Contents Wiring diagrams Section: Testing & Diagnostics All sections

Engine Control System - 6.0l - Alternative Fuel (Diagnostic Information & Procedures) Chevrolet Chevy Express G1500

Diagnostic Starting Point - Engine Controls

Begin the system diagnosis with Diagnostic System Check - Alternative Fuels (Engine Controls) . The Diagnostic System Check-Engine Controls will provide the following information

  1. The identification of the control modules which command the system
  2. The ability of the control modules to communicate through the serial data circuit
  3. The identification of any stored diagnostic trouble codes (DTCs) and the codes' statuses

The use of the Diagnostic System Check-Engine Controls will identify the correct procedure for diagnosing the system and where the procedure is located.

Description

The Diagnostic System Check-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 table reduces diagnostic time and prevents the replacement of good parts.

Test Description

The numbers below refer to the step numbers on the diagnostic table.

  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: The bi-fuel (KL6) vehicle and the dedicated CNG (KL8) vehicle require unique fuel injector control modules. DTC U0306 sets when the PCM detects an incorrect FICM has been installed for the vehicle application.
  4. 4: This step determines if the vehicle will start.
  5. 6: 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.
  6. 7: 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.
  7. 10: If there are other modules with DTCs set, refer to the DTC list. 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 table directs you otherwise. System level DTCs, for example, misfire DTCs, fuel trim DTCs, and catalyst DTCs.
  8. 12: This step determines if the vehicle will operate on the gasoline fuel system.
  9. 14: 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.
StepActionYesNo
IMPORTANT: 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 table. DO NOT clear the DTCs unless the diagnostic instructs you to do so. If there is a condition with the starter system, refer to Diagnostic System Check - Engine Electrical in Engine Electrical in the G/H Van Service Manual. Ensure the battery is fully charged and the cables are clean and tight. Ensure the PCM and the fuel injector control module (FICM) grounds are clean, tight, and in the proper location. Ensure the CNG and the gasoline fuel tanks are at least 1/2 full.
1Install a scan tool. Does the scan tool turn ON?Go to Step 2Go to Scan Tool Does Not Power Up in Data Link Communications in the G/H Van Service Manual
2Attempt 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: Powertrain control module (PCM) Body control module (BCM) Instrument panel cluster (IPC) Electronic brake control module (EBCM) Driver information center (DIC) Heating ventilation air conditioning (HVAC) Does the scan tool communicate with all the listed control modules?Go to Step 3Go to Scan Tool Does Not Communicate with Class 2 Device in Data Link Communications in the G/H Van Service Manual
3Select the DTC display function for the PCM. Does the scan tool display DTC U0306?Go to Fuel Injection Control Module ReplacementGo to Step 4
4Attempt to start the engine. Does the engine start and idle?Go to Step 5Go to DTC P1204 (KL8)
5Select the DTC display function for the following control modules: BCM IPC EBCM HVAC Does the scan tool display any DTCs?Go to Step 6Go to Step 11
6With a scan tool, select Captured Info in order to store the powertrain DTC information. Did you complete the action?Go to Step 7
7Does the scan tool display DTCs which begin with a "U" except U0306?Go to Scan Tool Does Not Communicate with Class 2 Device in Data Link Communications in the G/H Van Service ManualGo to Step 8
8Were any of the PCM DTCs P0601, P0602, or P1621 set?Go to DTC P0601-P0607, P1600, P1621, P1627, P1680, P1681, P1683, or P2610 in Engine Controls in the G/H Van Service ManualGo to Step 9
9Is DTC P0611 set?Go to DTC P0611Go to Step 10
10Does the scan tool display DTC P0562, P0563, P1637, or P1638?Go to Diagnostic Trouble Code (DTC) List in Engine Electrical in the G/H Van Service ManualGo to Diagnostic Trouble Code (DTC) List
11Is the vehicle equipped with the dedicated CNG fuel option (KL8)?Go to Step 13Go to Step 12
12Start and idle the engine. Force a switch over to gasoline operation with the scan tool in the Alternative Fuels special functions, output controls menu. Does the engine continue to idle?Go to Step 13Go to Engine Cranks but Does Not Run in the G/H Van Service Manual
13Is the customer's concern with the Transmission?Go to Diagnostic System Check - Automatic Transmission 4L80-E in Automatic Transmission in the G/H Van Service ManualGo to Step 14
14Is the customer's concern with the inspection/maintenance (I/M) testing?Go to Inspection/Maintenance (I/M) System Check in Engine Controls in the G/H Van Service ManualGo to Step 15
15If the customer's concern is a symptom, refer to Symptoms - Engine Controls Did you find and correct the condition?System OKGo to Intermittent Conditions
IMPORTANT
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 table. DO NOT clear the DTCs unless the diagnostic instructs you to do so. If there is a condition with the starter system, refer to Diagnostic System Check - Engine Electrical in Engine Electrical in the G/H Van Service Manual. Ensure the battery is fully charged and the cables are clean and tight. Ensure the PCM and the fuel injector control module (FICM) grounds are clean, tight, and in the proper location. Ensure the CNG and the gasoline fuel tanks are at least 1/2 full.

Engine Controls Diagnostic System Check

Scan Tool Data List

Scan Tool ParameterUnits DisplayedCold Key On 1Cold Idle 1Hot Idle 155 MPH Cruise 2
AFO Enable Circuit StatusFAULT/NO FAULTNO FAULTNO FAULTNO FAULTNO FAULT
AFO CommandALT FUEL/GASOLINEALT FUELALT FUELALT FUELALT FUEL
Consecutive CNG Starts0-1000-1000-1000-1000-100
FICM Diagnostic Circuit StatusFAULT/NO FAULTNO FAULTNO FAULTNO FAULTNO FAULT
Fuel Gauge Select SwitchRELEASED/APPLIEDRELEASEDRELEASEDRELEASEDRELEASED
Fuel Indicator Lamp CommandON/OFFOFFOFFOFFOFF
Fuel Mode CommandALT FUEL/GASOLINEALT FUELALT FUELALT FUELALT FUEL
Fuel Mode Lamp Circuit StatusFAULT/NO FAULTNO FAULTNO FAULTNO FAULTNO FAULT
Fuel Mode Switchover ReasonDTC SET/LOW FRP/LOW FTP/EXT. CRANK/100th START/ECT LOW TEMP/NOT SWITCHEDVariesVariesVariesVaries
Fuel Rail Pressure SensorPSI160 to 165 psi160 to 165 psi160 to 165 psi160 to 165 psi
Fuel Rail Pressure SensorVolts3.7V-4.0V3.7V-4.0V3.7V-4.0V3.7V-4.0V
Fuel Rail Temperature Sensor°C(°F)Near IATNear IATNear IATNear IAT
Fuel Rail Temperature SensorVoltsNear IATNear IAT3.63.6
Fuel Tank Pressure SensorPSI200 to 4000 psi200 to 4000 psi200 to 4000 psi200 to 4000 psi
Fuel Tank Pressure SensorVoltsVaries with Fuel LevelVaries with Fuel LevelVaries with Fuel LevelVaries with Fuel Level
Fuel Temperature Sensor°C(°F)Near IATCooler than IATCooler than IATCooler than IAT
Fuel Temperature SensorVolts1.0V-4.5V1.0V-4.5V1.0V-4.5V1.0V-4.5V
HPL Relay Circuit StatusFAULT/NO FAULTNO FAULTNO FAULTNO FAULTNO FAULT
High Pressure Lockoff Relay CommandFuel Flow/No Fuel FlowFlow for 1 second then No Fuel FlowFuel FlowFuel FlowFuel Flow
LPL Relay Circuit StatusFAULT/NO FAULTNO FAULTNO FAULTNO FAULTNO FAULT
Low Pressure Lockoff Relay CommandFuel Flow/No Fuel FlowNo Fuel FlowFuel FlowFuel FlowFuel Flow
1 For Cold Key On, Cold Idle, and Hot Idle ensure the following driving conditions are met: Vehicle in PARK A/C turned OFF No power steering load All accessories OFF Brake pedal released 2 For 89 km/h (55 mph) cruise ensure the following driving conditions are met: Vehicle in Drive AC turned ON No power steering load Record the data after driving for approximately 1.6 km/h (1 mile).

Scan Tool Data List

Scan Tool Output Controls

Scan Tool Output ControlAdditional Menu Selection(s)Description
Fuel Mode Indicator LampControls the fuel mode indicator lamp (FIL). The commanded states include None, ON, and OFF. When commanded ON or OFF, the system remains in the commanded state until cancelled by the scan tool.
AFO Signal EnableControls the AFO enable signal command. The commanded states include None, ON, and OFF. When commanded ON or OFF, the system remains in the commanded state until cancelled by the scan tool.
Fuel GaugeControls the fuel gauge. The PCM sends a serial data message to the IPC in order to control the gauge. The gauge will display full when commanded ON, and empty when commanded OFF.
High Pressure Lock-OffControls the high pressure lock-off (HPL) relay. The commanded states include None, ON, and OFF. When commanded ON or OFF, the system remains in the commanded state until cancelled by the scan tool. While operating on CNG the HPL relay is commanded ON.
Low Pressure Lock-OffControls the low pressure lock-off (LPL) relay. The commanded states include None, ON, and OFF. When commanded ON or OFF, the system remains in the commanded state until cancelled by the scan tool. While operating on CNG the LPL relay is commanded ON.
Forced Fuel Switch overControls which fuel system the vehicle is operating on. Fuel system can be switched from CNG to Gasoline, and Gasoline to CNG. A switch over from Gasoline to CNG will be disabled if the pressure in the CNG fuel tank is below 896 kPa (130 psi).

Scan Tool Output Controls

Diagnostic Trouble Code (DTC) List

DTCDiagnostic ProcedureModule(s)
P0005DTC P0005PCM 1
P0068DTC P0068 in Engine Controls in the G/H Van Service ManualPCM
P0101DTC P0101 (Without Throttle Actuator Control) DTC P0101 (With Throttle Actuator Control) in Engine Controls in the G/H Van Service ManualPCM
P0102DTC P0102 in Engine Controls in the G/H Van Service ManualPCM
P0103DTC P0103 in Engine Controls in the G/H Van Service ManualPCM
P0106DTC P0106 (Without Throttle Actuator Control) DTC P0106 (With Throttle Actuator Control) in Engine Controls in the G/H Van Service ManualPCM
P0107DTC P0107 in Engine Controls in the G/H Van Service ManualPCM
P0108DTC P0108 in Engine Controls in the G/H Van Service ManualPCM
P0112DTC P0112 in Engine Controls in the G/H Van Service ManualPCM
P0113DTC P0113 in Engine Controls in the G/H Van Service ManualPCM
P0116DTC P0116 in Engine Controls in the G/H Van Service ManualPCM
P0117DTC P0117 in Engine Controls in the G/H Van Service ManualPCM
P0118DTC P0118 in Engine Controls in the G/H Van Service ManualPCM
P0121DTC P0121 in Engine Controls in the G/H Van Service ManualPCM
P0122DTC P0122 in Engine Controls in the G/H Van Service ManualPCM
P0123DTC P0123 in Engine Controls in the G/H Van Service ManualPCM
P0125DTC P0125 in Engine Controls in the G/H Van Service ManualPCM
P0128DTC P0128 in Engine Controls in the G/H Van Service ManualPCM
P0131DTC P0131 or P0151 in Engine Controls in the G/H Van Service ManualPCM
P0132DTC P0132 or P0152 in Engine Controls in the G/H Van Service ManualPCM
P0133DTC P0133 or P0153 in Engine Controls in the G/H Van Service ManualPCM
P0134DTC P0134 or P0154 in Engine Controls in the G/H Van Service ManualPCM
P0135DTC P0135, P0141, P0155, or P0161 in Engine Controls in the G/H Van Service ManualPCM
P0136DTC P0136 or P0156 in Engine Controls in the G/H Van Service ManualPCM
P0137DTC P0137 or P0157 in Engine Controls in the G/H Van Service ManualPCM
P0138DTC P0138 or P0158 in Engine Controls in the G/H Van Service ManualPCM
P0140DTC P0140 or P0160 in Engine Controls in the G/H Van Service ManualPCM
P0141DTC P0135, P0141, P0155, or P0161 in Engine Controls in the G/H Van Service ManualPCM
P0151DTC P0131 or P0151 in Engine Controls in the G/H Van Service ManualPCM
P0152DTC P0132 or P0152 in Engine Controls in the G/H Van Service ManualPCM
P0153DTC P0133 or P0153 in Engine Controls in the G/H Van Service ManualPCM
P0154DTC P0134 or P0154 in Engine Controls in the G/H Van Service ManualPCM
P0155DTC P0135, P0141, P0155, or P0161 in Engine Controls in the G/H Van Service ManualPCM
P0156DTC P0136 or P0156 in Engine Controls in the G/H Van Service ManualPCM
P0157DTC P0137 or P0157 in Engine Controls in the G/H Van Service ManualPCM
P0158DTC P0138 or P0158 in Engine Controls in the G/H Van Service ManualPCM
P0160DTC P0140 or P0160 in Engine Controls in the G/H Van Service ManualPCM
P0161DTC P0135, P0141, P0155, or P0161 in Engine Controls in the G/H Van Service ManualPCM
P0171DTC P0171 or P0174 DTC P0171 or P0174 in Engine Controls in the G/H Van Service ManualPCM
P0172DTC P0172 or P0175 DTC P0172 or P0175 in Engine Controls in the G/H Van Service ManualPCM
P0174DTC P0171 or P0174 DTC P0171 or P0174 in Engine Controls in the G/H Van Service ManualPCM
P0175DTC P0172 or P0175 DTC P0172 or P0175 in Engine Controls in the G/H Van Service ManualPCM
P0182DTC P0182PCM 1
P0183DTC P0183PCM 1
P0186DTC P0186PCM 1
P0187DTC P0187PCM 1
P0188DTC P0188PCM 1
P0191DTC P0191 (w/o JL4)PCM 1
P0192DTC P0192 (w/o JL4)PCM 1
P0193DTC P0193 (w/o JL4)PCM 1
P0200DTC P0200PCM
P0218DTC P0218 in Automatic Transmission-4L80-E in the G/H Van Service ManualPCM
P0230DTC P0230 in Engine Controls in the G/H Van Service ManualPCM 2
P0300DTC P0300PCM
P0315DTC P0315 in Engine Controls in the G/H Van Service ManualPCM
P0325DTC P0325 in Engine Controls in the G/H Van Service ManualPCM
P0327DTC P0327 or P0332 in Engine Controls in the G/H Van Service ManualPCM
P0332DTC P0327 or P0332 in Engine Controls in the G/H Van Service ManualPCM
P0335DTC P0335 in Engine Controls in the G/H Van Service ManualPCM
P0336DTC P0336 in Engine Controls in the G/H Van Service ManualPCM
P0341DTC P0341 in Engine Controls in the G/H Van Service ManualPCM
P0342DTC P0342 in Engine Controls in the G/H Van Service ManualPCM
P0343DTC P0343 in Engine Controls in the G/H Van Service ManualPCM
P0351-P0358DTC P0351-P0358 in Engine Controls in the G/H Van Service ManualPCM
P0420DTC P0420 or P0430 in Engine Controls in the G/H Van Service ManualPCM 2
P0430DTC P0420 or P0430 in Engine Controls in the G/H Van Service ManualPCM 2
P0442DTC P0442 in Engine Controls in the G/H Van Service ManualPCM 2
P0443DTC P0443 in Engine Controls in the G/H Van Service ManualPCM 2
P0446DTC P0446 in Engine Controls in the G/H Van Service ManualPCM 2
P0449DTC P0449 in Engine Controls in the G/H Van Service ManualPCM 2
P0452DTC P0452 in Engine Controls in the G/H Van Service ManualPCM 2
P0453DTC P0453 in Engine Controls in the G/H Van Service ManualPCM 2
P0455DTC P0455 in Engine Controls in the G/H Van Service ManualPCM 2
P0461DTC P0461 in Instrument Panel, Gauges, and Console in the G/H Van Service ManualPCM 2 , IPC
P0462DTC P0462 in Instrument Panel, Gauges, and Console in the G/H Van Service ManualPCM 2 , IPC
P0463DTC P0463 in Instrument Panel, Gauges, and Console in the G/H Van Service ManualPCM 2 , IPC
P0496DTC P0496 in Engine Controls in the G/H Van Service ManualPCM 2
P0502DTC P0502 in Automatic Transmission-4L80-E in the G/H Van Service ManualPCM
P0503DTC P0503 in Automatic Transmission-4L80-E in the G/H Van Service ManualPCM
P0506DTC P0506 (Non-TAC) DTC P0506 (TAC) in Engine Controls in the G/H Van Service ManualPCM
P0507DTC P0507 (Non-TAC) DTC P0507 (TAC) in Engine Controls in the G/H Van Service ManualPCM
P0522DTC P0522 in Instrument, Panel, Gauges, and Console in the G/H Van Service ManualIPC
P0523DTC P0523 in Instrument, Panel, Gauges, and Console in the G/H Van Service ManualIPC
P0562DTC P0562 in Engine Electrical in the G/H Van Service ManualPCM
P0563DTC P0563 in Engine Electrical in the G/H Van Service ManualPCM
P0601-P0607DTC P0601-P0607, P1600, P1621, P1627, P1680, P1681, P1683, or P2610 in Engine Controls in the G/H Van Service ManualPCM
P0608DTC P0608 (With Throttle Actuator Control) DTC P0608 (Without Throttle Actuator Control) in Cruise Control in the G/H Van Service ManualPCM, IPC
P0611DTC P0611PCM 1
P0641DTC P0641 in Engine Controls in the G/H Van Service ManualPCM
P0650DTC P0650 in Engine Controls in the G/H Van Service ManualPCM
P0651DTC P0651 in Engine Controls in the G/H Van Service ManualPCM
P0706DTC P0706 in Auto Transmission-4L80-E in the G/H Van Service ManualPCM
P0711DTC P0711 in Automatic Transmission-4L80-E in the G/H Van Service ManualPCM
P0712DTC P0712 in Automatic Transmission-4L80-E in the G/H Van Service ManualPCM
P0713DTC P0713 in Automatic Transmission-4L80-E in the G/H Van Service ManualPCM
P0716DTC P0716 in Automatic Transmission-4L80-E in the G/H Van Service ManualPCM
P0717DTC P0717 in Automatic Transmission-4L80-E in the G/H Van Service ManualPCM
P0719DTC P0719 in Automatic Transmission-4L80-E in the G/H Van Service ManualPCM
P0724DTC P0724 in Automatic Transmission-4L80-E in the G/H Van Service ManualPCM
P0730DTC P0730 in Automatic Transmission-4L80-E in the G/H Van Service ManualPCM
P0741DTC P0741 in Automatic Transmission-4L80-E in the G/H Van Service ManualPCM
P0742DTC P0742 in Automatic Transmission-4L80-E in the G/H Van Service ManualPCM
P0748DTC P0748 in Automatic Transmission-4L80-E in the G/H Van Service ManualPCM
P0751DTC P0751 in Automatic Transmission-4L80-E in the G/H Van Service ManualPCM
P0752DTC P0752 in Automatic Transmission-4L80-E in the G/H Van Service ManualPCM
P0753DTC P0753 in Automatic Transmission-4L80-E in the G/H Van Service ManualPCM
P0756DTC P0756 in Automatic Transmission-4L80-E in the G/H Van Service ManualPCM
P0757DTC P0757 in Automatic Transmission-4L80-E in the G/H Van Service ManualPCM
P0758DTC P0758 in Automatic Transmission-4L80-E in the G/H Van Service ManualPCM
P0894DTC P0894 in Automatic Transmission 4L80E in the G/H Van Service ManualPCM
P1020DTC P1020PCM 1
P1106DTC P1106 in Engine Controls in the G/H Van Service ManualPCM
P1107DTC P1107 in Engine Controls in the G/H Van Service ManualPCM
P1111DTC P1111 in Engine Controls in the G/H Van Service ManualPCM
P1112DTC P1112 in Engine Controls in the G/H Van Service ManualPCM
P1114DTC P1114 in Engine Controls in the G/H Van Service ManualPCM
P1115DTC P1115 in Engine Controls in the G/H Van Service ManualPCM
P1121DTC P1121 in Engine Controls in the G/H Van Service ManualPCM
P1122DTC P1122 in Engine Controls in the G/H Van Service ManualPCM
P1133DTC P1133 or P1153 in Engine Controls in the G/H Van Service ManualPCM
P1134DTC P1134 or P1154 in Engine Controls in the G/H Van Service ManualPCM
P1153DTC P1133 or P1153 in Engine Controls in the G/H Van Service ManualPCM
P1154DTC P1134 or P1154 in Engine Controls in the G/H Van Service ManualPCM
P1204DTC P1204 (KL8)PCM 1
P1207DTC P1207PCM 1
P1208DTC P1208PCM 1
P1209DTC P1209PCM 1
P1258DTC P1258 in Engine Cooling in the G/H Van Service ManualPCM
P1380DTC P1380 in Engine Controls in the G/H Van Service ManualPCM
P1381DTC P1381 in Engine Controls in the G/H Van Service ManualPCM
P1431DTC P1431PCM 1
P1432DTC P1432PCM 1
P1433DTC P1433PCM 1
P1626DTC P1626 in Theft Deterrent in the G/H Van Service ManualPCM
P1631DTC P1631 in Theft Deterrent in the G/H Van Service ManualPCM
P1637DTC P1637 in Engine Electrical in the G/H Van Service ManualPCM
P1683DTC P0601-P0607, P1600, P1621, P1627, P1680, P1681, P1683, or P2610 in Engine Controls in the G/H Van Service ManualPCM
P1810DTC P1810 in Automatic Transmission-4L80-E in the G/H Van Service ManualPCM
P2146DTC P2146 (w/o JL4)PCM 1
P2665DTC P2665PCM 1
P2668DTC P2668PCM 1
U0306Diagnostic System Check - Alternative Fuels (Engine Controls)PCM
UXXXXDiagnostic Trouble Code (DTC) List in Data Link Communications in the G/H Van Service ManualPCM, BCM, IPC, VTD, EBCM
All DTCs operate on both fuel systems unless otherwise noted. 1 Tests only during CNG operation on KL6 vehicles. 2 Tests only during gasoline operation. These DTCs are disabled on KL8 vehicles.

Diagnostic Trouble Code (DTC) List