Engine Controls - Tests W/codes - 6.5l Diesel Chevrolet Suburban IX

MODEL IDENTIFICATION

MODEL IDENTIFICATION

INTRODUCTION

The 6.5L Diesel Electronic Control (DEC) system electronically controls EGR system operation, Torque Converter Clutch (TCC) engagement, fuel control and fuel injection timing, and is controlled by the Powertrain Control Module (PCM).

The PCM 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 BASIC TESTING article. Failure to perform these inspections can result in lost diagnostic time.

If no faults were found while performing visual and mechanical inspections in BASIC TESTING article, go to DIAGNOSTIC PROCEDURE under SELF-DIAGNOSTIC SYSTEM. If no diagnostic trouble codes are present and driveability problems exist, proceed to TESTS W/O CODES article for diagnosis by symptom (i.e., ROUGH IDLE, NO START, etc.). If only intermittent codes are present, see INTERMITTENTS in TESTS W/O CODES article.

TRANSMISSION APPLICATIONS

SELF-DIAGNOSTIC SYSTEM

Note. See BASIC TESTING article for On-Board Diagnostic System Check.

Note. SERVICE ENGINE SOON light, located on instrument cluster, is also referred to as the Malfunction Indicator Light (MIL).

The 6.5L DEC/electronically-controlled transmission systems includes a self-diagnostic system which can determine input signal circuit malfunctions. Input signal circuits determine engine/transmission function control. When a malfunction occurs, PCM will illuminate the Malfunction Indicator Light (MIL) located on instrument cluster. When malfunction is detected and light is turned on, a corresponding Diagnostic Trouble Code (DTC) will be stored in PCM memory. To retrieve stored codes, see ENTERING & EXITING DIAGNOSTIC MODE. Malfunctions are recorded as either hard failures or intermittent failures.

Preliminary Inspection

1. Check all vacuum hoses for correct routing, restrictions, cuts or other damage. Inspect difficult-to-see vacuum hoses beneath air cleaner assembly and other engine components.
2. Inspect all engine compartment wiring for proper connections. Also check wires for pinched or chafed spots, as well as contact with sharp edges or exhaust manifolds.
3. The preliminary inspection is very important and should be performed carefully and thoroughly, as it can often fix a problem without requiring further diagnosis.

Note. Begin all diagnosis with appropriate ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK in BASIC TESTING article. After any DEC/electronically-controlled transmission systems repair, repeat On-Board Diagnostic (OBD) system check.

Diagnostic Procedure

1. Ensure all non-controlled systems NOT related to the Diesel Electronic Control (DEC)/electronically-controlled transmission systems are operating properly. DO NOT proceed with testing unless all non-DEC/electronically-controlled transmission systems problems are repaired.
2. ALWAYS begin diagnosis with On-Board Diagnostic (OBD) system check to determine if DEC/electronically-controlled transmission systems and PCM are working properly. See ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK in BASIC TESTING article. If trouble codes are displayed, determine if they are hard or intermittent trouble codes.
3. A hard code is present when working on vehicle, and problem persists. Hard codes will cause Malfunction Indicator Light (MIL) to come on. NOTE: SERVICE ENGINE SOON light, located on instrument cluster, is also referred to as the Malfunction Indicator Light (MIL).
4. An intermittent code does not reset itself and is NOT present while working on vehicle. Intermittent codes are often caused by loose connections. MIL will go out 10 seconds after fault goes away. For intermittent diagnostic procedures, see TESTS W/O CODES article.

ENTERING & EXITING DIAGNOSTIC MODE

To enter diagnostic mode, use scan tool. With ignition on and engine off, connect a scan tool to Data Link Connector (DLC) located behind left side of dash. (Scheme 90) The Diesel Electronic Control (DEC)/electronically-controlled transmission systems will enter diagnostic mode. In this mode, PCM will display DTCs on scan tool. Refer to scan tool instructions provided by manufacturer for further information. To exit diagnostic mode, turn ignition off and remove scan tool from DLC.

Scheme 90

TROUBLE CODE IDENTIFICATION

Note. Trouble codes retrieved from PCM may be either engine or transmission related. Only engine related codes are covered in this article. For transmission related codes, see appropriate TRANSMISSION SERVICE & REPAIR manual for domestic vehicles. See DIAGNOSTIC TROUBLE CODE (DTC) IDENTIFICATION table to determine if code is engine or transmission related.

1. The DEC/electronically-controlled transmission systems codes 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 code. The PCM connector may be the problem. Connector terminals may have to be removed from connector to be checked properly. 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.

DIAGNOSTIC TROUBLE CODE (DTC) IDENTIFICATION

CLEARING TROUBLE CODES

Note. To prevent PCM damage, ensure ignition switch is in OFF position when disconnecting or reconnecting power to PCM.

Diagnostic trouble codes should be cleared after repairs have been completed. Also, some diagnostic procedures require codes to be cleared before performing diagnostic procedure.

To clear codes, use scan tool. With ignition on and engine off, connect a scan tool to Data Link Connector (DLC) located behind left side of dash. (Scheme 90) Refer to scan tool instructions provided by manufacturer for further information.

If no hard fault codes are present (only intermittent codes exist), proceed to TESTS W/O CODES article for intermittent diagnostic procedures.

PCM LOCATION

PCM is located behind right side of dash.

SPECIAL TOOLS (DIAGNOSTIC)

Special scan tools, plugged into the DLC, are used to read trouble codes, and check voltages in system on serial data line. Scan tools can save a great deal of time. Refer to scan tool instructions provided by manufacturer for further information.

SCAN TOOL USAGE

Note. Before connecting scan tool, check diagnostic system and ensure accurate information is received by scan tool. Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK in BASIC TESTING article. If vehicle does not pass On-Board Diagnostic (OBD) system check, information received by scan tool may be invalid.

Scan tool is a specialized tool which can diagnose on-board computer control systems by providing almost instant access to circuit voltage information without crawling under dash or hood to backprobe sensors and connectors. Scan tools reduce diagnostic time by furnishing input data (voltage signals) which can be compared to specification parameters. See TYPICAL TECH 1 DATA VALUES table.

Scan tools also furnish information on output device (solenoids and motors) status. However, status parameters are only an indication output signals have been sent to devices by the 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 trouble codes are not present, a problem may still exist. Driveability-related problems with codes displayed occur about 20 percent of the time, while driveability problems without codes occur about 80 percent of the time. Out-of-calibration sensors WILL NOT set a trouble code, but WILL cause driveability problems. A scan tool is the easiest method of checking sensor specifications and other data parameters. Scan tool is also useful in finding intermittent wiring problems by wiggling wiring harnesses and connections (key on, engine off) while observing data parameters. See TYPICAL TECH 1 DATA VALUES table.

Note. Information obtained by scan tool is only as accurate as the scan tool itself. If erroneous voltage signals are suspected, verify scan tool information using a digital voltmeter and wiring schematic.

TYPICAL TECH 1 DATA VALUES

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 instructions provided by manufacturer for further information.

TYPICAL TECH 1 DATA VALUES

TEST EQUIPMENT

A tachometer, test light, Digital Volt-Ohmmeter (DVOM) with a minimum 10-megohm input impedance, a vacuum gauge, and jumper wires are required to test and diagnose Diesel Electronic Control (DEC)/electronically-controlled transmission systems. A scan tool may also be used to access data parameters. Scan tool will supply a visual reading of most inputs, and some outputs, to PCM.

DIAGNOSTIC TROUBLE CODES

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.

Circuit Description

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.

Diagnostic Procedures

1. Perform Powertrain On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Install scan tool. Start engine. 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 display is less than or equal to -40°F (-40°C), go to step 7). If IAT display is greater than -40°F (-40°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. If any additional DTCs are set, go to applicable DTC test.
6. Repair short to ground in IAT signal circuit. Go to step 9).
7. Replace IAT sensor. Go to step 9).
8. Replace PCM. Go to next step.
9. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, 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.

Diagnostic Aids

Check harness routing for a potential short to ground in signal circuit. Scan tool displays intake air temperature in degrees centigrade. See appropriate TESTS W/O CODES article. A skewed sensor could result in poor driveability complaints.

DTC P0112 Schematic. Scheme 91

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. Intake air temperature is less than or equal to -40°F (-40°C).
3. Conditions are met for 2 seconds.

1. Perform Powertrain On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Install scan tool. Start engine. Monitor IAT display on scan tool. If IAT display is less than or equal to -40°F (-40°C), go to next step. If IAT display is greater than -40°F (-40°C), go to step 5).
3. Turn engine off. Disconnect IAT sensor connector. Turn ignition on. Connect a jumper wire between IAT sensor connector terminals. Monitor IAT display on scan tool. If IAT display is greater than or equal to 304°F (151°C), go to step 6). If IAT display 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 IAT display is greater than or equal to 304°F (151°C), go to step 7). If IAT display is less than 304°F (151°C), go to step 8).
5. DTC is intermittent. If no additional DTCs are set, see DIAGNOSTIC AIDS. If any additional DTCs are set, go to applicable DTC test.
6. Check for poor connections at IAT sensor and PCM. If a problem was found, go to step 9). If a problem is not found, go to step 10).
7. Check for open in IAT ground circuit between IAT sensor and PCM. If IAT ground circuit is open, go to step 9). 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 next step. If IAT signal circuit is not open, go to step 11).
9. Repair circuit as necessary. Go to step 12).
10. Replace IAT sensor. Go to step 12).
11. Replace PCM. Go to next step.
12. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, 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).
13. 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 TESTS W/O CODES article. A skewed sensor could result in poor driveability complaints.

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 coolant temperature is greater than or equal to 304°F (151°C) for 2 seconds.

1. Perform Powertrain On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Install scan tool. Start engine. Monitor ECT display on scan tool. If ECT display is greater than or equal to 304°F (151°C), go to next step. If ECT display 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 display is less than or equal to -40°F (-40°C), go to step 7). If ECT display is greater than -40°F (-40°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. If any additional DTCs are set, go to applicable DTC test.
6. Repair short to ground in ECT signal circuit. Go to step 9).
7. Replace ECT sensor. Go to step 9).
8. Replace PCM. Go to next step.
9. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, 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°). See appropriate TESTS W/O CODES article. A skewed sensor could result in poor driveability complaints.

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. Engine coolant temperature is less than -40°F (-40°C).
3. Conditions are met for 2 seconds.

1. Perform Powertrain On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Install scan tool. Start engine. Monitor ECT display on scan tool. If ECT display is less than or equal to -40°F (-40°C), go to next step. If ECT display is greater than -40°F (-40°C), go to step 5).
3. Turn engine off. Disconnect ECT sensor connector. Turn ignition on. Connect a jumper wire between ECT sensor connector terminals. Monitor ECT display on scan tool. If ECT display is greater than or equal to 304°F (151°C), go to step 6). If ECT display is less than 304°F (151°C), go to next step.
4. Connect a jumper wire between ECT signal circuit of ECT sensor connector and ground. Monitor ECT display on scan tool. If ECT display is greater than or equal to 304°F (151°C), go to step 7). If ECT display is less than 304°F (151°C), go to step 8).
5. DTC is intermittent. If no additional DTCs are set, see DIAGNOSTIC AIDS. If any additional DTCs are set, go to applicable DTC test.
6. Check for poor connections at ECT sensor and PCM. If a problem was found, go to step 9). If a problem is not found, go to step 10).
7. Check for open in ECT ground circuit between ECT sensor and PCM. If ECT ground circuit is open, go to step 9). 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 ECT signal circuit is open, go to next step. If ECT signal circuit is not open, go to step 11).
9. Repair circuit as necessary. Go to step 12).
10. Replace ECT sensor. Go to step 12).
11. Replace PCM. Go to next step.
12. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, 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).
13. 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°). See appropriate TESTS W/O CODES article. A skewed sensor could result in poor driveability complaints.

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. Perform Powertrain 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 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. 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 "G", "D" and "E") 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 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 terminals as necessary. If no repairs were required, go to step 11). If no terminals were replaced, go to step 10).
8. Turn ignition off. Disconnect PCM 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. Go to step 11).
10. Replace PCM. Go to next step.
11. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, 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 P0121 Schematic. Scheme 92

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. Voltage on APP 1 is less than .25 volt.
2. Conditions are met for 2 seconds.

1. Perform Powertrain 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 less than or equal to .25 volt, go to next step. If APP 1 voltage is greater than .25 volt, go to step 4).
3. DTC is intermittent. If no additional DTCs are set, see DIAGNOSTIC AIDS. 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 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 12). 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 terminals as necessary. If any terminals were replaced, go to step 12). If no terminals were replaced, go to step 11).
8. Turn ignition off. Disconnect PCM connector. Check for open or short to ground in APP 1 signal circuit. Repair as necessary. If open or short to ground was present in APP 1 signal circuit, go to step 12). If open or short to ground was not present in APP 1 signal circuit, go to next step.
9. Check for poor connections at APP 1 signal terminal of PCM. Repair terminal as necessary. If terminal was replaced, go to step 12). If terminal was not replaced, go to step 11).
10. Replace APP module. Go to step 12).
11. Replace PCM. Go to next step.
12. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, 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).
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 stopped 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 circuit are open.

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. Voltage on APP 1 is greater than 4.75 volts.
2. Conditions are met for 2 seconds.

1. Perform Powertrain 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. If any additional DTCs are set, go to applicable DTC test.
4. Disconnect APP sensor 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, probe APP 1 ground circuit of APP 1 sensor connector to battery voltage. 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. Repair as necessary. If short to voltage was present in APP 1 signal circuit, go to step 11). If short to voltage was not present in APP 1 signal circuit, go to step 10).
7. Check for poor connections at APP sensor connector. Repair terminals as necessary. If any terminals were replaced, go to step 11). If no terminals were replaced, go to step 10).
8. Check for open in APP 1 ground circuit. Repair as necessary. If open was present in APP 1 ground circuit, go to step 11). If open was not present in APP 1 ground circuit, go to step 10).
9. Replace APP module. Go to step 11).
10. Replace PCM. Go to next step.
11. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, 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).
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 stopped 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.

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. Fuel temperature is greater than 215°F (102°C).
2. Conditions are met for 2 seconds.

1. Perform Powertrain On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Install scan tool. Start engine. Monitor fuel temperature display on scan tool. If fuel temperature display is greater than 215°F (102°C), go to next step. If fuel temperature display 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 display is less than or equal to 63°F (17°C), go to step 7). If fuel temperature display 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. If any additional DTCs are set, go to applicable DTC test.
6. Repair short to ground in fuel temperature signal circuit. Go to step 9).
7. Replace fuel injection pump. If fuel injection pump is replaced, new pump must be timed. See appropriate ADJUSTMENTS article. Go to step 9).
8. Replace PCM. Go to next step.
9. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, 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 P0182 Schematic. Scheme 93

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. Perform Powertrain On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Install scan tool. Start engine. Monitor fuel temperature display on scan tool. If fuel temperature display is less to 63°F (17°C), go to next step. If display is greater than 63°F (17°C), 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 display on scan tool. If fuel temperature display is greater than 221°F (105°C), go to step 6). If fuel temperature display is less than 221°F (105°C), go to next step.
4. Connect a jumper wire between fuel temperature signal circuit of fuel temperature sensor connector and ground. Monitor fuel temperature display on scan tool. If fuel temperature display is greater than 221°F (105°C), go to step 7). If fuel temperature display is less than 221°F (105°C), go to step 8).
5. DTC is intermittent. If no additional DTCs are set, see DIAGNOSTIC AIDS. If any additional DTCs are set, go to applicable DTC test.
6. Check for poor connections at fuel temperature sensor and PCM. If a problem was found, go to step 9). If a problem is not found, go to step 10).
7. Check for open in fuel temperature ground circuit between fuel temperature sensor and PCM. If fuel temperature ground circuit is open, go to step 9). If ground circuit is not open, go to step 11).
8. Check for open in fuel temperature signal circuit between fuel temperature sensor and PCM. If fuel temperature signal circuit is open, go to next step. If fuel temperature signal circuit is not open, go to step 11).
9. Repair circuit as necessary. Go to step 12).
10. Replace fuel injection pump. If fuel injection pump is replaced, new pump must be timed. See appropriate ADJUSTMENTS article. Go to step 12).
11. Replace PCM. Go to next step.
12. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, 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).
13. 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.

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 greater 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 less than 8 volts.
3. Conditions are met for 2 seconds.

1. Perform Powertrain On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Ignition off. Unplug ESO connector. Ignition on, engine off. With test light to ground, probe ESO ignition feed circuit terminal of harness. If test light is on, go to next step. If not, go to step 5).
3. Ignition off. Using test light, jumper ESO harness connector terminals together. Ignition on, engine off. If test light is on, go to next step. If not, go to step 6).
4. Check for poor connections at solenoid control terminal of PCM. Repair terminal as necessary. If terminal was replaced, go to step 9). If terminal was not replaced, go to step 7).
5. Check ESO ignition feed circuit for open or faulty fuse and repair as necessary. After repairs, go to step 9).
6. Check for open, poor PCM connection or circuit shorted to ground. Repair as necessary. If repairs were performed, go to step 9). If no repairs were required, go to step 8).
7. Replace injection pump. After replacement, go to step 9).
8. Replace PCM. Program PCM using required equipment. Go to next step.
9. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, 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).
10. 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 engine shutoff solenoid on and off. This can be a quick operational check of solenoid.

DTC P0215 Schematic. Scheme 94

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 of top dead center. This test compares desired timing to measured timing when certain conditions are met. To 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 20.8 seconds.
2. A 5 degree difference between actual injection time and desired injection time.

1. Perform Powertrain On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
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 next step. If scan tool does not displays a difference of 5 degrees between actual and desired injection time at idle and at 1500 RPM, go to step 4).
3. DTC is intermittent. If no additional DTCs are set, see DIAGNOSTIC AIDS. If any additional DTCs are set, go to applicable DTC test.
4. Turn ignition off. Disconnect PCM connector. Using DVOM, check resistance between coil 1 low and coil 1 high circuits of PCM 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, check resistance between coil 2 low and coil 2 high circuits of PCM 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 connector. Disconnect injection timing stepper motor. 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. Using DVOM, check 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 15).
8. Check if injection timing is set correctly. Check for a sheared camshaft driven key. Repair as necessary. If a problem was found, go to step 18). If a problem was not found, go to step 16).
9. Turn ignition off. Disconnect PCM connector. Check for open in coil 1 low and coil 1 high circuits. Repair as necessary. If a problem was found, go to step 18). If a problem was not found, go to step 16).
10. Turn ignition off. Disconnect PCM connector. Check for open in coil 2 low and coil 2 high circuits. Repair as necessary. If a problem was found, go to step 18). If a problem was not found, go to step 16).
11. Check for poor connections at injection timing stepper motor. Repair terminals as necessary. If any terminals were replaced, go to next step. If no terminals were replaced, go to step 17).
12. Check for short to ground in any injection timing stepper motor circuits or for poor connections at PCM. Repair as necessary. If a problem was found, go to step 18). If a problem was not found, go to step 17).
13. Check for short to ground in crankshaft position sensor pigtail. Repair as necessary. If a problem was found, go to step 18). If a problem was not found, go to next step.
14. Check for poor connection and repair terminals as necessary. If terminal was replaced, go to step 18). If terminal was not replaced, go to step 17).
15. Replace crankshaft position sensor. Go to step 18).
16. Replace fuel injection pump. If fuel injection pump is replaced, new pump must be timed. See appropriate ADJUSTMENTS article. Go to step 18).
17. Replace PCM. Go to next step.
18. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, 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).
19. Using scan tool, select CAPTURE INFO, REVIEW INFO. If any undiagnosed DTC(s) are displayed, go to applicable DTC test.

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 ADJUSTMENTS article.

DTC P0216 Schematic. Scheme 95

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

DTC will set when the following conditions are present

1. Five engine shutoff cycles with an RPM drop.

1. Perform Powertrain On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Replace fuel injection pump. If fuel injection pump is replaced, new pump must be timed. See appropriate ADJUSTMENTS article. Go to next step.
3. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, 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.

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. Reference voltage on APP 2 is less than 4.8 volts.
2. Conditions are met for 2 seconds.

1. Perform Powertrain On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Turn ignition off. Disconnect APP sensor connector. Turn ignition on, with engine off. Using DVOM, check voltage between ground and 5-volt reference circuits (terminals "G", "D" and "E") of APP sensor connectors. If voltage on all circuits is 4.8 volts, go to step 4). If voltage on all circuits is not 4.8 volts, go to next step.
3. DTC is intermittent. If no additional DTCs are set, see DIAGNOSTIC AIDS. If any additional DTCs are set, go to applicable DTC test.
4. Turn ignition off. Disconnect PCM 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. Go to next step.
6. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, 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

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. Perform Powertrain 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 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. 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 "G", "D" and "E") 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 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 terminals as necessary. If any terminals were replaced, go to step 11). If no terminals were replaced, go to step 10).
8. Turn ignition off. Disconnect PCM 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. Go to step 11).
10. Replace PCM. Go to next step.
11. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, 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 TESTS W/O CODES article. Scan APP 2 sensor while depressing accelerator pedal with engine stopped and ignition on. Display should vary from about 4.5 volts with throttle closed to about 1.5 volts with throttle held at WOT.

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. Voltage on APP 2 is less than .25 volt.
2. Conditions are met for 2 seconds.

1. Perform Powertrain 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 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. If any additional DTCs are set, go to applicable DTC test.
4. Turn ignition off. Disconnect APP sensor connector. Using DVOM, check voltage on APP 2 sensor connector 5-volt reference circuit terminal. If voltage is greater than 5 volts, go to step 5). If voltage is less than 5 volts, go to step 6).
5. Using DVOM, check voltage on APP 2 sensor connector signal circuit terminal. If voltage is greater than 5 volts, go to step 10). If voltage is 5 volts or less, go to step 8).
6. Turn ignition off. Disconnect PCM 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 13). 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 terminals as necessary. If any terminals were replaced, go to step 13). If no terminals were replaced, go to step 12).
8. Turn ignition off. Disconnect PCM connector. Check for open or short to ground in APP 2 signal circuit. Repair as necessary. If open or short to ground was present in APP 2 signal circuit, go to step 13). If open or short to ground was not present in APP 2 signal circuit, go to next step.
9. Check for poor connections at APP 2 signal terminal of PCM. Repair terminal as necessary. If terminal was replaced, go to step 13). If terminal was not replaced, go to step 12).
10. Replace APP module. After repair, go to step 13).
11. Replace APP module. Go to step 13).
12. Replace PCM. Go to next step.
13. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, 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 TESTS W/O CODES article. Scan APP 2 sensor while depressing accelerator pedal with engine stopped and ignition on. Display should vary from about 4.5 volts with throttle closed to about 1.5 volts with throttle held at WOT.

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. Voltage on APP 2 is greater than 4.75 volts.
2. Conditions are met for 2 seconds.

1. Perform Powertrain 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 2 voltage. If APP 2 voltage is greater than or equal to 4.75 volts, go to step 4). If APP 2 voltage is less than 4.75 volts, go to next step.
3. DTC is intermittent. If no additional DTCs are set, see DIAGNOSTIC AIDS. If any additional DTCs are set, go to applicable DTC test.
4. Using test light, probe APP 2 ground circuit of APP 2 sensor connector to battery voltage. If test light illuminates, go to next step. If test light does not illuminate, go to step 7).
5. Disconnect APP sensor connector. Using a fused jumper wire, jumper APP 2 signal circuit to APP 2 ground circuit. Using scan tool, observe APP 2 voltage. If APP 2 voltage is less than .25 volt, go to step 8). If APP 2 voltage is greater than .25 volt, go to next step.
6. Check for an open in APP 2 signal circuit. Repair as necessary. If repairs are required, go to step 11). If no repairs were required, go to step 10).
7. Check for open in APP 2 ground circuit. Repair as necessary. If open was present in APP 2 ground circuit, go to step 11). If open was not present in APP 2 ground circuit, go to step 10).
8. Check for poor connections at APP sensor connector. Repair terminals as necessary. If any terminals were replaced, go to step 11). If no terminals were replaced, go to next step.
9. Replace APP module. Go to step 11).
10. Replace PCM. Go to next step.
11. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, 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).
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 TESTS W/O CODES article. Scan APP 2 sensor while depressing accelerator pedal with engine stopped 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.

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. Reference voltage on APP 3 is less than 4.8 volts.
2. Conditions are met for 2 seconds.

1. Perform Powertrain On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Turn ignition off. Disconnect APP sensor connector. Turn ignition on, with engine off. Using DVOM, check voltage between ground and 5-volt reference circuits (terminals "G", "D" and "E") of APP sensor connectors. If voltage on all circuits is 4.8 volts, go to step 4). If voltage on all circuits is not 4.8 volts, go to next step.
3. DTC is intermittent. If no additional DTCs are set, see DIAGNOSTIC AIDS. If any additional DTCs are set, go to applicable DTC test.
4. Turn ignition off. Disconnect PCM 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. Go to next step.
6. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, 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).
7. 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.

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. Perform Powertrain 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 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. 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 "G", "D" and "E") of APP sensor connectors to ground. If voltage on all circuits are 4.75 volts, go to next step. If voltage on all circuits are 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 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 terminals as necessary. If any terminals were replaced, go to step 11). If no terminals were replaced, go to step 10).
8. Turn ignition off. Disconnect PCM 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. Go to step 11).
10. Replace PCM. Go to next step.
11. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, 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 stopped and ignition on. Display should vary from about 4 volts with throttle closed to about 2 volts with throttle held at WOT.

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. Voltage on APP 3 is less than .25 volt.
2. Conditions are met for 2 seconds.

1. Perform Powertrain 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 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. 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 3 sensor connector. Using scan tool, observe APP 3 voltage. If APP 3 voltage is about 5 volts, go to next step. If 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 not about 5 volts, go to step 8).
6. Turn ignition off. Disconnect PCM 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 13). 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 terminals as necessary. If any terminals were replaced, go to step 13). If no terminals were replaced, go to step 12).
8. Turn ignition off. Disconnect PCM connector. Check for open or short to ground in APP 3 signal circuit. Repair as necessary. If open or short to ground was present in APP 3 signal circuit, go to step 13). If open or short to ground was not present in APP 3 signal circuit, go to next step.
9. Check for poor connections at APP 3 signal terminal of PCM. Repair terminal as necessary. If terminal was replaced, go to step 13). If terminal was not replaced, go to step 12).
10. Check for poor electrical connection at APP sensor. Repair as necessary and go to step 13). If no repairs were required, go to next step.
11. Replace APP module. Go to step 13).
12. Replace PCM. Go to next step.
13. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, 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 TESTS W/O CODES article. Scan APP 3 sensor while depressing accelerator pedal with engine stopped and ignition on. Display should vary from about 4 volts with throttle closed to about 2 volts with throttle held at WOT.

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. Voltage on APP 3 is greater than 4.75 volts.
2. Conditions are met for 2 seconds.

1. Perform Powertrain 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 3 voltage. If APP 3 voltage is greater than 4.75 volts, go to step 4). If APP 3 voltage is less than 4.75 volts, go to next step.
3. DTC is intermittent. If no additional DTCs are set, see DIAGNOSTIC AIDS. If any additional DTCs are set, go to applicable DTC test.
4. Using test light, probe APP 3 ground circuit of APP 3 sensor connector to battery voltage. If test light illuminates, go to next step. If test light does not illuminate, go to step 7).
5. Using a fused jumper, connect APP 3 harness signal circuit and ground circuit terminals together. 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 .25 volt, go to next step.
6. Check for open in APP 3 sensor signal circuit and repair as necessary. If repairs were required, go to step 11). If repairs were not required, go to step 10).
7. Check for open sensor ground circuit and repair as necessary. If repairs were required, go to step 11). If no repairs were required, go to step 10).
8. Check for poor connections at APP sensor connector. Repair terminals as necessary. If any terminals were replaced, go to step 11). If no terminals were replaced, go to next step.
9. Replace APP module. Go to step 11).
10. Replace PCM. Go to next step.
11. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, 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).
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 stopped 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. Twelve 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. Ignition voltage -4 volts.
3. Fuel lift pump voltage is less than ignition voltage value.
4. Conditions are met for 2 seconds.

1. Perform Powertrain On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Turn ignition off for 20 seconds. Turn ignition on. Using scan tool, command fuel pump on. If fuel lift pump operates, see DIAGNOSTIC AIDS. If fuel lift pump does not operate, go to next step.
3. Turn ignition off. Using a fused jumper wire, probe fuel pump test terminal to battery voltage. If fuel pump operates, go to step 9). If fuel pump does not operate, go to next step.
4. Remove fuel pump relay. Using a fused jumper wire, probe fuel pump test terminal to battery voltage. If fuel pump operates, go to next step. If fuel pump does not operate, go to step 6).
5. Replace fuel pump relay. Go to step 20).
6. Check for open in fuel pump signal circuit. If a problem was found, go to next step. If a problem was not found, go to step 8).
7. Repair fuel pump signal circuit. Go to step 20).
8. Replace fuel pump. Go to step 20).
9. Turn ignition off. Remove fuel pump relay. Using test light, probe battery feed circuit of fuel pump relay connector to ground. If test light illuminates, go to step 11). If test light does not illuminate, go to next step.
10. Repair open in fuel pump battery feed circuit. Go to step 20).
11. Connect test light between battery feed and ground circuits of fuel pump relay connector. If test light illuminates, go to step 13). If test light does not illuminate, go to next step.
12. Repair open in fuel pump ground circuit. Go to step 20).
13. Turn ignition off. Connect test light between fuel pump control circuit of fuel pump relay connector and ground. Observe test light and turn ignition on. If test light illuminates for 2 seconds then turns off, go to step 17). If test light does not illuminate for 2 seconds then turn off, go to next step.
14. Check for open in fuel pump control circuit. If a problem was found, go to next step. If a problem was not found, go to step 16).
15. Repair open in fuel pump control circuit. Go to step 20).
16. Replace PCM. Go to step 20).
17. Check for poor connection at control circuit of fuel pump relay. If a problem was found, go to next step. If a problem was not found, go to step 19).
18. Repair fuel pump relay control circuit connection. Go to step 20).
19. Replace fuel pump relay. Go to next step.
20. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, 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).
21. Using scan tool, select CAPTURE INFO, REVIEW INFO. If any undiagnosed DTC(s) are displayed, go to applicable DTC test.

DTC P0231 will result in a poor performance problem under heavy loads or grades.

DTC P0231 Schematic. Scheme 96

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 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 mm.
3. Boost pressure is less than or equal to 110 kPa or 100 kPa on BARO (internal to PCM).
4. Conditions are met for 2 seconds.

1. Perform Powertrain On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Install scan tool. Turn ignition, with engine off. Observe scan tool boost pressure and BARO parameters. If parameters are within 5 kPa of each other, go to next step. If not, go to step 7).
3. Disconnect and plug boost sensor vacuum source. Connect a vacuum pump to boost sensor. Start engine. Using DVOM, probe boost signal circuit of PCM connector to ground. Observe boost pressure voltage. Apply 10" Hg vacuum and observe voltage. Subtract second reading from first reading. If voltage difference is greater than 1.5 volts, go to next step. If voltage difference is less than 1.5 volts, go to step 5).
4. DTC is intermittent. If no additional DTCs are set, see DIAGNOSTIC AIDS. If any additional DTCs are set, go to applicable DTC test.
5. Check for poor connections at boost sensor. If a problem was found, go to next step. If a problem was not found, go to step 7).
6. Repair connections as necessary. Go to step 8).
7. Replace boost sensor. Go to next step.
8. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, 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).
9. 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. This diagnostic checks for a skewed sensor.

DTC P0236 Schematic. Scheme 97

PCM sends a 5-volt reference signal to boost sensor. As manifold pressure changes, resistance of boost sensor also changes. PCM detects amount of pressure being produced by turbocharger in intake manifold by monitoring sensor output voltage. PCM uses boost sensor to control turbo boost and fuel at different loads.

DTC will set when the following conditions are present

1. Boost pressure is less than 40 kPa.
2. Conditions are met for 2 seconds.

1. Perform Powertrain On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Install scan tool. Operate engine at idle. Using DVOM, probe boost signal circuit of PCM connector to ground. If voltage is one volt (40 kPa), go to next step. If voltage is not one volt (40 kPa), go to step 5).
3. Turn ignition off. Disconnect boost sensor 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 202 kPa, go to step 6). If scan tool does not display a boost pressure greater 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 202 kPa (4 volts), go to step 8). If scan tool does not display a boost pressure greater than 202 kPa (4 volts), go to step 7).
5. DTC is intermittent. If no additional DTCs are set, see DIAGNOSTIC AIDS. If any additional DTCs are set, go to applicable DTC test.
6. Check for poor connections at boost sensor. If a problem was found, go to step 11). If a problem was not found, go to step 10).
7. Check for open or short to ground in boost signal circuit. If a problem was found, go to step 11). If a problem was not found, go to step 12). 8) Check for open in 5-volt reference circuit. If a problem was found, go to step 11). If a problem was not found, go to next step.
8. Check for short to ground in 5-volt reference circuit. If a problem was found, go to step 11). If a problem was not found, go to step 12).
9. Replace boost sensor. Go to step 13).
10. Repair circuit as necessary. Go to step 13).
11. Replace PCM. Go to next step.
12. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, 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).
13. 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, boost pressure is equal to atmospheric pressure. To check accuracy of suspect sensor, compare reading with a known good vehicle with same sensor. Readings should be same plus .4 volt. 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. DVOM can be used to measure (actual) signal voltage at PCM connector.

PCM sends a 5-volt reference signal to boost sensor. As manifold pressure changes, resistance of boost sensor also changes. PCM detects amount of pressure being produced by turbocharger in intake manifold by monitoring sensor output voltage. PCM uses boost sensor to control turbo boost and fuel at different loads.

DTC will set when the following conditions are present

1. Boost pressure is greater than or equal to 4.8 volts (202 kPa).
2. Engine speed is less than 3506 RPM.

1. Perform Powertrain On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Install scan tool. Operate engine at idle. Using scan tool, monitor boost pressure. If scan tool displays a boost pressure greater than or equal to 4.8 volts (202 kPa), go to next step. If scan tool does not display a boost pressure greater than or equal to 4.8 volts (202 kPa), go to step 4).
3. Turn ignition off. Disconnect boost sensor connector. Using a fused jumper wire, probe boost signal circuit of boost sensor connector to ground. Turn ignition on. If scan tool displays a boost pressure less than or equal to 9 kPa, go to step 5). If scan tool does not display a boost pressure less than or equal to 9 kPa, go to step 9).
4. DTC is intermittent. If no additional DTCs are set, see DIAGNOSTIC AIDS. If any additional DTCs are set, go to applicable DTC test.
5. Ignition on, engine off. Using DVOM to ground, probe 5-volt reference circuit terminal at boost sensor connector. If voltage is greater than 5.2 volts, go to step 10). If not, go to next step.
6. Leave boost sensor connector disconnected. Connect test light between boost ground circuit of boost sensor connector and battery voltage. If test light illuminates, go to next step. If test light does not illuminate, go to step 11).
7. Check boost sensor for restriction. If a problem was found, go to step 12). If a problem was not found, go to next step.
8. Replace boost sensor. Go to step 14).
9. Check for short to voltage in boost signal circuit. If a problem was found, go to step 12). If a problem was not found, go to step 13)..
10. Check for short to voltage in 5-volt reference circuit. If a problem was found, go to step 12). If a problem was not found, go to step 13).
11. Repair boost ground circuit as necessary. Go to step 14).
12. Repair as necessary. Go to step 14).
13. Replace PCM. Go to next step.
14. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, 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).
15. 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, boost pressure is equal to atmospheric pressure. To check accuracy of suspect sensor, compare reading with a known good vehicle with same sensor. Readings should be same plus .4 volt. Very little boost can be attained by revving engine in Neutral. DVOM can be used to measure (actual) signal voltage at PCM connector.

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 more crank pulses are missed.

DTC will set when the following conditions are present

1. RPM is less than 300.
2. Eight consecutive cam pulses missing for 8 No. 1 cylinder events.

Or

1. RPM is greater than or equal to 300.
2. Eight consecutive cam pulses missing for 32 No. 1 cylinder events.

1. Perform Powertrain On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Install scan tool. Start and operate engine at idle. Using scan tool, with throttle closed, observe CAM 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. If any additional DTCs are set, go to applicable DTC test.
4. Turn ignition off. Disconnect optical/fuel temperature sensor connector. Turn ignition on, with engine off. Using DVOM, check voltage between 5-volt reference circuit of optical sensor connector and ground. If voltage is 5 volts, go to next step. If not 5 volts, go to step 7).
5. Using test light, probe ground circuit of optical sensor connector to battery voltage. If test light illuminates, go to next step. If test light does not illuminate, go to step 8).
6. Reconnect optical/fuel temperature sensor connector. Start and idle engine. Using scan tool, command engine speed to 900 RPM. Using DVOM on Hz scale, backprobe cam signal circuit of PCM. If DVOM reading is 57-63 Hz, go to step 12). If DVOM reading is not 57-63 Hz, go to step 11).
7. Remove electrical harness filter from vehicle. Using DVOM, check resistance at terminal "A" (5-volt reference circuit) of electrical harness filter. If resistance is greater than 2 ohms, go to step 15). If resistance is less than 2 ohms, go to next step.
8. Turn ignition off. Leave electrical harness filter removed from vehicle. Disconnect PCM connector. Check 5-volt reference circuit for open, short to ground, or short to sensor ground circuit. Repair as necessary. If 5-volt reference circuit is open or shorted to ground, go to step 16). If 5-volt reference circuit is not open or shorted to ground, go to step 10).
9. Check for open or poor connections at sensor ground terminals of PCM. Repair as necessary. If a problem was found, go to step 16). If a problem was not found, go to step 14).
10. Check for poor connections at 5-volt reference terminals of PCM. Repair terminals as necessary. If any terminals were replaced, go to step 16). If no terminals were replaced, go to step 14).
11. Turn ignition off. Check for open or short to ground in cam signal circuit. Repair as necessary. If cam signal circuit is open or shorted to ground, go to step 16). If cam signal circuit is not open or shorted to ground, go to step 13).
12. Check for poor connections at PCM. Repair terminals as necessary. If any terminals were replaced, go to step 16). If no terminals were replaced, go to step 14).
13. Replace injection pump. If fuel injection pump is replaced, new pump must be timed. See appropriate ADJUSTMENTS article. Go to step 16).
14. Replace PCM. Go to step 16).
15. Replace electrical harness filter. Go to next step.
16. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, 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).
17. Using scan tool, select CAPTURE INFO, REVIEW INFO. If any undiagnosed DTC(s) are displayed, go to applicable DTC test.

Fast idle and poor performance will exist when PCM is in backup fuel. If DTC P0370 is also set, possible problem exists with signal circuit. If vehicle runs out of fuel, DTCs P0251 and P0370 will set.

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 define limits.

DTC will set when the following conditions are present

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

1. Perform Powertrain On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Install scan tool. Start and idle engine. Operate engine at normal operating temperature. Ensure all DTCs are cleared. Using scan tool, cutout (injector balance) 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. If any additional DTCs are set, go to applicable DTC test.
4. Check for basic engine mechanical or fuel delivery problem in suspected cylinder. Repair as necessary. Go to next step.
5. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, 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).
6. 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 cutout specific cylinder requested. If vehicle is equipped with a manual transmission and multiple cylinder balance DTCs, dual mass flywheel could be at fault. If 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 snap shot 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 P0263 Schematic. Scheme 98

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 define limits.

DTC will set when the following conditions are present

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

1. Perform Powertrain On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
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) 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. If any additional DTCs are set, go to applicable DTC test.
4. Check for basic engine mechanical or fuel delivery problem in suspected cylinder. Repair as necessary. Go to next step.
5. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, 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).
6. 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 vehicle is equipped with a manual transmission and multiple cylinder balance DTCs, dual mass flywheel could be at fault. If 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 snap shot 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.

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 define limits.

DTC will set when the following conditions are present

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

1. Perform Powertrain On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Install scan tool. Start and idle engine. Operate engine at normal operating temperature. Ensure all DTCs are cleared. Using scan tool, cutout (injector balance) 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. If any additional DTCs are set, go to applicable DTC test.
4. Check for basic engine mechanical or fuel delivery problem in suspected cylinder. Repair as necessary. Go to next step.
5. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, 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).
6. 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 vehicle is equipped with a manual transmission and multiple cylinder balance DTCs, dual mass flywheel could be at fault. If 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 snap shot 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.

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 define limits.

DTC will set when the following conditions are present

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

1. Perform Powertrain On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
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) 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. If any additional DTCs are set, go to applicable DTC test.
4. Check for basic engine mechanical or fuel delivery problem in suspected cylinder. Repair as necessary. Go to next step.
5. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, 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).
6. 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 vehicle is equipped with a manual transmission and multiple cylinder balance DTCs, dual mass flywheel could be at fault. If 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 snap shot 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.

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 define limits.

DTC will set when the following conditions are present

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

1. Perform Powertrain On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
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) 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. If any additional DTCs are set, go to applicable DTC test.
4. Check for basic engine mechanical or fuel delivery problem in suspected cylinder. Repair as necessary. Go to next step.
5. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, 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).
6. 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 vehicle is equipped with a manual transmission and multiple cylinder balance DTCs, dual mass flywheel could be at fault. If 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 snap shot 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.

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 define limits.

DTC will set when the following conditions are present

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

1. Perform Powertrain On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
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) 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. If any additional DTCs are set, go to applicable DTC test.
4. Check for basic engine mechanical or fuel delivery problem in suspected cylinder. Repair as necessary. Go to next step.
5. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, 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).
6. 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 vehicle is equipped with a manual transmission and multiple cylinder balance DTCs, dual mass flywheel could be at fault. If 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 snap shot 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.

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 define limits.

DTC will set when the following conditions are present

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

1. Perform Powertrain On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
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) 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. If any additional DTCs are set, go to applicable DTC test.
4. Check for basic engine mechanical or fuel delivery problem in suspected cylinder. Repair as necessary. Go to next step.
5. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, 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).
6. 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 vehicle is equipped with a manual transmission and multiple cylinder balance DTCs, dual mass flywheel could be at fault. If 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 snap shot 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.

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 define limits.

DTC will set when the following conditions are present

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

1. Perform Powertrain On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
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) 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. If any additional DTCs are set, go to applicable DTC test.
4. Check for basic engine mechanical or fuel delivery problem in suspected cylinder. Repair as necessary. Go to next step.
5. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, 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).
6. 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 vehicle is equipped with a manual transmission and multiple cylinder balance DTCs, dual mass flywheel could be at fault. If 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 snap shot 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.

Crankshaft position sensor is a Hall Effect sensor that monitors crankshaft position and speed. Four teeth, 90 degrees apart generate a signal which is transmitted to PCM. Physical one-to-one correspondence exists between pump cam and crankshaft.

DTC will set when the following conditions are present

1. RPM is less than 300.
2. Eight consecutive crank pulses missing for 8 No. 1 cylinder events.

Or

1. RPM is greater than or equal to 300.
2. Eight consecutive crank pulses missing for 32 No. 1 cylinder events.

1. Perform Powertrain On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
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. If any additional DTCs are set, go to applicable DTC test.
4. Turn ignition off. Disconnect crankshaft position sensor connector. Turn ignition on, with engine off. Using DVOM, check voltage between 5-volt reference circuit of crankshaft position sensor connector and ground. If voltage is 5 volts, go to next step. If voltage is not 5 volts, go to step 7).
5. Using test light, probe ground circuit of crankshaft position sensor connector to battery voltage. If test light illuminates, go to next step. If test light does not illuminate, go to step 8).
6. Reconnect crankshaft position sensor connector. Using DVOM, backprobe crankshaft position sensor signal circuit of PCM connector to ground. Crank engine.If voltage is 4 volts, go to step 11). If voltage is not 4 volts, go to step 10).
7. Turn ignition off. Disconnect PCM connector. Check 5-volt reference circuit for open, short to ground, or short to sensor ground circuit. Repair as necessary. If 5-volt reference circuit is open or shorted to ground, go to step 14). If 5-volt reference circuit is not open or shorted to ground, go to step 9).
8. Check for open or poor connections at sensor ground terminals of PCM. Repair as necessary. If a problem was found, go to step 14). If a problem was not found, go to step 13).
9. Check for poor connections at 5-volt reference terminals of PCM. Repair terminals as necessary. If any terminals were replaced, go to step 14). If no terminals were replaced, go to step 13).
10. Turn ignition off. Disconnect PCM connector. Check crankshaft position sensor signal circuit for open, short to ground, or short to sensor ground circuit. Repair as necessary. If crankshaft position sensor circuit is open or shorted to ground, go to step 14). If crankshaft position sensor circuit is not open or shorted to ground, go to next step.
11. Check for poor connections at crankshaft position sensor terminals of PCM. Repair terminals as necessary. If any terminals were replaced, go to step 14). If no terminals were replaced, go to next step.
12. Replace crankshaft position sensor. If crankshaft position sensor is replaced, PCM must be programmed with new TDC offset. See appropriate ADJUSTMENTS article. Go to step 14).
13. Replace PCM. Go to next step.
14. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, 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).
15. Using scan tool, select CAPTURE INFO, REVIEW INFO. If any undiagnosed DTC(s) are displayed, go to applicable DTC test.

When PCM is in backup 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.

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 of occurred.

DTC will set when the following conditions are present

1. A number of high resolution pulses (internal to PCM) per every 8 cam reference pulses.

1. Perform Powertrain On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Turn ignition off. Disconnect optical/fuel temperature sensor connector. Turn ignition on, with engine off. Using DVOM, check voltage between 5-volt reference circuit of optical sensor connector and ground. If voltage is 5 volts, go to next step. If voltage is not 5 volts, go to step 5).
3. Using test light, probe ground circuit of optical sensor connector to battery voltage. If test light illuminates, go to next step. If test light does not illuminate, go to step 7).
4. Reconnect optical/fuel temperature sensor connector. Start and idle engine. Using scan tool, command engine speed to 900 RPM. Using DVOM on Hz scale, backprobe high resolution signal circuit of PCM. If DVOM reading is 3740-3940 Hz, go to step 10). If DVOM reading is not 3740-3940 Hz, go to step 9).
5. Remove electrical harness filter from vehicle. Using DVOM, check resistance at terminal "A" (5-volt reference circuit) of electrical harness filter. If resistance is greater than 2 ohms, go to step 13). If resistance is less than 2 ohms, go to next step.
6. Turn ignition off. Leave electrical harness filter removed from vehicle. Disconnect PCM connector. Check 5-volt reference circuit for open, short to ground, or short to sensor ground circuit. Repair as necessary. If 5-volt reference circuit is open or shorted to ground, go to step 14). If 5-volt reference circuit is not open or shorted to ground, go to step 8).
7. Check for open or poor connections at sensor ground terminals of PCM. Repair as necessary. If a problem was found, go to step 14). If a problem was not found, go to step 12).
8. Check for poor connections at 5-volt reference terminals of PCM. Repair terminals as necessary. If any terminals were replaced, go to step 14). If no terminals were replaced, go to step 12).
9. Turn ignition off. Check for open or short to ground in high resolution signal circuit. Repair as necessary. If high resolution signal circuit is open or shorted to ground, go to step 14). If high resolution signal circuit is not open or shorted to ground, go to step 11).
10. Check for poor connections at high resolution signal terminals of PCM. Repair terminals as necessary. If any terminals were replaced, go to step 14). If no terminals were replaced, go to step 12).
11. Replace injection pump. If fuel injection pump is replaced, new pump must be timed. See appropriate ADJUSTMENTS article. Go to step 14).
12. Replace PCM. Go to step 16).
13. Replace electrical harness filter. Go to next step.
14. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, 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).
15. Using scan tool, select CAPTURE INFO, REVIEW INFO. If any undiagnosed DTC(s) are displayed, go to applicable DTC test.

Fast idle and poor performance will exist when PCM is in backup fuel. If DTC P0251 is also set, use scan tool on snap shoot mode to properly identify fault. If air exists in fuel system (vehicle runs out of fuel), DTC could set.

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 the following conditions are present

1. PCM has commanded glow plugs on and voltage at glow plugs is less than .8 volts.

Or

1. PCM has commanded glow plugs off and voltage at glow plugs is greater than .8 volts.

Or

1. PCM has commanded glow plugs on and a greater than 2 volt difference exists between glow plug voltage and ignition voltage.

1. Perform Powertrain 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, command glow plugs on. Observe GLOW PLUG SYSTEM display on scan tool. If scan tool displays glow plug system enabled, go to next step. If scan tool does not display glow plug system enabled, go to step 7).
3. Turn ignition on, with engine off. Using scan tool, command glow plugs on. Observe GLOW PLUGS display on scan tool. If scan tool displays glow plugs at battery voltage, go to next step. If scan tool does not display glow plugs at battery voltage, go to step 5).
4. DTC is intermittent. If no additional DTCs are set, see DIAGNOSTIC AIDS. If any additional DTCs are set, go to applicable DTC test.
5. Turn ignition off. Disconnect glow plug relay connector. Turn ignition on, with engine off. Using test light, probe ignition feed circuit of glow plug relay connector to ground. If test light illuminates, go to next step. If test light does not illuminate, go to step 10).
6. Turn ignition on, with engine off. Connect test light between ignition feed circuit and ground circuit of glow plug relay connector. If test light illuminates, go to next step. If test light does not illuminate, go to step 11).
7. Turn ignition on, with engine off. Leave glow plug relay connector disconnected. Using DVOM, probe control circuit of glow plug relay connector to ground. Using scan tool, command glow plugs on. If voltage is battery voltage, go to next step. If voltage is not battery voltage, go to step 9).
8. Reconnect glow plug relay connector. Turn ignition on, with engine off. Using test light, probe glow plug side of glow plug relay connector to ground. 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 16).
9. Check for poor connections at glow plug relay control terminal of PCM. Repair terminal as necessary. If terminal was replaced, go to step 18). If terminal was not replaced, go to step 12).
10. Repair open or short to ground in ignition feed circuit. Go to step 18).
11. Repair open or poor connections in ground circuit. Go to step 18).
12. Check for open or short to ground in control circuit. Repair as necessary. If a problem was found, go to step 18). If a problem was not found, go to next step.
13. Check for poor connections at glow plug relay control terminal of PCM. Repair terminal as necessary. If terminal was replaced, go to step 18). If terminal was not replaced, go to step 17).
14. Check for open or short to ground in signal circuit. Repair as necessary. If a problem was found, go to step 18). If a problem was not found, go to next step.
15. Check for poor connections at glow plug relay signal terminal of PCM. Repair terminal as necessary. If terminal was replaced, go to step 18). If terminal was not replaced, go to step 17).
16. Replace glow plug relay. Go to step 18).
17. Replace PCM. Go to next step.
18. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, 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).
19. 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 then off for 12 seconds.

DTC P0380 Schematic. Scheme 99

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. DTC P0405 or P0406 is not set.
2. Engine speed is greater than 506 RPM.
3. Desired EGR pressure minus measured EGR pressure is greater than 50 kPa.
4. Conditions are present for at least 25.5 seconds.

1. Perform Powertrain On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Install vacuum gauge in place of EGR valve. Start engine and operate at idle. Observe vacuum gauge.If vacuum is 5-7 in. Hg, go to next step. If vacuum is not 5-7 in. Hg, to step 5).
3. Turn ignition off. Disconnect EGR vent solenoid connector. With vacuum gauge still installed, start engine and operate at idle. Observe vacuum gauge. If vacuum is present, go to step 10). If vacuum is not present, go to step 6).
4. DTC is intermittent. If no additional DTCs are set, see DIAGNOSTIC AIDS. 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 step 7). If vacuum is not 15 in. Hg, go to step 8).
6. Turn ignition off. Install vacuum pump on EGR valve. Apply 15 in. Hg vacuum. Observe EGR valve movement. If EGR valve moves, go to next step. If EGR valve does not move, go to step 11).
7. Check for plugged or leaking vacuum hoses. Go to step 12).
8. Check for plugged or leaking vacuum hose to vacuum pump. If a problem is found, go to step 12). If a problem is not found, go to next step.
9. Check vacuum pump output. Go to step 12).
10. Replace EGR vent solenoid. Go to step 12).
11. Replace EGR valve. Go to step 8).
12. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, 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).
13. 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 will cause DTC to set. Check all vacuum lines and components connected to hoses 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 P0404 Schematic. Scheme 100

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 the following conditions are present

1. Actual EGR is less than or equal to .24 volt (15 kPa).
2. Conditions are met for 2 seconds.

1. Perform Powertrain On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Install scan tool. With engine idling, observe actual EGR display using scan tool. If scan tool displays actual EGR less than or equal to .24 volt, go to next step. If scan tool displays actual EGR greater than .24 volt, go to step 5).
3. Turn ignition off. Disconnect EGR control pressure/BARO sensor connector. Connect a jumper wire between 5-volt reference circuit and signal circuit of EGR control pressure/BARO sensor connector. Turn ignition on. If scan tool displays actual EGR greater than 4 volts, go to step 6). If scan tool displays actual EGR less than 4 volts, go to next step.
4. Turn ignition off. Remove jumper wire. Using test light, probe signal circuit of EGR control pressure/BARO sensor connector to battery voltage. Turn ignition on. If scan tool displays actual EGR greater than 4 volts, go to step 9). If scan tool displays actual EGR less than 4 volts, go to step 7).
5. DTC is intermittent. If no additional DTCs are set, see DIAGNOSTIC AIDS. If any additional DTCs are set, go to applicable DTC test.
6. Check for poor connection at EGR control pressure/BARO sensor. If a problem was found, go to step 12). If a problem was not found, go to step 11).
7. Check for open in signal circuit. If a problem was found, go to step 12). If a problem was not found, go to next step.
8. Check for short to ground in signal circuit. If a problem was found, go to step 12). If a problem was not found, go to step 13).
9. Check for open in 5-volt reference circuit. If a problem was found, go to step 12). If a problem was not found, go to next step.
10. Check for short to ground in 5-volt reference circuit. If a problem was found, go to step 12). If a problem was not found, go to step 13).
11. Replace EGR control pressure/BARO sensor. Go to step 14).
12. Repair circuit as necessary. Go to step 14).
13. Replace PCM. Go to next step.
14. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, 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).
15. 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. To test accuracy of a suspect sensor, compare reading with a known good vehicle. Reading should be same plus or minus .4 volt. DTC will set if an intermittent open is present in signal circuit or 5-volt reference circuit.

DTC P0405 Schematic. Scheme 101

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 the following conditions are present

1. Actual EGR is greater than or equal to 3.96 volts (85 kPa).
2. Desired EGR is less than or equal to 60 kPa.
3. EGR vent is closed.
4. Conditions are met for 2 seconds.

1. Perform Powertrain On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Check if DTC P1653 is set. If DTC P1653 is set, go to DTC P1653. 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 using scan tool. If scan tool displays EGR control pressure/BARO sensor voltage greater than 4 volts, go to next step. If scan tool displays EGR control pressure/BARO sensor voltage less than 4 volts, go to step 5).
4. Turn ignition off. Disconnect EGR control pressure/BARO sensor connector. Turn ignition on. If scan tool displays actual EGR voltage less than one volt, go to step 6). If scan tool displays actual EGR voltage greater than one volt, go to step 10).
5. DTC is intermittent. If no additional DTCs are set, see DIAGNOSTIC AIDS. If any additional DTCs are set, go to applicable DTC test.
6. Ignition on, engine off. With DVOM to ground, probe 5-volt reference circuit at EGR connector. If voltage is greater than 5.2 volts, go to step 11). If not, go to next step.
7. Using test light, probe ground circuit of EGR control pressure/BARO sensor connector to battery voltage. 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 was found, go to step 13). If a problem was not found, go to next step.
9. Replace EGR control pressure/BARO sensor. Go to step 15).
10. Check for short to voltage in signal circuit. If a problem was found, go to step 13). If a problem was not found, go to step 14).
11. Check for short to voltage on 5-volt reference circuit and repair as necessary. After repairs, go to step 15). If no repairs were required, go to step 14).
12. Repair ground circuit. Go to step 15).
13. Repair as necessary. Go to step 15).
14. Replace PCM. Go to next step.
15. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, 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).
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. Information is used by PCM as an indication of vehicle altitude. To test accuracy of a suspect sensor, compare reading with a known good vehicle. Reading should be same plus or minus .4 volt. DTC will set if open is present in ground circuit. If DTC is intermittent, see appropriate TESTS W/O CODES article.

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 less than half transmission calculated speed.

Or

1. VSS buffer calculated speed is greater than transmission calculated speed by 20 MPH.
2. Conditions are met for 2 seconds.

1. Perform Powertrain On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Install scan tool. Raise drive wheels. With engine operating, 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, backprobe ignition feed circuit of VSS buffer/module connector to ground. If test light illuminates, go to next step. If test light does not illuminate, go to step 8).
4. Using test light, backprobe between ignition feed circuit and ground circuit of VSS buffer/module 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 of VSS buffer/module connector to each other. Place transmission in any drive range with drive wheels rotating. If voltage increases as drive wheels increase, go to next step. If voltage does not increase as drive wheels increase, go to step 10).
6. If scan tool displays a trans output speed (MPH) increase with drive wheel increase, go to step 11).
7. DTC is intermittent. If no additional DTCs are set, see DIAGNOSTIC AIDS. If any additional DTCs are set, go to applicable DTC test.
8. Repair open in ignition feed circuit. Go to step 15).
9. Repair open in ground circuit. Go to step 15).
10. Check for open or short to ground in complete VSS input circuit. Go to step 15).
11. Check for open or short to ground in VSS output circuit. If a problem was found, go to step 15). If a problem was not found, go to next step.
12. Check for poor connections at VSS output terminal of buffer/module and PCM. If a problem was found, go to step 15). If a problem was not found, go to step 14).
13. Replace VSS buffer module. Go to step 15).
14. Replace PCM. Go to next step.
15. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, 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).
16. 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 set, see appropriate TRANSMISSION SERVICE & REPAIR manual for domestic vehicles.

DTC P0501 Schematic. Scheme 102

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 the following conditions are present

1. Cruise switch off.
2. Ignition voltage on resume switch signal circuit.

Or

1. Cruise switch on.
2. Resume switch on for longer than 25.5 seconds.

1. Perform Powertrain 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. Turn cruise switch off. If scan tool displays resume switch on, go to next step. If scan tool does not display resume switch on, go to step 4).
3. Turn ignition off. Disconnect PCM connector. Turn ignition on. Using test light, probe resume switch signal circuit of PCM connector to ground. 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. If any additional DTCs are set, go to applicable DTC test.
5. Repair short to voltage in resume switch signal circuit. Go to step 7).
6. Replace PCM. Go to next step.
7. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, 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 P0567 Schematic. Scheme 103

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 switch is on.

DTC will set when the following conditions are present

1. Cruise switch off.
2. Ignition voltage on set switch signal circuit.

Or

1. Cruise switch on.
2. Set switch on for longer than 25.5 seconds.

1. Perform Powertrain 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. Turn cruise switch off. If scan tool displays set switch on, go to next step. If scan tool does not display set switch on, go to step 4).
3. Turn ignition off. Disconnect PCM connector. Turn ignition on. Using test light, probe set switch signal circuit of PCM connector to ground. 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. If any additional DTCs are set, go to applicable DTC test.
5. Repair short to voltage in set switch signal circuit. Go to step 7).
6. Replace PCM. Go to next step.
7. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, 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.

TCC normally closed brake switch supplies battery voltage signal on TCC/brake switch signal circuit to PCM. Circuit is opened when brakes are applied. Brake light/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 the following conditions are present

1. Switches disagree for 10 consecutive minutes.

Or

1. TCC and cruise control brake switches are not toggling open and closed during 6 brake applications on same ignition cycle.

1. Perform Powertrain 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. Apply brakes. If scan tool displays cruise brake switch closed then open when brakes are released, go to next step. If scan tool does not display cruise brake switch closed then open when brakes are released, go to step 4).
3. Apply brakes again. If scan tool displays cruise brake switch open then closed when brakes are released, go to step 8). If scan tool does not display cruise brake switch open then closed when brakes are released, go to step 6).
4. Turn ignition off. Disconnect brake light switch connector. Turn ignition on, with engine off. Using test light, probe normally open feed circuit of brake light switch connector to ground. If test light illuminates, go to next step. If test light does not illuminate, go to step 9).
5. Disconnect brake light switch connector. Connect a jumper wire between normally open feed circuit and normally open signal circuit of brake light switch connector. If scan tool displays cruise brake switch closed, go to next step. If scan tool does not display cruise brake switch closed, go to step 10).
6. Disconnect brake light switch connector. Turn ignition on, with engine off. Using test light, probe normally closed feed circuit of brake light switch connector to ground. If test light illuminates, go to next step. If test light does not illuminate, go to step 12).
7. Disconnect brake light switch connector. Connect a jumper wire between normally closed feed circuit and normally closed signal circuit of brake light switch connector. If scan tool displays cruise brake switch closed, go to step 15). If scan tool does not display cruise brake switch closed, go to step 14).
8. DTC is intermittent. If no additional DTCs are set, see DIAGNOSTIC AIDS. If any additional DTCs are set, go to applicable DTC test.
9. Check for open or short to ground in normally open feed circuit. Go to step 17).
10. Check for open or short to ground in normally open signal circuit. If a problem was found, go to step 17). If a problem was not found, go to next step.
11. Check for poor connection at normally open signal terminal of PCM. If a problem was found, go to step 17). If a problem was not found, go to step 16).
12. Check for open or short to ground in normally closed feed circuit. Go to step 17).
13. Check for open or short to ground in normally closed signal circuit. If a problem was found, go to step 17). If a problem was not found, go to next step.
14. Check for poor connection at normally closed signal terminal of PCM. If a problem was found, go to step 17). If a problem was not found, go to step 16).
15. Replace brake light switch. Go to step 17).
16. Replace PCM. Go to next step.
17. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, 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).
18. Using scan tool, select CAPTURE INFO, REVIEW INFO. If any undiagnosed DTC(s) are displayed, go to applicable DTC test.

See appropriate TESTS W/O CODES article. Check customer driving habits and/or unusual traffic conditions (i.e., stop and go, expressway traffic).

DTC P0571 Schematic. Scheme 104

1. Perform Powertrain On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Replace PCM. Go to next step.
3. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, 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. Perform Powertrain On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Check all PCM connections. If a problem was found, go to step 4). If a problem was not found, go to next step.
3. Check with manufacturer for latest software. If a problem was found, go to next step. If a problem was not found, go to step 5).
4. Try to reprogram again. If programming is complete, go to step 6). If programming is not complete, go to next step.
5. Replace PCM. Go to next step.
6. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, 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).
7. Using scan tool, select CAPTURE INFO, REVIEW INFO. If any undiagnosed DTC(s) are displayed, go to applicable DTC test.

1. Perform Powertrain On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Check if DTC P0370 is set. If DTC P0370 is set, go to DTC P0370. If DTC P0370 is not set, go to next step.
3. Replace PCM. Go to next step.
4. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, 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.

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 the following conditions are present

1. PCM has recognized an intermittent APP fault and no other current APP faults are stored.

1. Perform Powertrain On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Turn ignition off. Disconnect APP sensor connector. Turn ignition on, with engine off. Using DVOM, check voltage between all 5-volt reference circuits of APP sensor connector and ground. If voltage is less than 4.8 volts, go to step 4). If voltage is greater than 4.8 volts, go to next step.
3. DTC is intermittent. If no additional DTCs are set, see DIAGNOSTIC AIDS. If any additional DTCs are set, go to applicable DTC test.
4. Turn ignition off. Disconnect PCM connector. Check for short to ground in 5-volt reference circuit. Repair as necessary. If 5-volt reference circuit is shorted to ground, go to step 6). If 5-volt reference circuit is not shorted to ground, go to next step.
5. Replace PCM. Go to next step.
6. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, 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.

DTC P1125 will set along with multiple APP DTCs. Diagnose all other APP DTCs first.

1. Perform Powertrain On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Install scan tool. If scan tool displays a TDC offset greater than 2.5 or less than -2.5, go to step 4). If scan tool does not display a TDC offset greater than 2.5 or less than -2.5, go to next step.
3. DTC is intermittent. If no additional DTCs are set, see DIAGNOSTIC AIDS. If any additional DTCs are set, go to applicable DTC test.
4. Check if any other DTCs are set. If any other DTCs are set, go to appropriate DTC. If any other DTCs are not set, go to next step.
5. Clear all DTCs and reset injection timing until TDC offset is -.25 to -.75. See appropriate ADJUSTMENTS article. If timing is -.25 to -.75, go to step 7). If timing is not -.25 to -.75, go to next step.
6. Check crankshaft position sensor for proper installation or loose or broken sensor mounting tab. If repairs are required, repair as necessary and go to step 8). If no repairs are required, go to next step.
7. Replace PCM. Go to next step.
8. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, 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).
9. Using scan tool, select CAPTURE INFO, REVIEW INFO. If any undiagnosed DTC(s) are displayed, go to applicable DTC test.

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 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 and 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 less than .75 milliseconds.

1. Perform Powertrain On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Check if DTC P0219 is set. If DTC P0219 is set, go to DTC P0219. 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. With engine at normal operating temperature, using scan tool, observe injection pump closure time. If scan tool displays injection pump closure time less than .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, using scan tool, observe injection pump closure time. If scan tool displays injection pump closure time as 0.0 milliseconds, go to step 8). If scan tool does not display injection pump closure time as 0.0 millisecond, go to step 10).
6. DTC is intermittent. If no additional DTCs are set, see DIAGNOSTIC AIDS. If any additional DTCs are set, go to applicable DTC test.
7. Check for open in closure ground circuit. Repair as necessary. Go to step 12).
8. Check for open or short to ground in closure signal circuit. Repair as necessary. If a problem was found, go to step 12). If a problem was not found, go to next step.
9. Check for poor connection at closure signal terminal of PCM. Repair terminal as necessary. If terminal was replaced, go to step 12). If terminal was not replaced, go to next step.
10. Replace fuel injection pump. If fuel injection pump is replaced, new pump must be timed. See appropriate ADJUSTMENTS article. Go to step 12).
11. Replace PCM. Go to next step.
12. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, 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.

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 P1216 Schematic. Scheme 105

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 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 and 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 less than 2.5 milliseconds.

1. Perform Powertrain On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Check if DTC P0370 is set. If DTC P0370 is set, go to DTC P0370. If DTC P0370 is not set, go to next step.
3. With engine at normal operating temperature, using scan tool, observe injection pump closure time. If scan tool displays injection pump closure time greater than 2.4 milliseconds, go to next step. If scan tool displays injection pump closure time less than 2.4 millisecond, go to step 5).
4. Turn on all accessories. Engine idling. With DVOM to ground, check voltage at FUEL SOL fuse (fuel solenoid driver ignition feed circuit) in underhood relay center. If voltage is 11-16 volts, go to step 7). If not, go to step 6).
5. DTC is intermittent. If no additional DTCs are set, see DIAGNOSTIC AIDS. 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 and go to step 8).
7. Replace fuel injection pump. If fuel injection pump is replaced, new pump must be timed. See appropriate ADJUSTMENTS article. Go to next step.
8. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, 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.

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 the following conditions are present

1. PCM currently does not have a valid resistor value.
2. PCM is unable to read resistor value.

1. Perform Powertrain On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Check if any other DTCs are set. If any other DTCs are set, go to appropriate DTC. If any other DTCs are not set, go to next step.
3. Check connection at fuel solenoid driver. Clear DTCs and cycle engine. If DTC clears, go to step 5). If DTC does not clear, go to next step.
4. Replace fuel injection pump. If fuel injection pump is replaced, new pump must be timed. See appropriate ADJUSTMENTS article. Go to next step.
5. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, then enter DTC P1218. 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.

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

1. Capture and record freeze frame and failure records data. Perform Powertrain On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Replace PCM. Go to next step.
3. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, 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.

1. Perform Powertrain On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Replace PCM. Go to next step.
3. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, 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.

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 the following conditions are present

1. 5-volt reference is less than one volt.

1. Perform Powertrain On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Install scan tool. Start engine or crank engine for 15 seconds if engine does not start. 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 connector. Turn ignition on, with engine off. Using DVOM, probe 5-volt reference circuit of boost sensor connector. If voltage is less than 4 volts, go to next step. If voltage is greater than 4 volts, go to step 6).
4. Turn ignition off. Disconnect PCM connector. Using test light, probe boost sensor 5-volt reference circuit of PCM connector to battery voltage. 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. If any additional DTCs are set, go to applicable DTC test.
6. Replace boost sensor. Go to step 9).
7. Repair short to ground in 5-volt reference circuit. Go to step 9).
8. Replace PCM. Go to next step.
9. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, 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).
10. Using scan tool, select CAPTURE INFO, REVIEW INFO. If any undiagnosed DTC(s) are displayed, go to applicable DTC test.

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

MIL is illuminated by PCM if diagnostics have detected certain errors related to engine performance or engine sensor status. Illumination is accomplished by PCM providing a ground path for light circuit.

DTC will set when the following conditions are present

1. MIL is requested on.
2. No voltage drop on MIL control circuit.
3. Two consecutive faults detected.
4. Conditions are met for 2 seconds.

Or

1. MIL is requested off.
2. No ignition voltage on MIL control circuit.
3. Two consecutive faults detected.
4. Conditions are met for 2 seconds.

1. Perform Powertrain 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. Turn MIL on and off using scan tool. If MIL illuminates, go to next step. If MIL does not illuminate, go to step 4).
3. DTC is intermittent. If other DTC(s) exist, go to that DTC for diagnosis. If no other DTC(s) exist, see DIAGNOSTIC AIDS.
4. Turn ignition off. Disconnect PCM connector. Turn ignition on, with engine off. If MIL illuminates, go to next step. If MIL does not illuminate, go to step 7).
5. Ignition on, engine off. Using fused jumper, connect PCM connector MIL driver circuit terminal to ground. If MIL is on, go to next step. If not, go to step 8).
6. Check for poor connections at PCM. If problem was found, repair as necessary and go to step 10). If no repairs were required, go to step 9).
7. Repair short to ground in MIL control circuit. Go to step 10).
8. Check for the following conditions in MIL control circuit: Open ignition feed. Poor connections at PCM. Faulty bulb. Control circuit open or shorted to battery voltage. After repairs, go to step 10).
9. Replace PCM. Go to next step.
10. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, 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 in MIL control circuit will cause DTC P1641 to set.

DTC P1641 Schematic. Scheme 106

EGR flow is controlled by vacuum actuated EGR valve. EGR vent solenoid purges to atmosphere vacuum level at EGR valve actuator as commanded by PCM. This occurs when EGR flow is desired to turn off quickly. PCM controls EGR vent solenoid by providing a ground path.

DTC will set when the following conditions are present

1. PCM requested EGR vent solenoid on.
2. Control circuit voltage at PCM is greater than 8 volts.
3. Conditions are met for 2 seconds.

Or

1. PCM requested EGR vent solenoid off.
2. Control circuit voltage at PCM is less than 8 volts.
3. Conditions are met for 2 seconds.

1. Perform Powertrain On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Install scan tool. Start and idle engine. Using scan tool, command EGR vent solenoid on and off. If actual EGR responds to scan tool commands, go to next step. If actual EGR does not respond to scan tool commands, go to step 5).
3. Ignition off. Unplug PCM connector containing EGR vent solenoid control circuit. Ignition on. Using DVOM on 10-amp scale, measure current from ground to PCM connector EGR vent solenoid control circuit terminal for 2 minutes. If current draw is less than .75 amp (but not zero), go to step 8). If current draw is not less than .75 amp (or is zero), go to next step.
4. Ignition off. With PCM connector still unplugged, unplug EGR vent solenoid connector. Check resistance between ground and PCM connector EGR vent solenoid control circuit terminal. If resistance is infinite, go to step 13). If not, go to step 10).
5. Unplug EGR vent solenoid connector. Ignition on, engine off. Connect test light between solenoid connector power feed and control circuit terminals. Command solenoid on and off using scan tool. If light turns on and off, go to step 9). If not, go to next step.
6. Ignition on, engine off. With test light to ground, probe ignition feed circuit terminal at EGR vent solenoid connector. If test light is on, go to next step. If test light is not on, go to step 12).
7. Ignition off. Reconnect solenoid connector. Unplug PCM connector containing vent solenoid driver circuit. Ignition on. Using a fused jumper wire connected to ground, probe solenoid control circuit in PCM connector. If solenoid clicks, go to step 11). If not, go to step 10).
8. DTC is intermittent. If no additional DTCs are set, see DIAGNOSTIC AIDS. If any additional DTCs are set, go to applicable DTC test.
9. Check for poor connections at EGR vent solenoid. Repair terminals as necessary. If any terminals were replaced, go to step 15). If no terminals were replaced, go to step 13).
10. Repair EGR vent solenoid control circuit. After repairs, go to step 15).
11. Check for poor connection at EGR vent solenoid control terminal of PCM. If a problem was found, go to step 15). If a problem was not found, go to step 14).
12. Repair open in ignition feed circuit. Go to step 15).
13. Replace EGR vent solenoid. Go to step 15).
14. Replace PCM. Go to next step.
15. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, 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 solenoid is off.

SERVICE THROTTLE SOON indicator light is illuminated by PCM if diagnostics have detected certain errors related to Accelerator Pedal Position (APP) sensor. Illumination is accomplished by PCM providing a ground path for light circuit.

DTC will set when the following conditions are present

1. SERVICE THROTTLE SOON indicator light is requested on.
2. No voltage drop on SERVICE THROTTLE SOON indicator light control circuit.
3. Two consecutive faults detected.
4. Conditions are met for 2 seconds.

Or

1. SERVICE THROTTLE SOON indicator light is requested off.
2. No ignition voltage on SERVICE THROTTLE SOON indicator light control circuit.
3. Two consecutive faults detected.
4. Conditions are met for 2 seconds.

1. Perform Powertrain On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Ignition on, engine off. Using scan tool, command light on and off. If light turns on and off, go to next step. If not, go to step 4).
3. DTC is intermittent. If no additional DTCs are set, see DIAGNOSTIC AIDS. If any additional DTCs are set, go to applicable DTC test.
4. Ignition off. Unplug PCM connector containing the light control circuit. Ignition on, engine off. If light is on, go to next step. If not, go to step 7).
5. With fused jumper wire to ground, probe light control driver circuit at PCM connector. If light is on, go to next step. If not, go to step 8).
6. Check for poor PCM connections and repair as necessary. If repairs were required, go to step 10). If repairs were not required, go to step 9).
7. Repair short to ground in SERVICE THROTTLE SOON indicator light control circuit. Go to step 10).
8. Check for the following conditions in SERVICE THROTTLE SOON indicator light control circuit: Opens. Faulty bulb. Faulty fuse. After repairs, go to step 10).
9. Replace PCM. Go to next step.
10. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, then enter DTC P01654. 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 indicator light control circuit will cause DTC P1654 to set.

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. PCM controls EGR solenoid by providing a ground path.

DTC will set when the following conditions are present

1. PCM requested EGR solenoid on.
2. Control circuit voltage at PCM is greater than 8 volts.
3. Two consecutive faults detected.
4. Conditions are met for 2 seconds.

Or

1. PCM requested EGR solenoid off.
2. Control circuit voltage at PCM is less than 8 volts.
3. Two consecutive faults detected.
4. Conditions are met for 2 seconds.

1. Perform Powertrain On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Install scan tool. Start and idle engine. Using scan tool, command EGR solenoid on and off. If actual EGR responds to scan tool commands, go to step 5). If actual EGR does not respond to scan tool commands, go to next step.
3. Ignition off. Unplug PCM connector containing EGR solenoid control circuit. Ignition on. With DVOM to ground and set on 10-amp scale, measure current from PCM connector EGR solenoid control circuit terminal. If current draw is less than .75 amp (but not zero), go to step 8). If current is not less than .75 amp (or is zero), go to next step.
4. Ignition off. With PCM connector still unplugged, unplug EGR solenoid connector. Check resistance between ground and PCM connector EGR solenoid control circuit terminal. If resistance is infinite, go to step 13). If not, go to step 10).
5. Turn ignition off. Disconnect EGR solenoid connector. Turn ignition on, with engine off. Connect test light between control circuit and ignition feed circuit of EGR solenoid connector. If test light illuminates, go to step 9). If test light does not illuminate, go to next step.
6. Turn ignition on, with engine off. Using test light, probe ignition feed circuit of EGR solenoid connector to ground. If test light illuminates, go to next step. If test light does not illuminate, go to step 12).
7. Ignition off. Reconnect EGR solenoid. Unplug PCM connector containing EGR solenoid control circuit. Ignition on. Using fused jumper wire to ground, probe PCM connector EGR solenoid control circuit terminal. If solenoid clicks, go to step 11). If not, go to step 10).
8. DTC is intermittent. If no additional DTCs are set, see DIAGNOSTIC AIDS. If any additional DTCs are set, go to applicable DTC test.
9. Check for poor connections at EGR solenoid. Repair terminals as necessary. If any terminals were replaced, go to step 15). If no terminals were replaced, go to step 13).
10. Repair EGR solenoid control circuit and go to step 15).
11. Check for poor connection at EGR solenoid control terminal of PCM. If a problem was found, go to step 15). If a problem was not found, go to step 14).
12. Repair open in ignition feed circuit. Go to step 15).
13. Replace EGR solenoid. Go to step 15).
14. Replace PCM. Go to next step.
15. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, then enter DTC P01655. 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.

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. PCM controls wastegate solenoid by providing a ground path.

DTC will set when the following conditions are present

1. PCM requested wastegate solenoid on.
2. No voltage drop on wastegate solenoid control circuit.
3. Two consecutive faults detected.
4. Conditions are met for 2 seconds.

Or

1. PCM requested wastegate solenoid off.
2. No ignition voltage on wastegate solenoid control circuit.
3. Two consecutive faults detected.
4. Conditions are met for 2 seconds.

1. Perform Powertrain On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Install scan tool. Turn ignition off. Disconnect wastegate solenoid connector. Turn ignition on, with engine off. Connect test light between control circuit and ignition feed circuit of wastegate solenoid connector. Using scan tool, command wastegate solenoid on and off. If test light responds to scan tool commands, go to step 5). If test light does not respond to scan tool commands, go to next step.
3. Ignition off. Unplug PCM connector containing wastegate solenoid control circuit. Ignition on. With DVOM to ground and set on 10-amp scale, measure current from PCM connector wastegate solenoid control circuit terminal. If current draw is less than .75 amp (but not zero), go to step 8). If current is not less than .75 amp (or is zero), go to next step.
4. Ignition off. With PCM connector still unplugged, unplug wastegate solenoid connector. Check resistance between ground and PCM connector EGR solenoid control circuit terminal. If resistance is infinite, go to step 13). If not, go to step 10).
5. Turn ignition off. Disconnect wastegate solenoid connector. Turn ignition on, with engine off. Connect test light between control circuit and ignition feed circuit of wastegate solenoid connector. If test light illuminates, go to step 9). If test light does not illuminate, go to next step.
6. Turn ignition on, with engine off. Using test light, probe ignition feed circuit of wastegate solenoid connector to ground. If test light illuminates, go to step 7). If test light does not illuminate, go to step 12).
7. Ignition off. Reconnect solenoid. Unplug PCM connector containing wastegate solenoid control circuit. Ignition on. With fused jumper wire to ground, probe PCM connector wastegate solenoid control circuit terminal. If solenoid clicks, go to step 11). If not, 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.
9. Check for poor connections at wastegate solenoid. Repair terminals as necessary. If any terminals were replaced, go to step 15). If no terminals were replaced, go to step 13).
10. Repair wastegate solenoid control circuit. After repairs, go to step 15).
11. Check for poor connection at wastegate solenoid control terminal of PCM. If a problem was found, go to step 15). If a problem was not found, go to step 14).
12. Repair open in ignition feed circuit. Go to step 15).
13. Replace wastegate solenoid. Go to step 15).
14. Replace PCM. Go to next step.
15. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, 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 unable to achieve boost pressures greater than BARO at idle) or at any engine speed greater than idle (PCM control abort to prevent engine damage).

See also:
• ENTERING &
• DIAGNOSTIC TROUBLE CODE (DTC)
• P0221
• TYPICAL TECH 1 DATA VALUES