Monitors, Trips, Drive Cycles and Readiness Codes

2nd Trip Detect Logic:

PURPOSE
Certain DTC's (21, 25, 26 and 71), can be triggered by driving conditions without a malfunction present. To improve self diagnostic reliability, "2nd trip" detect logic is used.

OPERATION
When an a fault related to any of the above DTC's is detected, the electronic control module (ECM) retains a temporary record of the fault in memory. An actual code is set only if the same fault is recorded during the next ignition/driving cycle.

The malfunction indicator light (MIL) is only illuminated after the "2nd trip."

Because the ECM must see the fault for 2 consecutive trips, the chances of a false code are greatly reduced.

DIAGNOSIS
A specific driving pattern must be followed to recreate a fault code.

- Drive the vehicle in the same manner the customer has indicated caused the fault.
- Stop vehicle and turn ignition OFF.
- Restart vehicle and repeat test-drive.


VERIFICATION OF REPAIR
After repairs, clear ECM memory and follow the same driving pattern used for code detection.