Related Tests, Information and Procedures

A fault can occur in two ways, intermittently or permanently. An intermittent fault is defined as a fault which is temporary and, in certain cases, recurrent. A permanent fault is one which is present continuously.

If a signal which was faulty or missing returns to its correct value the engine control module (ECM) will start counting down rather than adopting a fixed substitute value. However, In the case of output signals the engine must have been switched off. The diagnostic trouble code (DTC) remains stored in the engine control module for some time.