CF18

What This Code Means

Code CF18 logs a missing or corrupted CAN speed message that the DSC module sends over the PT-CAN bus. The transmission control unit (TCU) uses wheel speed data to control shift points. If the message doesn't arrive or carries bad data, the TCU loses one of its key inputs and sets the fault.

Symptoms

• shifting problems;
• DSC warning light on the instrument cluster;
• speedometer malfunction.

Diagnosis and Repair

1. Check the DSC module for stored faults — a failure on its side is the most common cause of the missing message.
2. Inspect the PT-CAN wiring and connectors: a damaged line or poor contact disrupts speed data transfer between the DSC and TCU.
3. If the DSC module is faulty, replace it.

Secondary Issues

• loss of wheel speed data leads to incorrect shift synchronization;
• incorrect shifts cause transmission wear;
• handling problems are possible.