Circuit Description

PCM detects engine misfire by detecting variations in crankshaft deceleration between firing strokes. For accurate detection of engine misfire, PCM must be able to distinguish between crankshaft deceleration caused by actual misfire or deceleration caused by rough road conditions.

Electronic Brake Control Module (EBCM) transmits rough road information based on wheel acceleration/deceleration data supplied by the wheel speed sensors. If ABS system detects rough road above a predetermined threshold, information is sent to PCM through serial data circuit.

Conditions required to set DTC are:

• Engine load less than 87 percent.
• Engine speed less than 5000 RPM.
• Vehicle speed greater than 10 MPH.
• A misfire DTC is occurring and requesting MIL to be illuminated.
• PCM detects rough road data error for at least 10 seconds.