ERRATIC TURBO/TURBO OVERBOOST CODE 31 (PROM MAY REPAIR)

MODELS AFFECTED: 1987 SKYHAWKS WITH THE 2.OL OHC TURBO ENGINE (VIN CODE M) AND AUTOMATIC TRANSAXLE

Some 1987 turbo skyhawks may experience erratic turbo operation due to two known conditions:

Condition 1:

Under wide-open throttle operation and at the 2-3 upshift on an automatic transmission, a temporary turbo overboost can occur. A Code 31 "SERVICE ENGINE SOON" light may be triggered if overboost lasts too long. For the above specific driving overboost condition, the following PROM will correct the condition.

Transaxle PROM Part Number --------- ---------------- Automatic 16084410

To ensure completeness of the repair, refer to the Code 31 diagnostic section and check other possible causes of Code 31.

Condition 2:

Erratic turbo boost operation can also be caused by the boost solenoid sticking or oil plugged lines (refer to Code 31 diagnostics in the service manual). During engine operation, engine oil can deposit inside the boost solenoid lines and/or wastegate pressure line vent at the wastegate solenoid.

If the wastegate solenoids foam air vent is oil soaked, then replace the solenoid assembly. In addition, the wastegate-to-solenoid pressure line should be disconnected at both ends and blown clear. The wastegate solenoid-to-throttle body vacuum line should also be disconnected at the solenoid end and blown clear toward the throttle body. This line cleaning prevents turbo overboost from recurring and solenoid valve failure.

WARRANTY INFORMATION

Use applicable Labor Time and Number.

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.