P0318

DTC P0318

CIRCUIT DESCRIPTION
Correct engine misfire detection is dependent on whether or not the vehicle is experiencing a rough road condition. A rough road condition causes unexpected crankshaft fluctuations. In order to detect a rough road condition, the electronic brake control module (EBCM) communicates a wheel speed signal over the serial data circuit to the engine control module (ECM). The wheel speed sensor information allows the ECM to distinguish if the crankshaft speed variations are caused by a rough road condition or are caused by a true misfire. If the ECM does not receive the rough road information, this DTC sets.

DTC DESCRIPTOR
This diagnostic procedure supports the following DTC.
DTC P0318 Rough Road Sensor Circuit

CONDITIONS FOR RUNNING THE DTC
- There are no EBCM wheel speed sensor DTCs.
- The EBCM is communicating over the serial data circuit.
- DTC P0318 runs continuously once the above conditions are met.

CONDITIONS FOR SETTING THE DTC
The ECM does not detect a wheel speed signal from the EBCM for more than 5 seconds.

ACTION TAKEN WHEN THE DTC SETS
- The control module stores the DTC information into memory when the diagnostic runs and fails.
- The malfunction indicator lamp (MIL) will not illuminate.
- The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Failure Records.
- The driver information center, if equipped, may display a message.

CONDITIONS FOR CLEARING THE DTC
- A current DTC Last Test Failed clears when the diagnostic runs and passes.
- A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other non-emission related diagnostic.
- Clear the DTC with a scan tool.

TEST

Step 1: