U1421

U1421-IMPLAUSIBLE IGNITION KEY OFF TIME RECEIVED
For a complete wiring diagram, refer to the Wiring Information.
Theory of Operation

This monitor checks if the timer that counts the ignition off time is stuck.

- When Monitored:
Ignition on.

- Set Condition:
If the difference between coolant temperatures at the previous ignition off and next key on is greater than -12.2°C (10°F), and the ignition off time was less than two minutes, the Powertrain Control Module (PCM) increments a fail counter of one. If the fail counter reaches 16 counts, a DTC is set and MIL lamp turns on.





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

1. ACTIVE DTC

NOTE: Low battery voltage as well or an IOD fuse which is missing or not pushed in completely can cause the DTC to set. Make sure that the battery is fully charged and Ignition Off Draw (IOD) fuse is properly installed before continuing.

1. Ignition on, engine not running.
2. With a scan tool clear DTCs.
3. Turn the ignition off for 75 seconds.
4. Turn the ignition on.
5. With a scan tool read DTCs.

Is the DTC active at this time?

Yes

- Go To 3

No

- Perform the INTERMITTENT CONDITION diagnostic procedure. Intermittent Condition Test

2. CHECKING THE PCM POWERS AND GROUNDS
1. Checking The PCM Power And Grounds Perform the CHECKING THE PCM POWERS AND GROUNDS diagnostic procedure.

Were any problems found?

Yes

- Perform the appropriate repair.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

No

- Go To 3

3. CHECKING FOR TSB/PCM FLASH UPDATES
1. Check for any Service Bulletins or PCM flash updates that may apply.

Were any Service Bulletins or PCM flash updates found?

Yes

- Perform the appropriate repair.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

No

- Go To 4

4. CAN B BUS HARDWARE DTCs ALSO ACTIVE
1. With a scan tool check for DTCs in the TIPM.

Are any CAN B Hardware related DTCs active at this time?

Yes

- Testing and Inspection Perform the appropriate diagnostic procedure.

No

- Replace and program the Powertrain Control Module.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.