INTERMITTENT ENGINE ROUGHNESS INSPECT/REPAIR WIRING HARNESS

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

VEHICLES AFFECTED: 1988-91 S-TRUCKS W/2.5L - ENGINE CODE 'E'

Condition:

---------- A customer may comment of an 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 secure in place. The wire is allowed to rest against either the fuel filter or the rear most head bolt stud (See Illustration). 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 the most applicable Labour Operation and Time from the Canadian Labour Time Guide.

General Motors bulletins are intended for use by professional technicians, not a "do-it-yourselfer". They are written to inform those technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions and know-how to do a job properly and safely. If a condition is described, do not assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See a General Motors dealer servicing your brand of General Motors vehicle for information on whether your vehicle may benefit from the information.