For 1990-2009 cars

Refer to Antilock Brake System in Electrical Diagnosis.

### Circuit Description

The PCM receives rough road information from the EBCM on the serial data circuit (CKT 800). The PCM uses the rough road information to enhance the misfire diagnostic by distinguishing crankshaft speed variations caused by driving on rough road surfaces from variations caused by true misfires. The EBCM transmits rough road information based on inputs from the wheel speed sensors. If the EBCM detects a condition which will not allow it to properly identify rough road situations while a misfire condition is being detected by the PCM, DTC P1380 will be set.

### Conditions for Setting the DTC

• | The PCM has detected a EBCM rough road sensing error.

• | Engine load is less than 87%.

• | Engine speed is less than 5000 RPM.

• | Vehicle speed is greater than 10 mph.

• | A misfire DTC is occurring and requesting the MIL to be illuminated.

### Action Taken When the DTC Sets

• | The PCM will not illuminate the Malfunction Indicator Lamp (MIL).

• | The PCM will store conditions which were present when the DTC set as Fail Records data only. This information will not be stored as Freeze Frame data.

### Conditions for Clearing the MIL/DTC

• | A history DTC will clear after 40 consecutive warm-up cycles have occurred without a malfunction.

• | DTC can be cleared by using the scan tool Clear Information function or by disconnecting the PCM battery feed.

### Diagnostic Aids

DTC P1380 set indicates that the ABS system has detected a malfunction which will not allow the EBCM to transmit correct rough road data to the PCM. The ABS Functional Test in ABS section 5E should be used to diagnose this condition.

#### DTC P1380 - EBCM DTC Detected - Rough Road Data Unusable

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
1 | Was the Powertrain On-Board Diagnostic (OBD) System Check performed? | -- | Go to the On-Board Diagnostic System Check in ABS section 5E1 | Go to the Powertrain On Board Diagnostic (OBD) System Check