P1607

P1607-PCM INTERNAL SHUTDOWN TIMER SLOW RATIONALITY







Theory of Operation

The PCM compares actual shutdown time to a calculated shutdown time value. The calculated shut down time value is based on the amount the ECT should drop after a completely warmed up engine is shut down for a minimum of 8 hours. If the difference between actual shutdown time and the calculated shut down time is greater than a maximum value, a one trip failure will set. The shutdown time is measured again after 1 hour of ignition off time following the next engine warm up cycle. The PCM compares the shutdown time to a calculated value. If the difference is greater than a maximum value, the MIL is illuminated and a DTC will set.

- When Monitored:
With the engine running after a cycle when a complete engine warm up was achieved, the difference between engine coolant temperature and ambient air temperature less than or equal to 10° C (50° F), and battery voltage greater than 10 volts.

- Set Condition:
This DTC sets if the engine coolant temp drops too much during the measured engine off time. Two Trip Fault. Three good trips to turn off the MIL.





Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. Pre-Diagnostic Troubleshooting Procedure.

1. ENGINE COOLANT INSPECTION

NOTE: This DTC will set if the engine cools quicker than it should compared to engine off times. If the customer washed a hot engine with the engine off, a One Trip Failure will set. If the vehicle is parked in a highly ventilated area or has a large fan blowing on it which might cause the engine to cool quicker than expected this DTC may set.

WARNING: Do not remove or loosen the radiator cap with the system hot and under pressure. Serious burns from coolant can occur.

1. Turn the ignition off.
2. Allow the engine to cool enough to allow the pressure in the coolant system to drop enough to safely remove the radiator cap.
3. Check the coolant level and condition.

Is the engine coolant level filled to the proper level?

Yes

- Go To 2

No

- Add the appropriate type and amount of engine coolant and retest. Service and Repair
- Perform the PCM Verification Test. PCM Verification Test.

2. IGNITION OFF TIMER
1. Turn the ignition on.
2. With the scan tool under PCM/NGC Data Display, locate the Ignition Off Time value.
3. While monitoring a stop watch, turn the Ignition off for 10 minutes, watch the stop watch for those 10 minutes, and then turn the Ignition on.
4. With the scan tool under Data Functions, check the Ignition Off Time value again.

Does the Ignition Time Off value on the scan tool match the actual time you had the Ignition off on the stop watch?

Yes

- Refer to the CHECKING FOR AN INTERMITTENT DTC Diagnostic Procedure. Checking for an Intermittent DTC.

No

- Go To 3

3. CHECKING THE PCM POWER AND GROUND CIRCUITS
1. Perform the diagnostic procedure for CHECKING THE PCM POWER AND GROUND CIRCUITS. Checking the PCM Power and Ground Circuits.

Were any problems found?

Yes

- Repair the PCM power and ground circuit(s) as necessary.
- Perform the PCM Verification Test. PCM Verification Test.

No

- Go To 4

4. POWERTRAIN CONTROL MODULE (PCM)
1. Verify that the PCM is operating at the latest software version available.
2. Search for any Technical Service Bulletins that may apply.

Were any problems found?

Yes

- Repair as necessary and retest.
- Perform the PCM Verification Test. PCM Verification Test.

No

- Replace and program the Powertrain Control Module.
- Perform the PCM Verification Test. PCM Verification Test.