P1204

DTC P1204

Circuit Description

The 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 1 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.

Conditions for Running the DTC

The engine is cranking.

Conditions for Setting the DTC

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

Action Taken When the DTC Sets

- The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
- 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

- 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

- 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.
- Go to Intermittent Conditions.

Test Description

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

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