Circuit Description
The 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. When CNG operation is commanded, the PCM grounds the AF enable circuit, which energizes the AF relay. The AF relay energizes all of the AF injector relays. The PCM injector control signals are routed through the AF injector relays to the fuel injector control module (FICM). The FICM generates duplicate control signals 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 P1021-P1024 will set. DTC P1021 will set if there is a condition on a CNG fuel injector control circuit for cylinder 1, P1022 for cylinder 2 , etc.
Conditions for Running the DTC
| • | DTC P0336 is not set. |
| • | The ignition voltage is between 6 and 18 volts. |
| • | The engine speed is more than 50 RPM. |
| • | The vehicle is operating on CNG |
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 3 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 verifies that the FICM is able to control the 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 | |||
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 |
Do any of the DTCs P1021-P1024 fail this ignition cycle? | Go to Step 4 | Go to Step 3 |
3 |
Did the DTC fail this ignition? | Go to Step 4 | Go to Diagnostic Aids |
4 |
Does the test lamp illuminate? | Go to Step 5 | Go to Step 11 |
|
Important: The test lamp will blink until the vehicle switches over to gasoline.
Does the test lamp blink? | Go to Step 9 | Go to Step 6 | |
Does the test lamp remain illuminated? | Go to Step 8 | Go to Step 7 | |
7 | Test the CNG fuel injector control circuit for an open or a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems in the J Platform Service Manual. Did you find and correct the condition? | Go to Step 14 | Go to Step 10 |
8 | Test the CNG fuel injector control circuit for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems in the J Platform Service Manual. Did you find and correct the condition? | Go to Step 14 | Go to Step 13 |
9 | 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 J Platform Service Manual. Did you find and correct the condition? | Go to Step 14 | Go to Step 12 |
10 | 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 J Platform Service Manual. Did you find and correct the condition? | Go to Step 14 | Go to Step 13 |
11 | Repair the open or short to ground on the ignition 1 voltage circuit of the fuel injector. Refer to Circuit Testing and Wiring Repairs in Wiring Systems in the J Platform Service Manual. Did you find and correct the condition? | Go to Step 14 | -- |
12 | Replace the CNG fuel injector. Refer to Fuel Injector Replacement . Did you complete the replacement? | Go to Step 14 | -- |
13 | Replace the FICM. Refer to Fuel Injector Control Module Replacement . Did you complete the replacement? | Go to Step 14 | -- |
14 |
Did the DTC fail this ignition? | Go to Step 2 | Go to Step 15 |
15 | Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? | System OK | |
