DTC 77

DTC 77 PCM Detected EBTCM To PCM Interface Malfunction:

CIRCUIT DESCRIPTION
Traction control is simultaneously controlled by the EBTCM and the PCM. The PCM receives a "REQUESTED TORQUE" request via a Pulse Width Modulated (PWM) signal from the EBTCM requesting the desired torque level for proper traction control system operation.

DTC WILL SET WHEN
There is a TCS communication malfunction detected by the PCM and indicated to the EBTCM, by broadcasting a UART message.

ACTION TAKEN
A malfunction DTC is stored, TCS is disabled and the "TRACTION OFF" Indicator lamp is turned "ON." ABS remains functional.

DTC CHART TEST DESCRIPTION
Number(s) below refer to circled number(s) on the diagnostic chart.
1. The 39700 Pinout Box with the J 39700-25 adapter cable must be connected before this step is performed. This step determines if proper voltage is being supplied from the PCM.
2. Determines if there is a short to voltage in CKT 463.
3. Ensures malfunction was not due to physical damage of connectors.
4. Determines if there is an open in CKT 463 or damage to its terminals.
5. Determines whether the malfunction is an open in CKT 463 or internal to the PCM.

DIAGNOSTIC AIDS
Possible causes:
^ Open in CKT 463.
^ CKT 463 shorted to ground or voltage.
^ Communication frequency problem.
^ PCM not receiving UART information from EBTCM.

It is very important that a thorough inspection of the wiring and connectors be performed. Failure to carefully and fully inspect wiring and connectors may result in misdiagnosis, causing part replacement with reappearance of the malfunction.