Engine Controls - System & Component Testing - 6.0L W/bifuel & Cng — Chevrolet Chevy Express H2500 (2003-2003)

INTRODUCTION

Note. Unless specified otherwise, Savana information also applies to Savana Special.

Chevy Express and Savana are available as a bi-fuel vehicle (RPO KL6) or as CNG only vehicle (RPO KL8). Sierra and Silverado are available as CNG only vehicle (RPO KL8). This 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 or SELF-DIAGNOSTICS - 4.8L, 5.3L & 6.0L "C", "K" & "N" SERIES - FLEX FUEL & GASOLINE article. To properly diagnose and repair this vehicle, follow DIAGNOSTIC STARTING POINT - ENGINE CONTROLS under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - 4.8L, 5.3L & 6.0L "C", "K" & "N" SERIES - FLEX FUEL & GASOLINE article or DIAGNOSTIC STARTING POINT - ENGINE CONTROLS under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - 4.8L, 5.3L & 6.0L EXPRESS & SAVANA - GASOLINE article. If no Diagnostic Trouble Codes (DTC) are present and a no-start condition exists, proceed to 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, proceed to 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, ENGINE STALLS, etc.).

Note. Testing individual components does not isolate shorts or opens. Perform all voltage tests with a Digital Volt-Ohmmeter (DVOM) with a minimum 10-megohm input impedance, unless stated otherwise in test procedure. Use ohmmeter to isolate wiring harness shorts or opens.

COMPONENT LOCATIONS

Note. For component locations (Scheme 43)or (Scheme 44).

Scheme 43

Scheme 43: COMPONENT LOCATIONS

Scheme 44

COMPUTERIZED ENGINE CONTROLS

Note. For component locations, see COMPONENT LOCATIONS .

FUEL INJECTOR CONTROL MODULE & POWERTRAIN CONTROL MODULE

Note. To identify circuits referenced in the following ground and power tests, see WIRING DIAGRAMS or (Scheme 45)- (Scheme 58).

Ground Circuits

Check Fuel Injector Control Module (FICM) and PCM connectors for corroded or loose connections. Repair as necessary. Disconnect FICM or PCM connectors. Using a DVOM, measure resistance between negative battery terminal and ground terminals at FICM or PCM harness connector. If resistance is more than 5 ohms, repair open in affected ground circuit. If resistance is 5 ohms or less, ground circuits are okay.

Power Circuits

Check FICM or PCM connectors for corroded or loose connections. Repair as necessary. Disconnect FICM or PCM connectors. Using a DVOM, check for battery voltage between chassis ground and continuous power terminal(s) at FICM or PCM harness connector(s). If battery voltage is present, go to next step. If battery voltage is not present, check for open fuse or fusible link. If fuse or fusible link is okay, check for open in wire between FICM or PCM terminal and power source.
Turn ignition switch to RUN position. Using DVOM, check for battery voltage between chassis ground and ignition power terminals at FICM or PCM harness connector(s). If battery voltage is present, power circuits are okay. If battery voltage is not present, check related fuse. If fuse is okay, check for an open in wire between battery and ignition switch, and between ignition switch and FICM or PCM terminal. If wiring is okay, check for a defective ignition switch.

FICM/PCM Harness Resistance

Turn ignition switch to LOCK position. Disconnect FICM or PCM and appropriate component harness connectors. Check for open or short circuits between appropriate PCM harness connector terminal and appropriate component harness connector terminal. If harness is open or shorted, repair as necessary.

Scheme 45

Scheme 45: FICM/PCM Harness Resistance

Scheme 46

Scheme 47

Scheme 48

Scheme 49

Scheme 50

Scheme 51

Scheme 52

Scheme 53

Scheme 54

Scheme 55

Scheme 56

Scheme 57

Scheme 58

SENSORS & SWITCHES

Note. For component locations, see COMPONENT LOCATIONS . For circuit reference, see WIRING DIAGRAMS .

Note. For additional sensor testing specifications, see SENSOR OPERATING RANGE CHARTS - TRUCKS article.

Manufacturer does not provide testing procedures for many individual systems and components. For sensor and switch testing not listed, perform related DTC testing procedure. See DIAGNOSTIC TROUBLE CODE DEFINITIONS in SELF-DIAGNOSTICS - 6.0L CHEVY EXPRESS & SAVANA - BI-FUEL & CNG article or DIAGNOSTIC TROUBLE CODE DEFINITIONS in SELF-DIAGNOSTICS - 6.0L SIERRA & SILVERADO - BI-FUEL & CNG article.

CAMSHAFT POSITION SENSOR

A malfunction in Camshaft Position (CMP) sensor can set a DTC. For testing procedures and specifications, perform appropriate diagnostic test. See DIAGNOSTIC TROUBLE CODE DEFINITIONS in SELF-DIAGNOSTICS - 4.8L, 5.3L & 6.0L "C", "K" & "N" SERIES - FLEX FUEL & GASOLINE article or DIAGNOSTIC TROUBLE CODE DEFINITIONS in SELF-DIAGNOSTICS - 4.8L, 5.3L & 6.0L EXPRESS & SAVANA - GASOLINE article.

CRANKSHAFT POSITION SENSOR

A malfunction in Crankshaft Position (CKP) sensor can set a DTC. For testing procedures and specifications, perform appropriate diagnostic test. See DIAGNOSTIC TROUBLE CODE DEFINITIONS in SELF-DIAGNOSTICS - 4.8L, 5.3L & 6.0L "C", "K" & "N" SERIES - FLEX FUEL & GASOLINE article or DIAGNOSTIC TROUBLE CODE DEFINITIONS in SELF-DIAGNOSTICS - 4.8L, 5.3L & 6.0L EXPRESS & SAVANA - GASOLINE article.

ENGINE COOLANT TEMPERATURE SENSOR

A malfunction in Engine Coolant Temperature (ECT) sensor circuit can set a DTC. For testing procedures and specifications, perform appropriate diagnostic test. See DIAGNOSTIC TROUBLE CODE DEFINITIONS in SELF-DIAGNOSTICS - 4.8L, 5.3L & 6.0L "C", "K" & "N" SERIES - FLEX FUEL & GASOLINE article or DIAGNOSTIC TROUBLE CODE DEFINITIONS in SELF-DIAGNOSTICS - 4.8L, 5.3L & 6.0L EXPRESS & SAVANA - GASOLINE article. An out-of-calibration ECT sensor may not set a DTC. Use the following procedure to test sensor calibration.

Disconnect ECT sensor harness connector. See COMPONENT LOCATIONS . Using DVOM, measure resistance of ECT sensor at specified temperatures. See SENSOR TEMPERATURE VS RESISTANCE table. Resistance should be high when engine is cold and drop as engine warms. With vehicle sitting overnight, IAT sensor and ECT sensor should have close to the same resistance reading. If resistance is not within specification, replace ECT sensor.

Temperature - °F (°C)	(1) Ohms
302 (150)	47
284 (140)	60
266 (130)	77
248 (120)	100
230 (110)	132
212 (100)	177
194 (90)	241
176 (80)	332
158 (70)	467
140 (60)	667
122 (50)	973
113 (45)	1188
104 (40)	1459
95 (35)	1802
86 (30)	2238
77 (25)	2796
68 (20)	3520
59 (15)	4450
50 (10)	5670
41 (5)	7280
32 (0)	9420
23 (-5)	12,300
14 (-10)	16,180
5 (-15)	21,450
4 (-20)	28,680
22 (-30)	52,700
40 (-40)	100,700
(1) Measure resistance across sensor terminals.

(1)	Measure resistance across sensor terminals.

SENSOR TEMPERATURE VS RESISTANCE

HEATED OXYGEN SENSORS

A malfunction in Heated Oxygen Sensor (HO2S) circuit can set a DTC. For testing procedures and specifications, perform appropriate diagnostic test. See DIAGNOSTIC TROUBLE CODE DEFINITIONS in SELF-DIAGNOSTICS - 4.8L, 5.3L & 6.0L "C", "K" & "N" SERIES - FLEX FUEL & GASOLINE article or DIAGNOSTIC TROUBLE CODE DEFINITIONS in SELF-DIAGNOSTICS - 4.8L, 5.3L & 6.0L EXPRESS & SAVANA - GASOLINE article.

INTAKE AIR TEMPERATURE SENSOR

A malfunction in IAT sensor circuit can set a DTC. For testing procedures and specifications, perform appropriate diagnostic test. See DIAGNOSTIC TROUBLE CODE DEFINITIONS in SELF-DIAGNOSTICS - 4.8L, 5.3L & 6.0L "C", "K" & "N" SERIES - FLEX FUEL & GASOLINE article or DIAGNOSTIC TROUBLE CODE DEFINITIONS in SELF-DIAGNOSTICS - 4.8L, 5.3L & 6.0L EXPRESS & SAVANA - GASOLINE article. An out-of-calibration IAT sensor may not set a DTC. Use the following procedure to test sensor calibration.

Disconnect IAT sensor harness connector. See COMPONENT LOCATIONS . Using DVOM, measure resistance of IAT sensor at specified temperatures. See SENSOR TEMPERATURE VS RESISTANCE table. Resistance should be high when air temperature is cold and drop as air temperature warms. With vehicle sitting overnight, ECT sensor and IAT sensor should have close to the same resistance reading. If resistance is not within specification, replace IAT sensor.

KNOCK SENSOR

A malfunction in Knock Sensor (KS) circuit can set a DTC. For testing procedures and specifications, perform appropriate diagnostic test. See DIAGNOSTIC TROUBLE CODE DEFINITIONS in SELF-DIAGNOSTICS - 4.8L, 5.3L & 6.0L "C", "K" & "N" SERIES - FLEX FUEL & GASOLINE article or DIAGNOSTIC TROUBLE CODE DEFINITIONS in SELF-DIAGNOSTICS - 4.8L, 5.3L & 6.0L EXPRESS & SAVANA - GASOLINE article.

MANIFOLD ABSOLUTE PRESSURE SENSOR

A malfunction in Manifold Absolute Pressure (MAP) sensor circuit can set a DTC. For testing procedures and specifications, perform appropriate diagnostic test. See DIAGNOSTIC TROUBLE CODE DEFINITIONS in SELF-DIAGNOSTICS - 4.8L, 5.3L & 6.0L "C", "K" & "N" SERIES - FLEX FUEL & GASOLINE article or DIAGNOSTIC TROUBLE CODE DEFINITIONS in SELF-DIAGNOSTICS - 4.8L, 5.3L & 6.0L EXPRESS & SAVANA - GASOLINE article.

THROTTLE POSITION SENSOR

Note. Throttle Position (TP) sensor is not adjustable. Replace TP sensor as necessary.

A malfunction in TP sensor circuit can set a DTC. For testing procedures and specifications, perform appropriate diagnostic test. See DIAGNOSTIC TROUBLE CODE DEFINITIONS in SELF-DIAGNOSTICS - 4.8L, 5.3L & 6.0L "C", "K" & "N" SERIES - FLEX FUEL & GASOLINE article or DIAGNOSTIC TROUBLE CODE DEFINITIONS in SELF-DIAGNOSTICS - 4.8L, 5.3L & 6.0L EXPRESS & SAVANA - GASOLINE article.

TRANSMISSION RANGE SWITCH

See appropriate DIAGNOSIS article in AUTOMATIC TRANSMISSIONS.

VEHICLE SPEED SENSOR

See appropriate DIAGNOSIS article in AUTOMATIC TRANSMISSIONS.

MODULES, MOTORS, RELAYS & SOLENOIDS

Note. For component locations, see COMPONENT LOCATIONS . For circuit reference, see WIRING DIAGRAMS .

Note. Manufacturer does not provide testing procedures for many individual systems and components. For module, motor, relay and solenoid testing not listed, perform related DTC testing procedure. See DIAGNOSTIC TROUBLE CODE DEFINITIONS in SELF-DIAGNOSTICS - 4.8L, 5.3L & 6.0L "C", "K" & "N" SERIES - FLEX FUEL & GASOLINE article or DIAGNOSTIC TROUBLE CODE DEFINITIONS in SELF-DIAGNOSTICS - 4.8L, 5.3L & 6.0L EXPRESS & SAVANA - GASOLINE article.

A/C COMPRESSOR CLUTCH RELAY

See appropriate AUTOMATIC A/C-HEATER SYSTEMS or MANUAL A/C-HEATER SYSTEMS article in AIR CONDITIONING & HEATING.

Scheme 59

Scheme 59: ALTERNATIVE FUEL LOCK-OFF RELAY

Circuit Description

The PCM controls the fuel system while the vehicle is operating on CNG. A High Pressure Lock-Off (HPL) solenoid in each CNG tank and a Low Pressure Lock-Off (LPL) solenoid in fuel rail prevent fuel flow. The PCM commands ONLY the HPL's open for one second at every ignition on for a CNG prime pulse. The CNG prime pulse is performed in order to charge the fuel line and also allows the Fuel Tank Pressure (FTP) sensor to monitor the amount of fuel pressure in the tanks. The PCM commands both the HPL and LPL open when engine RPM indicates the engine is cranking or running on CNG.

The Alternative Fuel (AF) lock-off relay's coil and switch are supplied power whenever the ignition is in the Start or Run position. The PCM controls the ground path. When the AF lock-off relay is energized, power is supplied to the HPL and LPL solenoids.

Diagnostic Procedures

Perform diagnostic system check. See «DIAGNOSTIC SYSTEM CHECK - ALTERNATIVE FUELS»(/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 in SELF-DIAGNOSTICS - 6.0L CHEVY EXPRESS & SAVANA - BI-FUEL & CNG or «DIAGNOSTIC SYSTEM CHECK - ALTERNATIVE FUELS»(ref-159297-S00366181602003112400000) under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - 6.0L SILVERADO & SIERRA - BI-FUEL & CNG article. After performing diagnostic system check, go to next step.
Is DTC P0005 or P2665 set? If yes, diagnose affected DTC(s). 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) in SELF-DIAGNOSTICS - 6.0L CHEVY EXPRESS & SAVANA - BI-FUEL & CNG article or «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-159297-S15239216512003112400000) in SELF-DIAGNOSTICS - 6.0L SIERRA & SILVERADO - BI-FUEL & CNG article. If no, go to next step.
Turn ignition on, with engine off. Command the HPL on and off with a scan tool. Listen for operation of the HPLs. HPL is threaded into CNG tank. Do the HPLs respond to the scan tool commands? If yes, go to next step. If no, go to step 5.
Command the LPL solenoid on and off with a scan tool. Listen for operation of the LPL. LPL is located on left engine valve cover. Does the LPL respond to the scan tool commands? If yes, go to step 18. If no, go to step 6.
Command the HPL solenoids on and off with a scan tool. Listen or feel for operation of the AF lock-off relay. AF lock-off relay is located on rear center of engine compartment. Does the relay respond to the scan tool commands? If yes, go to step 14. If no, go to step 15.
Command the LPL solenoid on and off with a scan tool. Listen or feel for operation of the AF lock-off relay. AF lock-off relay is attached to left side of underhood fuse/relay block. Does the relay respond to the scan tool commands? If yes, go to step 8. If no, go to next step.
Disconnect AF lock-off relay harness connector. Probe AF lock-off relay switch ignition circuit terminal No. 30 (Orange wire) with a test light connected to ground. (Scheme 59) Turn ignition on, with engine off. Is test light illuminated? If yes, go to step 10. If no, go to step 11.
Disconnect the LPL solenoid. Probe the LPL solenoid ground circuit terminal "B" (Red wire) with a test light connected to battery voltage. (Scheme 59) Is test light illuminated? If yes, go to next step. If no, go to step 13.
Probe the LPL solenoid ignition voltage circuit terminal "A" (Gray wire) with a test light connected to ground. Command the LPL solenoid on and off with a scan tool. Does the test light respond to the scan tool commands? If yes, go to step 17. If no, go to step 12.
Test for an intermittent and for a poor connection at the AF lock-off relay. Did you find and correct the condition? If yes, go to step 18. If no, go to step 16.
Repair open in AF lock-off relay switch power circuit. (Scheme 59) After repairs, go to step 18.
Repair LPL solenoid power circuit between relay and solenoid for open. After repairs, go to step 18.
Repair open in LPL solenoid ground circuit. After repairs, go to step 18.
Repair open in HPL solenoid's ground circuit. After repairs, go to step 18.
Replace AF lock-off relay. After replacing relay, go to step 18.
Replace AF lock-off relay. After replacing relay, go to 18.
Replace LPL solenoid. After replacing solenoid, go to next step.
Clear DTC information from PCM using scan tool. Turn ignition off and wait 30 seconds. Start and operate engine at idle. Observe the MIL. Observe vehicle performance and driveability. Does the vehicle operate on CNG with normal driveability and no MIL illumination? If yes, system is okay. If no, see «DIAGNOSTIC SYSTEM CHECK - ALTERNATIVE FUELS»(/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 in SELF-DIAGNOSTICS - 6.0L CHEVY EXPRESS & SAVANA - BI-FUEL & CNG or «DIAGNOSTIC SYSTEM CHECK - ALTERNATIVE FUELS»(ref-159297-S00366181602003112400000) under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - 6.0L SILVERADO & SIERRA - BI-FUEL & CNG article.

TORQUE CONVERTER CLUTCH SOLENOID

See appropriate DIAGNOSIS article in AUTOMATIC TRANSMISSIONS.

FUEL INJECTOR BALANCE TEST WITH SPECIAL TOOL

Note. For component locations, see COMPONENT LOCATIONS . For circuit reference, see WIRING DIAGRAMS .

The Fuel Injector Tester (J-39021) energizes the CNG fuel injector for a precise amount of time allowing a measured amount of fuel into the manifold. This causes a drop in system fuel pressure that can be recorded and used to compare each fuel injector.

Test Description

The number below refers to step number in diagnostic procedure.

3 - The fuel pressure should be within the specified range. See «FUEL SYSTEM PRESSURE TEST»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-system-component-testing-60l-wbifuel-cng__fuel-system-pressure-test) .
5 - If the pressure drop value for each fuel injector is within 2.0 psi (14 kPa) of the average pressure drop value, the fuel injectors are flowing properly. Calculate pressure drop value for each fuel injector by subtracting the second pressure reading from the first pressure reading.

Perform Diagnostic System Check Alternative Fuels - Engine Controls. See «DIAGNOSTIC SYSTEM CHECK - ALTERNATIVE FUELS»(/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 in SELF-DIAGNOSTICS - 6.0L CHEVY EXPRESS & SAVANA - BI-FUEL & CNG or «DIAGNOSTIC SYSTEM CHECK - ALTERNATIVE FUELS»(ref-159297-S00366181602003112400000) under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - 6.0L SILVERADO & SIERRA - BI-FUEL & CNG article. After performing Diagnostic System Check - Engine Controls, go to next step.
Perform «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) . After performing Fuel Injector Coil Test, go to next step.
Start and operate engine at idle. Observe the fuel rail pressure sensor parameter with a scan tool. Is the fuel pressure within 160-170 psi (1103-1172 kPa)? If yes, go to next step. If no, diagnose fuel system. Refer to «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.
Turn ignition off. Turn ignition on, with engine off. Monitor the fuel rail pressure sensor parameter with a scan tool. Does the fuel rail pressure remain constant? If yes, go to next step. If no, diagnose fuel system. Refer to «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.
Turn ignition off. Connect the Fuel Injector Tester (J-39021) to a fuel injector. Set the amperage supply selector switch on the fuel injector tester to the Balance Test 0.5-2.5 amp position. Turn ignition on, with engine off. Record fuel pressure indicated by the fuel rail pressure sensor after fuel pressure stabilizes. This is the first pressure reading. Record fuel pressure value immediately after the CNG fuel injector stops pulsing. The fuel pressure may rise after fuel injector stops pulsing. DO NOT record the higher fuel pressure value. Energize the CNG fuel injector by depressing the Push to Start Test button on the fuel injector tester. Record fuel pressure indicated by the fuel rail pressure sensor. This is the second fuel pressure reading. Repeat procedure for each fuel injector. Subtract the second pressure reading from the first pressure reading for one fuel injector. The result is the pressure drop value. Obtain a pressure drop value for each fuel injector. Add all of the individual pressure drop values. This is the total pressure drop. Divide the total pressure drop by the number of fuel injectors. This is the average pressure drop. Does any fuel injector have a pressure drop value that is more than the average pressure drop or less than the average pressure drop by 2.0 psi (14 kPa)? If yes, go to next step. If no, refer to «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.
Replace the affected CNG fuel injector. After replacing injector(s), go to next step.
Operate system in order to verify repair. Did you correct the condition? If yes, system is okay. If no, go to «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.

FUEL INJECTOR CIRCUIT DIAGNOSIS

A malfunction in the fuel injection circuit can set a DTC. For testing procedures and specifications, perform appropriate diagnostic test. See DIAGNOSTIC TROUBLE CODE DEFINITIONS in SELF-DIAGNOSTICS - 6.0L CHEVY EXPRESS & SAVANA - BI-FUEL & CNG article or DIAGNOSTIC TROUBLE CODE DEFINITIONS in SELF-DIAGNOSTICS - 6.0L SIERRA & SILVERADO - BI-FUEL & CNG article.

FUEL INJECTOR COIL TEST

Note. For component locations, see COMPONENT LOCATIONS . For circuit reference, see WIRING DIAGRAMS .

The PCM enables the appropriate CNG fuel injector on the intake stroke for each cylinder. The PCM is not capable of operating the high current CNG fuel injectors. The PCM injector pulse width signals are received by the Fuel Injector Control Module (FICM) and duplicate pulse width signals are generated by the FICM in order to operate the CNG injectors. The FICM controls each fuel injector by grounding the control circuit via a solid state device called a driver. A fuel injector coil winding resistance that is too high or low, will affect engine driveability. A fuel injector control circuit DTC may not set, but a misfire may be apparent. The fuel injector coil windings are affected by temperature. The resistance of the fuel injector coil windings will increase as the temperature of the fuel injector increases.

Diagnostic Aids

Operating vehicle over a wide temperature range may help isolate the fuel injector that is causing the condition.
Perform fuel injector coil test within the conditions of the customer's concern. A fuel injector condition may only be apparent at a certain temperature or under certain conditions.
If fuel injector coil test does not isolate the condition, perform fuel injector balance test. Refer to «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) .

The number below refers to step number in diagnostic procedure.

3 - This step tests each fuel injector resistance within a specific temperature range. If any of the fuel injectors display a resistance outside of the specified value, replace the fuel injector.
4 - This step determines if all of the fuel injectors are within 0.5 ohm of each other. If the highest resistance value is within 0.5 ohm of the lowest resistance value, then all of the fuel injector coil windings are okay.
5 - This step determines which fuel injector is faulty. After subtracting the highest and lowest resistance values from the average value, replace the fuel injector that has the greatest resistance difference from the average.

Perform Diagnostic System Check Alternative Fuels - Engine Controls. See «DIAGNOSTIC SYSTEM CHECK - ALTERNATIVE FUELS»(/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 in SELF-DIAGNOSTICS - 6.0L CHEVY EXPRESS & SAVANA - BI-FUEL & CNG article or «DIAGNOSTIC SYSTEM CHECK - ALTERNATIVE FUELS»(ref-159297-S00366181602003112400000) under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - 6.0L SILVERADO & SIERRA - BI-FUEL & CNG article. After performing Diagnostic System Check - Engine Controls, go to next step.
Observe Engine Coolant Temperature (ECT) parameter with scan tool. Is ECT value within 50-90°F (10-32°C)? If yes, go to next step. If no, go to step 4 .
Disconnect CNG fuel injectors multi-way harness connector. Using a DVOM, measure resistance of each CNG fuel injector. Do any of the fuel injectors display a resistance outside the specified range of 1-2 ohms? If yes, go to step 6 . If no, see «DIAGNOSTIC AIDS»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-system-component-testing-60l-wbifuel-cng__diagnostic-aids) .
Measure resistance of each CNG fuel injector with a DVOM. Record each fuel injector value. Subtract the lowest resistance value from the highest resistance value. Is the difference equal to or less than 0.5 ohm? If yes, go to «DIAGNOSTIC AIDS»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-system-component-testing-60l-wbifuel-cng__diagnostic-aids) . If no, go to next step.
Add all of the CNG fuel injector resistance values to obtain a total resistance value. Divide the total resistance value by the number of fuel injectors to obtain an average resistance value. Subtract the lowest and the highest individual fuel injector resistance values from the average resistance value. Replace CNG fuel injector that displays the greatest resistance difference, above or below the average. After replacing injector(s), go to step 7 .
Replace fuel injector(s) that are out of the specified range. After replacing injector(s), go to next step.
Operate the system in order to verify the repair. Did you correct the condition? If yes, system is okay. If no, go to step 2 .

FUEL SYSTEM PRESSURE TEST

Note. For fuel system pressure testing, see FUEL SYSTEM DIAGNOSIS under FUEL SYSTEMS in BASIC DIAGNOSTIC PROCEDURES - 6.0L CHEVY EXPRESS, SAVANA, SIERRA & SILVERADO - BI-FUEL/CNG article.

IDLE CONTROL SYSTEM

Note. For component locations, see COMPONENT LOCATIONS .

Note. For idle control system testing, perform related DTC testing procedure. Perform Diagnostic System Check Alternative Fuels - Engine Controls. See DIAGNOSTIC SYSTEM CHECK - ALTERNATIVE FUELS under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - 6.0L CHEVY EXPRESS & SAVANA - BI-FUEL & CNG article or DIAGNOSTIC SYSTEM CHECK - ALTERNATIVE FUELS under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - 6.0L SILVERADO & SIERRA - BI-FUEL & CNG article.

IGNITION SYSTEMS

Note. For ignition system testing not listed, perform related DTC testing procedure. See DIAGNOSTIC TROUBLE CODE DEFINITIONS in SELF-DIAGNOSTICS - 4.8L, 5.3L & 6.0L "C", "K" & "N" SERIES - FLEX FUEL & GASOLINE article or DIAGNOSTIC TROUBLE CODE DEFINITIONS in SELF-DIAGNOSTICS - 4.8L, 5.3L & 6.0L EXPRESS & SAVANA - GASOLINE article.

ELECTRONIC IGNITION SYSTEM DIAGNOSIS

See ELECTRONIC IGNITION SYSTEM under IGNITION SYSTEMS in BASIC DIAGNOSTIC PROCEDURES - 6.0L CHEVY EXPRESS, SAVANA, SIERRA & SILVERADO - BI-FUEL/CNG article.

EMISSION SYSTEMS & SUB-SYSTEMS

Note. For component locations, see COMPONENT LOCATIONS .

Note. For emission and sub-system testing not listed, perform related DTC testing procedure. See DIAGNOSTIC TROUBLE CODE DEFINITIONS in SELF-DIAGNOSTICS - 6.0L CHEVY EXPRESS & SAVANA - BI-FUEL & CNG article or DIAGNOSTIC TROUBLE CODE DEFINITIONS in SELF-DIAGNOSTICS - 6.0L SIERRA & SILVERADO - BI-FUEL & CNG article.

EXHAUST GAS RECIRCULATION

Note. For EGR system diagnosis, perform the following. On Chevy Express and Savana, see appropriate INSPECTION/MAINTENANCE PROCEDURES under DRIVE CYCLES in SELF-DIAGNOSTICS - 4.8L, 5.3L & 6.0L EXPRESS & SAVANA - GASOLINE article. On Sierra & Silverado, see appropriate INSPECTION/MAINTENANCE PROCEDURES under DRIVE CYCLES in SELF-DIAGNOSTICS - 4.8L, 5.3L & 6.0L "C", "K" & "N" SERIES - GASOLINE article.

FUEL EVAPORATION

Note. Ensure all vacuum line and EVAP system components are not damaged or missing before proceeding with this test.

EVAP Control System Diagnosis

For EVAP control system diagnosis, perform the following. On Chevy Express and Savana, see appropriate INSPECTION/MAINTENANCE PROCEDURES under DRIVE CYCLES in SELF-DIAGNOSTICS - 4.8L, 5.3L & 6.0L EXPRESS & SAVANA - GASOLINE article. On Sierra & Silverado, see appropriate INSPECTION/MAINTENANCE PROCEDURES under DRIVE CYCLES in SELF-DIAGNOSTICS - 4.8L, 5.3L & 6.0L "C", "K" & "N" SERIES - GASOLINE article.

Required Service

The PCV system may require service for obstructions if any of the following conditions exist

Rough idle.
Stalling or low idle speed.
Oil leaks.
Oil in air cleaner.
Sludge in engine.

A leaking PCV valve or hose could cause

Rough idle.
Stalling.
High idle speed.

If engine idles rough, check for clogged PCV valve, or for plugged or broken PCV hoses BEFORE adjusting idle. Check PCV valve application to ensure valve is fitted. Replace PCV valve if required.

Checking PCV Valve Function

Disconnect PCV valve vacuum hose from cylinder head cover. Run engine at idle. Place thumb over open end of PCV valve vacuum hose to check for vacuum. If vacuum does not exist, check for obstruction in source vacuum supply. If source vacuum supply is okay, replace PCV valve.
Turn ignition off. Remove PCV valve. Shake valve and listen for rattle of check valve inside PCV valve. If a clear rattle is not heard, replace PCV valve.
Visually inspect valve for varnish or deposits that may make PCV valve operation sticky or restricted, or cause incomplete seating of valve. Replace as necessary.
Engine must be sealed for PCV system to function as designed. If leakage, sludging or dilution of oil is noted and PCV system is functioning properly, check engine for cause and repair as required to ensure PCV system will continue to function properly.
An engine operating without any crankcase ventilation can be damaged, so it is important to replace PCV valve and air cleaner breather (if equipped) at regular intervals (at least every 30,000 miles). Check all hoses and clamps for failure or deterioration.

MISCELLANEOUS CONTROLS

Note. For component locations, see COMPONENT LOCATIONS .

Note. Although some of the controlled devices listed here are not technically engine performance components, they can affect driveability if they malfunction.

Manufacturer does not provide testing procedures for many individual systems and components. For system and component testing not listed, perform related DTC testing procedure. See DIAGNOSTIC TROUBLE CODE DEFINITIONS in SELF-DIAGNOSTICS - 6.0L CHEVY EXPRESS & SAVANA - BI-FUEL & CNG article or DIAGNOSTIC TROUBLE CODE DEFINITIONS in SELF-DIAGNOSTICS - 6.0L SIERRA & SILVERADO - BI-FUEL & CNG article.

A/C COMPRESSOR CLUTCH CONTROLS

Note. For A/C compressor clutch circuit testing, see appropriate AUTOMATIC A/C-HEATER SYSTEMS or MANUAL A/C-HEATER SYSTEMS article in AIR CONDITIONING & HEATING. See appropriate SYSTEM WIRING DIAGRAMS article in ELECTRICAL for terminal and wire color identification.

TRANSMISSION

Note. For transmission electronic controls and component testing, see appropriate DIAGNOSIS article in AUTOMATIC TRANSMISSIONS. For component circuit identification, see appropriate SYSTEM WIRING DIAGRAMS article in ELECTRICAL.