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 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.
• | DTCs P0005, P0148, P0191, P0192, P0193, P0611, P1020, P1021-P1028, P1209, P2146, or P2665 are not set. |
• | The ignition voltage is between 6 and 18 volts. |
• | CNG operation is not inhibited. |
The cranking time to start in CNG mode is more than 8 seconds.
• | 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. |
• | 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. |
The numbers below refer to the step numbers on the diagnostic table.
This step determines if a CNG related DTC is set.
This step determines if the condition is present.
This step determines if the CNG fuel system is the cause of the concern.
Step | Action | Value(s) | Yes | No |
---|---|---|---|---|
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 | Observe the DTC information with a scan tool. Are there any DTCs set? | -- | Go to Step 3 | Go to Step 5 |
3 | With a scan tool, select Captured Info in order to store the powertrain DTC information. Did you complete the action? | -- | Go to Step 4 | -- |
Does the scan tool display DTC P0005, P0191, P0611, P2146, or P2665? | -- | Go to Step 5 | ||
Attempt to start the engine. Does the engine start and idle? | -- | Go to Step 6 | Go to Step 7 | |
6 |
Does the DTC fail this ignition cycle? | -- | Go to Step 7 | Go to Intermittent Conditions |
Does the FRP display remain steady near the specified value? | 310 kPa (45 psi) | Go to Engine Cranks but Does Not Run in Engine Controls in the C/K Pickup Service Manual | Go to Fuel System Diagnosis |