Circuit Description
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 compressed natural gas (CNG) fuel injectors. The PCM injector pulse width (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.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P1020 Injector Output Circuit
Conditions for Running the DTC
The ignition is ON.
Conditions for Setting the DTC
| • | The fuel injector control module (FICM) detects an incorrect voltage on a CNG fuel injector control circuit. |
| • | The condition exists for 5 seconds. |
Action Taken When the DTC Sets
| • | The control module illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails. |
| • | The control module switches over to gasoline fuel operation. |
| • | 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. |
Conditions for Clearing the MIL/DTC
| • | The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail. |
| • | A current DTC, Last Test Failed, clears when the diagnostic runs and passes. |
| • | A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic. |
| • | Clear the MIL and the DTC with a scan tool. |
Diagnostic Aids
| • | Performing the Fuel Injector Coil Test may help to isolate an intermittent condition. Refer to Fuel Injector Solenoid Coil Test . |
| • | For an intermittent condition, refer to Intermittent Conditions . |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
This step tests for ignition voltage at the appropriate fuel injector.
-
This step tests if a ground is constantly being applied to the fuel injector.
Step | Action | Yes | No |
|---|---|---|---|
Schematic Reference: Engine Controls Schematics Connector End View Reference: Engine Controls Connector End Views or Fuel Injector Control Module Connector End Views | |||
1 | Did you perform the Diagnostic System Check Alternative Fuels - Engine Controls? | Go to Step 2 | Go to Diagnostic System Check - Alternative Fuels (Engine Controls) |
2 |
Did the DTC fail this ignition? | Go to Step 3 | Go to Diagnostic Aids |
3 |
Do all of the CNG fuel injector circuits illuminate the test lamp? | Go to Step 8 | Go to Step 4 |
Does the test lamp illuminate? | Go to Step 5 | Go to Step 10 | |
Probe the control circuit of the CNG fuel injector with a test lamp connected to B+. Does the test lamp illuminate? | Go to Step 9 | Go to Step 6 | |
6 | Test the control circuit of the CNG fuel injector for an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems in the G/H Van Service Manual. Did you find and correct the condition? | Go to Step 13 | Go to Step 7 |
7 | Test for an intermittent and for a poor connection at the CNG fuel injector. Refer to Testing for Intermittent Conditions and Poor Connections and Repairing Connector Terminals in Wiring Systems in the G/H Van Service Manual. Did you find and correct the condition? | Go to Step 13 | Go to Step 11 |
8 | Test for an intermittent and for a poor connection at the FICM. Refer to Testing for Intermittent Conditions and Poor Connections and Repairing Connector Terminals in Wiring Systems in the G/H Van Service Manual. Did you find and correct the condition? | Go to Step 13 | Go to Step 12 |
9 | Repair the short to ground on the control circuit of the CNG fuel injector. Refer to Wiring Repairs in Wiring Systems in the G/H Van Service Manual. Did you complete the repair? | Go to Step 13 | -- |
10 |
Important: The INJ fuse also supplies voltage to the ignition coil modules. If the fuse is open, inspect all related circuits and components for a short to ground. Refer to Circuit Testing in Wiring Systems. Repair the ignition 1 voltage circuit of the fuel injector for an open or for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems in the G/H Van Service Manual. Did you complete the repair? | Go to Step 13 | -- |
11 | Replace the CNG fuel injector. Refer to Fuel Injector Replacement . Did you complete the replacement? | Go to Step 13 | -- |
12 | Replace the FICM. Refer to Fuel Injector Control Module Replacement . Did you complete the replacement? | Go to Step 13 | -- |
13 |
Did the DTC fail this ignition? | Go to Step 2 | Go to Step 14 |
14 | Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? | System OK | |
