Engine Controls - MIL ON/Driveability/Codes Set

91chevy24

GMC NUMBER: 91-6-115

GROUP: 6 Engine Diagnosis

DATE: August, 1991


CORPORATE NUMBER: 136513


SUBJECT: INTERMITTENT ENGINE ROUGHNESS, CEL CODE 13 AND 44 (INSPECT/REPAIR WIRING HARNESS AND SECURE)

MODELS: 1988-91 S TRUCKS WITH 2.5L ENGINE


Condition: Customers may comment of engine roughness or CEL (check engine light) with a stored code of either 13 (02 sensor failure) or 44 (02 sensor lean). This could be an intermittent condition.

Cause: The cause is an abrasion of the insulation on the oxygen sensor wire in the engine wiring harness between the plastic conduit and the connector to the oxygen sensor. This abrasion occurs when the wire is not properly secured in place.

Figure 1:

The wire is allowed to rest against either the fuel filter or the rear most head bolt stud (See Figure 1). Over time, the wire will abrade through the insulation and short out on either the fuel filter or the head bolt.

Correction: Any time that a problem with the oxygen sensor is suspect, the wiring harness should be inspected for any signs of abrasion. If any evidence of abrasion is found, the wiring should be repaired and secured to the fuel return line in such a way that the abrasion can no longer occur.

Use applicable labor operation and time.