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 Descriptor

DTC P1381: Misfire Detected - No Communication With Brake Control Module

### System Description

The engine control module (ECM) detects engine misfire by detecting variations in crankshaft deceleration between firing strokes. For accurate detection of engine misfire the ECM must distinguish between crankshaft deceleration caused by actual misfire and deceleration caused by rough road conditions. The antilock brake system (ABS) can detect if the vehicle is on a rough road based on wheel acceleration/deceleration data supplied by the wheel speed sensors. If the ABS detects rough road above a predetermined threshold, this information is sent to the ECM. The ECM uses the rough road information when calculating engine misfire. If the ABS is malfunctioning and cannot detect rough roads, the misfire diagnostic will continue to run; however, if an engine misfire DTC sets, this DTC also sets indicating that there was no communication with the brake control module during the misfire calculation due to an ABS malfunction.

### Conditions for Running the DTC

DTC P1381 runs continuously.

### Conditions for Setting the DTC

• | An ABS malfunction exists for more than 10 seconds, preventing the ECM from receiving rough road detection data.

• | Engine misfire is detected and DTC P0300 set.

### Action Taken When the DTC Sets

DTC P1381 is a Type C DTC.

### Conditions for Clearing the MIL/DTC

DTC P1381 is a Type C DTC.

### Reference Information

#### DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

#### Scan Tool Reference

Control Module References for scan tool information

### Circuit/System Verification

Monitor the ABS DTCs on the scan tool.

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

⇒ | If there are no ABS DTCs set refer to Symptoms - Antilock Brake System.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.