P1204

DTC P1204

CIRCUIT DESCRIPTION
The powertrain control module (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) solenoid, and the high pressure lock-off (HPL) solenoid. The PCM commands the HPL solenoid open for 1 second at every ignition ON, in order to prime the compressed natural gas (CNG) fuel system. The PCM commands the HPL, 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 8 seconds.

DTC DESCRIPTOR
This diagnostic procedure supports the following DTC:
DTC P1204 Excessive Crank Time Using Alternative Fuel

CONDITIONS FOR RUNNING THE DTC
- DTCs P0005, P0148, P0191, P0192, P0193, P0611, P1020, P1021-P1028, P1209, P2146, or P2665 are not set.
- The ignition voltage is between 6-18 volts.
- CNG operation is not inhibited.

CONDITIONS FOR SETTING THE DTC
The cranking time to start in CNG mode is more than 8 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.

TEST DESCRIPTION

Step 1 - Step 7:

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.