Powertrain Controls - ECM/PCM

Trans Component Slipping:

CIRCUIT DESCRIPTION
The Powertrain Control Module (PCM) monitors the difference in engine speed and input speed. With transmission in drive," and Torque Converter Clutch (TCC) locked, the scan tool should display engine speed closely matching input speed.

DIAGNOSTIC TROUBLE CODE (DTC) 68 WILL SET WHEN
- No DTC(s) 28, 71, 74.
- TCC is locked.
- TCC slip speed greater than 200 RPM.
- Not in park/neutral.
- Fourth gear is indicated.
- All conditions are met for 2 seconds.

ACTION TAKEN (PCM WILL DEFAULT TO)
- Inhibit TCC operation.

DTC 68 WILL CLEAR WHEN
The fault condition(s) no longer exist, and the ignition switch is cycled "OFF" then "ON."

DTC CHART TEST DESCRIPTION
Number(s) below refer to circled number(s) on the diagnostic chart.

1. This test checks the indicated range signal to the actual selected range. A faulty switch could set DTC 68.
2. This test checks the torque converter for slippage while in a commanded lock-up state.

DIAGNOSTIC AIDS
- Check for deformed connectors at pass-thru connector.
- DTC 68 will set when going to default (second gear).
- Refer to PCM Intermittent DTC(s) or Performance. Testing and Inspection
- An intermittent incorrect engine speed signal will set a DTC 68 if the incorrect signal lasts for greater than 2 seconds.
- A mechanical failure in the 1-2 shift solenoid (stuck "OFF") or 2-3 shift solenoid (stuck "ON"), could set DTC 68.