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DTC P1390-P1393 or P1395-P1398

The engine control module (ECM) identifies engine misfire by detecting variations in crankshaft speed. Crankshaft speed variations can also occur when a vehicle is operating over a rough road. The ECM receives a rough road signal by a rough road sensor (wheel speed sensor). The rough road sensor can detect if the vehicle is on the rough surface based on wheel acceleration/deceleration data supplied by each wheel speed sensor. The rough road sensor is a wheel speed sensor. The wheel speeds are detected by active wheel speed sensors. Each wheel speed sensor receives a 12 V reference voltage from the electronic brake control module (EBCM) and provides an alternating current square wave signal to the EBCM. As the wheel spins, the EBCM uses the frequency of the square wave signal to calculate the wheel speed. The EBCM sends the wheel speed information as a high speed controller area network (CAN) serial data message. The ECM can determine if the vehicle is on a rough road surface based on the signal from the wheel speed sensor. When the ECM detects a rough road condition, misfire diagnostics will be disabled.

Vehicle speed is greater than 14 km/h (9 MPH).

The engine control module (ECM) detects wheel speed differences between one wheel and the others.

Specific subsystems will not function or operate in degraded mode.

A current DTC clears when the diagnostic runs and passes.

Schematic Reference

Antilock Brake System Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

ABS Description and Operation

Electrical Information Reference

Scan Tool Reference

Control Module References for scan tool information

Ignition ON, observe the EBCM scan tool Wheel Speed Sensor parameters. The reading should be the same speed on all sensors when driving in a straight line at a speed greater than 20 km/h (13 MPH).

1. Ignition ON, verify that DTC C0035, C0040, C0045, or C0050 is not present in the EBCM.

⇒	If any listed DTC is present, refer to Diagnostic Trouble Code (DTC) List - Vehicle to diagnose that DTC prior to this diagnostic.

2. Program the K20 Engine Control Module and verify that the DTCs not reset.

⇒	If the DTCs reset, replace the K20 Engine Control Module.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for control module replacement, programming and setup