Engine Controls Self-Diagnostics - 6.0l Bi-Fuel & Cng Chevrolet Chevy Express H2500

INTRODUCTION

Chevy Express & Savana vehicles are available as a Bi-Fuel vehicle (RPO KL6) or as a CNG only vehicle (RPO KL8). This alternative fuels article applies to both versions. This article should be used in conjunction with the SELF-DIAGNOSTICS - 4.8L, 5.3L, 6.0L EXPRESS & SAVANA - GASOLINE article. This article covers only the Bi-Fuel & CNG self-diagnostics. To properly diagnose and repair this vehicle, follow DIAGNOSTIC STARTING POINT - ENGINE CONTROLS under SELF-DIAGNOSTIC SYSTEM. If no Diagnostic Trouble Codes (DTC) are present and a no-start condition exists, see NO-START DIAGNOSIS in BASIC DIAGNOSTIC PROCEDURES - 6.0L CHEVY EXPRESS, SAVANA, SIERRA & SILVERADO - BI-FUEL & CNG article. If no DTCs are present and a driveability condition exists, see TROUBLE SHOOTING - NO CODES - 6.0L CHEVY EXPRESS, SAVANA, SIERRA & SILVERADO - BI-FUEL & CNG article for diagnosis by symptom (i.e., ROUGH IDLE, ENGINE STALLS, etc.).

ON-BOARD DIAGNOSTICS

PCM is equipped with a self-diagnostic system which detects system failures or abnormalities. When a malfunction occurs, PCM will store a Diagnostic Trouble Code (DTC) and, in most cases, illuminate the Malfunction Indicator Light (MIL) located on instrument cluster.

The PCM also monitors the Fuel Injector Control Module (FICM) diagnostic input circuit in order to set FICM related DTCs. The FICM is a non-flashable control module that is not capable of serial data communication. The FICM diagnostic circuit is a 5-volt circuit that is Pulse Width Modulated (PWM) by the FICM in order to communicate diagnostic information to the PCM.

There are 2 paths for accessing on-board diagnostics. It is necessary to access information through both paths, as each path presents some different information.

1. Generic OBD-II This provides all generic codes and some OEM codes, serial data PIDs required for generic OBD-II and some OEM PIDs, monitor status, pending codes and freeze frame.
2. OEM All DTCs, all PIDs, failure records, enhanced scan tool information and all other OEM scanner functions.

Code Types

There are 4 types of DTC categories

1. Type "A" Emissions related. Illuminates MIL the first time DTC sets.
2. Type "B" Emissions related. Illuminates MIL if fault is active for 2 consecutive driving cycles.
3. Type "C" Non-emissions related. Does not illuminate MIL, but will illuminate SERVICE light.
4. Type "D" Non-emissions related. Does not illuminate MIL or SERVICE light.

Freeze Frame/Failure Records

PCM stores one freeze frame record for the first failed test that sets a DTC and illuminates MIL. Freeze frame will not be overwritten unless a misfire or fuel trim DTC is set. Failure records are stored when any DTC is set. Some control modules can store up to 5 failure records. Failure records will be stored for all types of codes, whether or not the MIL is illuminated.

Typical data includes

1. Air/fuel ratio.
2. Airflow rate.
3. Fuel trim.
4. Engine speed.
5. Engine load.
6. Engine coolant temperature.
7. Vehicle speed.
8. Throttle position angle.
9. Manifold absolute pressure.
10. Injector base pulse width.
11. Loop status.

Monitors

Note. Not all monitors will run while operating in CNG mode. In order to complete all monitors, the vehicle will also need to operate in gasoline mode.

1. Comprehensive Component Monitor Monitors PCM systems for opens, shorts grounds and out-of-range sensors. Also monitors rationality of sensors. Rationality is whether the sensors value is consistent with the operating conditions of the other sensors.
2. Misfire Monitor Monitors engine misfire using crankshaft sensor to determine location and severity of misfire. A catalyst damaging misfire will flash the MIL, and a non-catalyst damaging misfire is a normal type "B" code.
3. Fuel Trim Monitor Monitors short and long term fuel trim for being at maximum lean or rich limit.
4. Oxygen Sensor Monitor Monitors all oxygen sensors for maximum voltage level, minimum voltage level and lean rich/rich lean switching rate.
5. Oxygen Sensor Heater Monitor Monitors oxygen sensor heater by watching sensor's time-to-activity after a cold start.
6. Catalyst Monitor Monitors catalyst efficiency by comparing activity rate of pre-catalyst oxygen sensor and post-catalyst oxygen sensor.
7. EVAP Monitor Monitors EVAP system for large leaks, small leaks and purge flow.

INTERMITTENT CONDITIONS

Note. Intermittent is a DTC or symptom, with a condition that cannot be duplicated.

Preliminary

Perform the Diagnostic System Check - Engine Controls before starting. See DIAGNOSTIC SYSTEM CHECK - ALTERNATIVE FUELS - ENGINE CONTROLS .

Harness or Connector Intermittents

Many intermittent open or shorted circuits come and go with harness or connector movement caused by the following type conditions

1. Vibration.
2. Engine torque.
3. Bumps or rough pavement.

Test for intermittents by performing the applicable procedure from the following list

1. Move related connectors and wiring while monitoring the appropriate scan tool data.
2. Move related connectors and wiring with the component commanded ON and OFF, with the scan tool. Observe the component operation.
3. With engine running, move related connectors and wiring while monitoring engine operation.

Verify whether the harness or connector movement affects any of the following systems

1. Data displayed.
2. Component or system operation.
3. Engine operation.

Repair the components as necessary.

Electrical Connections or Wiring

1. Intermittents are usually caused by one or more of the following conditions: Poor electrical connections. Terminal tension. Wiring problems.
2. Carefully inspect the suspected circuit for the following conditions: Poor mating of the connector halves. Terminals backed out or not fully seated in the connector body. Improperly formed or damaged terminals. Test for poor terminal tension. Poor terminal to wire connections including terminals crimped over insulation. This requires removing the terminal from the connector body. Corrosion or water intrusion. Pierced or damaged insulation can allow moisture to enter the wiring. The conductor can corrode inside the insulation, with little visible evidence. Look for swollen and stiff sections of wire in the suspect circuits. Wires that are broken inside the insulation. Pinched, cut, or rubbed through wiring in the harness. Wiring that is in contact with hot exhaust components.
3. Repair the condition as necessary.

Control Module Power & Grounds, & Component Power & Grounds

Poor power or ground connections can cause widely varying symptoms.

1. Test all control module power circuits. Many vehicles have multiple circuits supplying power to the control module. Other components in the system may have separate power circuits that may also need to be tested. Inspect connections at the module or component connectors, fuses, and any intermediate connections between the power source and the module or component. A test light or a Digital Multimeter (DVOM) may indicate that voltage is present, but neither tests the ability of a circuit to carry sufficient current. Ensure that the circuit can carry the current necessary to operate the component. See «WIRING DIAGRAMS»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-60l-bi-fuel-cng) .
2. Test all control module ground and system ground circuits. The control module may have multiple ground circuits. Other components in the system may have separate grounds that may also need to be tested. Inspect grounds for clean and tight connections at the grounding point. Inspect the connections at the component and in splice packs, where applicable. Ensure that the circuit can carry the current necessary to operate the component. See «WIRING DIAGRAMS»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-60l-bi-fuel-cng) .

Temperature Sensitivity

1. An intermittent condition may occur when a component or connection reaches normal operating temperature. The condition may occur only when the component or connection is cold, or only when the connection is hot.
2. The following data may help to diagnose this type of intermittent condition: Freeze Frame/Failure Records. Scan tool snapshot. Vehicle data recorder.
3. If the intermittent is related to heat, review the following data: High ambient temperatures. Underhood or engine generated heat. Circuit generated heat due to a poor connection, or high electrical load. Higher than normal load conditions, such as towing.
4. If the intermittent is related to cold, review the following data: Low ambient temperatures. In extremely low temperatures, ice may form in a connection or component. Test for water intrusion. The condition only occurs on a cold start. The condition is not present after the vehicle warms up.
5. Information from the customer may help to determine if the trouble follows a pattern that is temperature related.

Electromagnetic Interference & Electrical Noise

Some electrical components or circuits are sensitive to EMI or other types of electrical noise. Perform the following procedures

1. Inspect for a misrouted harness that is too close to a high voltage or high current device. This condition may induce electrical noise on a circuit that could interfere with normal circuit operation. Inspect for wires that are too close to the following devices: Secondary ignition components. Motors. The generator.
2. Determine whether the electrical system interference is caused by a malfunctioning relay, PCM driven solenoid or switch. These components may cause a sharp electrical surge. Normally, the problem will occur when the malfunctioning component is operating.
3. Determine whether non-factory or aftermarket add-on accessories are installed in the vehicle. These accessories may lead to an emission related OBD-II failure. Determine if any of the following non-factory or aftermarket add-on accessories is causing the intermittent: Lights. 2-way radios. Amplifiers. Electric motors. Remote starters. Alarm systems. Cell phones.
4. Test for an open diode across the A/C compressor clutch and for other open diodes. Some relays may contain a lighting diode.
5. Test for proper performance of the generator. See ON-VEHICLE TESTING in appropriate GENERATORS & REGULATORS article in ELECTRICAL.

Incorrect PCM Programming

1. There are only a few situations when reprogramming a PCM is appropriate, such as the following: A new service PCM is installed. A PCM from another vehicle is installed. Revised software or calibration files have been released for this vehicle. NOTE: DO NOT reprogram the PCM with the SAME software or calibration files that are already present in the PCM. This is not an effective repair for any type of driveability problem.
2. Verify that the PCM contains the correct software or calibration. If incorrect programming is found, reprogram the PCM with the most current software or calibration. See «PROGRAMMING»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-60l-bi-fuel-cng__programming) .

Duplicating Failure Conditions

1. If none of the previous tests are successful, attempt to duplicate or capture the failure conditions.
2. Freeze Frame/Failure Records data, where applicable, contains the conditions that were present when the DTC set. Perform the following procedure: Review and record Freeze Frame/Failure Records data. Clear the DTCs using the scan tool. Turn the key to OFF and wait 15 seconds. Operate the vehicle under the same conditions that were noted in Freeze Frame/Failure Records data, as closely as possible. The vehicle must also be operating within the Conditions for Running the DTC. Monitor DTC Status for the DTC being tested. The scan tool will indicate Ran, when the enabling conditions have been satisfied long enough for the DTC to run. The scan tool will also indicate whether the DTC passed or failed.
3. An alternate method is to drive the vehicle with the Digital Multimeter (DVOM) connected to a suspected circuit. An abnormal reading on the DVOM when problem occurs, may help you locate the problem.

Scan Tool Snapshot

The scan tool can be set up to take a snapshot of the parameters available via serial data. The snapshot function records live data over a period of time. The recorded data can be played back and analyzed. The scan tool can also graph parameters singly or in combinations of parameters for comparison. The snapshot can be triggered manually at the time the symptom is noticed, or set up in advance to trigger when a DTC sets. An abnormal value captured in the recorded data may point to a system or component that needs to be investigated further. Refer to scan tool user instructions for more information on the Snapshot function.

DIAGNOSTIC STARTING POINT - ENGINE CONTROLS

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

1. Ensure all engine systems not related to computer system are operating properly. DO NOT proceed with testing unless all other problems have been repaired. Diagnostic system check must be performed before using specific DTC testing procedure. See «DIAGNOSTIC SYSTEM CHECK - ALTERNATIVE FUELS - ENGINE CONTROLS»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-60l-bi-fuel-cng__diagnostic-system-check-alternative-fuels) .
2. If no DTCs are present and a driveability problem exists, see «SYMPTOMS»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-trouble-shooting-no-codes-60l-wbifuel-cng__symptoms) in TROUBLE SHOOTING - NO CODES - 6.0L CHEVY EXPRESS, SAVANA, SIERRA & SILVERADO - BI-FUEL & CNG article. Doing so will help identify proper system or component to check in «SYSTEM & COMPONENT TESTING - 6.0L CHEVY EXPRESS, SAVANA, SIERRA & SILVERADO - BI-FUEL & CNG»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-system-component-testing-60l-wbifuel-cng) article.
3. After necessary repairs are made, clear DTCs, verify vehicle will enter "closed loop" operation and ensure DTC does not reset.

DIAGNOSTIC SYSTEM CHECK - ALTERNATIVE FUELS - ENGINE CONTROLS

Note. Check for applicable Technical Service Bulletins (TSB) before proceeding. DO NOT perform the following procedure if driveability conditions are not present. DO NOT turn ignition off during the following procedure or clear DTCs unless instructed to do so.

Description

The Diagnostic System Check - Alternative Fuels - Engine Controls is an organized approach to identifying a condition that is created by a malfunction in the engine control system. The diagnostic system check must be the starting point for any driveability concern. The diagnostic system check directs the service technician to the next logical step in order to diagnose the concern. Understanding and correctly using the diagnostic test procedure reduces diagnostic time and prevents the replacement of good parts.

Test Description

The numbers below refer to the step numbers in the diagnostic procedure.

1. 1 Lack of communication may be because of a partial or a total malfunction of the class 2 serial data circuit. The specified procedure determines the particular condition.
2. 2 Lack of communication may be because of a partial or a total malfunction of the class 2 serial data circuit. The specified procedure determines the particular condition.
3. 3 This step determines if the vehicle will start.
4. 5 This step stores the Powertrain Control Module (PCM) Diagnostic Trouble Code (DTC) information into the scan tools memory. After you complete the diagnostic procedure, review the captured information in order to catch the next DTC if the control module stores multiple DTCs. Review the Freeze Frame/Failure Records data. Use this information in order to determine how frequently and how recently the DTC set. This information may help diagnose an intermittent condition. Information about the operating conditions at the time that the DTC set may also help diagnose an intermittent condition. Capturing the stored information saves the data that the PCM loses during the following conditions: When a diagnostic procedures instructs you to clear the DTCs. When a diagnostic procedure instructs you to disconnect the PCM connectors. When a diagnostic procedure instructs you to replace the PCM.
5. 6 The presence of DTCs which begin with "U", indicate that some other module is not communicating. Following the specified procedure will gather all the available information before you perform the tests.
6. 9 If there are other modules with DTCs set, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-60l-bi-fuel-cng__diagnostic-trouble-code-definitions) . The DTC list directs you to the appropriate diagnostic procedure. If the control module stores multiple powertrain DTCs, diagnose the DTCs in the following order: Component level DTCs, such as sensor DTCs, solenoid DTCs, and relay DTCs. Diagnose the multiple DTCs within this category in numerical order. Begin with the lowest numbered DTC, unless the diagnostic test directs you otherwise. System level DTCs, for example, misfire DTCs, fuel trim DTCs, and catalyst DTCs.
7. 11 This step determines if the vehicle will operate on the gasoline fuel system.
8. 13 This step is for areas that have inspection and maintenance testing procedures for emissions testing. Use this step if the testing facility found one or more I/M system statuses that did not set.

Diagnostic Procedure

Note. DO NOT perform this test if no driveability condition exists. Search for applicable bulletins before proceeding with the diagnosis. DO NOT turn OFF the ignition when performing this diagnostic test. DO NOT clear the DTCs unless the diagnostic instructs you to do so. If there is a condition with the starter system, see appropriate STARTERS article in ELECTRICAL. Ensure the battery is fully charged and the cables are clean and tight. Ensure the PCM and the FICM grounds are clean, tight, and in the proper location. Ensure the CNG and the gasoline fuel tanks are at least 1/2 full.

1. Install a scan tool. Does the scan tool turn ON? If yes, go to next step. If no, see SCAN TOOL DOES NOT POWER UP in appropriate BODY CONTROL MODULES article in ACCESSORIES & EQUIPMENT.
2. Attempt to establish communication with the listed control modules. If you are using a Tech 2, obtain the information with the Class 2 Message Monitor feature: The Powertrain Control Module (PCM). The Body Control Module (BCM). The Instrument Panel Cluster (IPC). The Electronic Brake Control Module (EBCM). Driver Information Center (DIC). Heating Ventilation Air Conditioning (HVAC). If scan tool communicates with all the listed control modules, go to next step. If scan tool does not communicate with all listed components, see SCAN TOOL DOES NOT COMMUNICATE WITH CLASS 2 DEVICE in appropriate BODY CONTROL MODULES article in ACCESSORIES & EQUIPMENT.
3. Attempt to start the engine. If engine starts and idles, go to next step. If engine does not start and idle, see «DTC P1204: VEHICLE DOES NOT START ON CNG»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-60l-bi-fuel-cng__dtc-p1204-vehicle-does-not-start) under DIAGNOSTIC TESTS.
4. Select the DTC display function for the following control modules: The PCM. The BCM. The IPC. The EBCM. The HVAC. If scan tool displays any DTCs, go to next step. If no DTCs are displayed, go to step 10 .
5. Using a scan tool, select Captured Info in order to store the powertrain DTC information. When complete, go to next step.
6. If scan tool displays DTCs which begin with a "U", see SCAN TOOL DOES NOT COMMUNICATE WITH CLASS 2 DEVICE in appropriate BODY CONTROL MODULES article in ACCESSORIES & EQUIPMENT. If no "U" codes are displayed, go to next step.
7. Were any of the PCM DTCs P0601, P0602, or P1621 set? If yes, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-48l-53l-60l-gasoline__diagnostic-trouble-code-definitions) in SELF-DIAGNOSTICS - 4.8L, 5.3L & 6.0L EXPRESS & SAVANA - GASOLINE article. If no, go to next step.
8. If DTC P0611 is set, go to «DTC P0611: FUEL INJECTOR CONTROL MODULE PERFORMANCE»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-60l-bi-fuel-cng__dtc-p0611-fuel-injector-control-module) under DIAGNOSTIC TESTS. If DTC P0611 is not set, go to next step.
9. Does the scan tool display DTC P0562, P0563, P1637, or P1638? If yes, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-48l-53l-60l-gasoline__diagnostic-trouble-code-definitions) in SELF-DIAGNOSTICS - 4.8L, 5.3L & 6.0L EXPRESS & SAVANA - GASOLINE article. If no, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-60l-bi-fuel-cng__diagnostic-trouble-code-definitions) .
10. If vehicle is equipped with the dedicated CNG fuel option (KL8), go to step 12 . If vehicle is not equipped with the dedicated CNG fuel option (KL8), go to next step.
11. Start and idle the engine. Force a switch over to gasoline operation with the scan tool in the Alternative Fuels special functions, output controls menu. If the engine continues to idle, go to next step. If engine does not continue to run, see «NO-START - ENGINE CRANKS OKAY»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-basic-diagnostic-procedures-48l-53l-60l-flex-fuel-gasoline-engines) under NO-START DIAGNOSIS in BASIC DIAGNOSTIC PROCEDURES - 4.8L, 5.3L & 6.0L "C", "G", "H", "K", "N" "S" & "T" SERIES - FLEX FUEL & GASOLINE article.
12. If the customer's concern is with the transmission, see appropriate DIAGNOSIS article in AUTOMATIC TRANSMISSIONS. If concern is not with the transmission, go to next step.
13. If the customer's concern is with the Inspection/Maintenance (I/M) testing, see «INSPECTION/MAINTENANCE COMPLETE SYSTEM SET PROCEDURE»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-48l-53l-60l-gasoline) under DRIVE CYCLES in SELF-DIAGNOSTICS - 4.8L, 5.3L & 6.0L EXPRESS & SAVANA - GASOLINE article. If customer's concern is not with I/M testing, go to next step.
14. If the customer's concern is a symptom, see «SYMPTOMS»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-trouble-shooting-no-codes-60l-wbifuel-cng__symptoms) in TROUBLE SHOOTING - NO CODES - 6.0L CHEVY EXPRESS, SAVANA, SIERRA & SILVERADO - BI-FUEL & CNG - GASOLINE article. Did you find and correct the condition? If yes, system is okay. If no, see «INTERMITTENT CONDITIONS»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-60l-bi-fuel-cng__intermittent-conditions) .

RETRIEVING DIAGNOSTIC TROUBLE CODES

DTCs are retrieved using a Tech 2 scan tool, or other OBD-II compatible scan tool connected to OBD-II 16-pin Data Link Connector (DLC). See DIAGNOSTIC SYSTEM CHECK - ALTERNATIVE FUELS - ENGINE CONTROLS . DLC is located below left side of dash.

CLEARING DIAGNOSTIC TROUBLE CODES

There are 3 methods to clear DTCs.

Scan Tool

Scan tool is preferable way to clear DTC information. Freeze frame and failure record data will also be cleared. PCM adaptive learning and system monitors will only be cleared for those system which had a stored DTC.

Disconnect Battery

Note. On many OBD-II systems, PCM will retain memory for an extended period of time with battery disconnected. Memory may be retained for several days.

Disconnecting PCM power or battery ground will clear all PCM memory including DTCs, freeze frame, failure records, adaptive learning and system monitors.

Warm-up Cycles

If fault that caused DTC to set is repaired, PCM will begin to count warm-up cycles. After 40 consecutive warm-up cycles with no further faults, PCM will automatically clear DTC from memory.

SCAN TOOL USAGE

Scan tool is a specialized tester which, when connected to DLC, can be used to diagnose on-board computer control systems by providing instant access to circuit voltage information without need to crawl under dash or hood to backprobe sensors and connectors.

Scan tool reduces diagnostic time dramatically by furnishing input data (voltage signals) which can be compared to specification parameters. They may also furnish information on output device (solenoids and motors) status. However, status parameters only indicate output signals have been sent to devices by PCM; they do not indicate whether devices have responded properly to signal. Verify proper response at output device using a voltmeter or test light.

A problem may exist even if DTCs are not present. Many driveability problems occur without setting DTCs.

Using 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.

Note. If erroneous voltage signals are suspected, verify tester information using a digital voltmeter and wiring schematic. If nonexistent codes are displayed, DO NOT use scan tool for diagnosis. Contact tester manufacturer for additional information.

Scan Tool Display

Note. OBD-II vehicles have options available in the scan tool DTC mode to display enhanced information available. However, to fully utilize information and procedures requires the use of a Tech 2 scan tool. See scan tool operator's manual for additional information.

The following are Tech 2 scan tool sub-menus in the DTC INFO and SPECIFIC DTC modes

1. DTC INFO MODE Used to search for specific type of stored DTC information. There are 7 choices in this mode. Technician may be instructed to test DTCs in a certain manner. Follow the affected DTC test procedures. To get complete description of any status, hit ENTER key before pressing the desired "F" key.
2. DTC STATUS This selection will display any DTCs that have not run during the current ignition cycle or have reported a test failure during this ignition up to a maximum of 33 DTCs. A DTC test that runs and passes will cause affected DTC to be removed from scan tool screen.
3. FAIL THIS IGN. This selection will display all DTCs that have failed during the present ignition cycle.
4. HISTORY This selection will display only DTCs that are stored in the control module's history memory. It will not display type "D" DTCs. It will display all type "A" and type "B" DTCs that have the MIL illuminated and have failed within the last 40 warm-up cycles. It will also display type "C" DTCs that have failed within the 40 warm-up cycles.
5. LAST TEST FAIL This selection will only display DTCs that have failed the last time the test ran. If type "A" or "B" DTCs are displayed, the last test may have ran during the previous ignition cycle. For type "C" DTCs, the last failure must have occurred during the current ignition cycle to be displayed as LAST TEST FAIL.
6. MIL REQUEST This selection will only display DTCs that are requesting MIL illumination. Type "C" DTCs cannot be displayed using this option. This selection will report type "B" DTCs only after MIL illumination has been requested.
7. NOT RUN SCC Not Run Since Code Clear option will display up to 33 DTCs that have not run since DTCs were last cleared. Since any displayed DTCs have not run, their condition (passing or failing) is unknown.
8. TEST FAIL SCC Test Fail Since Code Clear selection will display all active and history DTCs that have reported a test failure since the last time DTCs were cleared. DTCs that last failed more than 40 warm-up cycles before this option is selected will not be displayed.
9. FAILED SINCE CLEAR This message indicates the DTC has failed at least once within the last 40 warm-up cycles since the last time DTCs were cleared.
10. NOT RUN SINCE CL. Not Run Since Cleared message indicates that the selected diagnostic test has not run since the last time DTCs were cleared. Therefore, the diagnostic test status (passed or failed) is unknown. After DTCs are cleared, this message will continue to be displayed until the diagnostic test runs.
11. NOT RUN THIS IGN. Not Run This Ignition message indicates the selected diagnostic test has not run this ignition cycle.
12. TEST RAN AND PASSED This message indicates the selected diagnostic test has: Passed the last test. Ran and passed during this ignition cycle. Ran and passed since DTCs were last cleared. Test has not failed since DTCs were last cleared. If this message is displayed, repair is complete. If FAILED THIS IGN. message is displayed, repair is incomplete and further diagnosis is required.

FUEL INJECTION CONTROL MODULE

On Bi-Fuel and CNG engines, an Fuel Injection Control Module (FICM) is used. The FICM is located on the left side of the radiator support. (Scheme 409)

PROGRAMMING

Note. Programming is not required for the Fuel Injection Control Module. For all gasoline related programming, see PROGRAMMING in SELF-DIAGNOSTICS - 4.8L, 5.3L & 6.0L EXPRESS & SAVANA - GASOLINE article.

DRIVE CYCLES

Note. For Drive Cycle and Inspection/Maintenance procedures, see DRIVE CYCLES in SELF-DIAGNOSTICS - 4.8L, 5.3L & 6.0L EXPRESS & SAVANA - GASOLINE article.

SUMMARY

If no Diagnostic Trouble Codes (DTC) are present and a no-start condition exists, see NO-START DIAGNOSIS in BASIC DIAGNOSTIC PROCEDURES - 6.0L CHEVY EXPRESS, SAVANA, SIERRA & SILVERADO - BI-FUEL & CNG article. If no DTCs are present and a driveability condition exists, see SYMPTOMS in TROUBLE SHOOTING - NO CODES - 6.0L CHEVY EXPRESS, SAVANA, SIERRA & SILVERADO - BI-FUEL & CNG article for diagnosis by symptom (i.e., ROUGH IDLE, NO-START, etc.).

DIAGNOSTIC TROUBLE CODE DEFINITIONS

Note. Diagnostic Trouble Code Definitions listed in the DIAGNOSTIC TROUBLE CODE DEFINITIONS table apply to Bi-Fuel & CNG vehicles only. For all other Diagnostic Trouble Code Definitions, see DIAGNOSTIC TROUBLE CODE DEFINITIONS in SELF-DIAGNOSTICS - 4.8L, 5.3L & 6.0L EXPRESS & SAVANA - GASOLINE article.

Note. Use of Tech 2 or generic OBD-II scan tool is required to retrieve DTCs. Refer to user reference manual supplied with scan tool.

DIAGNOSTIC TROUBLE CODE DEFINITIONS

COMPONENT LOCATIONS

Note. For location of gasoline related components, see COMPONENT LOCATIONS in SELF-DIAGNOSTICS - 4.8L, 5.3L & 6.0L EXPRESS & SAVANA - GASOLINE article.

Scheme 409

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SYSTEM TESTS

Note. See SYSTEM TESTS in SELF-DIAGNOSTICS - 4.8L, 5.3L & 6.0L EXPRESS & SAVANA - GASOLINE article.

DIAGNOSTIC TESTS

Note. Before clearing DTCs, perform powertrain diagnostic system check. See DIAGNOSTIC SYSTEM CHECK - ALTERNATIVE FUELS - ENGINE CONTROLS under SELF-DIAGNOSTIC SYSTEM. Record FREEZE FRAME and FAILURE RECORDS for reference during testing. Data will be erased when DTCs are cleared.

DTC P0005: FUEL SHUTOFF VALVE "A" CONTROL CIRCUIT/OPEN

Note. To locate components, see COMPONENT LOCATIONS . For circuit reference, see WIRING DIAGRAMS . For connector terminal identification, see CONNECTOR IDENTIFICATION . If an intermittent condition exists, see INTERMITTENT CONDITIONS under SELF-DIAGNOSTIC SYSTEM.

Note. For removal and installation of Bi-Fuel and CNG related components, see REMOVAL & INSTALLATION - CHEVY EXPRESS & SAVANA - BI-FUEL article. For removal and installation of gasoline related components, see REMOVAL & INSTALLATION - CHEVY EXPRESS & SAVANA - GASOLINE article.

Circuit Description

An ignition voltage is supplied to the High Pressure Lock-Off (HPL) solenoid through the HPL relay. The Powertrain Control Module (PCM) controls the HPL relay by grounding the control circuit via an internal switch called a driver. The primary function of the driver is to supply the ground for the controlled component. The PCM monitors the status of the driver. If the PCM detects an incorrect voltage for the commanded state of the driver, DTC P0005 sets.

Conditions For Running The DTC

The ignition is on.

Conditions For Setting The DTC

1. The control module detects that the commanded state of the driver and the actual state of the control circuit do not match.
2. The condition exists for at least one second.

Action Taken When The DTC Sets

1. The control module illuminates the Malfunction Indicator Light (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

Conditions For Clearing The MIL/DTC

1. The control module turns off the Malfunction Indicator Light (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC using a scan tool.

The numbers below refer to the step numbers in the diagnostic procedure.

1. 2 This step tests if the concern is active. You should hear a clicking sound when the High Pressure Lock-Off (HPL) relay is commanded ON and OFF. Repeat the commands as necessary.
2. 5 This step verifies that the control module is providing ground to the HPL relay.
3. 6 This step tests if a ground is constantly being applied to the HPL relay.

1. Did you perform the Diagnostic System Check - Alternative Fuels - Engine Controls. If yes, go to next step. If no, see «DIAGNOSTIC SYSTEM CHECK - ALTERNATIVE FUELS - ENGINE CONTROLS»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-60l-bi-fuel-cng__diagnostic-system-check-alternative-fuels) under SELF-DIAGNOSTIC SYSTEM.
2. Turn ignition on, with engine off. Command the High Pressure Lock-Off (HPL) relay on and off using a scan tool. If the HPL relay responds to the commanded state, go to next step. If HPL relay does not respond to the commanded stated, go to step 4 .
3. Observe the Freeze Frame/Failure Records for this DTC. Turn the ignition off for 30 seconds. Turn ignition on, with engine off. Operate the vehicle within the Conditions For Running The DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records. Did the DTC fail this ignition cycle? If yes, go to next step. If no, see «INTERMITTENT CONDITIONS»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-60l-bi-fuel-cng__intermittent-conditions) under SELF-DIAGNOSTIC SYSTEM.
4. Turn ignition off. Disconnect the HPL relay. Turn ignition on, with engine off. Probe the HPL relay ignition voltage circuit with a test light that is connected to a good ground. If the test light illuminates, go to next step. If test light does not illuminate, go to step 11 .
5. Connect a test light between the HPL relay control circuit and the HPL relay ignition voltage circuit. Command the HPL relay on and off using a scan tool. If the test light turns on and off with each command, go to step 9 . If test light does not turn on and off with each command, go to next step.
6. If the test light remains illuminated with each command, go to step 8 . If the test light does not remain illuminated with each command, go to next step.
7. Test the HPL relay control circuit for an open or for a short to voltage. Did you find and correct and open or a short? If yes, go to step 14 . If no, go to step 10 .
8. Test the HPL relay control circuit for a short to ground. Did you find and correct a short to ground? If yes, go to step 14 . If no, go to step 13 .
9. Inspect for poor connections at the HPL relay. Did you find and correct t a poor connection? If yes, go to step 14 . If no, go to step 12 .
10. Inspect for poor connections at the control module harness connector. Did you find and correct a poor connection at the control module harness connector? If yes, go to step 14 . If no, go to step 13 .
11. Repair the open or short to ground in the ignition voltage circuit. After repair is complete, go to step 14 .
12. Replace the HPL relay. After replacement is complete, go to step 14 .
13. Replace the PCM. See After replacement is complete, go to next step.
14. Observe the Freeze Frame/Failure Records for this DTC. Turn the ignition off for 30 seconds. Turn ignition on, with engine off. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records. Did the DTC fail this ignition cycle? If yes, go to step 2 . If no, go to next step.
15. Observe the Capture Info using a scan tool. Are there any DTCs that have not been diagnosed? If yes, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-60l-bi-fuel-cng__diagnostic-trouble-code-definitions) . If no, system is okay.

DTC P0148: FUEL DELIVERY ERROR

Note. To locate components, see COMPONENT LOCATIONS . For circuit reference, see WIRING DIAGRAMS . For connector terminal identification, see CONNECTOR IDENTIFICATION . If an intermittent condition exists, see INTERMITTENT CONDITIONS under SELF-DIAGNOSTIC SYSTEM.

Note. For removal and installation of Bi-Fuel and CNG related components, see REMOVAL & INSTALLATION - CHEVY EXPRESS & SAVANA - BI-FUEL article. For removal and installation of gasoline related components, see REMOVAL & INSTALLATION - CHEVY EXPRESS & SAVANA - GASOLINE article.

The Powertrain Control Module (PCM) grounds the Alternative Fuel (AF) enable circuit when operating on CNG. When the AF enable circuit is grounded the Fuel Injector Control Module (FICM) operates the CNG injectors based upon the PCM fuel injector control pulse width signals. On Bi-Fuel (KL6) vehicles the PCM opens the AF enable circuit when gasoline operation is desired. Switch-over from one fuel to the other is always performed in an orderly, sequential manner. Since some injectors are in the middle of injecting the previous fuel, the FICM will wait until that cylinders fuel delivery is complete and will then switch over in sequential firing order.

The ignition is on.

The Powertrain Control Module (PCM) detects that the commanded state and the actual state of the Alternative Fuel (AF) Enable circuit do not match.

1. The control module illuminates the Malfunction Indicator Light (MIL) when the diagnostic runs and fails.
2. The control module switches over to gasoline fuel operation.
3. The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Freeze Frame/Failure Records.

1. The control module turns off the Malfunction Indicator Light (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC using a scan tool.

The numbers below refer to the step numbers in the diagnostic procedure.

1. 2 This step determines if the condition is active. The Powertrain Control Module (PCM) grounds the Alternative Fuel (AF) enable circuit when operating on CNG.
2. 4 This step tests for a short to ground on the AF enable circuit. The test light should not illuminate with the ignition off.

1. Did you perform the Diagnostic System Check - Alternative Fuels - Engine Controls. If yes, go to next step. If no, see «DIAGNOSTIC SYSTEM CHECK - ALTERNATIVE FUELS - ENGINE CONTROLS»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-60l-bi-fuel-cng__diagnostic-system-check-alternative-fuels) under SELF-DIAGNOSTIC SYSTEM.
2. Turn ignition on, with engine off. Observe the FUEL MODE COMMAND parameter using a scan tool. If the scan tool displays ALT FUEL, go to next step. If the scan tool does not display ALT FUEL, go to step 4 .
3. Observe the Freeze Frame and/or the Failure records data for this DTC. Turn ignition off for 30 seconds. Start the engine. Operate the vehicle within the Conditions for running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame and/or the Failure records data. If the DTC failed this ignition cycle, go to next step. If the DTC does not fail this ignition cycle, see «INTERMITTENT CONDITIONS»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-60l-bi-fuel-cng__intermittent-conditions) under SELF-DIAGNOSTIC SYSTEM.
4. Turn ignition off. Disconnect the Fuel Injection Control Module (FICM). Probe the AF enable circuit with a test light connected to battery positive. If the test light illuminates, go to step 7 . If test light does not illuminate, go to next step.
5. Turn ignition on. Command the AF enable circuit ON and OFF using a scan tool. Observe the test light. If the test light responds to the scan tool commands, go to step 9 . If the test light does not respond to the scan tool commands, go to next step.
6. Test the AF enable circuit for an open. Did you find and correct an open? If yes, go to step 12 . If no, go to step 8 .
7. Test the AF enable circuit for a short to ground. Did you find and correct a short to ground? If yes, go to step 12 . If no, go to step 10 .
8. Test for an intermittent and/or a poor connection at the PCM. Did you find and correct an intermittent condition? If yes, go to step 12 . If no, go to step 10 .
9. Test for an intermittent and/or a poor connection at the FICM. Did you find and correct an intermittent condition? If yes, go to step 12 . If no, go to step 11 .
10. Replace the PCM. After replacement is complete, go to step 12 .
11. Replace the FICM. After replacement is complete, go to step 12 .
12. Observe the Freeze Frame/Failure Records for this DTC. Turn the ignition off for 30 seconds. Turn ignition on, with engine off. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records. If the DTC failed this ignition cycle, go to step 2 . If the DTC did not fail this ignition cycle, go to next step.
13. Observe the Capture Info using a scan tool. Are there any DTCs that have not been diagnosed? If yes, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-60l-bi-fuel-cng__diagnostic-trouble-code-definitions) . If no, system is okay.

DTC P0171: FUEL TRIM SYSTEM LEAN - BANK 1 & DTC P0174: FUEL TRIM SYSTEM LEAN - BANK 2

Note. To locate components, see COMPONENT LOCATIONS . For circuit reference, see WIRING DIAGRAMS . For connector terminal identification, see CONNECTOR IDENTIFICATION . If an intermittent condition exists, see INTERMITTENT CONDITIONS under SELF-DIAGNOSTIC SYSTEM.

Note. For removal and installation of Bi-Fuel and CNG related components, see REMOVAL & INSTALLATION - CHEVY EXPRESS & SAVANA - BI-FUEL article. For removal and installation of gasoline related components, see REMOVAL & INSTALLATION - CHEVY EXPRESS & SAVANA - GASOLINE article.

The Powertrain Control Module (PCM) controls the air/fuel metering system in order to provide the best possible combination of driveability, fuel economy, and emission control. CNG Fuel delivery is controlled differently during Open and Closed Loop. During Open Loop, the PCM determines fuel delivery based on sensor signals without Oxygen Sensor (O2S) input. During Closed Loop, the O2S inputs are added and used by the PCM to calculate short and long term fuel trim fuel delivery adjustments. If the O2S indicate a lean condition, fuel trim values will be above zero percent. If the O2S indicate a rich condition, fuel trim values will be below zero percent. Short term fuel trim values change rapidly in response to the Heated Oxygen Sensor (HO2S) voltage signals. Long term fuel trim makes coarse adjustments in order to maintain an air/fuel ratio of 16.5:1 while operating on CNG. If the PCM detects an excessively lean condition, DTC P0171 or P0174 sets.

Conditions For Running DTC

1. DTCs P0101, P0102, P0103, P0106, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0121, P0122, P0123, P0125, P0200, P0300, P0327, P0332, P0335, P0336, P0351-P0358, P0401, P0402, P0403, P0443, P0446, P0449, P0496, P0502, P0503, P1020, or P1258 are not set.
2. The Engine Coolant Temperature (ECT) is 167-239°F (75-115°C).
3. The Intake Air Temperature (IAT) is 4-194°F (-20 to 90°C).
4. The Manifold Absolute Pressure (MAP) is 3.7-13.0 psi (26-90 kPa).
5. The vehicle speed is less than 85 mph.
6. The engine speed is 400-3000 RPM.
7. The Barometric Pressure (BARO) is more than 10.7 psi (74 kPa).
8. The Mass Airflow (MAF) is 5-90 g/s.
9. The fuel level is more than 10 percent.
10. The Throttle Position (TP) is less than 90 percent.

Conditions For Setting DTC

1. The average long term fuel trim cell value is above 28 percent.
2. All conditions exist for at least 6 seconds.

Actions Taken When DTC Sets

1. The control module illuminates the Malfunction Indicator Light (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

Conditions For Clearing MIL/DTC

1. The control module turns off the Malfunction Indicator Light (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC using a scan tool.

Diagnostic Aids

1. The system will go lean if an injector is not supplying enough fuel.
2. A lean condition could be present during high fuel demand.
3. Use a scan tool in order to review Failure Records. If an intermittent condition is suspected, see «INTERMITTENT CONDITIONS»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-60l-bi-fuel-cng__intermittent-conditions) under SELF-DIAGNOSTIC SYSTEM.

The numbers below refer to the step numbers in the diagnostic procedure.

1. 5 If conditions were not corrected, see «FUEL SYSTEM DIAGNOSIS»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-basic-diagnostic-procedures-60l-wbifuel-cng-engines) under FUEL SYSTEMS in BASIC DIAGNOSTIC PROCEDURES - 6.0L CHEVY EXPRESS, SAVANA, SIERRA & SILVERADO - BI-FUEL & CNG article.
2. 6 If conditions were not corrected, a worn cam, worn intake or exhaust valves, or other engine mechanical failure may be the problem.

Diagnostic Procedures

1. Did you perform the Diagnostic System Check - Alternative Fuels - Engine Controls. If yes, go to next step. If no, see «DIAGNOSTIC SYSTEM CHECK - ALTERNATIVE FUELS - ENGINE CONTROLS»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-60l-bi-fuel-cng__diagnostic-system-check-alternative-fuels) under SELF-DIAGNOSTIC SYSTEM.
2. Install the scan tool. Start and idle the engine at the normal operating temperature in Closed Loop. Record the long term fuel trim. Turn the engine off. Turn ignition on, with engine off. Review the Freeze Frame/Failure Records and record the displayed data for this DTC. If the scan tool indicates that the long term fuel trim is greater than 28 percent, go to next step. If scan tool indicates long term fuel trim is less than 28 percent, see «DIAGNOSTIC AIDS»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-60l-bi-fuel-cng__diagnostic-aids) .
3. Operate engine at idle. Observe the HO2S parameters using a scan tool. If the scan tool indicates that the HO2S parameter is 200-800 mV and fluctuating, go to next step. If the scan tool indicates that the HO2S parameter is not 200-800 mV and fluctuating, go to step 5 .
4. Turn the engine off. Visually and physically inspect the vacuum hoses for splits, kinks, and proper connections. See «VACUUM DIAGRAMS - EXPRESS & SAVANA»(ref-157779) article. Ensure that the vehicle has sufficient fuel rail pressure. If the fuel rail pressure is too low this DTC may set. See «FUEL SYSTEM DIAGNOSIS»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-basic-diagnostic-procedures-60l-wbifuel-cng-engines) under FUEL SYSTEMS in BASIC DIAGNOSTIC PROCEDURES - 6.0L CHEVY EXPRESS, SAVANA, SIERRA & SILVERADO - BI-FUEL & CNG article. Did you find and correct the condition? If yes, go to step 7 . If no, go to step 6 .
5. Turn the engine off. Inspect the HO2S for proper installation. Verify the electrical connectors and the wires are secure and not contacting the exhaust system. Test for continuity between the HO2S signal circuit and the low reference circuit. Did you find and correct the condition? If yes, go to step 7 . If no, see «FUEL SYSTEM DIAGNOSIS»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-basic-diagnostic-procedures-48l-53l-60l-flex-fuel-gasoline-engines) under FUEL SYSTEMS in BASIC DIAGNOSTIC PROCEDURES - 4.8L, 5.3L & 6.0L "C", "G", "H", "K", "N", "S" & "T" SERIES - FLEX FUEL & GASOLINE article.
6. Operate the engine at idle. Inspect for any missing, loose, or leaking exhaust components forward of the HO2S. Inspect for vacuum leaks at the intake manifold, throttle body, and injector "O" rings. Inspect the air induction system and the air intake ducts for leaks. Inspect the crankcase ventilation system for leaks. Did you find and correct the condition? If yes, go to next step. If no, check engine mechanical condition. See appropriate article in ENGINES.
7. Using a scan tool, clear the DTCs. Turn ignition off for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records. If the DTC failed this ignition cycle, go to step 2 . If the DTC did not fail this ignition cycle, go to next step.
8. Observe the Capture Info using a scan tool. Are there any DTCs that have not been diagnosed? If yes, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-60l-bi-fuel-cng__diagnostic-trouble-code-definitions) . If no, system is okay.

DTC P0172: FUEL TRIM SYSTEM RICH - BANK 1 & DTC P0175: FUEL TRIM SYSTEM RICH - BANK 2

Note. To locate components, see COMPONENT LOCATIONS . For circuit reference, see WIRING DIAGRAMS . For connector terminal identification, see CONNECTOR IDENTIFICATION . If an intermittent condition exists, see INTERMITTENT CONDITIONS under SELF-DIAGNOSTIC SYSTEM.

Note. For removal and installation of Bi-Fuel and CNG related components, see REMOVAL & INSTALLATION - CHEVY EXPRESS & SAVANA - BI-FUEL article. For removal and installation of gasoline related components, see REMOVAL & INSTALLATION - CHEVY EXPRESS & SAVANA - GASOLINE article.

The Powertrain Control Module (PCM) controls the air/fuel metering system in order to provide the best possible combination of driveability, fuel economy, and emission control. CNG Fuel delivery is controlled differently during Open and Closed Loop. During Open Loop, the PCM determines fuel delivery based on sensor signals without Oxygen Sensor (O2S) input. During Closed Loop, the O2S inputs are added and used by the PCM to calculate short and long term fuel trim fuel delivery adjustments. If the O2S indicate a lean condition, fuel trim values will be above zero percent. If the O2S indicate a rich condition, fuel trim values will be below zero percent. Short term fuel trim values change rapidly in response to the Heated Oxygen Sensor (HO2S) voltage signals. Long term fuel trim makes coarse adjustments in order to maintain an air/fuel ratio of 16.5:1 while operating on CNG. If the PCM detects an excessively lean condition, DTC P0171 or P0174 sets.

1. DTCs P0101, P0102, P0103, P0106, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0121, P0122, P0123, P0125, P0200, P0300, P0327, P0332, P0335, P0336, P0351-P0358, P0401, P0402, P0403, P0443, P0446, P0449, P0496, P0502, P0503, P1020, or P1258 are not set.
2. The Engine Coolant Temperature (ECT) is 167-239°F (75-115°C).
3. The Intake Air Temperature (IAT) is 4-194°F (-20 to 90°C).
4. The Manifold Absolute Pressure (MAP) is 3.7-13 psi (26-90 kPa).
5. The vehicle speed is less than 85 mph.
6. The engine speed is between 400-3000 RPM.
7. The Barometric Pressure (BARO) is more than 10.7 psi (74 kPa).
8. The Mass Airflow (MAF) is 5-90 g/s.
9. The fuel level is more than 10 percent.
10. The Throttle Position (TP) is less than 90 percent.

1. The average long term fuel trim value is below -15 percent.
2. All of the conditions exist for at least 40 seconds.

1. The control module illuminates the Malfunction Indicator Light (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

1. The control module turns off the Malfunction Indicator Light (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC using a scan tool.

1. Fuel contamination, such as water will effect fuel trim.
2. A malfunctioning Mass Airflow sensor can cause a rich condition and set this DTC. See «DTC P0101: MASS AIR FLOW SENSOR PERFORMANCE»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-48l-53l-60l-gasoline__dtc-p0101-mass-air-flow-sensor) under DIAGNOSTIC TESTS in SELF-DIAGNOSTICS - 4.8L, 5.3L & 6.0L EXPRESS & SAVANA - GASOLINE article.
3. Use a scan tool in order to review Failure Records. If an intermittent condition is suspected, see «INTERMITTENT CONDITIONS»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-60l-bi-fuel-cng__intermittent-conditions) under SELF-DIAGNOSTIC SYSTEM.

The numbers below refer to the step numbers in the diagnostic procedure.

1. 5 If the cause of the DTC is not found and corrected, see «FUEL SYSTEM DIAGNOSIS»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-basic-diagnostic-procedures-60l-wbifuel-cng-engines) under FUEL SYSTEMS in BASIC DIAGNOSTIC PROCEDURES - 6.0L CHEVY EXPRESS, SAVANA, SIERRA & SILVERADO - BI-FUEL & CNG article.
2. 6 On KL6 equipped vehicles, an EVAP canister that is saturated will cause a rich condition. If the condition is not found, a worn cam, worn intake or exhaust valves, or other engine mechanical failure may be the cause of the DTC.

1. Did you perform the Diagnostic System Check - Alternative Fuels - Engine Controls. If yes, go to next step. If no, see «DIAGNOSTIC SYSTEM CHECK - ALTERNATIVE FUELS - ENGINE CONTROLS»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-60l-bi-fuel-cng__diagnostic-system-check-alternative-fuels) under SELF-DIAGNOSTIC SYSTEM.
2. Install scan tool. Start and idle the engine at the normal operating temperature in Closed Loop. Record the long term fuel trim data. Turn the engine off. Turn ignition on, with engine off. Review the Freeze Frame/Failure Records, and record the displayed data for this DTC. If the scan tool indicates that the long term fuel trim is less than -15 percent, go to next step. If the scan tool indicates that the long term fuel trim is more than -15 percent, see «DIAGNOSTIC AIDS»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-60l-bi-fuel-cng) .
3. Operate engine at idle. Observe the HO2S parameters using a scan tool. If the scan tool indicates that the HO2S parameter is 200-800 mV and fluctuating, go to next step. If the scan tool indicates that the HO2S parameter is not 200-800 mV and fluctuating, go to step 5 .
4. Turn engine off. Visually and physically inspect the following: EVAP lines and components, if equipped, for damage or blockage. Mass Airflow (MAF) sensor inlet screen for blockage. Vacuum hoses for splits, kinks, and proper connections. See «VACUUM DIAGRAMS - EXPRESS & SAVANA»(ref-157779) article. Air intake duct for being collapsed or restricted. Air filter for being dirty or restricted. Objects blocking the throttle body. Did you find and correct the condition? If yes, go to step 7 . If no, go to step 6 .
5. Turn the engine off. Inspect the HO2S for proper installation. Verify the electrical connectors and the wires are secure and not contacting the exhaust system. Test for continuity between the HO2S signal circuit and the low reference circuit. Did you find and correct the condition? If yes, go to step 7 . If no, see «FUEL SYSTEM DIAGNOSIS»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-basic-diagnostic-procedures-48l-53l-60l-flex-fuel-gasoline-engines) under FUEL SYSTEMS in BASIC DIAGNOSTIC PROCEDURES - 4.8L, 5.3L & 6.0L "C", "G", "H", "K", "N", "S" & "T" SERIES - FLEX FUEL & GASOLINE article.
6. Inspect for the following: Excessive fuel in the crankcase (KL6 only). Proper operation of the gasoline fuel pressure regulator (KL6 only). See «FUEL SYSTEM DIAGNOSIS»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-basic-diagnostic-procedures-48l-53l-60l-flex-fuel-gasoline-engines) under FUEL SYSTEMS in BASIC DIAGNOSTIC PROCEDURES - 4.8L, 5.3L & 6.0L "C", "G", "H", "K", "N", "S" & "T" SERIES - FLEX FUEL & GASOLINE article. All CNG fuel injectors are functioning properly. See «FUEL INJECTOR COIL TEST»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-system-component-testing-60l-wbifuel-cng__fuel-injector-coil-test) under FUEL SYSTEMS in SYSTEM & COMPONENT TESTING - 6.0L CHEVY EXPRESS, SAVANA, SIERRA & SILVERADO - BI-FUEL & CNG article. All gasoline fuel injectors are functioning properly. See «FUEL INJECTOR COIL TEST»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-system-component-testing-48l-53l-60l-flex-fuel-gasoline__fuel-injector-coil-test) under FUEL SYSTEMS in SYSTEM & COMPONENT TESTING - 4.8L, 5.3L & 6.0L "C", "G", "H", "K", "N", "S" & "T" SERIES - FLEX FUEL & GASOLINE article. Did you find and correct the condition? If yes, go to next step. If no, check engine mechanical condition. See appropriate article in ENGINES.
7. Using a scan tool, clear the DTCs. Turn ignition off for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records. If the DTC failed this ignition cycle, go to step 2 . If the DTC did not fail this ignition cycle, go to next step.
8. Observe the Capture Info using a scan tool. Are there any DTCs that have not been diagnosed? If yes, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-60l-bi-fuel-cng__diagnostic-trouble-code-definitions) . If no, system is okay.

DTC P0182: FUEL TANK TEMPERATURE SENSOR CIRCUIT - LOW VOLTAGE

Note. To locate components, see COMPONENT LOCATIONS . For circuit reference, see WIRING DIAGRAMS . For connector terminal identification, see CONNECTOR IDENTIFICATION . If an intermittent condition exists, see INTERMITTENT CONDITIONS under SELF-DIAGNOSTIC SYSTEM.

Note. For removal and installation of Bi-Fuel and CNG related components, see REMOVAL & INSTALLATION - CHEVY EXPRESS & SAVANA - BI-FUEL article. For removal and installation of gasoline related components, see REMOVAL & INSTALLATION - CHEVY EXPRESS & SAVANA - GASOLINE article.

The Fuel Tank Temperature (FTT) sensor is a variable resistor that measures the temperature of the fuel in the CNG fuel tank. The PCM supplies 5 volts to the FTT signal circuit. This DTC sets when the FTT signal voltage is below the normal operating range of the sensor.

1. The ignition is on.
2. The Intake Air Temperature (IAT) is more than -31°F (-35°C).

1. The FTT sensor voltage is less than 0.05 volt.
2. The condition exists for more than 5 seconds.

1. The Powertrain Control Module (PCM) stores the DTC information into memory when the diagnostic runs and fails.
2. The Malfunction Indicator Light (MIL) will not illuminate.
3. The PCM records the operating conditions at the time the diagnostic fails. The PCM stores this information in the Failure Records.

1. A last test failed, or current DTC, clears when the diagnostic runs and does not fail.
2. A history DTC will clear after 40 consecutive warm-up cycles, if no failures are reported by this or any other non-emission related diagnostic.
3. Use a scan tool in order to clear the DTC.

1. Use the Temperature Vs. Resistance table in order to test the FTT sensor at various temperature levels in order to evaluate the possibility of a skewed sensor. A skewed sensor could result in a driveability condition. If the engine has sat overnight, the FTT sensor and the IAT sensor values should display within a few degrees. If the temperatures are not within 5°F (Scheme 440)
2. Use a scan tool in order to review Failure Records. If an intermittent condition is suspected, see «INTERMITTENT CONDITIONS»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-60l-bi-fuel-cng__intermittent-conditions) under SELF-DIAGNOSTIC SYSTEM.

Scheme 440

1. Did you perform the Diagnostic System Check - Alternative Fuels - Engine Controls. If yes, go to next step. If no, see «DIAGNOSTIC SYSTEM CHECK - ALTERNATIVE FUELS - ENGINE CONTROLS»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-60l-bi-fuel-cng__diagnostic-system-check-alternative-fuels) under SELF-DIAGNOSTIC SYSTEM.
2. Turn ignition on, with engine off. Using a scan tool, observe the Fuel Tank Temperature (FTT) parameter. If the scan tool indicates that the FTT is less than 0.05 volt, go to step 4 . If the scan tool indicates that the FTT is more than 0.05 volt, go to next step.
3. Observe the Freeze Frame and/or the Failure records data for this DTC. Turn ignition off for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame and/or the Failure records data. If the DTC failed this ignition cycle, go to next step. If the DTC does not fail this ignition cycle, see «DIAGNOSTIC AIDS»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-60l-bi-fuel-cng) .
4. Disconnect the FTT sensor harness connector. Turn ignition on, with engine off. Using a scan tool, observe the FTT parameter. If the scan tool indicates that the FTT sensor voltage is more than 4.6 volts, go to step 6 . If the scan tool indicates that the FTT sensor voltage is less than 4.6 volts, go to next step.
5. Turn ignition off. Disconnect PCM connector C2. Test the FTT sensor signal circuit for a short to ground. Did you find and correct a short to ground? If yes, go to step 8 . If no, go to step 7 .
6. Replace the FTT sensor. The FTT sensor is not serviceable separately from the High Pressure Lock-Off (HPL) solenoid. After replacement is complete, go to step 8 .
7. Replace the PCM. After replacement is complete, go to next step.
8. Using a scan tool, clear the DTCs. Turn ignition off for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records. If the DTC failed this ignition cycle, go to step 2 . If the DTC did not fail this ignition cycle, go to next step.
9. Observe the Capture Info using a scan tool. Are there any DTCs that have not been diagnosed? If yes, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-60l-bi-fuel-cng__diagnostic-trouble-code-definitions) . If no, system is okay.

DTC P0183: FUEL TANK TEMPERATURE SENSOR CIRCUIT - HIGH VOLTAGE

Note. To locate components, see COMPONENT LOCATIONS . For circuit reference, see WIRING DIAGRAMS . For connector terminal identification, see CONNECTOR IDENTIFICATION . If an intermittent condition exists, see INTERMITTENT CONDITIONS under SELF-DIAGNOSTIC SYSTEM.

Note. For removal and installation of Bi-Fuel and CNG related components, see REMOVAL & INSTALLATION - CHEVY EXPRESS & SAVANA - BI-FUEL article. For removal and installation of gasoline related components, see REMOVAL & INSTALLATION - CHEVY EXPRESS & SAVANA - GASOLINE article.

The Fuel Tank Temperature (FTT) sensor is a variable resistor that measures the temperature of the fuel in the CNG fuel tank. The PCM supplies 5 volts to the FTT signal circuit. This DTC sets when the FTT signal voltage is above the normal operating range of the sensor.

1. The ignition is on.
2. The Intake Air Temperature is more than -31°F (-35°C).

1. The FTT sensor voltage is more than 4.95 volts.
2. The condition exists for more than 5 seconds.

1. The Powertrain Control Module (PCM) stores the DTC information into memory when the diagnostic runs and fails.
2. The Malfunction Indicator Light (MIL) will not illuminate.
3. The PCM records the operating conditions at the time the diagnostic fails. The PCM stores this information in the Failure Records.

1. A last test failed, or current DTC, clears when the diagnostic runs and does not fail.
2. A history DTC will clear after 40 consecutive warm-up cycles, if no failures are reported by this or any other non-emission related diagnostic.
3. Use a scan tool in order to clear the DTC.

1. Use the Temperature Vs. Resistance table in order to test the FTT sensor at various temperature levels in order to evaluate the possibility of a skewed sensor. A skewed sensor could result in a driveability condition. If the engine has sat overnight, the FTT sensor and the IAT sensor values should display within a few degrees. If the temperatures are not within 5°F (Scheme 440)
2. Use a scan tool in order to review Failure Records. If an intermittent condition is suspected, see «INTERMITTENT CONDITIONS»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-60l-bi-fuel-cng__intermittent-conditions) under SELF-DIAGNOSTIC SYSTEM.

The numbers below refer to the step numbers in the diagnostic procedure.

1. 4 Tests for the proper operation of the circuit in the low voltage range. If the fuse in the jumper opens when you perform this test, the signal circuit is shorted to voltage.
2. 8 This step tests the signal circuit of the FTT sensor for a short to another 5-volt reference circuit.

1. Did you perform the Diagnostic System Check - Alternative Fuels - Engine Controls. If yes, go to next step. If no, see «DIAGNOSTIC SYSTEM CHECK - ALTERNATIVE FUELS - ENGINE CONTROLS»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-60l-bi-fuel-cng__diagnostic-system-check-alternative-fuels) under SELF-DIAGNOSTIC SYSTEM.
2. Turn ignition on, with engine off. Using a scan tool, observe the FTT sensor parameter. If the scan tool indicates that the FTT sensor parameter is near 5 volts, go to step 4 . If the scan tool does not indicate that the FTT sensor parameter near 5 volts, go to next step.
3. Observe the Freeze Frame and/or the Failure records data for this DTC. Turn ignition off for 30 seconds. Start the engine. Operate the vehicle within the Conditions for running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame and/or the Failure records data. If the DTC failed this ignition cycle, go to next step. If the DTC does not fail this ignition cycle, see «DIAGNOSTIC AIDS»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-60l-bi-fuel-cng) .
4. Turn ignition off. Disconnect the FTT sensor. Connect a 3-amp fused jumper wire between the FTT sensor signal circuit and the FTT sensor low reference circuit. Turn ignition on, with engine off. Using a scan tool, observe the FTT sensor parameter. If the scan tool indicates that the FTT sensor parameter is zero volts, go to step 7 . If the scan tool indicates a FTT sensor parameter other than zero, go to next step.
5. Turn ignition off. Connect a 3-amp fused jumper wire between the signal circuit of the FTT sensor and a good ground. Turn ignition on, with engine off. Using a scan tool, observe the FTT sensor parameter. If the scan tool indicates that the FTT sensor parameter is zero volts, go to step 9 . If the scan tool indicates a FTT sensor parameter other than zero, go to next step.
6. Test the FTT sensor signal circuit for an open circuit or for high resistance. Did you find and correct an open circuit or high resistance? If yes, go to step 12 . If no, go to step 8 .
7. Test for an intermittent and/or a poor connection at the FTT sensor. Did you find and correct an intermittent and/or poor connection? If yes, go to step 12 . If no, go to step 10 .
8. Test for an intermittent and/or a poor connection at the PCM. Did you find and correct an intermittent and/or a poor connection? If yes, go to step 12 . If no, go to step 11 .
9. Repair the FTT sensor low reference circuit for a high resistance or an open. Did you find and correct a high resistance or an open? If yes, go to step 12 .
10. Replace the FTT sensor. The FTT sensor is not serviceable separately from the High Pressure Lock-Off (HPL) Solenoid. After repairs are complete, go to step 12 .
11. Replace the PCM. After repairs are complete, go to next step.
12. Using a scan tool, clear the DTCs. Turn ignition off for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records. If the DTC failed this ignition cycle, go to step 2 . If the DTC did not fail this ignition cycle, go to next step.
13. Observe the Capture Info using a scan tool. Are there any DTCs that have not been diagnosed? If yes, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-60l-bi-fuel-cng__diagnostic-trouble-code-definitions) . If no, system is okay.

DTC P0187: FUEL RAIL TEMPERATURE SENSOR CIRCUIT - LOW VOLTAGE

Note. To locate components, see COMPONENT LOCATIONS . For circuit reference, see WIRING DIAGRAMS . For connector terminal identification, see CONNECTOR IDENTIFICATION . If an intermittent condition exists, see INTERMITTENT CONDITIONS under SELF-DIAGNOSTIC SYSTEM.

Note. For removal and installation of Bi-Fuel and CNG related components, see REMOVAL & INSTALLATION - CHEVY EXPRESS & SAVANA - BI-FUEL article. For removal and installation of gasoline related components, see REMOVAL & INSTALLATION - CHEVY EXPRESS & SAVANA - GASOLINE article.

The Fuel Rail Temperature (FRT) sensor is a variable resistor that measures the temperature of the fuel in the CNG fuel rail. The Fuel Injector Control Module (FICM) supplies 5 volts to the FRT signal circuit and supplies a ground to the low reference circuit. The FICM monitors the FRT sensor voltage and communicates the data to the PCM by a dedicated Pulse Width Modulated (PWM) circuit. This DTC sets when the FRT signal voltage is below the normal operating range of the sensor.

1. The ignition is on.
2. The Intake Air Temperature is more than -31°F (-35°C).

1. The FRT sensor voltage is less than 0.05 volt.
2. The condition exists for more than 5 seconds.

1. The control module illuminates the Malfunction Indicator Light (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

1. The control module turns off the Malfunction Indicator Light (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC using a scan tool.

1. Use the Temperature Vs. Resistance table in order to test the FTT sensor at various temperature levels in order to evaluate the possibility of a skewed sensor. A skewed sensor could result in a driveability condition. If the engine has sat overnight, the FTT sensor and the IAT sensor values should display within a few degrees. If the temperatures are not within 5°F (Scheme 440)
2. Use a scan tool in order to review Failure Records. If an intermittent condition is suspected, see «INTERMITTENT CONDITIONS»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-60l-bi-fuel-cng__intermittent-conditions) under SELF-DIAGNOSTIC SYSTEM.

The numbers below refer to the step numbers in the diagnostic procedure.

1. 2 This step determines if the condition exists.
2. 3 This step determines if an open low reference circuit is the cause of the condition. If DTC P0192 is also set, an open low reference circuit may be the cause. The Fuel Rail Temperature (FRT) sensor, and the Fuel Rail Pressure (FRP) sensor share a low reference circuit.

1. Did you perform the Diagnostic System Check - Alternative Fuels - Engine Controls. If yes, go to next step. If no, see «DIAGNOSTIC SYSTEM CHECK - ALTERNATIVE FUELS - ENGINE CONTROLS»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-60l-bi-fuel-cng__diagnostic-system-check-alternative-fuels) under SELF-DIAGNOSTIC SYSTEM.
2. Turn ignition on, with engine off. Using a scan tool, observe the Fuel Rail Temperature (FRT) sensor parameter. If the scan tool indicates that the FRT sensor parameter is less than 0.05 volt, go to next step. If the scan tool indicates that the FRT sensor parameter is more than 0.05 volt, go to step 4 .
3. If DTC P0192 also set, go to step 8 . If DTC P0192 is not set, go to step 5 .
4. Observe the Freeze Frame and/or the Failure records data for this DTC. Turn ignition off for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame and/or the Failure records data. If the DTC failed this ignition cycle, go to next step. If the DTC does not fail this ignition cycle, see «DIAGNOSTIC AIDS»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-60l-bi-fuel-cng) .
5. Disconnect the FRT sensor harness connector. Turn ignition on, with engine off. Using a scan tool, observe the FRT sensor parameter. If the scan tool indicates that the FRT sensor voltage is more than 4.6 volts, go to next step. If the scan tool indicates that the FRT sensor voltage is less than 4.6 volts, go to step 7 .
6. Probe the FRT sensor low reference circuit using a test light connected to battery positive. If the test light illuminates, go to step 9 . If the test light does not illuminate, go to step 8 .
7. Turn ignition off. Test the FRT sensor signal circuit for a short to ground. Did you find and correct a short to ground? If yes, go to step 13 . If no, go to step 12 .
8. Test the FRT sensor low reference circuit for an open. Did you find and correct and open? If yes, go to step 13 . If no, go to step 10 .
9. Test for an intermittent and/or a poor connection at the FRT sensor. Did you find and correct an intermittent and/or poor connection? If yes, go to step 13 . If no, go to step 11 .
10. Test for an intermittent and/or a poor connection at the Fuel Injection Control Module (FICM). Did you find and correct an intermittent and/or poor connection? If yes, go to step 13 . If no, go to step 12 .
11. Replace the FRT sensor. After replacement is complete, go to step 13 .
12. Replace the FICM. After replacement is complete, go to next step.
13. Using a scan tool, clear the DTCs. Turn ignition off for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records. If the DTC failed this ignition cycle, go to step 2 . If the DTC did not fail this ignition cycle, go to next step.
14. Observe the Capture Info using a scan tool. Are there any DTCs that have not been diagnosed? If yes, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-60l-bi-fuel-cng__diagnostic-trouble-code-definitions) . If no, system is okay.

DTC P0188: FUEL RAIL TEMPERATURE SENSOR CIRCUIT - HIGH VOLTAGE

Note. To locate components, see COMPONENT LOCATIONS . For circuit reference, see WIRING DIAGRAMS . For connector terminal identification, see CONNECTOR IDENTIFICATION . If an intermittent condition exists, see INTERMITTENT CONDITIONS under SELF-DIAGNOSTIC SYSTEM.

Note. For removal and installation of Bi-Fuel and CNG related components, see REMOVAL & INSTALLATION - CHEVY EXPRESS & SAVANA - BI-FUEL article. For removal and installation of gasoline related components, see REMOVAL & INSTALLATION - CHEVY EXPRESS & SAVANA - GASOLINE article.

The Fuel Rail Temperature (FRT) sensor is a variable resistor that measures the temperature of the fuel in the CNG fuel rail. The Fuel Injector Control Module (FICM) supplies 5 volts to the FRT signal circuit and supplies a ground to the low reference circuit. The FICM monitors the FRT sensor voltage and communicates the data to the PCM by a dedicated Pulse Width Modulated (PWM) circuit. This DTC sets when the FRT signal voltage is above the normal operating range of the sensor.

1. The ignition is on.
2. The Intake Air Temperature is more than -31°F (-35°C).

1. The FRT sensor voltage is more than 4.95 volts.
2. The condition exists for more than 5 seconds.

1. The control module illuminates the Malfunction Indicator Light (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

1. The control module turns off the Malfunction Indicator Light (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC using a scan tool.

1. Use the Temperature Vs. Resistance table in order to test the FTT sensor at various temperature levels in order to evaluate the possibility of a skewed sensor. A skewed sensor could result in a driveability condition. If the engine has sat overnight, the FTT sensor and the IAT sensor values should display within a few degrees. If the temperatures are not within 5°F (Scheme 440)
2. Use a scan tool in order to review Failure Records. If an intermittent condition is suspected, see «INTERMITTENT CONDITIONS»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-60l-bi-fuel-cng__intermittent-conditions) under SELF-DIAGNOSTIC SYSTEM.

The number below refer to the step number in the diagnostic procedure.

1. 4 Tests for the proper operation of the circuit in the low voltage range. If the fuse in the jumper opens when you perform this test, the signal circuit is shorted to voltage.

1. Did you perform the Diagnostic System Check - Alternative Fuels - Engine Controls. If yes, go to next step. If no, see «DIAGNOSTIC SYSTEM CHECK - ALTERNATIVE FUELS - ENGINE CONTROLS»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-60l-bi-fuel-cng__diagnostic-system-check-alternative-fuels) under SELF-DIAGNOSTIC SYSTEM.
2. Turn ignition on, with engine off. Using a scan tool, observe the FRT sensor parameter. If the scan tool indicates that the FRT sensor parameter is near 5 volts, go to step 4 . If the scan tool indicates that the FRT sensor parameter is not near 5 volts, go to next step.
3. Observe the Freeze Frame and/or the Failure records data for this DTC. Turn ignition off for 30 seconds. Start the engine. Operate the vehicle within the Conditions for running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame and/or the Failure records data. If the DTC failed this ignition cycle, go to next step. If the DTC does not fail this ignition cycle, see «DIAGNOSTIC AIDS»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-60l-bi-fuel-cng) .
4. Turn ignition off. Disconnect the FRT sensor. Connect a 3-amp fused jumper wire between the FRT sensor signal circuit and the FRT sensor low reference circuit. Turn ignition on, with engine off. Using a scan tool, observe the FRT sensor parameter. If the scan tool indicates that the FRT sensor parameter is zero volts, go to step 8 . If the scan tool indicates that the FRT sensor parameter is other than zero volts, go to next step.
5. Turn ignition off. Connect a 3-amp fused jumper wire between the FRT sensor signal circuit and a good ground. Turn ignition on, with engine off. Using a scan tool, observe the FRT sensor parameter. If the scan tool indicates that the FRT sensor parameter is zero volts, go to step 7 . If the scan tool indicates that the FRT sensor parameter is other than zero volts, go to next step.
6. Test the FTT sensor signal circuit for an open circuit or for high resistance. Did you find and correct an open circuit or high resistance? If yes, go to step 12 . If no, go to step 9 .
7. Test the FTT sensor low reference circuit for an open circuit or for high resistance. Did you find and correct an open circuit or high resistance? If yes, go to step 12 . If no, go to step 9 .
8. Test for an intermittent and/or a poor connection at the FTT sensor. Did you find and correct an intermittent and/or a poor connection? If yes, go to step 12 . If no, go to step 10 .
9. Test for an intermittent and/or a poor connection at the Fuel Injection Control Module (FICM). Did you find and correct an intermittent and/or a poor connection? If yes, go to step 12 . If no, go to step 11 .
10. Replace the FRT sensor. After replacement is complete, go to step 12 .
11. Replace the FICM. After replacement is complete, go to next step.
12. Using a scan tool, clear the DTCs. Turn ignition off for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records. If the DTC failed this ignition cycle, go to step 2 . If the DTC did not fail this ignition cycle, go to next step.
13. Observe the Capture Info using a scan tool. Are there any DTCs that have not been diagnosed? If yes, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-60l-bi-fuel-cng__diagnostic-trouble-code-definitions) . If no, system is okay.

DTC P0191: FUEL RAIL PRESSURE SENSOR CIRCUIT PERFORMANCE

Note. To locate components, see COMPONENT LOCATIONS . For circuit reference, see WIRING DIAGRAMS . For connector terminal identification, see CONNECTOR IDENTIFICATION . If an intermittent condition exists, see INTERMITTENT CONDITIONS under SELF-DIAGNOSTIC SYSTEM.

Note. For removal and installation of Bi-Fuel and CNG related components, see REMOVAL & INSTALLATION - CHEVY EXPRESS & SAVANA - BI-FUEL article. For removal and installation of gasoline related components, see REMOVAL & INSTALLATION - CHEVY EXPRESS & SAVANA - GASOLINE article.

The Fuel Rail Pressure (FRP) sensor is a pressure sensor. The Fuel Injector Control Module (FICM) supplies about 5 volts on the FRP sensor reference voltage circuit. The FICM also supplies a ground circuit and a signal circuit to the FRP sensor. When the fuel rail pressure is normal, the FRP signal voltage rises to near 2.5 volts. If the fuel rail pressure increases, the FRP signal voltage increases. The FICM monitors the FRP sensor voltage and communicates the data to the PCM by a dedicated Pulse Width Modulated (PWM) circuit. This DTC sets when the FRP sensor signal voltage is outside of the normal operating range of the sensor.

1. The CNG fuel tank pressure is more than 750 psi (5171 kPa).
2. The Engine Coolant Temperature (ECT) is more than 68°F (20°C).
3. The engine speed is more than 600 RPM.
4. The Mass Airflow (MAF) is less than 175 g/s.

1. The FRP sensor is less than 120 psi (827 kPa), or more than 220 psi (1517 kPa).
2. The condition exists for at least 5 seconds.

1. The control module illuminates the Malfunction Indicator Light (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

1. The control module turns off the Malfunction Indicator Light (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC using a scan tool.

The numbers below refer to the step numbers in the diagnostic procedure.

1. 2 This step determines if the condition is present.
2. 4 This step tests the FRP sensor signal circuit and the low reference circuit. The scan tool should display zero volts when the circuits are jumpered together.
3. 5 This step determines if the signal circuit of the FRP sensor is the cause of the condition. The scan tool should display zero volts when the signal circuit is jumpered to a good ground.
4. 6 This step determines if the 5-volt reference circuit is the cause of the condition. The DVOM should display 5.0 volts across the test light.
5. 7 This step verifies that a mechanical fuel system condition is not the cause of the concern. A fuel pressure regulator condition may cause this DTC to set.

1. Did you perform the Diagnostic System Check - Alternative Fuels - Engine Controls. If yes, go to next step. If no, see «DIAGNOSTIC SYSTEM CHECK - ALTERNATIVE FUELS - ENGINE CONTROLS»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-60l-bi-fuel-cng__diagnostic-system-check-alternative-fuels) under SELF-DIAGNOSTIC SYSTEM.
2. Turn ignition on, with engine off. Using a scan tool, observe the Fuel Rail Pressure (FRP) parameter. If the scan tool displays the FRP sensor parameter within 120-220 psi (827-1517 kPa), go to next step. If the scan tool does not display the FRP sensor parameter within 120-220 psi (827-1517 kPa), go to step 4 .
3. Observe the Freeze Frame and/or the Failure records data for this DTC. Turn the ignition OFF for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame and/or the Failure records data. If the DTC failed this ignition cycle, go to next step. If the DTC did not fail this ignition cycle, see «INTERMITTENT CONDITIONS»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-60l-bi-fuel-cng__intermittent-conditions) under SELF-DIAGNOSTIC SYSTEM.
4. Disconnect the FRP sensor. Jumper the FRP sensor signal circuit to the FRP sensor low reference circuit. Using a scan tool, observe the FRP sensor parameter. If the scan tool indicates that the FRT sensor parameter is zero volts, go to next step. If the scan tool indicates that the FRT sensor parameter is other than zero volts, go to step 6 .
5. Jumper the FRP sensor signal circuit to a known good ground. Observe the FRP sensor data display using a scan tool. If the scan tool indicates that the FRT sensor parameter is zero volts, go to step 9 . If the scan tool indicates that the FRT sensor parameter is other than zero volts, go to step 8 .
6. Probe the FRP sensor 5-volt reference circuit with a test light connected to a good ground. Measure the voltage drop across the test light with a DVOM. If the voltage reading is 5 volts, go to next step. If the volage reading is not 5 volts, go to step 10 .
7. Perform the Fuel System Diagnosis procedure. See «FUEL SYSTEM DIAGNOSIS»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-basic-diagnostic-procedures-60l-wbifuel-cng-engines) under FUEL SYSTEMS in BASIC DIAGNOSTIC PROCEDURES - 6.0L CHEVY EXPRESS, SAVANA, SIERRA & SILVERADO - BI-FUEL & CNG article. Did find and correct the condition? If yes, go to step 14 . If no, go to step 12 .
8. Test the FRP sensor signal circuit for an open or high resistance. Did you find and correct an open or high resistance? If yes, go to step 14 . If no, go to step 11 .
9. Test the FRP sensor low reference circuit for high resistance. Did you find and correct a high resistance? If yes, go to step 14 . If no, go to step 11 .
10. Test the FRP sensor 5-volt reference circuit for high resistance. Did you find and correct a high resistance? If yes, go to step 14 . If no, go to next step.
11. Test for an intermittent and/or a poor connection at the Fuel Injection Control Module (FICM). Did you find and correct an intermittent and/or a poor connection? If yes, go to step 14 . If no, go to step 13 .
12. Replace the FRP sensor. After replacement is complete, go to step 14 .
13. Replace the FICM. After replacement is complete, go to next step.
14. Using a scan tool, clear the DTCs. Turn ignition off for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records. If the DTC failed this ignition cycle, go to step 2 . If the DTC did not fail this ignition cycle, go to next step.
15. Observe the Capture Info using a scan tool. Are there any DTCs that have not been diagnosed? If yes, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-60l-bi-fuel-cng__diagnostic-trouble-code-definitions) . If no, system is okay.

DTC P0192: FUEL RAIL PRESSURE SENSOR CIRCUIT - LOW VOLTAGE

Note. To locate components, see COMPONENT LOCATIONS . For circuit reference, see WIRING DIAGRAMS . For connector terminal identification, see CONNECTOR IDENTIFICATION . If an intermittent condition exists, see INTERMITTENT CONDITIONS under SELF-DIAGNOSTIC SYSTEM.

Note. For removal and installation of Bi-Fuel and CNG related components, see REMOVAL & INSTALLATION - CHEVY EXPRESS & SAVANA - BI-FUEL article. For removal and installation of gasoline related components, see REMOVAL & INSTALLATION - CHEVY EXPRESS & SAVANA - GASOLINE article.

The Fuel Rail Pressure (FRP) sensor is a pressure sensor. The Fuel Injector Control Module (FICM) supplies about 5 volts on the FRP sensor reference voltage circuit. The FICM also supplies a ground circuit and a signal circuit to the FRP sensor. When the fuel rail pressure is normal, the FRP signal voltage rises to near 2.5 volts. If the fuel rail pressure increases, the FRP signal voltage increases. The FICM monitors the FRP sensor voltage and communicates the data to the PCM by a dedicated Pulse Width Modulated (PWM) circuit. This DTC sets when the FRP sensor signal voltage is below the normal operating range of the sensor.

The ignition is on.

1. The FRP sensor signal voltage is less than 0.45 volts.
2. The condition exists for at least 5 seconds.

1. The control module illuminates the Malfunction Indicator Light (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

1. The control module turns off the Malfunction Indicator Light (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC using a scan tool.

The numbers below refer to the step numbers in the diagnostic procedure.

1. 2 This step determines if the condition is present.
2. 4 This step determines if the signal circuit of the Fuel Rail Pressure (FRP) sensor is the cause of the condition. The FRP sensor voltage will increase from zero volts to above one volt, with the sensor disconnected.
3. 5 This step determines if the 5-volt reference circuit is the cause of the condition.

1. Did you perform the Diagnostic System Check - Alternative Fuels - Engine Controls. If yes, go to next step. If no, see «DIAGNOSTIC SYSTEM CHECK - ALTERNATIVE FUELS - ENGINE CONTROLS»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-60l-bi-fuel-cng__diagnostic-system-check-alternative-fuels) under SELF-DIAGNOSTIC SYSTEM.
2. Turn ignition on, with engine off. Using a scan tool, observe the Fuel Rail Pressure (FRP) sensor parameter. If the scan tool displays the FRP sensor parameter less than 0.45 volts, go to next step. If the scan tool displays the FRP sensor parameter more than 0.45 volts, go to step 4 .
3. If DTC P0187 also set, see «DTC P0187: FUEL RAIL TEMPERATURE SENSOR CIRCUIT - LOW VOLTAGE»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-60l-bi-fuel-cng__dtc-p0187-fuel-rail-temperature-sensor) . If DTC P0187 is not set, go to step 5 .
4. Observe the Freeze Frame and/or the Failure records data for this DTC. Turn the ignition OFF for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame and/or the Failure records data. If the DTC failed this ignition cycle, go to next step. If the DTC did not fail this ignition cycle, see «INTERMITTENT CONDITIONS»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-60l-bi-fuel-cng__intermittent-conditions) under SELF-DIAGNOSTIC SYSTEM.
5. Turn ignition off. Disconnect the FRP sensor. Turn ignition on, with engine off. Using a scan tool, observe the FRP sensor data display for one minute. If the FRP sensor voltage increases, go to next step. If the FRP sensor voltage does not increase, go to step 7 .
6. Measure the voltage at the FRP sensor 5-volt reference circuit with a DVOM. If the voltage is less than 4.95 volts, go to step 8 . If the voltage is more than 4.95 volts, go to step 9 .
7. Test for a short to ground on the FRP sensor signal circuit. Did you find and correct a short to ground? If yes, go to step 13 . If no, go to step 11 .
8. Test the FRP sensor 5-volt reference for an open or a short to ground. Did you find and correct an open or a short to ground? If yes, go to step 13 . If no, go to step 10 .
9. Test for an intermittent and/or a poor connection at the FRP sensor. Did you find and correct an intermittent and/or a poor connection? If yes, go to step 13 . If no, go to step 11 .
10. Test for an intermittent and/or a poor connection at the Fuel Injection Control Module (FICM). Did you find and correct an intermittent and/or a poor connection? If yes, go to step 13 . If no, go to step 12 .
11. Replace the FRP sensor. After replacement is complete, go to step 13 .
12. Replace the FICM. After replacement is complete, go to next step.
13. Using a scan tool, clear the DTCs. Turn ignition off for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records. If the DTC failed this ignition cycle, go to step 2 . If the DTC did not fail this ignition cycle, go to next step.
14. Observe the Capture Info using a scan tool. Are there any DTCs that have not been diagnosed? If yes, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-60l-bi-fuel-cng__diagnostic-trouble-code-definitions) . If no, system is okay.

DTC P0193: FUEL RAIL PRESSURE SENSOR CIRCUIT - HIGH VOLTAGE

Note. To locate components, see COMPONENT LOCATIONS . For circuit reference, see WIRING DIAGRAMS . For connector terminal identification, see CONNECTOR IDENTIFICATION . If an intermittent condition exists, see INTERMITTENT CONDITIONS under SELF-DIAGNOSTIC SYSTEM.

Note. For removal and installation of Bi-Fuel and CNG related components, see REMOVAL & INSTALLATION - CHEVY EXPRESS & SAVANA - BI-FUEL article. For removal and installation of gasoline related components, see REMOVAL & INSTALLATION - CHEVY EXPRESS & SAVANA - GASOLINE article.

The Fuel Rail Pressure (FRP) sensor is a pressure sensor. The Fuel Injector Control Module (FICM) supplies about 5 volts on the FRP sensor reference voltage circuit. The FICM also supplies a ground circuit and a signal circuit to the FRP sensor. When the fuel rail pressure is normal, the FRP signal voltage rises to near 2.5 volts. If the fuel rail pressure increases, the FRP signal voltage increases. The FICM monitors the FRP sensor voltage and communicates the data to the PCM by a dedicated Pulse Width Modulated (PWM) circuit. This DTC sets when the FRP sensor signal voltage is more than the normal operating range of the sensor.

The ignition is on.

1. The FRP sensor signal voltage is more than 5 volts.
2. The condition exists for at least 5 seconds.

1. The control module illuminates the Malfunction Indicator Light (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

1. The control module turns off the Malfunction Indicator Light (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC using a scan tool.

The numbers below refer to the step numbers in the diagnostic procedure.

1. 2 This step determines if the condition is present.
2. 4 This step determines if an open sensor ground circuit condition the cause of the condition. The Fuel Rail Pressure (FRP) sensor and the Fuel Rail Temperature (FRT) sensor share a common ground. An open circuit between the splice and the FICM will cause both signal circuits to indicate a high voltage.
3. 5 This step determines if an open or shorted signal circuit is the cause of the condition.
4. 6 This step determines if a shorted 5-volt reference circuit is the cause of the condition.
5. 7 This step determines if an open sensor ground circuit between the harness connector of the FRP sensor and the splice is the cause of the condition.

1. Did you perform the Diagnostic System Check - Alternative Fuels - Engine Controls. If yes, go to next step. If no, see «DIAGNOSTIC SYSTEM CHECK - ALTERNATIVE FUELS - ENGINE CONTROLS»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-60l-bi-fuel-cng__diagnostic-system-check-alternative-fuels) under SELF-DIAGNOSTIC SYSTEM.
2. Turn ignition on, with engine off. Using a scan tool, observe the Fuel Rail Pressure (FRP) sensor parameter. If the scan tool displays the FRP sensor voltage of more than 5 volts, go to step 4 . If the scan tool displays the FRP sensor voltage of less than 5 volts, go to next step.
3. Observe the Freeze Frame and/or the Failure records data for this DTC. Turn the ignition OFF for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame and/or the Failure records data. If the DTC failed this ignition cycle, go to next step. If the DTC did not fail this ignition cycle, see «INTERMITTENT CONDITIONS»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-60l-bi-fuel-cng__intermittent-conditions) under SELF-DIAGNOSTIC SYSTEM.
4. Using a scan tool, observe the Fuel Rail Temperature (FRT) sensor parameter. If the scan tool displays the FRT sensor voltage of more than 4.7 volts, go to step 8 . If the scan tool displays the FRT sensor volage of less than 4.7 volts, go to next step.
5. Disconnect the FRP sensor. Connect a 3-amp fused jumper wire between the FRP sensor signal circuit and a good ground. Using a scan tool, observe the FRP sensor parameter. If the scan tool displays the FRP sensor voltage of less than 0.05 volts, go to next step. If the scan tool displays the FRP sensor voltage of more that 0.05 volt, go to step 9 .
6. Remove the jumper. Measure the voltage at the FRP sensor 5-volt reference circuit with a DVOM. If the DVOM displays a voltage of more than 5.2 volts, go to next step. If the DVOM displays a voltage of less than 5.2 volts, go to step 10 .
7. Probe the FRP sensor ground circuit with a test light connected to battery positive. If the test light illuminates, go to step 11 . If the test light does not illuminate, go to step 13 .
8. Test the FRP sensor ground circuit for an open between the Fuel Injection Control Module (FICM) and the splice. Did you find and correct an open? If yes, go to step 16 . If no, go to step 12 .
9. Test the FRP sensor signal circuit for a short to voltage or an open. Did you find and correct a short to voltage or an open? If yes, go to step 16 . If no, go to step 12 .
10. Test the FRP sensor 5-volt reference circuit for a short to voltage. Did you find and correct a short to voltage? If yes, go to step 16 . If no, go to step 15 .
11. Test for an intermittent and/or a poor connection at the FRP sensor. Did you find and correct an intermittent and/or a poor connection? If yes, go to step 16 . If no, go to step 14 .
12. Test for an intermittent and/or a poor connection at the FICM. Did you find and correct an intermittent and/or a poor connection? If yes, go to step 16 . If no, go to step 15 .
13. Repair the FRP sensor ground circuit for an open or high resistance, between the FRP sensor harness connector and the splice. Did you find and correct an open or high resistance? If yes, go to step 16 .
14. Replace the FRP sensor. After replacement is complete, go to next step.
15. Replace the FICM. After replacement is complete, go to next step.
16. Using a scan tool, clear the DTCs. Turn ignition off for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records. If the DTC failed this ignition cycle, go to step 2 . If the DTC did not fail this ignition cycle, go to next step.
17. Observe the Capture Info using a scan tool. Are there any DTCs that have not been diagnosed? If yes, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-60l-bi-fuel-cng__diagnostic-trouble-code-definitions) . If no, system is okay.

DTC P0200: INJECTOR CONTROL CIRCUIT VOLTAGE

Note. To locate components, see COMPONENT LOCATIONS . For circuit reference, see WIRING DIAGRAMS . For connector terminal identification, see CONNECTOR IDENTIFICATION . If an intermittent condition exists, see INTERMITTENT CONDITIONS under SELF-DIAGNOSTIC SYSTEM.

Note. For removal and installation of Bi-Fuel and CNG related components, see REMOVAL & INSTALLATION - CHEVY EXPRESS & SAVANA - BI-FUEL article. For removal and installation of gasoline related components, see REMOVAL & INSTALLATION - CHEVY EXPRESS & SAVANA - GASOLINE article.

The Powertrain Control Module (PCM) controls fuel delivery and determines fuel system operation on Bi-Fuel (KL6) vehicles. The PCM is not capable of operating the high current CNG fuel injectors. The PCM injector control signals are received by the Fuel Injector Control Module (FICM) and duplicate control signals are generated by the FICM in order to operate the CNG injectors. On Bi-Fuel equipped vehicles, the FICM switches off the CNG fuel injectors and re-routes the injector control signals from the PCM to the gasoline fuel injectors. A fused ignition voltage is supplied to all of the fuel injectors. The PCM monitors the status of each injector control circuit. DTC P0200 will set if there is condition on a control circuit between the PCM and FICM. On Bi-Fuel (KL6) vehicles, DTC P0200 can set during gasoline operation, if a circuit condition is detected between the FICM and a gasoline fuel injector.

The ignition is on.

1. The Powertrain Control Module (PCM) detects an incorrect voltage on a fuel injector control circuit.
2. The condition exists for 5 seconds.

1. The control module illuminates the Malfunction Indicator Light (MIL) when the diagnostic runs and fails.
2. The control module switches over to gasoline fuel operation.
3. The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Freeze Frame/Failure Records.

1. The control module turns off the Malfunction Indicator Light (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC using a scan tool.

1. Performing the Fuel Injector Coil Test on the gasoline fuel injectors may help to isolate an intermittent condition. See «FUEL INJECTOR COIL TEST»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-system-component-testing-48l-53l-60l-flex-fuel-gasoline__fuel-injector-coil-test) under FUEL SYSTEMS in SYSTEM & COMPONENT TESTING - 4.8L, 5.3L & 6.0L "C", "G", "H", "K", "N", "S" & "T" SERIES - FLEX FUEL & GASOLINE article.
2. Use a scan tool in order to review Failure Records. If an intermittent condition is suspected, see «INTERMITTENT CONDITIONS»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-60l-bi-fuel-cng__intermittent-conditions) under SELF-DIAGNOSTIC SYSTEM.

The numbers below refer to the step numbers in the diagnostic procedure.

1. 2 This step verifies that a condition exists.
2. 4 The step determines if the condition occurs during gasoline operation. If the vehicle misfires while on gasoline, then the condition is between the Fuel Injection Control Module (FICM) and the gasoline fuel injector.
3. 6 This step tests the control circuit between the PCM and the FICM. The test light should blink while the engine is cranking.
4. 10 This step verifies that an ignition voltage is supplied to the gasoline fuel injector. If the ignition voltage circuit is open DTC P0200 will set while operating on gasoline.
5. 11 This step tests the control circuit between the FICM and the gasoline fuel injector. A switch to gasoline is necessary in order to pulse the gasoline fuel injectors. The test light should blink while the engine is operating.

1. Did you perform the Diagnostic System Check - Alternative Fuels - Engine Controls. If yes, go to next step. If no, see «DIAGNOSTIC SYSTEM CHECK - ALTERNATIVE FUELS - ENGINE CONTROLS»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-60l-bi-fuel-cng__diagnostic-system-check-alternative-fuels) under SELF-DIAGNOSTIC SYSTEM.
2. Using a scan tool, clear the DTCs. Idle the engine at the normal operating temperature. Monitor the misfire current counters using a scan tool. If any of the misfire current counters are incrementing, go to step 6 . If no misfire current counters are incrementing, go to next step.
3. If vehicle equipped with the Bi-Fuel option (KL6), go to next step. If vehicle is not equipped with Bi-Fuel option (KL6), go to step 5 .
4. Using a scan tool, force a fuel system switch-over to gasoline. Using a scan tool, monitor the misfire current counters. If any of the misfire current counters are incrementing, go to step 10 . If no misfire current counters are incrementing, go to next step.
5. Observe the Freeze Frame/Failure Records for this DTC. Turn ignition off for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records. If the DTC failed this ignition cycle, go to next step. If DTC did not fail this ignition cycle, see «DIAGNOSTIC AIDS»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-60l-bi-fuel-cng) .
6. Turn ignition off. Disconnect the harness connector of the FICM. Probe the injector control circuit from the PCM, which displays the highest number of misfire current counters, with a test light connected to battery positive. Crank the engine, while observing the test light. If the test light blinks, go to step 16 . If the test light does not blink, go to next step.
7. If the test light remains illuminated, go to step 9 . If the test light does not remain illuminated, go to next step.
8. Test the fuel injector control circuit for an open, or a short to voltage between the PCM and the FICM. Did you find and correct an open or a short to voltage? If yes, go to step 22 . If no, go to step 17 .
9. Test the fuel injector control circuit for a short to ground between the PCM and the FICM. Did you find and correct a short to ground? If yes, go to step 22 . If no, go to step 21 .
10. Turn ignition off. Disconnect the harness connector of the gasoline fuel injector which displays the highest level of misfire. Probe the ignition voltage circuit of the gasoline fuel injector with a test light connected to a good ground. Turn ignition on, with engine off. If the test light illuminates, go to next step. If the test light does not illuminate, go to step 18 .
11. Probe the control circuit of the gasoline fuel injector with a test light connected to battery positive. Start and idle the engine. Using a scan tool, force a fuel system switch-over to gasoline. Observe the test light. If the test light blinks, go to step 15 . If the test light does not blink, go to next step.
12. If the test light remains illuminated, go to next step. If the test light does not remain illuminated, go to step 14 .
13. Test for a short to ground on the control circuit of the gasoline fuel injector, between the injector and the FICM. Did you find and correct a short to ground? If yes, go to step 22 . If no, go to step 20 .
14. Test for an open or short to voltage on the control circuit of the gasoline fuel injector, between the injector and the FICM. Did you find and correct an open or a short to voltage? If yes, go to step 22 . If no, go to step 16 .
15. Test for an intermittent and/or a poor connection at the gasoline fuel injector. Did you find and correct an intermittent and/or a poor connection? If yes, go to step 22 . If no, go to step 19 .
16. Test for an intermittent and/or a poor connection at the FICM. Did you find and correct an intermittent and/or a poor connection? If yes, go to step 22 . If no, go to step 20 .
17. Test for an intermittent and/or a poor connection at the PCM. Did you find and correct an intermittent and/or a poor connection? If yes, go to step 22 . If no, go to step 21 .
18. Repair the ignition 1 voltage circuit of the fuel injector for an open or for a short to ground. After repairs are complete, go to step 22 .
19. Replace the gasoline fuel injector. After replacement is complete, go to step 22 .
20. Replace the FICM. After replacement is complete, go to step 22 .
21. Replace the PCM. After replacement is complete, go to next step.
22. Using a scan tool, clear the DTCs. Turn ignition off for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records. If the DTC failed this ignition cycle, go to step 2 . If the DTC did not fail this ignition cycle, go to next step.
23. Observe the Capture Info using a scan tool. Are there any DTCs that have not been diagnosed? If yes, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-60l-bi-fuel-cng__diagnostic-trouble-code-definitions) . If no, system is okay.

DTC P0300: RANDOM/MULTIPLE CYLINDER MISFIRE DETECTED

Note. To locate components, see COMPONENT LOCATIONS . For circuit reference, see WIRING DIAGRAMS . For connector terminal identification, see CONNECTOR IDENTIFICATION . If an intermittent condition exists, see INTERMITTENT CONDITIONS under SELF-DIAGNOSTIC SYSTEM.

Note. For removal and installation of Bi-Fuel and CNG related components, see REMOVAL & INSTALLATION - CHEVY EXPRESS & SAVANA - BI-FUEL article. For removal and installation of gasoline related components, see REMOVAL & INSTALLATION - CHEVY EXPRESS & SAVANA - GASOLINE article.

Note. Spark Tester (J-26792) is required to perform this procedure.

The Powertrain Control Module (PCM) uses information from the Crankshaft Position (CKP) sensor and the Camshaft Position (CMP) sensor in order to determine when an engine misfire is occurring. By monitoring variations in the crankshaft rotation speed for each cylinder, the PCM is able to detect misfire events.

1. DTCs P0101, P0102, P0103, P0106, P0107, P0108, P0117, P0112, P0113, P0116, P0117, P0118, P0121, P0122, P0123, P0125, P0128, P0315, P0335, P0336, P0341, P0342, P0343, P0502, P0503, P1114, P1115, P1121, P1122, and P1258 are not set.
2. If the start-up Engine Coolant Temperature (ECT) is less than 20°F (-7°C), misfire detection is delayed until ECT is more than 20°F (-7°C). If the start-up ECT is more than 20°F (-7°C), misfire detection begins after a 5 second delay.
3. The fuel level is more than 10 percent.
4. The ECT is less than 266°F (130°C).
5. The engine speed is 400-5200 RPM.
6. The system voltage is 11-18 volts.
7. The Throttle Position (TP) is steady.
8. The A/C compressor clutch is steady.

The Powertrain Control Module (PCM) detects a deceleration in the crankshaft speed that is characteristic of either an emission type misfire or a catalyst-damaging type misfire.

1. The control module illuminates the Malfunction Indicator Light (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

1. The control module turns off the Malfunction Indicator Light (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC using a scan tool.

The misfire index counts the number of misfires. The scan tool can monitor the misfire index. There is a current misfire counter and a history misfire counter for each cylinder. Use the current misfire counter in order to determine which cylinder is misfiring. Use the history misfire counter for misfires that are not currently present.

Many different conditions can cause an intermittent misfire. Inspect the following conditions

1. Inspect the Ignition Control (IC) circuit for an intermittent short to ground.
2. Ensure that the spark plug wires are securely attached to the spark plugs and the ignition coil.
3. If the misfire occurs when the weather is damp, the condition could be due to worn spark plug wires.
4. Test or inspect for contaminated fuel or a fuel filter restriction. A restricted fuel filter can cause a misfire.
5. Inspect for sticking intake or exhaust valves.
6. Inspect the Heated Oxygen Sensor (HO2S) for abnormal voltage readings.
7. Inspect for a vacuum leak as a possible cause of the engine misfire.

The numbers below refer to the step numbers in the diagnostic procedure.

1. 5 This step determines if the engine is misfiring while operating on the gasoline fuel system.
2. 7 If the Misfire Current Counters are incrementing, but the engine is NOT misfiring, this indicates a mechanical condition. For example, an accessory drive belt could cause this condition.
3. 8 This step verifies that the Crankshaft Variation Learn Procedure is performed. A crankshaft variation that is not learned may cause the misfire counters to increment.
4. 10 The spark should be consistent when you test the spark at the spark plug wires. The presence of few sparks then nothing indicates no spark.
5. 14 A misfiring cylinder may cause more than one misfire counter to increment. Diagnose the fuel injector circuit of the cylinder that displays the highest level of misfire.
6. 20 This step verifies that the catalytic convertors are operating correctly.

1. Did you perform the Diagnostic System Check - Alternative Fuels - Engine Controls. If yes, go to next step. If no, see «DIAGNOSTIC SYSTEM CHECK - ALTERNATIVE FUELS - ENGINE CONTROLS»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-60l-bi-fuel-cng__diagnostic-system-check-alternative-fuels) under SELF-DIAGNOSTIC SYSTEM.
2. Turn ignition on, with engine off. Using a scan tool, observe the DTC information. If any other DTCs are set, g to «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-60l-bi-fuel-cng__diagnostic-trouble-code-definitions) . If no other DTCs are set, go to next step.
3. Start the engine. Using a scan tool, clear the DTCs. Allow the engine to reach operating temperature. Observe the Misfire Current Counters using a scan tool. If any of the misfire current counters are incrementing, go to step 7 . If none of the misfire current counters are incrementing, go to next step.
4. If the vehicle is equipped with the Bi-Fuel option (KL6), go to next step. If vehicle is not equipped with the Bi-Fuel option (KL6), go to step 6 .
5. Using the scan tool output controls function, force a switch over to gasoline. Using a scan tool, observe the Misfire Current Counters. If any of the Misfire Current Counters are incrementing, see «DTC P0200: INJECTOR CONTROL CIRCUIT VOLTAGE»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-60l-bi-fuel-cng__dtc-p0200-injector-control-circuit-voltage) , If none of the Misfire Current Counters are incrementing, go to next step.
6. Observe the Freeze Frame and the Failure records data for this DTC. Turn ignition off for 30 seconds. Start the engine. Operate the vehicle within the conditions for running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame, and the Failure Records data. If the DTC failed this ignition cycle, go to next step. If the DTC does not fail this ignition cycle, see «DIAGNOSTIC AIDS»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-60l-bi-fuel-cng) .
7. If the engine is misfiring, go to step 9 . If the engine is not misfiring, go to next step.
8. Perform the Crankshaft Variation Learn Procedure. See «CKP SYSTEM VARIATION LEARN PROCEDURE»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-48l-53l-60l-gasoline__ckp-system-variation-learn-procedure) under PROGRAMMING in SELF-DIAGNOSTICS - 4.8L, 5.3L & 6.0L EXPRESS & SAVANA - GASOLINE article. Start the engine. Using a scan tool, observe the Misfire Current Counters. If any of the Misfire Current Counters are incrementing, see appropriate article in ENGINES. If none of the Misfire Current Counters are incrementing, go to step 21 .
9. Using a scan tool, observe the Misfire Current Counters. Is there only one Misfire Current Counter incrementing? If yes, go to next step. If no, go to step 16 .
10. Turn ignition off. Disconnect the spark plug wire from the spark plug that indicates a misfire. Connect the Spark Tester to the spark plug wire and a good ground. Start and idle the engine. If the Spark Tester sparks and is the spark consistent go to step 12 . If the Spark Tester does not spark or spark is not consistent, go to next step.
11. Turn ignition off. Remove the spark plug wire from the cylinder that indicates a misfire. Measure the resistance of the spark plug wire with a DVOM. If the resistance is less than 625 ohms per 12" (per 30 cm), see «ELECTRONIC IGNITION SYSTEM DIAGNOSIS»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-basic-diagnostic-procedures-48l-53l-60l-flex-fuel-gasoline-engines) under IGNITION SYSTEMS in BASIC DIAGNOSTIC PROCEDURES - 4.8L, 5.3L & 6.0L "C", "G", "H", "K", "N", "S" & "T" SERIES - FLEX FUEL & GASOLINE article. If the resistance is more than 625 ohms per 12" (per 30 cm), go to step 18 .
12. Remove the spark plug from the cylinder that indicates a misfire. Inspect the spark plug. If you found and corrected a misfire condition, go to step 19 . If you did not find and correct a misfire condition, go to next step.
13. Swap the suspected spark plug with another cylinder that is operating correctly. Start the engine. Operate the engine within the conditions that the misfire occurred. Using a scan tool, monitor the misfire current counters. If the misfire moved with the spark plug, go to step 17 . If the misfire did not move with the spark plug, go to next step.
14. Perform the Fuel Injector Coil Test. See «FUEL INJECTOR COIL TEST»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-system-component-testing-60l-wbifuel-cng__fuel-injector-coil-test) under FUEL SYSTEMS in SYSTEM & COMPONENT TESTING - 6.0L CHEVY EXPRESS, SAVANA, SIERRA & SILVERADO - BI-FUEL & CNG article. Did you find and correct the condition performing fuel injector coil test? If yes, go to step 19 . If no, go to next step.
15. Perform the Fuel System Diagnosis. See «FUEL SYSTEM DIAGNOSIS»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-basic-diagnostic-procedures-60l-wbifuel-cng-engines) under FUEL SYSTEMS in BASIC DIAGNOSTIC PROCEDURES - 6.0L CHEVY EXPRESS, SAVANA, SIERRA & SILVERADO - BI-FUEL & CNG article. Did you find and correct a fuel system condition? If yes, go to step 19 . If no, see appropriate article in ENGINES.
16. Inspect or test for the following conditions: Vacuum hoses for splits, kinks, and the correct connections. Vacuum leaks at the throttle body and at the intake manifold. PCM grounds for being clean, tight, and in the correct location. Correct fuel pressure. See «FUEL SYSTEM DIAGNOSIS»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-basic-diagnostic-procedures-60l-wbifuel-cng-engines) under FUEL SYSTEMS in BASIC DIAGNOSTIC PROCEDURES - 6.0L CHEVY EXPRESS, SAVANA, SIERRA & SILVERADO - BI-FUEL & CNG article. Faulty spark plug wires. Fouled or damaged spark plugs. Exhaust system for restrictions. See «RESTRICTED EXHAUST»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-trouble-shooting-no-codes-60l-wbifuel-cng__restricted-exhaust) under SYMPTOMS in TROUBLE SHOOTING - NO CODES - 6.0L CHEVY EXPRESS, SAVANA, SIERRA & SILVERADO - BI-FUEL & CNG article. Did you find and correct the condition? If yes, go to step 19 . If no, see appropriate article in ENGINES.
17. Replace the spark plug. After replacement is complete, go to step 19 .
18. Replace the spark plug wire. After replacement is complete, go to next step.
19. If the customers concern was a flashing MIL, go to next step. If the customers concern was not a flashing MIL, go to step 21 .
20. Operate the vehicle at 2500 RPM for 4 minutes. Operate the vehicle within the Conditions For Running the DTC P0420 or P0430 as specified in the supporting text. See «DTC P0420: TWC SYSTEM - LOW EFFICIENCY - BANK 1 & P0430: TWC SYSTEM - LOW EFFICIENCY - BANK 2»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-48l-53l-60l-gasoline__dtc-p0420-twc-system-low) under DIAGNOSTIC TEST in SELF-DIAGNOSTICS - 4.8L, 5.3L & 6.0L EXPRESS & SAVANA - GASOLINE article. If the DTC did not fail this ignition cycle, go to next step. If the DTC failed this ignition cycle, see «DTC P0420: TWC SYSTEM - LOW EFFICIENCY - BANK 1 & P0430: TWC SYSTEM - LOW EFFICIENCY - BANK 2»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-48l-53l-60l-gasoline__dtc-p0420-twc-system-low) under DIAGNOSTIC TEST in SELF-DIAGNOSTICS - 4.8L, 5.3L & 6.0L EXPRESS & SAVANA - GASOLINE article.
21. Using a scan tool, clear the DTCs. Turn the ignition off for 30 seconds. Start the engine. Operate the vehicle within the Conditions For Running The DTC. If the DTC did not fail this ignition cycle, go next step. If DTC failed this ignition cycle, go to step 2 .
22. Observe the Capture Info using a scan tool. Are there any DTCs that have not been diagnosed? If yes, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-60l-bi-fuel-cng__diagnostic-trouble-code-definitions) . If no, system is okay.

DTC P0611: FUEL INJECTOR CONTROL MODULE PERFORMANCE

Note. To locate components, see COMPONENT LOCATIONS . For circuit reference, see WIRING DIAGRAMS . For connector terminal identification, see CONNECTOR IDENTIFICATION . If an intermittent condition exists, see INTERMITTENT CONDITIONS under SELF-DIAGNOSTIC SYSTEM.

Note. For removal and installation of Bi-Fuel and CNG related components, see REMOVAL & INSTALLATION - CHEVY EXPRESS & SAVANA - BI-FUEL article. For removal and installation of gasoline related components, see REMOVAL & INSTALLATION - CHEVY EXPRESS & SAVANA - GASOLINE article.

The Fuel Injector Control Module (FICM) monitors the Fuel Rail Pressure (FRP) sensor voltage, and the Fuel Rail Temperature (FRT) sensor voltage. The FRP and FRT sensor values, and diagnostic data, is communicated to the Powertrain Control Module (PCM) by 3 Pulse Width Modulated (PWM) circuits. This DTC sets when the PCM does not receive any PWM signals from the FICM.

The ignition is on.

The PCM detects an incorrect PWM signal on the FICM diagnostic output circuit.

1. The control module illuminates the Malfunction Indicator Light (MIL) when the diagnostic runs and fails.
2. The control module switches over to gasoline fuel operation.
3. The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Freeze Frame/Failure Records.

1. The control module turns off the Malfunction Indicator Light (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC using a scan tool.

The number below refers to the step number on the diagnostic table.

1. 2 This step verifies that the condition is active.
2. 3 This step verifies that the ignition voltage circuit to the FICM is OK. If the ignition voltage circuit is open, DTCs P1207, P1208, and P1209 may also be set.

1. Did you perform the Diagnostic System Check - Alternative Fuels - Engine Controls. If yes, go to next step. If no, see «DIAGNOSTIC SYSTEM CHECK - ALTERNATIVE FUELS - ENGINE CONTROLS»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-60l-bi-fuel-cng__diagnostic-system-check-alternative-fuels) under SELF-DIAGNOSTIC SYSTEM.
2. Turn ignition on, with engine OFF. Using a scan tool, clear the DTC information. Attempt to start and idle the engine. Using a scan tool, observe the DTC information. If DTC P0611 resets, go to next step. If DTC P0611 does not reset. see «INTERMITTENT CONDITIONS»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-60l-bi-fuel-cng__intermittent-conditions) under SELF-DIAGNOSTIC SYSTEM.
3. Turn ignition off. Disconnect the FICM harness connector. Turn ignition on, with engine off. Probe the FICM ignition feed circuit with a test light connected to a good ground. If the test light illuminates, go to next step. If the test light does not illuminate, go to step 5 .
4. Probe the FICM ground circuits with a test light connected to battery positive. If the test light illuminates for both ground circuits, go to step 7 . If the test light does not illuminate for both ground circuits, go to step 6 .
5. Repair the open or short to ground on the FICM ignition feed circuit. After repairs are complete, go to step 9 .
6. Repair the open on the FICM ground circuit. After repairs are complete, go to step 9 .
7. Test for an intermittent and/or a poor connection at the control module. Did you find and an intermittent and/or poor connection? If yes, go to step 9 . If no, go to next step.
8. Replace the FICM. After replacement is complete, go to next step.
9. Turn the ignition off for 30 seconds. Turn ignition on, with engine off. If the DTC failed this ignition cycle, go to step 2 . If the DTC did not fail this ignition cycle, go to next step.
10. Observe the Capture Info using a scan tool. Are there any DTCs that have not been diagnosed? If yes, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-60l-bi-fuel-cng__diagnostic-trouble-code-definitions) . If no, system is okay.

DTC P1020: INCORRECT VOLTAGE ON A CNG FUEL INJECTOR CONTROL CIRCUIT

Note. To locate components, see COMPONENT LOCATIONS . For circuit reference, see WIRING DIAGRAMS . For connector terminal identification, see CONNECTOR IDENTIFICATION . If an intermittent condition exists, see INTERMITTENT CONDITIONS under SELF-DIAGNOSTIC SYSTEM.

Note. For removal and installation of Bi-Fuel and CNG related components, see REMOVAL & INSTALLATION - CHEVY EXPRESS & SAVANA - BI-FUEL article. For removal and installation of gasoline related components, see REMOVAL & INSTALLATION - CHEVY EXPRESS & SAVANA - GASOLINE article.

The Powertrain Control Module (PCM) controls fuel delivery and determines fuel system operation on Bi-Fuel (KL6) vehicles. The PCM is not capable of operating the high current CNG fuel injectors. The PCM injector Pulse Width Modulation (PWM) signals are received by the Fuel Injector Control Module (FICM) and duplicate PWM signal are generated by the FICM in order to operate the CNG injectors. Ignition voltage is supplied to the fuel injectors. The FICM controls each CNG fuel injector by grounding the control circuit via a solid state device called a driver. The FICM monitors the status of each driver. If the control module detects an incorrect voltage for the commanded state of the driver, a fuel injector control DTC sets.

The ignition is on.

1. The FICM detects an incorrect voltage on a CNG fuel injector control circuit.
2. The condition exists for 5 seconds.

1. The control module illuminates the Malfunction Indicator Light (MIL) when the diagnostic runs and fails.
2. The control module switches over to gasoline fuel operation.
3. The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Freeze Frame/Failure Records.

1. The control module turns off the Malfunction Indicator Light (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC using a scan tool.

1. Performing the Fuel Injector Coil Test may help to isolate an intermittent condition. See «FUEL INJECTOR COIL TEST»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-system-component-testing-60l-wbifuel-cng__fuel-injector-coil-test) under FUEL SYSTEMS in SYSTEM & COMPONENT TESTING - 6.0L CHEVY EXPRESS, SAVANA, SIERRA & SILVERADO - BI-FUEL & CNG article.
2. For an intermittent condition, see «INTERMITTENT CONDITIONS»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-60l-bi-fuel-cng__intermittent-conditions) under SELF-DIAGNOSTIC SYSTEM.

The numbers below refer to the step numbers in the diagnostic procedure.

1. 5 This step verifies that the Fuel Injector Control Module (FICM) is able to control the fuel injector.
2. 6 This step tests if a ground is constantly being applied to the fuel injector.

1. Did you perform the Diagnostic System Check - Alternative Fuels - Engine Controls. If yes, go to next step. If no, see «DIAGNOSTIC SYSTEM CHECK - ALTERNATIVE FUELS - ENGINE CONTROLS»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-60l-bi-fuel-cng__diagnostic-system-check-alternative-fuels) under SELF-DIAGNOSTIC SYSTEM.
2. Perform the fuel injector balance test on each CNG fuel injector, in order to isolate the inoperative injector. See «FUEL INJECTOR BALANCE TEST WITH SPECIAL TOOL»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-system-component-testing-60l-wbifuel-cng__fuel-injector-balance-test-with-special) under FUEL SYSTEMS in SYSTEM & COMPONENT TESTING - 6.0L CHEVY EXPRESS, SAVANA, SIERRA & SILVERADO - BI-FUEL & CNG article. Listen for an audible clicking as each CNG fuel injector operates. If all of the CNG fuel injectors operate correctly, go to next step. If all CNG fuel injectors do not operate correctly, go to step 4 .
3. Observe the Freeze Frame/Failure Records for this DTC. Turn ignition off for 30 seconds. Start the engine. Operate the vehicle within the Conditions For Running The DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records. If the DTC failed this ignition cycle, go to next step. If the DTC did not fail this ignition cycle, see «DIAGNOSTIC AIDS»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-60l-bi-fuel-cng) .
4. Turn ignition off. Disconnect the CNG fuel injector that was isolated during the fuel injector balance test. Turn ignition on, with engine off. Probe the CNG fuel injector ignition 1 voltage circuit with a test light connected to a good ground. If the test light illuminates, go to next step. If the test light does not illuminate, go to step 11 .
5. Probe the CNG fuel injector control circuit with a test light connected to battery positive. Start the engine. If the test light flashes, go to step 9 . If the test light does not flash, go to next step.
6. If the test light remains illuminated, go to step 8 . If the test light does not remain illuminate, go to next step.
7. Test the CNG fuel injector control circuit for an open or a short to voltage. Did you find and correct an open or short to voltage? If yes, go to step 14 . If no, go to step 10 .
8. Test the CNG fuel injector control circuit for a short to ground. Did you find and correct a short to ground? If yes, go to step 14 . If no, go to step 13 .
9. Test for an intermittent and/or a poor connection at the CNG fuel injector. Did you find and correct an intermittent and/or a poor connection? If yes, go to step 14 . If no, go to step 12 .
10. Test for an intermittent and/or a poor connection at the FICM. Did you find and correct an intermittent and/or a poor connection? If yes, go to step 14 . If no, go to step 13 .
11. Test the CNG fuel injector ignition 1 voltage circuit for an open or for a short to ground. Did you find and correct an open or short to ground. If yes, go to step 14 .
12. Replace the CNG fuel injector. After replacement is complete, go to step 14 .
13. Replace the FICM. After replacement is complete, go to next step.
14. Using a scan tool, clear the DTCs. Turn ignition off for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records. If the DTC failed this ignition cycle, go to step 2 . If the DTC did not fail this ignition cycle, go to next step.
15. Observe the Capture Info using a scan tool. Are there any DTCs that have not been diagnosed? If yes, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-60l-bi-fuel-cng__diagnostic-trouble-code-definitions) . If no, system is okay.

DTC P1204: VEHICLE DOES NOT START ON CNG

Note. To locate components, see COMPONENT LOCATIONS . For circuit reference, see WIRING DIAGRAMS . For connector terminal identification, see CONNECTOR IDENTIFICATION . If an intermittent condition exists, see INTERMITTENT CONDITIONS under SELF-DIAGNOSTIC SYSTEM.

Note. For removal and installation of Bi-Fuel and CNG related components, see REMOVAL & INSTALLATION - CHEVY EXPRESS & SAVANA - BI-FUEL article. For removal and installation of gasoline related components, see REMOVAL & INSTALLATION - CHEVY EXPRESS & SAVANA - GASOLINE article.

The Powertrain Control Module (PCM) controls fuel delivery and for KL6 vehicles, determines which fuel system the engine is operating on. The PCM controls the Low Pressure Lock-Off (LPL) solenoids, and the High Pressure Lock-Off (HPL) solenoids. The PCM commands the HPL solenoids open for one second at every ignition ON, in order to prime the CNG fuel system. The PCM commands the HPLs, and the LPL open, when the engine is cranking or running on CNG. This DTC sets if the vehicle does not start on CNG within 4 seconds.

The engine is cranking.

The cranking time to start in CNG mode is more than 4 seconds.

1. The control module illuminates the Malfunction Indicator Light (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

1. The control module turns off the Malfunction Indicator Light (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC using a scan tool.

1. Inspect the FICM for the proper part number. Bi-Fuel (KL6) and dedicated (KL8) CNG equipped vehicles utilize unique FICM's that are not interchangeable.
2. Use a scan tool in order to review Failure Records. If an intermittent condition is suspected, see «INTERMITTENT CONDITIONS»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-60l-bi-fuel-cng__intermittent-conditions) under SELF-DIAGNOSTIC SYSTEM.

The numbers below refer to the step numbers in the diagnostic procedure.

1. 4 This step determines if a CNG related DTC is set.
2. 5 This step determines if the condition is present.
3. 7 This step determines if the CNG fuel system is the cause of the concern.

1. Did you perform the Diagnostic System Check - Alternative Fuels - Engine Controls. If yes, go to next step. If no, see «DIAGNOSTIC SYSTEM CHECK - ALTERNATIVE FUELS - ENGINE CONTROLS»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-60l-bi-fuel-cng__diagnostic-system-check-alternative-fuels) under SELF-DIAGNOSTIC SYSTEM.
2. Using a scan tool, observe the DTC information. If any DTCs are set, go to next step. If no DTCs are set go to step 5 .
3. Using a scan tool, select Captured Info in order to store the powertrain DTC information. After storing DTC information, go to next step.
4. Turn ignition on, with engine off. Using a scan tool, observe the DTC information. If the scan tool displays DTC P0005, P0191, P0611, P2146, or P2665, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-60l-bi-fuel-cng__diagnostic-trouble-code-definitions) . If the scan tool does not display DTC P0005, P0191, P0611, P2146, or P2665 go to next step.
5. Attempt to start the engine. If the engine starts and idles, go to next step. If the engine does not start and idle, go to step 7 .
6. Observe the Freeze Frame and/or the Failure records data for this DTC. Turn the ignition off for 30 seconds. Start the engine. Operate the vehicle within the Conditions For Running The DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame and/or the Failure records data. If the DTC failed this ignition cycle, go to next step. If the DTC did not fail this ignition cycle, see «DIAGNOSTIC AIDS»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-60l-bi-fuel-cng) .
7. Turn ignition on, with engine off. using a scan tool, observe the Fuel Rail Pressure (FRP) sensor parameter. If the FRP display remain steady near 160 psi (1103 kPa), see «NO-START - ENGINE CRANKS OKAY»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-basic-diagnostic-procedures-60l-wbifuel-cng-engines) under NO-START DIAGNOSIS in BASIC DIAGNOSTIC PROCEDURES - 6.0L CHEVY EXPRESS, SAVANA, SIERRA & SILVERADO - BI-FUEL & CNG article. If the FRP display does not remain steady near 160 psi (1103kPa), see «FUEL SYSTEM DIAGNOSIS»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-basic-diagnostic-procedures-60l-wbifuel-cng-engines) under FUEL SYSTEMS in BASIC DIAGNOSTIC PROCEDURES - 6.0L CHEVY EXPRESS, SAVANA, SIERRA & SILVERADO - BI-FUEL & CNG article.

DTC P1207: FUEL RAIL PRESSURE OUTPUT PWM SIGNAL NOT RECEIVED BY PCM

Note. To locate components, see COMPONENT LOCATIONS . For circuit reference, see WIRING DIAGRAMS . For connector terminal identification, see CONNECTOR IDENTIFICATION . If an intermittent condition exists, see INTERMITTENT CONDITIONS under SELF-DIAGNOSTIC SYSTEM.

Note. For removal and installation of Bi-Fuel and CNG related components, see REMOVAL & INSTALLATION - CHEVY EXPRESS & SAVANA - BI-FUEL article. For removal and installation of gasoline related components, see REMOVAL & INSTALLATION - CHEVY EXPRESS & SAVANA - GASOLINE article.

The Fuel Injector Control Module (FICM) monitors the fuel rail pressure (FRP) sensor voltage, and the Fuel Rail Temperature (FRT) sensor voltage. The FICM communicates the data to the PCM by dedicated Pulse Width Modulated (PWM) circuits. This DTC sets when the rail pressure output PWM signal is not received by the PCM.

The ignition is on.

1. The rail pressure output PWM signal is not received by the PCM.
2. The condition exists for at least 5 seconds.

1. The control module illuminates the Malfunction Indicator Light (MIL) when the diagnostic runs and fails.
2. The control module switches over to gasoline fuel operation.
3. The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Freeze Frame/Failure Records.

1. The control module turns off the Malfunction Indicator Light (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC using a scan tool.

The numbers below refer to the step numbers in the diagnostic procedure.

1. 2 This step determines if the condition is present.
2. 3 If any of the listed DTCs are set, diagnose those DTCs first.
3. 5 This step determines if a Fuel Rail Pressure (FRP) sensor circuit may be the cause of the condition. If a FRP sensor circuit condition exists, the FICM will output zero percent PWM to the PCM. With the FRP sensor disconnected, the fuel rail pressure should slowly rise.
4. 6 This step verifies that the FICM is supplying 5 volts on the FRP sensor reference circuit. An open, or a short to ground, on the 5 volt reference circuit may set this DTC.
5. 7 This step verifies that the FICM is supplying a low reference circuit. An open on the FRP sensor low reference circuit may set this DTC.
6. 8 This step determines if the signal circuit of the FRP sensor is shorted to a voltage. A short to a voltage on the signal circuit of the FRP sensor may set this DTC.
7. 9 This step determines if the signal circuit of the FRP sensor is shorted to ground. A short to ground on the signal circuit of the FRP sensor may set this DTC. The DVOM will display OL If the signal circuit is not grounded.
8. 10 This step verifies that the FICM is supplying the correct output voltage on the FRP output PWM circuit. The open circuit voltage should be 5.0 volts.

1. Did you perform the Diagnostic System Check - Alternative Fuels - Engine Controls. If yes, go to next step. If no, see «DIAGNOSTIC SYSTEM CHECK - ALTERNATIVE FUELS - ENGINE CONTROLS»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-60l-bi-fuel-cng__diagnostic-system-check-alternative-fuels) under SELF-DIAGNOSTIC SYSTEM.
2. Using a scan tool, observe the Fuel Injection Control Module (FICM) odd bank circuit status. Does the scan tool display FAULT? If yes, go to next step. If no, go to step 4 .
3. Do any of the DTCs P0187, P0188, P0191, P0192, P0193, or P0611 also set this ignition cycle? If yes, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-60l-bi-fuel-cng__diagnostic-trouble-code-definitions) . If no, go to step 5 .
4. Observe the Freeze Frame and/or the Failure records data for this DTC. Turn the ignition off for 30 seconds. Start the engine. Operate the vehicle within the Conditions For Running The DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame and/or the Failure records data. If the DTC failed this ignition cycle, go to next step. If the DTC does not fail this ignition cycle, see «INTERMITTENT CONDITIONS»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-60l-bi-fuel-cng__intermittent-conditions) under SELF-DIAGNOSTIC SYSTEM.
5. Turn ignition off. Disconnect the FRP sensor harness connector. Turn ignition on, with engine off. Using a scan tool, observe the FRP sensor pressure parameter. Does the scan tool display a pressure of 0 psi (0 kPa)? If yes, go to step 8 . If no, go to next step.
6. Measure the FRP sensor voltage from the 5-volt reference circuit with a DVOM. Does the DVOM display a voltage near 5.0 volts. If yes, go to next step. If no, go to step 14 .
7. Probe the FRP sensor low reference circuit with a test light connected to battery positive. If the test light illuminates, go to step 18 . If test light does not illuminate, go to step 15 .
8. Measure the voltage from the signal circuit of the FRP sensor. If the DVOM displays less than 1.0 volt, go to next step. If the DVOM displays more than 1.0 volt, go to step 17 .
9. Using a DVOM, measure the resistance of the FRP sensor signal circuit to a good ground. If the DVOM displays OL, go to next step. If the DVOM does not display OL, go to step 16 .
10. Turn ignition off. Connect the harness connector of the FRP sensor. Disconnect the PCM harness connector C1. Turn ignition on, with engine off. Measure the voltage from the rail pressure output PWM circuit with a DVOM. If the DVOM displays 5.0 volts, go to step 19 . If the DVOM does not display 5.0 volts, go to next step.
11. If the voltage is more than 5.3 volts, go to step 13 . If the voltage is less than 5.3 volts, go to next step.
12. Test for an open, or a short to ground on the rail pressure output PWM circuit. Did you find and correct an open or a short to ground? If yes, go to step 24 . If no, go to step 20 .
13. Test for a short to voltage on the rail pressure output PWM circuit. Did you find and correct a short to voltage? If yes, go to step 24 . If no, go to step 23 .
14. Test for an open, or a short to ground on the FRP sensor 5 volt reference circuit. Did you find and correct an open or a short to ground? If yes, go to step 24 . If no, go to step 20 .
15. Test for an open on the FRP sensor low reference circuit. Did you find and correct an open? If yes, go to step 24 . If no, go to step 20 .
16. Test for a short to ground on the FRP sensor signal circuit. Did you find and correct a short to ground? If yes, go to step 24 . If no, go to step 23 .
17. Test for a short to voltage on the FRP sensor signal circuit. Did you find and correct a short to voltage? If yes, go to step 24 . If no, go to step 23 .
18. Test for an intermittent and/or a poor connection at the FRP sensor. Did you find and correct an intermittent and/or a poor connection? If yes, go to step 24 . If no, go to step 21 .
19. Test for an intermittent and/or a poor connection at the PCM. Did you find and correct an intermittent and/or a poor connection? If yes, go to step 24 . If no, go to step 22 .
20. Test for an intermittent and/or a poor connection at the FICM. Did you find and correct an intermittent and/or a poor connection? If yes, go to step 24 . If no, go to step 23 .
21. Replace the FRP sensor. After replacement is complete, go to step 24 .
22. Replace the PCM. After replacement is complete, go to step 24 .
23. Replace the FICM. After replacement is complete, go to next step.
24. Using a scan tool, clear the DTCs. Turn ignition off for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records. If the DTC failed this ignition cycle, go to step 2 . If the DTC did not fail this ignition cycle, go to next step.
25. Observe the Capture Info using a scan tool. Are there any DTCs that have not been diagnosed? If yes, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-60l-bi-fuel-cng__diagnostic-trouble-code-definitions) . If no, system is okay.

DTC P1208: FUEL RAIL TEMPERATURE OUTPUT PWM SIGNAL NOT RECEIVED BY PCM

Note. To locate components, see COMPONENT LOCATIONS . For circuit reference, see WIRING DIAGRAMS . For connector terminal identification, see CONNECTOR IDENTIFICATION . If an intermittent condition exists, see INTERMITTENT CONDITIONS under SELF-DIAGNOSTIC SYSTEM.

Note. For removal and installation of Bi-Fuel and CNG related components, see REMOVAL & INSTALLATION - CHEVY EXPRESS & SAVANA - BI-FUEL article. For removal and installation of gasoline related components, see REMOVAL & INSTALLATION - CHEVY EXPRESS & SAVANA - GASOLINE article.

The Fuel Injector Control Module (FICM) monitors the Fuel Rail Pressure (FRP) sensor voltage, and the Fuel Rail Temperature (FRT) sensor voltage. The FICM communicates the data to the PCM by dedicated Pulse Width Modulated (PWM) circuits. This DTC sets when the rail temperature output PWM signal is not received by the PCM.

The ignition is on.

1. The FRT output PWM signal is not received by the PCM.
2. The condition exists for at least 5 seconds.

1. The control module illuminates the Malfunction Indicator Light (MIL) when the diagnostic runs and fails.
2. The control module switches over to gasoline fuel operation.
3. The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Freeze Frame/Failure Records.

1. The control module turns off the Malfunction Indicator Light (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC using a scan tool.

The numbers below refer to the step numbers in the diagnostic procedure.

1. 2 This step determines if the condition is present.
2. 3 If any of the listed DTCs are set, diagnose those DTCs first.
3. 5 This step tests the signal circuit of the Fuel Rail Temperature (FRT) sensor. The DVOM should display 5 volts.
4. 7 This step tests the low reference circuit of the FRT sensor. An open FRT sensor low reference circuit may cause this DTC to set.
5. 8 This step determines if the FICM, PCM, and the rail temperature output PWM circuit are OK. If the temperature parameter changes when the FRT signal circuit is grounded, the FICM, PCM, and wiring are OK. Repeat the procedure as necessary in order to verify correct operation of the FICM, PCM, and the rail temperature output PWM circuit.
6. 9 This step verifies that the FICM is supplying the correct output voltage. The open circuit voltage should be 5.0 volts.

1. Did you perform the Diagnostic System Check - Alternative Fuels - Engine Controls. If yes, go to next step. If no, see «DIAGNOSTIC SYSTEM CHECK - ALTERNATIVE FUELS - ENGINE CONTROLS»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-60l-bi-fuel-cng__diagnostic-system-check-alternative-fuels) under SELF-DIAGNOSTIC SYSTEM.
2. Using a scan tool, observe the FICM even bank circuit status. Does the scan tool display FAULT? If yes, go to next step. If no, go to step 4 .
3. Are any of the DTCs P0187, P0188, P0191, P0192, P0193, or P0611 also set? If yes, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-60l-bi-fuel-cng__diagnostic-trouble-code-definitions) . If no, go to step 5 .
4. Observe the Freeze Frame and/or the Failure records data for this DTC. Turn the ignition off for 30 seconds. Start the engine. Operate the vehicle within the Conditions For Running The DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame and/or the Failure records data. If the DTC failed this ignition cycle, go to next step. If the DTC does not fail this ignition cycle, see «INTERMITTENT CONDITIONS»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-60l-bi-fuel-cng__intermittent-conditions) under SELF-DIAGNOSTIC SYSTEM.
5. Turn ignition off. Disconnect the FRT sensor harness connector. Turn ignition on, with engine off. Measure the voltage from the signal circuit of the FRP sensor with a DVOM. Does the DVOM display a voltage near 5.0 volts? If yes, go to step 7 . If no, go to next step.
6. If the voltage is above 5.3 volts, go to step 14 . If the voltage is below 5.3 volts, go to step 13 .
7. Probe the FRT sensor low reference circuit with a test light connected to battery positive. If the test lights illuminates, go to next step. If the test light does not illuminate, go to step 15 .
8. Using a scan tool, observe the FRT sensor temperature parameter. Jumper the FRT sensor signal circuit to a good ground. If the FRT temperature display fluctuates when the circuit is grounded, go to step 16 . If the FRT temperature display does not fluctuate when the circuit is grounded, go to next step.
9. Turn ignition off. Connect the FRT sensor harness connector. Disconnect the PCM harness connector C2. Turn ignition on, with engine off. Measure the voltage from the rail temperature output PWM circuit with a DVOM. Does the DVOM display 5.0 volts? If yes, go to step 17 . If no, go to next step.
10. If the voltage is more than 5.3 volts, go to step 12 . If the voltage is less than 5.3 volts, go to next step.
11. Test for an open or a short to ground on the rail temperature output PWM circuit. Did you find and correct an open or a short to ground? If yes, go to step 22 . If no, go to step 18 .
12. Test for a short to voltage on the rail temperature output PWM circuit. Did you find and correct a short to voltage? If yes, go to step 22 . If no, go to step 21 .
13. Test for an open on the FRT sensor signal circuit. Did you find and correct an open? If yes, go to step 22 . If no, go to step 18 .
14. Test for a short to voltage on the FRT sensor signal circuit. Did you find and correct a short to voltage? If yes, go to step 22 . If no, go to step 21 .
15. Test for an open on the FRT sensor low reference circuit. Did you find and correct an open? If yes, go to step 22 . If no, go to step 18 .
16. Test for an intermittent and/or a poor connection at the FRT sensor. Did you find and correct an intermittent and/or a poor connection? If yes, go to step 22 . If no, go to step 19 .
17. Inspect for proper terminal contact at the harness connector of the PCM. Did you find and correct an intermittent and/or a poor connection? If yes, go to step 22 . If no, go to step 20 .
18. Test for an intermittent and/or a poor connection at the FICM. Did you find and correct an intermittent and/or a poor connection? If yes, go to step 22 . If no, go to step 21 .
19. Replace the FRT sensor. After replacement is complete, go to step 22 .
20. Replace the PCM. After replacement is complete, go to step 22 .
21. Replace the FICM. After replacement is complete, go to next step.
22. Using a scan tool, clear the DTCs. Turn ignition off for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records. If the DTC failed this ignition cycle, go to step 2 . If the DTC did not fail this ignition cycle, go to next step.
23. Observe the Capture Info using a scan tool. Are there any DTCs that have not been diagnosed? If yes, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-60l-bi-fuel-cng__diagnostic-trouble-code-definitions) . If no, system is okay.

DTC P1209: FICM DIAGNOSTIC OUTPUT PWM SIGNAL NOT RECEIVED BY PCM

Note. To locate components, see COMPONENT LOCATIONS . For circuit reference, see WIRING DIAGRAMS . For connector terminal identification, see CONNECTOR IDENTIFICATION . If an intermittent condition exists, see INTERMITTENT CONDITIONS under SELF-DIAGNOSTIC SYSTEM.

Note. For removal and installation of Bi-Fuel and CNG related components, see REMOVAL & INSTALLATION - CHEVY EXPRESS & SAVANA - BI-FUEL article. For removal and installation of gasoline related components, see REMOVAL & INSTALLATION - CHEVY EXPRESS & SAVANA - GASOLINE article.

The Fuel Injector Control Module (FICM) monitors the Fuel Rail Pressure (FRP) sensor voltage, and the Fuel Rail Temperature (FRT) sensor voltage. When the FICM detects a condition with the FRP or FRT sensors, the diagnostic data is communicated to the PCM by a dedicated Pulse Width Modulated (PWM) circuit. This DTC sets when the FICM diagnostic output PWM signal is not received by the PCM.

The ignition is on.

1. The FICM diagnostic output PWM signal is not received by the PCM.
2. The condition exists for at least 5 seconds.

1. The control module illuminates the Malfunction Indicator Light (MIL) when the diagnostic runs and fails.
2. The control module switches over to gasoline fuel operation.
3. The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Freeze Frame/Failure Records.

1. The control module turns off the Malfunction Indicator Light (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC using a scan tool.

The numbers below refer to the step numbers in the diagnostic procedure.

1. 2 This step determines if the condition is present.
2. 3 If any of the listed DTCs are set, diagnose those DTCs first.
3. 5 This step verifies that the Fuel Injection Control Module (FICM) is supplying the correct output voltage. The open circuit voltage should be 5.0 volts.

1. Did you perform the Diagnostic System Check - Alternative Fuels - Engine Controls. If yes, go to next step. If no, see «DIAGNOSTIC SYSTEM CHECK - ALTERNATIVE FUELS - ENGINE CONTROLS»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-60l-bi-fuel-cng__diagnostic-system-check-alternative-fuels) under SELF-DIAGNOSTIC SYSTEM.
2. Using a scan tool, observe the Fuel Injection Control Module (FICM) diagnostic circuit status. Does the scan tool display FAULT? If yes, go to next step. If no, go to step 4 .
3. Are any of the DTCs P0187, P0188, P0191, P0192, P0193, P0611, or P1208 also set? If yes, see «INTERMITTENT CONDITIONS»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-60l-bi-fuel-cng__intermittent-conditions) under SELF-DIAGNOSTIC SYSTEM. If no, go to step 5 .
4. Observe the Freeze Frame and/or the Failure records data for this DTC. Turn the ignition off for 30 seconds. Start the engine. Operate the vehicle within the Conditions For Running The DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame and/or the Failure records data. If the DTC failed this ignition cycle, go to next step. If the DTC does not fail this ignition cycle, see «INTERMITTENT CONDITIONS»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-60l-bi-fuel-cng__intermittent-conditions) under SELF-DIAGNOSTIC SYSTEM.
5. Turn ignition off. Disconnect the PCM harness connector C2. Turn ignition on, with engine off. Measure the voltage from the FICM diagnostic output PWM circuit with a DVOM. Does the DVOM display 5.0 volts? If yes, go to step 9 . If no, go to next step.
6. If the voltage is more than 5.3 volts, go to step 8 . If the voltage is less than 5.3 volts, go to next step.
7. Test for an open, or a short to ground on the FICM diagnostic output PWM circuit. Did you find and correct an open, or a short to ground? If yes, go to step 13 . If no, go to step 10 .
8. Test for a short to voltage on the FICM diagnostic output PWM circuit. Did you find and correct a short to voltage? If yes, go to step 13 . If no, go to step 12 .
9. Test for an intermittent and/or a poor connection at the PCM. Did you find and correct an intermittent and/or a poor connection? If yes, go to step 13 . If no, go to step 11 .
10. Test for an intermittent and/or a poor connection at the FICM. Did you find and correct an intermittent and/or a poor connection? If yes, go to step 13 . If no, go to step 12 .
11. Replace the PCM. After replacement is complete, go to step 13 .
12. Replace the FICM. After replacement is complete, go to step 13 .
13. Using a scan tool, clear the DTCs. Turn ignition off for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records. If the DTC failed this ignition cycle, go to step 2 . If the DTC did not fail this ignition cycle, go to next step.
14. Observe the Capture Info using a scan tool. Are there any DTCs that have not been diagnosed? If yes, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-60l-bi-fuel-cng__diagnostic-trouble-code-definitions) . If no, system is okay.

DTC P1432: FUEL TANK PRESSURE SENSOR SIGNAL LOW

Note. To locate components, see COMPONENT LOCATIONS . For circuit reference, see WIRING DIAGRAMS . For connector terminal identification, see CONNECTOR IDENTIFICATION . If an intermittent condition exists, see INTERMITTENT CONDITIONS under SELF-DIAGNOSTIC SYSTEM.

Note. For removal and installation of Bi-Fuel and CNG related components, see REMOVAL & INSTALLATION - CHEVY EXPRESS & SAVANA - BI-FUEL article. For removal and installation of gasoline related components, see REMOVAL & INSTALLATION - CHEVY EXPRESS & SAVANA - GASOLINE article.

The Fuel Tank Pressure (FTP) sensor is a pressure transducer. The Powertrain Control Module (PCM) supplies about 5 volts on the FTP sensor reference voltage circuit. The PCM also supplies a signal circuit to the FTP sensor. When fuel level/tank pressure is full the FTP signal voltage rises to 4.1 volts. As fuel level/tank pressure decreases to empty, the FTP signal voltage drops to around 0.5 volts. The PCM monitors the FTP signal circuit voltage and the Fuel Tank Temperature (FTT) sensor and determines the amount of fuel within the fuel tank. This DTC sets when the FTP sensor signal voltage is below the normal operating range of the sensor.

1. DTCs P0182, P0183 are not set.
2. The Fuel Tank Temperature (FTT) is less than 149°F (65°C).

1. The FTP signal voltage is less than 0.45 volts.
2. The condition exists for at least one second.

1. The control module illuminates the Malfunction Indicator Light (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

1. The control module turns off the Malfunction Indicator Light (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC using a scan tool.

The numbers below refer to the step numbers in the diagnostic procedure.

1. 2 This step determines if the failure condition is present.
2. 4 This step determines if the Fuel Tank Pressure (FTP) sensor is the cause of the failure condition.
3. 5 This step determines if the 5-volt reference circuit is the cause of the failure condition.

1. Did you perform the Diagnostic System Check - Alternative Fuels - Engine Controls. If yes, go to next step. If no, see «DIAGNOSTIC SYSTEM CHECK - ALTERNATIVE FUELS - ENGINE CONTROLS»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-60l-bi-fuel-cng__diagnostic-system-check-alternative-fuels) under SELF-DIAGNOSTIC SYSTEM.
2. Turn ignition on, with engine off. Using a scan tool, observe the Fuel Tank Pressure (FTP) data parameter. Does the scan tool display a FTP sensor voltage less than 0.45 volt? If yes, go to step 4 . if no, go to next step.
3. Observe the Freeze Frame and/or the Failure records data for this DTC. Turn the ignition off for 30 seconds. Start the engine. Operate the vehicle within the Conditions For Running The DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame and/or the Failure records data. If the DTC failed this ignition cycle, go to next step. If the DTC did not fail this ignition cycle, see «INTERMITTENT CONDITIONS»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-60l-bi-fuel-cng__intermittent-conditions) under SELF-DIAGNOSTIC SYSTEM.
4. Remove the fuel tank cover. Measure the voltage from the 5-volt reference circuit of the FTP sensor with a DVOM. If the voltage is more than 4.8 volts, go to next step. If the voltage is less than 4.8 volts, go to step 7 .
5. Connect a 3-amp fused jumper wire between the FTP sensor signal circuit and the FTP sensor 5-volt reference circuit. Using a scan tool, observe the FTP sensor data parameter. If the scan tool display the FTP sensor voltage is more than 4.7 volts, go to step 8 . If the scan tool display is less than 4.7 volts, go to next step.
6. Test for a short to ground or open on the FTP sensor signal circuit. Did you find and correct a short to ground or open? If yes, go to step 12 . If no, go to step 9 .
7. Test for an open or a short to ground on the FTP sensor 5-volt reference circuit. Did you find and correct an open or a short to ground? If yes, go to step 12 . If no, go to step 9 .
8. Test for an intermittent and/or a poor connection at the FTP sensor. Did you find and correct an intermittent and/or a poor connection? If yes, go to step 12 . If no, go to step 10 .
9. Test for an intermittent and/or a poor connection at the PCM. Did you find and correct an intermittent and/or a poor connection? If yes, go to step 12 . If no, go to step 11 .
10. Replace the FTP sensor. After replacement is complete, go to step 12 .
11. Replace the PCM. After replacement is complete, go to step 12 .
12. Using a scan tool, clear the DTCs. Turn ignition off for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records. If the DTC failed this ignition cycle, go to step 2 . If the DTC did not fail this ignition cycle, go to next step.
13. Observe the Capture Info using a scan tool. Are there any DTCs that have not been diagnosed? If yes, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-60l-bi-fuel-cng__diagnostic-trouble-code-definitions) . If no, system is okay.

DTC P1433: FUEL PRESSURE SENSOR SIGNAL HIGH

Note. To locate components, see COMPONENT LOCATIONS . For circuit reference, see WIRING DIAGRAMS . For connector terminal identification, see CONNECTOR IDENTIFICATION . If an intermittent condition exists, see INTERMITTENT CONDITIONS under SELF-DIAGNOSTIC SYSTEM.

Note. For removal and installation of Bi-Fuel and CNG related components, see REMOVAL & INSTALLATION - CHEVY EXPRESS & SAVANA - BI-FUEL article. For removal and installation of gasoline related components, see REMOVAL & INSTALLATION - CHEVY EXPRESS & SAVANA - GASOLINE article.

The Fuel Tank Pressure (FTP) sensor is a pressure transducer. The Powertrain Control Module (PCM) supplies about 5 volts on the FTP sensor reference voltage circuit. The PCM also supplies a signal circuit to the FTP sensor. When fuel level/tank pressure is full the FTP signal voltage rises to 4.1 volts. As fuel level/tank pressure decreases to empty, the FTP signal voltage drops to around 0.5 volts. The PCM monitors the FTP signal circuit voltage and the Fuel Tank Temperature (FTT) sensor and determines the amount of fuel within the fuel tank. This DTC sets when the FTP sensor signal voltage is greater than the normal operating range of the sensor.

1. DTCs P0182, P0183 are not set.
2. The FTT is less than 149°F (65°C).

1. The FTP signal voltage is more than 4.75 volts.
2. The condition exists for at least one second.

1. The control module illuminates the Malfunction Indicator Light (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

1. The control module turns off the Malfunction Indicator Light (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC using a scan tool.

The numbers below refer to the step numbers in the diagnostic procedure.

1. 2 This step determines if the failure condition is present.
2. 4 This step determines if an open sensor ground circuit condition is present. The Fuel Tank Pressure (FTP) and Fuel Tank Temperature (FTT) sensors share a common ground. An open circuit between the splice and the ground terminal will cause both signal circuits to indicate high voltage.
3. 5 This step determines if an open or shorted signal circuit is the cause of the failure condition.
4. 6 This step determines if a shorted 5-volt reference circuit is the cause of the failure condition.
5. 7 This step determines if an open sensor ground circuit between the FTP connector and the circuit splice is the cause of the failure condition.

1. Did you perform the Diagnostic System Check - Alternative Fuels - Engine Controls. If yes, go to next step. If no, see «DIAGNOSTIC SYSTEM CHECK - ALTERNATIVE FUELS - ENGINE CONTROLS»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-60l-bi-fuel-cng__diagnostic-system-check-alternative-fuels) under SELF-DIAGNOSTIC SYSTEM.
2. Turn ignition on, with engine off. Observe the Fuel Tank Pressure (FTP) data parameter using a scan tool. If the scan tool displays a FTP sensor voltage of more than 4.75 volts, go to step 4 . If the scan tool displays a FTP sensor voltage of less than 4.75 volts, go to next step.
3. Observe the Freeze Frame and/or the Failure records data for this DTC. Turn the ignition off for 30 seconds. Start the engine. Operate the vehicle within the Conditions For Running The DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame and/or the Failure records data. If the DTC failed this ignition cycle, go to next step. If the DTC did not fail this ignition cycle, see «INTERMITTENT CONDITIONS»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-60l-bi-fuel-cng__intermittent-conditions) under SELF-DIAGNOSTIC SYSTEM.
4. Using a scan tool, observe the Fuel Tank Temperature (FTT) sensor data parameter. If the scan tool displays a FTT sensor voltage of more 4.75 volts, go to step 12 . If the scan tool displays a FTT sensor voltage of less than 4.75 volts, go to next step.
5. Remove the fuel tank cover. Disconnect the FTP sensor harness connector. Connect a 3-amp fused jumper wire between the FTP sensor signal circuit and a good ground. Using a scan tool, observe the FTP sensor data parameter. If the scan tool displays a FTP sensor voltage of less than 0.25 volts, go to next step. If the scan tool displays a FTP sensor voltage of more than 0.25 volts, go to step 8 .
6. Remove the jumper. Measure the voltage from the 5-volt reference circuit of the FTP sensor with a DVOM. If the DVOM display a voltage of more than 5.2 volts, go to step. If the DVOM displays a voltage of less than 5.2 volts, go to next step.
7. Probe the FTP sensor ground circuit with a test light connected to battery positive. If the test light illuminates, go to step 10 . If the test light does not illuminate, go to step 13 .
8. Test the FTP sensor signal circuit for a short to voltage or an open. Did you find and correct the a short to voltage or an open? If yes, go to step 16 . If no, go to step 11 .
9. Test the FTP sensor 5-volt reference circuit for a short to voltage. Did you find and correct a short to voltage? If yes, go to step 16 . If no, go to step 15 .
10. Test for an intermittent and/or a poor connection at the FTP sensor. Did you find and correct an intermittent and/or a poor connection? If yes, go to step 16 . If no, go to step 14 .
11. Test for an intermittent and/or a poor connection at the PCM. Did you find and correct an intermittent and/or a poor connection? If yes, go to step 16 . If no, go to step 15 .
12. Repair the FTP sensor ground circuit for an open between the ground terminal and the splice. After repair is complete, go to step 16 .
13. Repair the FTP sensor ground circuit for an open, or high resistance, between the FTP sensor harness connector and the splice. After repair is complete, go to step 16 .
14. Replace the FTP sensor. After replacement is complete, go to next step.
15. Replace the PCM. After replacement is complete, go to next step.
16. Using a scan tool, clear the DTCs. Turn ignition off for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records. If the DTC failed this ignition cycle, go to step 2 . If the DTC did not fail this ignition cycle, go to next step.
17. Observe the Capture Info using a scan tool. Are there any DTCs that have not been diagnosed? If yes, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-60l-bi-fuel-cng__diagnostic-trouble-code-definitions) . If no, system is okay.

DTC P2146: INCORRECT VOLTAGE DETECTED - COMMAND STATE OF AFO ENABLE CIRCUIT

Note. To locate components, see COMPONENT LOCATIONS . For circuit reference, see WIRING DIAGRAMS . For connector terminal identification, see CONNECTOR IDENTIFICATION . If an intermittent condition exists, see INTERMITTENT CONDITIONS under SELF-DIAGNOSTIC SYSTEM.

Note. For removal and installation of Bi-Fuel and CNG related components, see REMOVAL & INSTALLATION - CHEVY EXPRESS & SAVANA - BI-FUEL article. For removal and installation of gasoline related components, see REMOVAL & INSTALLATION - CHEVY EXPRESS & SAVANA - GASOLINE article.

The Powertrain Control Module (PCM) grounds the AFO enable circuit when operating on CNG. When the AFO enable circuit is grounded the Fuel Injector Control Module (FICM) will operate the CNG injectors based upon the PCM pulse width signals. The PCM controls alternative fuel operation by grounding the AFO enable circuit via an internal switch called a driver. The primary function of the driver is to supply the ground for the controlled component. The PCM monitors the status of the driver. If the PCM detects an incorrect voltage for the commanded state of the driver, DTC P2146 sets.

The ignition is on.

1. The PCM detects that the commanded state of the driver and the actual state of the control circuit do not match.
2. The above condition exists for at least one seconds.

1. The control module illuminates the Malfunction Indicator Light (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

1. The control module turns off the Malfunction Indicator Light (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC using a scan tool.

The numbers below refer to the step numbers in the diagnostic procedure.

1. 2 This step tests if the concern is active.
2. 4 This step tests if a ground is constantly being applied to the AFO enable circuit. With the FICM disconnected, the PCM will command gasoline operation. The AFO enable circuit should not illuminate the test light.
3. 5 This step verifies that the PCM is providing ground to the AFO enable circuit.

1. Did you perform the Diagnostic System Check - Alternative Fuels - Engine Controls. If yes, go to next step. If no, see «DIAGNOSTIC SYSTEM CHECK - ALTERNATIVE FUELS - ENGINE CONTROLS»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-60l-bi-fuel-cng__diagnostic-system-check-alternative-fuels) under SELF-DIAGNOSTIC SYSTEM.
2. Turn ignition on, with engine off. Using a scan tool, observe the DTC information. If the scan tool displays DTC P0611, see «DTC P0611: FUEL INJECTOR CONTROL MODULE PERFORMANCE»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-60l-bi-fuel-cng__dtc-p0611-fuel-injector-control-module) . If the scan tool does not display DTC P0611, go to next step.
3. Observe the Freeze Frame/Failure Records for this DTC. Turn the ignition off for 30 seconds. Turn ignition on, with engine off. Operate the vehicle within the Conditions For Running The DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records. If the DTC failed this ignition cycle, go to next step. If the DTC did not fail this ignition cycle, see «INTERMITTENT CONDITIONS»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-60l-bi-fuel-cng__intermittent-conditions) under SELF-DIAGNOSTIC SYSTEM.
4. Turn ignition off. Disconnect the Fuel Injection Control Module (FICM). Turn ignition on, with engine off. Probe the AFO enable circuit with a test light that is connected to battery positive. If the test light illuminates, go to step 7 . If the test light does not illuminate, go to next step.
5. Measure the resistance of the AFO enable circuit between the FICM connector terminal and ground with a DVOM. Using a scan tool, observe the circuit resistance as you command the AFO signal enable ON and OFF. If the circuit resistance changes from 3000 ohms on gasoline (OFF) to 75 ohms on alternative fuel (ON), go to step 8 . If the circuit resistance does not change from 3000 ohms on gasoline (OFF) to 75 ohms on alternative fuel (ON), go to next step.
6. Test the AFO enable circuit for an open or for a short to voltage. Did you find and correct a short to voltage? If yes, go to step 12 . If no, go to step 9 .
7. Test the AFO enable circuit for a short to ground. Did you find and correct a short to ground? If yes, go to step 12 . If no, go to step 11 .
8. Test for an intermittent and/or a poor connection at the FICM. Did you find and correct an intermittent and/or a poor connection? If yes, go to step 12 . If no, go to step 10 .
9. Test for an intermittent and/or a poor connection at the PCM. Did you find and correct an intermittent and/or a poor connection? If yes, go to step 12 . If no, go to step 11 .
10. Replace the FICM. After replacement is complete, go to step 12 .
11. Replace the PCM. After replacement is complete, go to step 12 .
12. Using a scan tool, clear the DTCs. Turn ignition off for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records. If the DTC failed this ignition cycle, go to step 2 . If the DTC did not fail this ignition cycle, go to next step.
13. Observe the Capture Info using a scan tool. Are there any DTCs that have not been diagnosed? If yes, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-60l-bi-fuel-cng__diagnostic-trouble-code-definitions) . If no, system is okay.

DTC P2665: INCORRECT VOLTAGE DETECTED - LOW PRESSURE LOCK-OFF SOLENOID

Note. To locate components, see COMPONENT LOCATIONS . For circuit reference, see WIRING DIAGRAMS . For connector terminal identification, see CONNECTOR IDENTIFICATION . If an intermittent condition exists, see INTERMITTENT CONDITIONS under SELF-DIAGNOSTIC SYSTEM.

Note. For removal and installation of Bi-Fuel and CNG related components, see REMOVAL & INSTALLATION - CHEVY EXPRESS & SAVANA - BI-FUEL article. For removal and installation of gasoline related components, see REMOVAL & INSTALLATION - CHEVY EXPRESS & SAVANA - GASOLINE article.

An ignition voltage is supplied to the Low Pressure Lock-Off (LPL) solenoid through the LPL relay. The PCM controls the LPL relay by grounding the control circuit via an internal switch called a driver. The primary function of the driver is to supply the ground for the controlled component. The PCM monitors the status of the driver. If the PCM detects an incorrect voltage for the commanded state of the driver, DTC P2665 sets.

The ignition is on.

1. The control module detects that the commanded state of the driver and the actual state of the control circuit do not match.
2. The above condition exists for at least one second.

1. The control module illuminates the Malfunction Indicator Light (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

1. The control module turns off the Malfunction Indicator Light (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC using a scan tool.

1. 2 This step tests if the concern is active. You should hear a clicking sound when the Low Pressure Lock-Off (LPL) relay is commanded on and off. Repeat the commands as necessary.
2. 5 This step verifies that the control module is providing ground to the LPL relay.
3. 6 This step tests if a ground is constantly being applied to the LPL relay.

1. Did you perform the Diagnostic System Check - Alternative Fuels - Engine Controls. If yes, go to next step. If no, see «DIAGNOSTIC SYSTEM CHECK - ALTERNATIVE FUELS - ENGINE CONTROLS»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-60l-bi-fuel-cng__diagnostic-system-check-alternative-fuels) under SELF-DIAGNOSTIC SYSTEM.
2. Turn ignition on, with engine off. Using a scan tool, command the Low Pressure Lock-Off (LPL) relay on and off. If the LPL relay responds to the scan tool commands, go to next step. If the LPL relay does not respond to the scan tool commands, go to step 4 .
3. Observe the Freeze Frame/Failure Records for this DTC. Turn the ignition off for 30 seconds. Turn ignition on, with engine off. Operate the vehicle within the Conditions For Running The DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records. If the DTC failed this ignition cycle, go to next step. If the DTC did not fail this ignition cycle, see «INTERMITTENT CONDITIONS»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-60l-bi-fuel-cng__intermittent-conditions) under SELF-DIAGNOSTIC SYSTEM.
4. Turn ignition off. Disconnect the LPL relay. Turn ignition on, with engine off. Probe the ignition voltage circuit of the LPL relay with a test light that is connected to a good ground. If the test light illuminates, go to next step. If the test light does not illuminate, go to step 11 .
5. Connect a test light between the LPL Relay control circuit and the LPL Relay ignition voltage circuit. Using a scan tool, command the LPL relay on and off. If the test light turns on and off with each command, go to step 9 . If the test light does not turn on and off with each command, go to next step.
6. If the test light remains illuminated with each command, go to step 8 . If the test light does not remain illuminated with each command, go to next step.
7. Test the LPL relay control circuit for an open or for a short to voltage. Did you find and correct an open or a short to voltage? If yes, go to step 14 . If no, go to step 10 .
8. Test the LPL relay control circuit for a short to ground. Did you find and correct for a short to ground? If yes, go to step 14 . If no, go to step 13 .
9. Test for an intermittent and/or a poor connection at the LPL relay. Did you find and correct an intermittent and/or a poor connection? If yes, go to step 14 . If no, go to step 12 .
10. Test for an intermittent and/or a poor connection at the control module. Did you find and correct an intermittent and/or a poor connection? If yes, go to step 14 . If no, go to step 13 .
11. Repair the open or short to ground in the ignition voltage circuit. After repair is complete, go to step 14 .
12. Replace the LPL relay. After replacement is complete, go to step 14 .
13. Replace the PCM. After replacement is complete, go to next step.
14. Using a scan tool, clear the DTCs. Turn ignition off for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records. If the DTC failed this ignition cycle, go to step 2 . If the DTC did not fail this ignition cycle, go to next step.
15. Observe the Capture Info using a scan tool. Are there any DTCs that have not been diagnosed? If yes, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-60l-bi-fuel-cng__diagnostic-trouble-code-definitions) . If no, system is okay.

DTC P2668: INCORRECT VOLTAGE DETECTED - FUEL INDICATOR LIGHT

Note. To locate components, see COMPONENT LOCATIONS . For circuit reference, see WIRING DIAGRAMS . For connector terminal identification, see CONNECTOR IDENTIFICATION . If an intermittent condition exists, see INTERMITTENT CONDITIONS under SELF-DIAGNOSTIC SYSTEM.

Note. For removal and installation of Bi-Fuel and CNG related components, see REMOVAL & INSTALLATION - CHEVY EXPRESS & SAVANA - BI-FUEL article. For removal and installation of gasoline related components, see REMOVAL & INSTALLATION - CHEVY EXPRESS & SAVANA - GASOLINE article.

The Fuel Indicator Light (FIL) is located within the headlamp switch assembly. The FIL indicates which fuel system is utilized to operate the vehicle. The FIL illuminates for a few seconds at start up for a bulb check. The FIL remains illuminated while the vehicle is operating on gasoline. The PCM controls the FIL by grounding the control circuit via an internal switch called a driver. The primary function of the driver is to supply the ground for the controlled component. The PCM monitors the status of the driver. If the PCM detects an incorrect voltage for the commanded state of the driver, DTC P2668 sets.

The ignition is on.

1. The control module detects that the commanded state of the driver and the actual state of the control circuit do not match.
2. The condition exists for at least 5 seconds.

1. The Powertrain Control Module (PCM) stores the DTC information into memory when the diagnostic runs and fails.
2. The Malfunction Indicator Light (MIL) will not illuminate.
3. The PCM records the operating conditions at the time the diagnostic fails. The PCM stores this information in the Failure Records.

1. A last test failed, or current DTC, clears when the diagnostic runs and does not fail.
2. A history DTC will clear after 40 consecutive warm-up cycles, if no failures are reported by this or any other non-emission related diagnostic.
3. Use a scan tool in order to clear the DTC.

The numbers below refer to the step numbers in the diagnostic procedure.

1. 2 This step tests if the concern is active. The Fuel Indicator Light (FIL) should turn on and off with the scan tool commands. Repeat the commands as necessary.
2. 5 This step verifies that the control module is providing ground to the FIL.
3. 6 This step tests if a ground is constantly being applied to the FIL.

1. Did you perform the Diagnostic System Check - Alternative Fuels - Engine Controls. If yes, go to next step. If no, see «DIAGNOSTIC SYSTEM CHECK - ALTERNATIVE FUELS - ENGINE CONTROLS»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-60l-bi-fuel-cng__diagnostic-system-check-alternative-fuels) under SELF-DIAGNOSTIC SYSTEM.
2. Turn ignition on, with engine off. Using a scan tool, command the Fuel Indicator Light (FIL) on and off. If the FIL responds to the scan tool commands, go to next step. If the FIL does not respond to the scan tool commands, go to step 4 .
3. Observe the Freeze Frame/Failure Records for this DTC. Turn the ignition off for 30 seconds. Turn ignition on, with engine off. Operate the vehicle within the Conditions For Running The DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records. If the DTC failed this ignition cycle, go to next step. If the DTC did not fail this ignition cycle, see «INTERMITTENT CONDITIONS»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-60l-bi-fuel-cng__intermittent-conditions) under SELF-DIAGNOSTIC SYSTEM.
4. Turn ignition off. Remove the headlamp switch assembly. Turn ignition on, with engine off. Probe the FIL ignition voltage circuit with a test light that is connected to a good ground. If the test light illuminates, go to next step. If the test light does not illuminate, go to step 11 .
5. Connect a test light between the FIL control circuit and the FIL ignition voltage circuit. Using a scan tool, command the FIL on and off. If the test light turns on and off with each command, go to step 9 . If the test light does not turn on and off with each command, go to next step.
6. If the test light remains illuminated with each command, go to step 8 . If the test light does not remain illuminated with each command, go to next step.
7. Test the FIL control circuit for an open or for a short to voltage. Did you find and correct an open or a short to voltage? If yes, go to step 14 . If no, go to step 10 .
8. Test the FIL control circuit of the for a short to ground. Did you find and correct a short to ground? If yes, go to step 14 . If no, go to step 13 .
9. Test for an intermittent and/or a poor connection at the Headlamp Switch. Did you find and correct an intermittent and/or a poor connection? If yes, go to step 14 . If no, go to step 12 .
10. Test for an intermittent and/or a poor connection at the control module harness connector. Did you find and correct an intermittent and/or a poor connection? If yes, go to step 14 . If no, go to step 13 .
11. Repair the open or short to ground in the ignition voltage circuit. After repairs are complete, go to step 14 .
12. Replace the Headlamp Switch Assembly. After replacement is complete, go to step 14 .
13. Replace the PCM. After replacement is complete, go to next step.
14. Using a scan tool, clear the DTCs. Turn ignition off for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records. If the DTC failed this ignition cycle, go to step 2 . If the DTC did not fail this ignition cycle, go to next step.
15. Observe the Capture Info using a scan tool. Are there any DTCs that have not been diagnosed? If yes, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-60l-bi-fuel-cng__diagnostic-trouble-code-definitions) . If no, system is okay.

CHEVY EXPRESS 2500

See ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article in ELECTRICAL.

CHEVY EXPRESS 3500

See ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article in ELECTRICAL.

SAVANA 2500

See ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article in ELECTRICAL.

SAVANA 3500

See ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article in ELECTRICAL.

See also:
• SELF-DIAGNOSTICS - 4.8L, 5.3L, 6.0L EXPRESS & SAVANA - GASOLINE
• NO-START DIAGNOSIS
• TROUBLE SHOOTING - NO CODES - 6.0L CHEVY EXPRESS, SAVANA, SIERRA & SILVERADO - BI-FUEL & CNG
• SYMPTOMS
• SYSTEM & COMPONENT TESTING - 6.0L CHEVY EXPRESS, SAVANA, SIERRA & SILVERADO - BI-FUEL & CNG
• DIAGNOSTIC TROUBLE CODE DEFINITIONS
• NO-START - ENGINE CRANKS OKAY
• DRIVE CYCLES
• REMOVAL & INSTALLATION - CHEVY EXPRESS & SAVANA - BI-FUEL
• REMOVAL & INSTALLATION - CHEVY EXPRESS & SAVANA - GASOLINE
• FUEL SYSTEM DIAGNOSIS
• DTC P0101: MASS AIR FLOW SENSOR PERFORMANCE
• FUEL INJECTOR COIL TEST
• FUEL INJECTOR COIL TEST
• CKP SYSTEM VARIATION LEARN PROCEDURE
• DTC P0172: FUEL TRIM SYSTEM RICH - BANK 1 & DTC P0175: FUEL TRIM SYSTEM RICH - BANK 2
• RESTRICTED EXHAUST
• DTC P0420: TWC SYSTEM - LOW EFFICIENCY - BANK 1 & P0430: TWC SYSTEM - LOW EFFICIENCY - BANK 2
• FUEL INJECTOR BALANCE TEST WITH SPECIAL TOOL
• DIAGNOSTIC STARTING POINT - ENGINE CONTROLS
• DIAGNOSTIC SYSTEM CHECK - ALTERNATIVE FUELS - ENGINE CONTROLS
• WIRING DIAGRAMS
• PROGRAMMING
• DIAGNOSTIC TROUBLE CODE DEFINITIONS
• DTC P1204: VEHICLE DOES NOT START ON CNG
• DTC P0611: FUEL INJECTOR CONTROL MODULE PERFORMANCE
• INTERMITTENT CONDITIONS
• P0005
• P0148
• P0171
• P0172
• P0182
• P0183
• P0187
• P0188
• P0191
• P0192
• P0193
• P0200
• P0300
• P1020
• P1207
• P1208
• P1209
• P1432
• P1433
• P2146
• P2665
• P2668
• CODE TYPES
• COMPONENT LOCATIONS
• DIAGNOSTIC AIDS