Intermittent Diagnosis Guidelines

INTERMITTENT DIAGNOSTIC GUIDELINES
As previously mentioned, intermittent concerns are the most difficult concerns to diagnose.

An understanding of code storage and automatic code erasure is important.

First, codes can only be stored if the anti-lock brake control module (2B373) has power. The anti-lock brake control module gets primary power from the ignition feed into Pin 20. If this voltage is missing or less than 9.5V, the anti-lock brake control module will not initialize and therefore, a code cannot be stored. A System Pass (system OK) will be present whenever the module sees the required voltage assuming no other failures are present.

A previously stored diagnostic trouble code will be automatically erased if no system concerns occur for 80 ignition cycles.

Therefore, some codes read out in the System Precheck may not result in any trouble found in the pinpoint test performed. In most cases, this is an indication of an intermittent electrical concern. Inspection and Verification (Start Testing Here)

To minimize misdiagnosis, use the Intermittent Diagnosis Procedure if no resolution has been reached by the end of a particular pinpoint test.

If you are at this point because the warning light is on and you have been unable to obtain any code, go to Pinpoint Test V. V No DTC This procedure is only meant to address those problems that have been reduced to an intermittent wiring concern.