For 1990-2009 cars

### Diagnostic Instructions

• | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

• | Review Strategy Based Diagnosis for an overview of the diagnostic approach.

• | Diagnostic Procedure Instructions provides an overview of each diagnostic category.

### DTC Descriptors

DTC P1380: Misfire Detected - Rough Road Data Not Available
DTC P1381: Misfire Detected - No Communication with Brake Control Module

### Circuit/System Description

The Engine Control Module (ECM) detects engine misfire by detecting variations in crankshaft speed. The ECM should be distinguished from actual misfire resulting in crankshaft speed degrade to rough road conditions resulting in deceleration in order to detect accurately Engine Misfire. The Antilock Brake System (ABS) can detect if the vehicle is on a rough surface based on wheel acceleration/deceleration data supplied by each wheel speed sensor. If the ABS detects a rough road condition above a predetermined threshold, the information will be send to the ECM. The ECM uses the rough road information When calculating the engine misfire. If the ABS has a condition and can not detect rough road, the misfire diagnosis will continue to operate. However, if a misfire DTC is set along with DTC, it indicates that rough road data not available during misfires counted or due to ABS condition, No communication with brake control module.

### Conditions for Running the DTC

#### P1380

• | The vehicle speed is greater than 0 km/h (0 mph).

• | DTC P0180 runs continuously when the above conditions are met.

#### P1381

DTC P1381 runs continuously.

### Conditions for Setting the DTC

#### P1380

• | ABS control module sends a message to the ECM, indicating that conditions occurs in the ABS module.

• | Engine misfire is detected and DTC P0300 is set.

• | It occurs at least 40 times during 80 tests.

• | DTC P1380 is set when the above conditions are met.

#### P1381

• | An ABS malfunction exists preventing the ECM from receiving rough road detection data.

• | Engine misfire is detected and DTC P300 is set.

• | It occurs at least 40 times during 80 tests.

• | DTC P1381 is set when the above conditions are met.

### Action Taken When the DTC Sets

DTC P1380 and P1381 are Type C DTCs.

### Conditions for Clearing the DTC

DTC P1380 and P1381 are Type C DTCs.

### Reference Information

#### DTC Type Reference

Diagnostic Trouble Code (DTC) Type Definitions

### Circuit/System Verification

Monitor ABS DTCs on the scan tool.

⇒ | if any ABS DTCs is set, diagnose those DTCs first. Refer to Diagnostic Trouble Code (DTC) List - Vehicle.

⇒ | if ABS DTCs are not set, refer to Symptoms - Antilock Brake System.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.