 RPM.
4. Requested fuel rate is greater than 0.0 mm.
5. Injection pump closure time is greater than 2.5 milliseconds.

1. If OBD system check has been performed, go to next step. If OBD system check has not been performed, go to «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel__on-board-diagnostic-obd-system-check) under SELF-DIAGNOSTIC SYSTEM.
2. Check if DTC P0370 is set. If DTC P0370 is set, go to DTC P0370 test. If DTC P0370 is not set, go to next step.
3. Start and warm engine to normal operating temperature. Using scan tool, observe injection pump closure time. If scan tool displays injection pump closure time is greater than 2.4 milliseconds, go to next step. If scan tool displays injection pump closure time is 2.4 milliseconds or less, go to step 5 .
4. Turn on all accessories. Start and idle engine. Ensure all post glow plug cycles are complete. Using DVOM connected to ground, measure voltage at FUEL SOL fuse (fuel solenoid driver ignition feed circuit) in underhood relay center. If voltage is 12-15 volts, go to step 7 . If voltage is not 12-15 volts, go to step 6 .
5. DTC is intermittent. If no additional DTCs are set, see «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel) . If any additional DTCs are set, go to applicable DTC test.
6. Check fuel solenoid driver ignition feed circuit for poor connections or aftermarket add-ons. Repair as necessary. After repairs, go to step 8 .
7. Replace fuel injection pump. If fuel injection pump is replaced, new pump must be timed. See appropriate ON-VEHICLE ADJUSTMENTS article. After replacing injection pump, go to next step.
8. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, and then enter DTC P1217. Operate vehicle within the conditions for setting this DTC. If scan tool indicates that this test ran and passed, go to next step. If scan tool does not indicate that this test ran and passed, repeat step 2 .
9. Using scan tool, select CAPTURE INFO, REVIEW INFO. If any undiagnosed DTC(s) are displayed, go to applicable DTC test.

A weak (mechanical failure) fuel solenoid will cause DTC P1217 to set. If any other DTCs are set with DTC P1217, diagnose other DTCs first. If vehicle is running close to DTC setting closure time, vehicle should be checked during cold start-ups and during hot conditions.

DTC P1218: INJECTION PUMP CALIBRATION CIRCUIT ("C", "G", "K" & "P" SERIES)

Note. For circuit reference, refer to DTC P0215 schematics. (Scheme 6), (Scheme 7) or (Scheme 8).

PCM uses a calibrated resistor mounted internally in injection pump to determine fuel rates. Resistor value is stored in PCM memory. If PCM memory is disturbed or PCM is replaced, PCM will relearn resistor value on next ignition cycle.

DTC will set when ignition is on, and PCM currently does not have a valid resistor value and PCM is unable to read resistor value.

1. If OBD system check has been performed, go to next step. If OBD system check has not been performed, go to «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel__on-board-diagnostic-obd-system-check) under SELF-DIAGNOSTIC SYSTEM.
2. Check if any other DTC(s) are set. If other DTC(s) are set, diagnose using applicable DTC. If no other DTC(s) are set, go to next step.
3. Check connection at fuel solenoid driver. Clear DTCs and cycle ignition. Start and idle engine. Using scan tool, activate time set procedure (diagnostic will only run when time set procedure is performed). Exit time set procedure. Select DTC, SPECIFIC, and then enter DTC P1218. If scan tool indicates test ran and passed, go to step 5 . If scan tool does not indicate test ran and passed, go to next step.
4. Replace fuel injection pump. If fuel injection pump is replaced, new pump must be timed. See appropriate ON-VEHICLE ADJUSTMENTS article. After replacing fuel injection pump, go to step 6 .
5. DTC is intermittent. If no additional DTCs are set, see «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel) . If any additional DTCs are set, go to applicable DTC test.
6. Check if any other DTC(s) are set. If other DTC(s) are set, diagnose using applicable DTC. If no other DTC(s) are set, system is okay.

Check connection at fuel injector driver. Clear DTCs and cycle engine. If DTC clears, treat condition as an intermittent.

DTC P1406: EGR VALVE POSITION ("C" & "K" SERIES)

Note. For circuit reference, refer to DTC P0101 schematic. (Scheme 2)

The Mass Airflow (MAF) sensor measures the amount of air entering the engine during a given time. PCM uses MAF sensor information to monitor EGR flow rates. A large quantity of air entering the engine indicates acceleration, high load situation or no EGR flow, while a small quantity of air entering the engine indicates deceleration, idle or full EGR operation. PCM will monitor MAF and EGR pressures at different ranges to determine correct EGR flow rates.

DTC will also set when the following conditions are present

1. DTCs P0102, P0103, P0405 or P0406 not set.
2. All MAF and EGR control pressure tests are complete (internal to PCM).
3. IAT is greater than or equal to 68°F (20°C), and less than or equal to 203°F (95°C).
4. ALM cells not changed for more than 2 seconds.
5. Fuel rate is 10-25 mm.
6. Engine speed is 1500-2100 RPM.
7. Engine speed stable.
8. Listed conditions are met for more than 3 seconds.

1. If OBD system check has been performed, go to next step. If OBD system check has not been performed, go to «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel__on-board-diagnostic-obd-system-check) under SELF-DIAGNOSTIC SYSTEM.
2. Check if any other EGR DTC(s) are set. If other EGR DTC(s) are set, diagnose using applicable DTC. If no other EGR DTC(s) are set, go to next step.
3. Check for restriction in vacuum line from EGR valve to vacuum "T" fitting. Check for faulty EGR valve. Repair or replace as necessary. After repairs, go to next step.
4. After repairs, reset EGR Adaptive Learn Matrix (ALM) cells using scan tool. After resetting EGR ALM cells, go to next step.
5. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, and then enter DTC P1406. Operate vehicle within the conditions for setting this DTC. If scan tool indicates that this test ran and passed, go to next step. If scan tool does not indicate that this test ran and passed, repeat step 2 .
6. Using scan tool, select CAPTURE INFO, REVIEW INFO. If any undiagnosed DTC(s) are displayed, go to applicable DTC test.

A vacuum leak will cause DTC P1406 to set. Check all vacuum lines and components connected to hoses for leaks or deformities. Check vacuum source to EGR solenoid assembly or EGR valve. Check for proper vacuum hose routing.

DTC P1409: EGR VACUUM SYSTEM LEAK ("C" & "K" SERIES)

Note. For circuit reference, refer to DTC P0101 schematic. (Scheme 2)

The Mass Airflow (MAF) sensor measures the amount of air entering the engine during a given time. PCM uses MAF sensor information to monitor EGR flow rates. A large quantity of air entering the engine indicates acceleration, high load situation or no EGR flow, while a small quantity of air entering the engine indicates deceleration, idle or full EGR operation. PCM will monitor MAF and EGR pressures at different ranges to determine correct EGR flow rates.

DTC will also set when the following conditions are present

1. DTCs P0102, P0103, P0405 or P0406 not set.
2. Engine at operating temperature.
3. IAT is greater than or equal to 68°F (20°C), and less than or equal to 203°F (95°C).

1. If OBD system check has been performed, go to next step. If OBD system check has not been performed, go to «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel__on-board-diagnostic-obd-system-check) under SELF-DIAGNOSTIC SYSTEM.
2. Install vacuum gauge in place of EGR valve. Start and idle engine. Apply parking brakes and block drive wheels. Place transmission in Drive. Using scan tool, command EGR solenoid from zero to 100 percent duty cycle. Observe vacuum gauge. If vacuum is greater than or equal to 15 in. Hg, go to step 4 . If vacuum is less than 15 in. Hg, go to next step.
3. Disconnect vacuum hose to EGR vent solenoid. Install vacuum gauge to EGR vent solenoid hose. Start and idle engine. Place transmission in Drive. Observe vacuum gauge. If vacuum is greater than or equal to 15 in. Hg, go to step 7 . If vacuum is less than 15 in. Hg, go to step 5 .
4. Turn ignition off. Install a hand-held vacuum pump to EGR valve. Apply 15 in. Hg to EGR valve. If EGR valve holds vacuum, go to step 6 . If EGR valve does not hold vacuum, go to step 11 .
5. Disconnect vacuum hose to EGR solenoid. Install vacuum gauge to EGR solenoid hose. Start and idle engine. Observe vacuum gauge. If vacuum is greater than or equal to 15 in. Hg, go to step 10 . If vacuum is less than 15 in. Hg, go to step 8 .
6. DTC is intermittent. If no additional DTCs are set, see «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel) . If any additional DTCs are set, go to applicable DTC test.
7. Check for leaking, restricted or deformed vacuum hose from EGR vent solenoid to EGR valve and EGR pressure control/BARO sensor. Check for faulty EGR vent solenoid. Repair as necessary. After repairs, go to step 12 .
8. Check for leaking or deformed vacuum hose to vacuum pump. Repair as necessary. After repairs, go to step 12 . If vacuum hose is okay, go to next step.
9. Replace vacuum pump. After replacing vacuum pump, go to step 12 .
10. Repair leaking, restricted or deformed vacuum hoses between EGR solenoid and EGR vent solenoid, or faulty EGR solenoid. Repair or replace as necessary. After repairs, go to step 12 .
11. Replace EGR valve. After replacing EGR valve, go to next step.
12. After repairs, reset EGR Adaptive Learn Matrix (ALM) cells using scan tool. After resetting EGR ALM cells, go to next step.
13. Using scan tool, select CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, and then enter DTC P1409. Operate vehicle within the conditions for setting this DTC. If scan tool indicates that this test ran and passed, go to next step. If scan tool does not indicate that this test ran and passed, repeat step 2 .
14. Using scan tool, select CAPTURE INFO, REVIEW INFO. If any undiagnosed DTC(s) are displayed, go to applicable DTC test.

A vacuum leak will cause DTC P1409 to set. Check all vacuum lines and components connected to hoses for leaks or deformities. Check vacuum source to EGR solenoid assembly or EGR valve. Check for proper vacuum hose routing.

1. If OBD system check has been performed, go to next step. If OBD system check has not been performed, go to «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel__on-board-diagnostic-obd-system-check) under SELF-DIAGNOSTIC SYSTEM.
2. Replace PCM. Program PCM using required equipment. After replacing PCM, go to next step.
3. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, and then enter DTC P1621. Operate vehicle within the conditions for setting this DTC. If scan tool indicates that this test ran and passed, go to next step. If scan tool does not indicate that this test ran and passed, repeat step 2 .
4. Using scan tool, select CAPTURE INFO, REVIEW INFO. If any undiagnosed DTC(s) are displayed, go to applicable DTC test. If no other DTC(s) are displayed, system is okay.

Scheme 15

Scheme 16

The Passlock® module receives the code from Hall Effect sensor in steering column and compares it to the code Passlock® module learned during first power up at the factory. If this code matches code stored in Passlock® module, module will send a fuel continue message to PCM. PCM enables fuel injection temporarily until fuel continue/disable decision is made. If module does not send a code or if PCM does not receive it, vehicle will not start (start and stall).

If Passlock® module and PCM loose communication with each other while engine is running, Passlock® module will fail-enable and allow driver to restart vehicle on future ignition cycles until communications between module and PCM are restored. If battery is disconnected during this period, vehicle will loose its fail-enable status and will no longer start until communications have been reestablished.

If Passlock® module and PCM loose communication with each other while engine is not running, system will disable fuel until communications are restored to prevent vehicle theft. In both cases, DTC P1626 will set. PCM will not disable fuel injection once it has been enabled within a given ignition cycle to prevent stalling as a result of Passlock® system faults.

DTC will set when the following conditions are present

1. VTD is enabled.
2. Fuel enable decision point has been reached.
3. System has fail-enabled due to loss of communication while engine is running.

Or

1. No password/code message is received by PCM from Passlock® control module prior to VTD fuel decision point.

Perform OBD system check. See ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK under SELF-DIAGNOSTIC SYSTEM. After performing OBD system check, diagnose VTD system. See appropriate ANTI-THEFT SYSTEMS article in ACCESSORIES & EQUIPMENT.

DTC can be set due to loss of serial data communication to Passlock® module. Check for loss of power to Passlock® module or for other causes of communication loss. Use CLASS 2 CIRCUIT CHECK in scan tool to determine if Passlock® module is active (CLASS 2 MESSAGE MONITOR on scan tool). See appropriate ANTI-THEFT SYSTEMS article in ACCESSORIES & EQUIPMENT.

1. If OBD system check has been performed, go to next step. If OBD system check has not been performed, go to «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel__on-board-diagnostic-obd-system-check) under SELF-DIAGNOSTIC SYSTEM.
2. Replace PCM. Program PCM using required equipment. After replacing PCM, go to next step.
3. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, and then enter DTC P1627. Operate vehicle within the conditions for setting this DTC. If scan tool indicates that this test ran and passed, go to next step. If scan tool does not indicate that this test ran and passed, repeat step 2 .
4. Using scan tool, select CAPTURE INFO, REVIEW INFO. If any undiagnosed DTC(s) are displayed, go to applicable DTC test.

DTC P1630: THEFT DETERRENT PCM IN LEARN MODE ("C" & "K" SERIES)

Note. For circuit reference, refer to DTC P1626 schematics. (Scheme 15)or (Scheme 16).

This test checks for the enable password learning flag indicating PCM is in the learn password mode. This mode allows PCM to learn the password from the Passlock® module at assembly or when being serviced. The password needs to be learned whenever PCM or Passlock® module is replaced. DTC will set when ignition is on and enable learning flag is set.

Perform OBD system check. See ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK under SELF-DIAGNOSTIC SYSTEM. After performing OBD system check, diagnose VTD system. See appropriate ANTI-THEFT SYSTEMS article in ACCESSORIES & EQUIPMENT.

The PCM in learn mode means that the PCM is now ready to learn a new password.

DTC P1631: THEFT DETERRENT PASSWORD INCORRECT ("C", "G" & "K" SERIES)

Note. For circuit reference, refer to DTC P1626 schematics. (Scheme 15)or (Scheme 16).

This test checks for mismatched/incorrect passwords between Passlock® module and PCM. Whenever Passlock® module or PCM are replaced, a theft learn procedure must be followed in order for the new password to be learned. DTC will set when anti-theft system is enabled, fuel disable is set and incorrect fuel continue password has been received from Passlock® module.

1. If OBD system check has been performed, go to next step. If OBD system check has not been performed, go to «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel__on-board-diagnostic-obd-system-check) under SELF-DIAGNOSTIC SYSTEM.
2. Before proceeding with test, check if any other VTD DTCs are set. If VTD DTCs are set, go to applicable DTC test. If you were sent here after replacing PCM, go to next step.
3. If Tech 2 scan tool is used, go to step 5 . If Tech 2 scan tool is not used, go to next step.
4. Turn ignition on, with engine off for 11 minutes. Turn ignition off for 30 seconds. Turn ignition on, with engine off for 11 minutes. Turn ignition off for 30 seconds. Turn ignition on, with engine off for 11 minutes or until DTC P1630 sets. Turn ignition off for 30 seconds. Turn ignition on and wait 30 seconds. Attempt to start engine. If engine starts and operates normally, go to step 6 . If engine does not start or does not operate normally, go to step 7 .
5. Using Tech 2 scan tool, enter SERVICE PROGRAMMING SYSTEM (SPS) mode. Enter vehicle information and choose REQUEST INFO. Select DONE and follow scan tool instructions. Disconnect scan tool and connect Techline® terminal. At Techline® terminal select SPS and select TERMINAL TO TECH 2 programming method. Select DONE. Follow instructions on remaining screens. Select VEHICLE THEFT RELEARN. Select PROGRAM at summary screen. Terminal will download information to Tech 2. Reconnect Tech 2 scan tool to DLC. Select SERVICE PROGRAMMING on scan tool main menu. Follow on screen instructions. Press THEFT RELEARN on scan tool. Follow instructions on remaining screens. Security timer will be on for about 11 minutes or until DTC P1630 sets. Ensure terminal is connected to vehicle during the 11 minute wait. When PCM and VTD control module are prepared to relearn, turn ignition off for 30 seconds, and then start engine. If engine starts and operates normally, go to next step. If engine does not start or does not operate normally, go to step 7 .
6. Before clearing DTCs, monitor all DTC status parameters and note any additional DTCs. Clear PCM DTCs. Turn ignition off for 30 seconds. Attempt to start engine. If engine starts and operates normally, system is okay. If engine does not start or does not operate normally, go to next step.
7. Check if DTC P1626, P1630 or P1631 is set. If DTC(s) is set, go to applicable DTC test. If DTC(s) is not set, repeat step 2 .

DTC P1635: PCM 5-VOLT REFERENCE LOW ("C", "G", "K" & "P" SERIES)

Note. For circuit reference, refer to DTC P0182 and P0236 schematics. (Scheme 5), (Scheme 10), (Scheme 11) or (Scheme 12).

PCM provides a 5-volt supply for use in powering up sensors. This test monitors voltage present at PCM 5-volt reference terminals of boost and crankshaft position sensors, and optical/fuel temperature sensor (cam/hi res). DTC will set when ignition is on and 5-volt reference is less than one volt.

1. If OBD system check has been performed, go to next step. If OBD system check has not been performed, go to «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel__on-board-diagnostic-obd-system-check) under SELF-DIAGNOSTIC SYSTEM.
2. Install scan tool. Crank engine for 15 seconds or until engine starts. Check if DTC P1635 sets. If DTC P1635 sets, go to next step. If DTC P1635 does not set, go to step 5 .
3. Turn ignition off. Disconnect boost sensor harness connector. Turn ignition on, with engine off. Using DVOM, probe 5-volt reference circuit of boost sensor harness connector. If voltage is less than 4 volts, go to next step. If voltage is 4 volts or greater, go to step 6 .
4. Turn ignition off. Disconnect PCM harness connector containing boost sensor 5-volt reference circuit. Using test light connected to battery voltage, probe boost sensor 5-volt reference circuit at PCM harness connector. If test light illuminates, go to step 7 . If test light does not illuminate, go to step 8 .
5. DTC is intermittent. If no additional DTCs are set, see «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel) . If any additional DTCs are set, go to applicable DTC test.
6. Replace boost sensor. After replacing sensor, go to step 11 .
7. Ensure test light is still connected to boost sensor 5-volt reference circuit at PCM harness connector. Disconnect sensors, one at a time, that share the 5-volt reference with boost sensor. If test light turns off when one of the sensors are disconnected, go to step 9 . If test light does not turn off when one of the sensors are disconnected, go to step 11 .
8. Turn ignition off. Disconnect PCM harness connector containing optical/fuel temperature sensor 5-volt reference circuit. Using test light connected to battery voltage, probe optical/fuel temperature sensor 5-volt reference circuit at PCM harness connector. If test light illuminates, go to step 10 . If test light does not illuminate, go to step 11 .
9. Repair short to ground in 5-volt reference circuit. After repairs, go to step 11 .
10. Replace PCM. Program PCM using required equipment. After replacing PCM, go to next step.
11. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, and then enter DTC P1635. Operate vehicle within the conditions for setting this DTC. If scan tool indicates that this test ran and passed, go to next step. If scan tool does not indicate that this test ran and passed, repeat step 2 .
12. Using scan tool, select CAPTURE INFO, REVIEW INFO. If any undiagnosed DTC(s) are displayed, go to applicable DTC test.

During the time failure is present, setting of additional DTCs that share a 5-volt reference may also set.

Scheme 17

The MIL is illuminated by PCM if diagnostics have detected certain errors related to engine performance or engine sensor status. When PCM is commanding the MIL on, voltage potential of the circuit will be low (near zero volts). When PCM is commanding the MIL off, voltage potential of the circuit will be high (near battery voltage). Primary function of PCM is to supply ground to the MIL control circuit.

DTC will set when the following conditions are present

1. MIL is requested on.
2. Voltage to MIL control circuit is high (near battery voltage).

Or

1. MIL is requested off.
2. Voltage to MIL control circuit is low (near zero volts).

1. If OBD system check has been performed, go to next step. If OBD system check has not been performed, go to «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel__on-board-diagnostic-obd-system-check) under SELF-DIAGNOSTIC SYSTEM.
2. Install scan tool. Start and idle engine. Using scan tool, command MIL on and off. If MIL illuminates, go to next step. If MIL does not illuminate, go to step 4 .
3. DTC is intermittent. If other DTC(s) are set, go to applicable DTC test for diagnosis. If no other DTC(s) are set, see «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel) .
4. Turn ignition off. Disconnect PCM harness connector containing MIL control circuit. Turn ignition on, with engine off. If MIL does not illuminate, go to next step. If MIL illuminates, go to step 7 .
5. Turn ignition on, with engine off. Connect a fused jumper wire between ground and MIL control circuit of PCM harness connector. If MIL illuminates, go to next step. If MIL does not illuminate, go to step 8 .
6. Check for poor connections at PCM. Repair as necessary. After repairs, go to step 10 . If connections are okay, go to step 9 .
7. Repair short to ground in MIL control circuit. After repairs, go to step 10 .
8. Check MIL control circuit for open ignition feed circuit, faulty bulb, or open or shorted to battery voltage. Repair as necessary. After repairs, go to step 10 .
9. Replace PCM. Program PCM using required equipment. After replacing PCM, go to next step.
10. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, and then enter DTC P1641. Operate vehicle within the conditions for setting this DTC. If scan tool indicates that this test ran and passed, go to next step. If scan tool does not indicate that this test ran and passed, repeat step 2 .
11. Using scan tool, select CAPTURE INFO, REVIEW INFO. If any undiagnosed DTC(s) are displayed, go to applicable DTC test.

A faulty bulb, or short to ground or voltage in MIL control circuit will cause DTC P1641 to set.

The WAIT TO START light is illuminated by the PCM when the glow plugs are commanded on. When PCM is commanding the WAIT TO START light on, voltage potential of the circuit will be low (near zero volts). When PCM is commanding the WAIT TO START light off, voltage potential of the circuit will be high (near battery voltage). Primary function of PCM is to supply ground to the WAIT TO START light control circuit.

DTC will set when the following conditions are present

1. WAIT TO START light is requested on.
2. Voltage to WAIT TO START light control circuit is high (near battery voltage).

Or

1. WAIT TO START light is requested off.
2. Voltage to WAIT TO START light control circuit is low (near zero volts).

1. If OBD system check has been performed, go to next step. If OBD system check has not been performed, go to «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel__on-board-diagnostic-obd-system-check) under SELF-DIAGNOSTIC SYSTEM.
2. Install scan tool. Turn ignition on, with engine off. Using scan tool, command glow plug light on and off. If WAIT TO START light illuminates, go to next step. If WAIT TO START light does not illuminate, go to step 4 .
3. DTC is intermittent. If no additional DTCs are set, see «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel) . If any additional DTCs are set, go to applicable DTC test.
4. Turn ignition off. Disconnect PCM harness connector containing the WAIT TO START light control circuit. Turn ignition on, with engine off. If WAIT TO START light does not illuminate, go to next step. If WAIT TO START light illuminates, go to step 7 .
5. Connect a fused jumper wire between ground and WAIT TO START light control circuit of PCM harness connector. If WAIT TO START light illuminates, go to next step. If WAIT TO START light does not illuminate, go to step 8 .
6. Check for poor connections at PCM. Repair as necessary. After repairs, go to step 10 . If connections are okay, go to step 9 .
7. Check for short to ground in WAIT TO START light control circuit. Repair as necessary. After repairs, go to step 10 .
8. Check WAIT TO START light control circuit for open ignition feed circuit, faulty bulb, or open or shorted to battery voltage. Repair as necessary. After repairs, go to step 10 .
9. Replace PCM. Program PCM using required equipment. After replacing PCM, go to next step.
10. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, and then enter DTC P1643. Operate vehicle within the conditions for setting this DTC. If scan tool indicates that this test ran and passed, go to next step. If scan tool does not indicate that this test ran and passed, repeat step 2 .
11. Using scan tool, select CAPTURE INFO, REVIEW INFO. If any undiagnosed DTC(s) are displayed, go to applicable DTC test.

A faulty bulb or short to ground in WAIT TO START control circuit will cause DTC P1643 to set.

DTC P1653: EGR VENT SOLENOID CONTROL CIRCUIT ("C" & "K" SERIES)

Note. For circuit reference, refer to DTC P0101 schematic. (Scheme 2)

EGR flow is controlled by a vacuum actuated EGR valve. The EGR vent solenoid purges to atmosphere the vacuum level at the EGR valve actuator as commanded by the PCM. This is done when the EGR flow is desired to turn off quickly.

When the PCM is commanding the EGR vent solenoid on, the voltage potential of the circuit will be low (near zero volts). When the PCM is commanding the EGR vent solenoid off, the voltage potential of the circuit will be high (near battery voltage). The primary function of the PCM is to supply the ground to the EGR vent solenoid.

DTC will set when the following conditions are present

1. PCM requested EGR vent on.
2. Voltage on EGR vent control circuit is high (near battery voltage).

Or

1. PCM requested EGR vent solenoid off.
2. Voltage on EGR vent control circuit is low (near zero volts).

1. If OBD system check has been performed, go to next step. If OBD system check has not been performed, go to «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel__on-board-diagnostic-obd-system-check) under SELF-DIAGNOSTIC SYSTEM.
2. Install scan tool. Start and idle engine. Apply parking brake. Place transmission in Drive. Using scan tool, command EGR vent solenoid on and off, listening for an audible click. If EGR vent solenoid turns on and off, go to next step. If EGR vent solenoid does not turn on and off, go to step 5 .
3. Turn ignition off. Disconnect PCM harness connector containing EGR vent solenoid control circuit. Turn ignition on, with engine off. Using DVOM in 10-amp scale, measure current between ground and solenoid control circuit of PCM harness connector for 2 minutes. If current draw is less than .75 amp., but not zero, go to step 8 . If current draw is .75 amp. or greater, go to next step.
4. Turn ignition off. Leave PCM harness connector disconnected. Disconnect EGR vent solenoid harness connector. Using DVOM, check resistance between ground and solenoid control circuit of PCM harness connector. If resistance is infinite, go to step 13 . If resistance is not infinite, go to step 10 .
5. Turn ignition off. Disconnect EGR vent solenoid harness connector. Turn ignition on, with engine off. Connect a test light between solenoid control circuit and ignition feed circuit at EGR vent solenoid harness connector. Using scan tool, command EGR vent solenoid on and off. If test light illuminates with each command, go to step 9 . If test light does not illuminate with each command, go to next step.
6. Turn ignition on, with engine off. Using test light connected to ground, probe ignition feed circuit at EGR vent solenoid harness connector. If test light illuminates, go to next step. If test light does not illuminate, go to step 12 .
7. Turn ignition off. Reconnect EGR vent solenoid harness connector. Disconnect PCM harness connector containing EGR vent solenoid control circuit. Turn ignition on, with engine off. Connect a fused jumper wire between ground and EGR vent solenoid control circuit of PCM harness connector. If EGR vent solenoid operates, go to step 11 . If EGR vent solenoid does not operate, go to step 10 .
8. DTC is intermittent. If no additional DTCs are set, see «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel) . If any additional DTCs are set, go to applicable DTC test.
9. Check for poor connection at EGR vent solenoid. Repair as necessary. After repairs, go to step 15 . If connection is okay, go to step 13 .
10. Repair EGR vent solenoid control circuit. After repairs, go to step 15 .
11. Check EGR vent solenoid control circuit for poor connection at PCM. Repair as necessary. After repairs, go to step 15 . If connection is okay, go to step 14 .
12. Repair open in ignition feed circuit. After repairs, go to step 15 .
13. Replace EGR vent solenoid. After replacing solenoid, go to step 15 .
14. Replace PCM. Program PCM using required equipment. After replacing PCM, go to next step.
15. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, and then enter DTC P1653. Operate vehicle within the conditions for setting this DTC. If scan tool indicates that this test ran and passed, go to next step. If scan tool does not indicate that this test ran and passed, repeat step 2 .
16. Using scan tool, select CAPTURE INFO, REVIEW INFO. If any undiagnosed DTC(s) are displayed, go to applicable DTC test.

Scan tool has a 5 second on-time abort. EGR vent solenoid can be commanded on as many times as needed in 5 second intervals. Other EGR DTCs may also set when DTC P1653 is set. This diagnostic can be checked at key up. A quick operational check may be performed by commanding EGR vent solenoid on and off using scan tool while monitoring actual EGR. Actual EGR will display BARO (approximately) when EGR vent solenoid is off. Full EGR will be achieved when EGR vent solenoid is commanded on using scan tool.

DTC P1654: SERVICE THROTTLE SOON LIGHT CONTROL CIRCUIT ("C", "G", "K"& "P" SERIES)

Note. For circuit reference, refer to DTC P1641 schematic. (Scheme 17)

The SERVICE THROTTLE SOON light is illuminated by PCM if diagnostics have detected certain errors related to Accelerator Pedal Position (APP) sensor. When PCM is commanding the SERVICE THROTTLE SOON light on, voltage potential of the circuit will be low (near zero volts). When PCM is commanding the SERVICE THROTTLE SOON light off, voltage potential of the circuit will be high (near battery voltage). Primary function of PCM is to supply ground to the SERVICE THROTTLE SOON light control circuit.

DTC will set when the following conditions are present

1. SERVICE THROTTLE SOON light is requested on.
2. Voltage to SERVICE THROTTLE SOON light control circuit is high (near battery voltage).

Or

1. SERVICE THROTTLE SOON light is requested off.
2. Voltage to SERVICE THROTTLE SOON light control circuit is low (near zero volts).

1. If OBD system check has been performed, go to next step. If OBD system check has not been performed, go to «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel__on-board-diagnostic-obd-system-check) under SELF-DIAGNOSTIC SYSTEM.
2. Install scan tool. Turn ignition on, with engine off. Using scan tool, command SERVICE THROTTLE SOON light on and off. If SERVICE THROTTLE SOON light illuminates, go to next step. If SERVICE THROTTLE SOON light does not illuminate, go to step 4 .
3. DTC is intermittent. If no additional DTCs are set, see «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel) . If any additional DTCs are set, go to applicable DTC test.
4. Turn ignition off. Disconnect PCM harness connector containing the SERVICE THROTTLE SOON light control circuit. Turn ignition on, with engine off. If SERVICE THROTTLE SOON light does not illuminate, go to next step. If SERVICE THROTTLE SOON light illuminates, go to step 7 .
5. Connect a fused jumper wire between ground and SERVICE THROTTLE SOON light control circuit of PCM harness connector. If SERVICE THROTTLE SOON light illuminates, go to next step. If SERVICE THROTTLE SOON light does not illuminate, go to step 8 .
6. Check for poor connections at PCM. Repair as necessary. After repairs, go to step 10 . If connections are okay, go to step 9 .
7. Repair short to ground in SERVICE THROTTLE SOON light control circuit. After repairs, go to step 10 .
8. Check SERVICE THROTTLE SOON light control circuit for open ignition feed circuit, faulty bulb, or open or shorted to battery voltage. Repair as necessary. After repairs, go to step 10 .
9. Replace PCM. Program PCM using required equipment. After replacing PCM, go to next step.
10. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, and then enter DTC P1654. Operate vehicle within the conditions for setting this DTC. If scan tool indicates that this test ran and passed, go to next step. If scan tool does not indicate that this test ran and passed, repeat step 2 .
11. Using scan tool, select CAPTURE INFO, REVIEW INFO. If any undiagnosed DTC(s) are displayed, go to applicable DTC test.

A faulty bulb or short to ground in SERVICE THROTTLE SOON light control circuit will cause DTC P1654 to set.

DTC P1655: EGR SOLENOID CONTROL CIRCUIT ("C" & "K" SERIES)

Note. For circuit reference, refer to DTC P0101 schematic. (Scheme 2)

EGR flow is controlled by vacuum actuated EGR valve. EGR pulse width modulated solenoid meters vacuum level at EGR valve actuator as commanded by PCM. When the PCM is commanding the EGR solenoid on, the voltage potential of the circuit will be low (near zero volts). When the PCM is commanding the EGR solenoid off, the voltage potential of the circuit will be high (near battery voltage). The primary function of the PCM is to supply the ground to the EGR solenoid.

DTC will set when the following conditions are present

1. PCM requested EGR solenoid on.
2. Voltage on EGR solenoid control circuit is high (near battery voltage).

Or

1. PCM requested EGR solenoid off.
2. Voltage on EGR solenoid control circuit is low (near zero volts).

1. If OBD system check has been performed, go to next step. If OBD system check has not been performed, go to «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel__on-board-diagnostic-obd-system-check) under SELF-DIAGNOSTIC SYSTEM.
2. Install scan tool. Start and idle engine. Apply parking brake. Place transmission in Drive. Using scan tool, command EGR solenoid on and off, listening for an audible click. If EGR solenoid turns on and off, go to next step. If EGR solenoid does not turn on and off, go to step 5 .
3. Turn ignition off. Disconnect PCM harness connector containing EGR solenoid control circuit. Turn ignition on, with engine off. Using DVOM in 10-amp scale, measure current between ground and solenoid control circuit of PCM harness connector for 2 minutes. If current draw is less than .75 amp., but not zero, go to step 8 . If current is .75 amp or greater, go to next step.
4. Turn ignition off. Leave PCM harness connector disconnected. Disconnect EGR solenoid harness connector. Using DVOM, check resistance between ground and solenoid control circuit of PCM harness connector. If resistance is infinite, go to step 13 . If resistance is not infinite, go to step 10 .
5. Turn ignition off. Disconnect EGR solenoid harness connector. Turn ignition on, with engine off. Connect a test light between solenoid control circuit and ignition feed circuit at EGR solenoid harness connector. Using scan tool, command EGR solenoid on and off. If test light illuminates with each command, go to step 9 . If test light does not illuminate, go to next step.
6. Turn ignition on, with engine off. Using test light connected to ground, probe ignition feed circuit at EGR solenoid harness connector. If test light illuminates, go to next step. If test light does not illuminate, go to step 12 .
7. Turn ignition off. Reconnect EGR solenoid harness connector. Disconnect PCM harness connector containing EGR solenoid control circuit. Turn ignition on, with engine off. Connect a fused jumper wire between ground and EGR solenoid control circuit of PCM harness connector. If EGR solenoid operates, go to step 11 . If EGR solenoid does not operate, go to step 10 .
8. DTC is intermittent. If no additional DTCs are set, see «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel) . If any additional DTCs are set, go to applicable DTC test.
9. Check for poor connection at EGR solenoid. Repair as necessary. After repairs, go to step 15 . If connection is okay, go to step 13 .
10. Repair EGR solenoid control circuit. After repairs, go to step 15 .
11. Check EGR solenoid control circuit for poor connection at PCM. Repair as necessary. After repairs, go to step 15 . If connection is okay, go to step 14 .
12. Repair open in ignition feed circuit. After repairs, go to step 15 .
13. Replace EGR solenoid. After replacing solenoid, go to step 15 .
14. Replace PCM. Program PCM using required equipment. After replacing PCM, go to next step.
15. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, and then enter DTC P1655. Operate vehicle within the conditions for setting this DTC. If scan tool indicates that this test ran and passed, go to next step. If scan tool does not indicate that this test ran and passed, repeat step 2 .
16. Using scan tool, select CAPTURE INFO, REVIEW INFO. If any undiagnosed DTC(s) are displayed, go to applicable DTC test.

Scan tool has a 5 second on-time abort. EGR solenoid can be commanded on as many times as needed in 5 second intervals. Other EGR DTCs may also set when DTC P1655 is set. This diagnostic can be checked at key up. A quick operational check may be performed by commanding EGR solenoid on and off using scan tool while monitoring actual EGR. Actual EGR will display BARO (approximately) when EGR solenoid is off. Full EGR will be achieved when EGR solenoid is commanded on using scan tool.

DTC P1656: WASTEGATE SOLENOID CONTROL CIRCUIT ("C", "G", "K" & "P" SERIES)

Note. For circuit reference, refer to DTC P0101 schematic. (Scheme 2)

Turbocharger wastegate is a vacuum actuated valve used to control exhaust gas heat sent to turbo. Wastegate pulse width modulated solenoid meters vacuum level at wastegate valve actuator as commanded by PCM. When the PCM is commanding the wastegate solenoid on, the voltage potential of the circuit will be low (near zero volts). When the PCM is commanding the wastegate solenoid off, the voltage potential of the circuit will be high (near battery voltage). The primary function of the PCM is to supply the ground to the wastegate solenoid.

DTC will set when the following conditions are present

1. PCM requested wastegate solenoid on.
2. Voltage on wastegate solenoid control circuit is high (near battery voltage).
3. Two consecutive faults detected.
4. Conditions are met for 2 seconds.

Or

1. PCM requested wastegate solenoid off.
2. Voltage on wastegate solenoid control circuit is low (near zero volts).
3. Two consecutive faults detected.
4. Conditions are met for 2 seconds.

1. If OBD system check has been performed, go to next step. If OBD system check has not been performed, go to «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel__on-board-diagnostic-obd-system-check) under SELF-DIAGNOSTIC SYSTEM.
2. Install scan tool. Turn ignition on, with engine off. Using scan tool, command wastegate solenoid on and off, listening for an audible click. If wastegate solenoid turns on and off, go to next step. If wastegate solenoid does not turn on and off, go to step 5 .
3. Turn ignition off. Disconnect PCM harness connector containing wastegate solenoid control circuit. Turn ignition on, with engine off. Using DVOM in 10-amp scale, measure current between ground and solenoid control circuit of PCM harness connector for 2 minutes. If current draw is less than .75 amp., but not zero, go to step 8 . If current is .75 amp or greater, go to next step.
4. Turn ignition off. Leave PCM harness connector disconnected. Disconnect wastegate solenoid harness connector. Using DVOM, check resistance between ground and solenoid control circuit of PCM harness connector. If resistance is infinite, go to step 13 . If resistance is not infinite, go to step 10 .
5. Turn ignition off. Disconnect wastegate solenoid connector. Turn ignition on, with engine off. Connect a test light between solenoid control circuit and ignition feed circuit at wastegate solenoid harness connector. Using scan tool, command wastegate solenoid on and off. If test light illuminates with each command, go to step 9 . If test light does not illuminate, go to next step.
6. Turn ignition on, with engine off. Using test light connected to ground, probe ignition feed circuit at wastegate solenoid harness connector. If test light illuminates, go to next step. If test light does not illuminate, go to step 12 .
7. Turn ignition off. Reconnect wastegate solenoid harness connector. Disconnect PCM harness connector containing wastegate solenoid control circuit. Turn ignition on, with engine off. Connect a fused jumper wire between ground and wastegate solenoid control circuit of PCM harness connector. If wastegate solenoid operates, go to step 11 . If wastegate solenoid does not operate, go to step 10 .
8. DTC is intermittent. If additional DTC(s) are set, diagnose those DTC(s). If no DTC(s) are set, see «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel) .
9. Check for poor connection at wastegate solenoid. Repair as necessary. After repairs, go to step 15 . If connection is okay, go to step 13 .
10. Repair wastegate solenoid control circuit. After repairs, go to step 15 .
11. Check wastegate solenoid control circuit for poor connection at PCM. Repair as necessary. After repairs, go to step 15 . If connection is okay, go to step 14 .
12. Repair open in ignition feed circuit. After repair, go to step 15 .
13. Replace wastegate solenoid. After replacing solenoid, go to step 15 .
14. Replace PCM. Program PCM using required equipment. After replacing PCM, go to next step.
15. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, and then enter DTC P1656. Operate vehicle within the conditions for setting this DTC. If scan tool indicates that this test ran and passed, go to next step. If scan tool does not indicate that this test ran and passed, repeat step 2 .
16. Using scan tool, select CAPTURE INFO, REVIEW INFO. If any undiagnosed DTC(s) are displayed, go to applicable DTC test.

This diagnostic will set when control circuit does not follow PCM command (when solenoid is requested on, voltage will drop; when solenoid is requested off, ignition voltage will be present). Scan tool has a 5 second on-time abort. Wastegate solenoid can be commanded on as many times as needed in 5 second intervals. DTC P0236 may also set when DTC P1656 is set. This diagnostic can be checked at key up. Engine will not respond to scan tool commands at idle (engine is unable to achieve boost pressures greater than BARO at idle) or at any engine speed greater than idle (PCM control aborts to prevent engine damage).

DTC U1026: LOSS OF ATC CLASS II COMMUNICATION (6.5L "C" & "K" SERIES)

Note. For circuit reference, see appropriate wiring diagram in WIRING DIAGRAMS article.

PCM monitors the Class II serial data circuit for communications from the Automatic Transfer Case (ATC) controller. If ATC controller is not communicating with PCM, DTC will set.

Before clearing DTCs, record FREEZE FRAME and FAILURE RECORDS information for reference. Perform On-Board Diagnostic (OBD) system check. See ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK . After performing OBD system check, diagnose ATC controller. See appropriate ELECTRONIC CONTROLS article in AUTOMATIC TRANSMISSIONS.

DTC will not set unless PCM and ATC controllers have already established communications first. This DTC will only diagnose an open or intermittent connection from ATC controller to splice.

DTC U1192: LOSS OF EVO/VTD PASSLOCK® COMMUNICATION (6.5L "C" & "K" SERIES)

Note. For circuit reference, see WIRING DIAGRAM article.

PCM monitors the Class II serial data circuit for communications from the EVO/Passlock® controller. DTC will set when controller is not communicating with PCM or no serial data is present between controller to PCM.

Before clearing DTCs, record Freeze Frame and Failure Records information for reference. Perform On-Board Diagnostic (OBD) system check. See ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK . After performing OBD system check, diagnose EVO/Passlock® controller. See appropriate ANTI-THEFT SYSTEMS article in ACCESSORIES & EQUIPMENT.

DTC will not set unless PCM and ATC controllers have already established communications first. This DTC will only diagnose an open or intermittent connection from the EVO/Passlock® controller to splice.

DTC U1192: LOSS OF EVO/PASSLOCK® COMMUNICATION (6.5L "G" SERIES)

Note. For circuit reference, see WIRING DIAGRAM article.

PCM monitors the Class II serial data circuit for communications from the EVO/Passlock® controller. If controller is not communicating with PCM, DTC will set.

1. Before clearing DTCs, record Freeze Frame and Failure Records information for reference. Perform On-Board Diagnostic (OBD) system check. See «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel__on-board-diagnostic-obd-system-check) . After performing OBD system check, go to next step.
2. Turn ignition on, with engine off. Using scan tool, select DIAGNOSTIC CIRCUIT CHECK and CLASS II MESSAGE MONITOR. If scan tool displays EVO/Passlock® active, go to next step. If scan tool displays that controller is not active, go to step 4 .
3. DTC is intermittent. If no additional DTCs are set, see «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-diesel) . If additional DTCs are set, diagnose affected DTCs.
4. Check Class II serial data circuit from EVO/Passlock® controller to splice for open circuit or proper connection to controller. Repair as necessary. After repairs, go to next step. If circuit or connection is okay, diagnose EVO/Passlock® system. See appropriate ANTI-THEFT SYSTEMS article in ACCESSORIES & EQUIPMENT.
5. Clear DTCs using scan tool. Warm engine to normal operating temperature. Using scan tool, select DTC, SPECIFIC then enter this DTC. Operate vehicle within conditions for setting this DTC. If scan tool indicates that this diagnostic passed, go to next step. If scan tool does not indicate that this diagnostic passed, repeat step 2 .
6. Check if additional DTCs are set. Diagnose affected DTCs. If no additional DTCs are set, system is okay.

DTC will not set unless PCM and ATC controllers have already established communications first. This DTC will only diagnose an open or intermittent connection from the EVO/Passlock® controller to splice.

See also:
• MODEL IDENTIFICATION
• DIAGNOSTIC PROCEDURE
• ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK
• HARD OR INTERMITTENT TROUBLE CODE DETERMINATION
• DIAGNOSTIC TESTS
• NO MALFUNCTION INDICATOR LIGHT (MIL)
• DATA LINK CONNECTOR (DLC) DIAGNOSIS
• P0102
• P0103
• P0113
• P0117
• P0118
• P0122
• P0123
• P0126
• P0183
• P0219
• P0220
• P0221
• P0222
• P0223
• P0225
• P0226
• P0227
• P0228
• P0237
• P0238
• P0251
• P0266
• P0269
• P0272
• P0275
• P0278
• P0281
• P0284
• P0300
• P0301
• P0302
• P0303
• P0304
• P0305
• P0306
• P0307
• P0308
• P0335
• P0370
• P0400
• P0402
• P0404
• P0405
• P0406
• P0568
• P0571
• P1125
• P1191
• P1216
• P1217
• P1218
• P1406
• P1409
• P1630
• P1631
• P1635
• P1653
• P1654
• P1655
• P1656
• CLEARING DTCS
• SCAN TOOL DATA