ERRATIC TURBO/TURBO OVERBOOST CODE 31 (PROM MAY REPAIR). Pontiac Sunbird 1987

For 1990-2009 cars

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

ERRATIC TURBO AND TURBO OVERBOOST OPERATION

#### VEHICLES AFFECTED: 1987 J CAR WITH 2.0L TURBO ------------------ ENGINE (VIN CODE M)

Some 1987 vehicles with 2.0L turbo engine may experience erratic turbo operation for 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 PROMs will correct the condition.

Pontiac J Auto. Trans. P/N 16120036 Buick J Auto. Trans. P/N 16084410

To insure correctness of the repair, refer to the Code 31 diagnostic chart and check other possible causes of Code 31.

#### Condition 2:

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

If the foam air vent is oil soaked, replace the wastegate control valve. Also, the wastegate actuator-to-wastegate control valve pressure line should be disconnected at both ends and blown clear. The vacuum/pressure line from the throttle body to the wastegate control valve should be disconnected at the valve end and blown clear towards the throttle body. Cleaning the lines prevents reoccurrence of turbo overboost and wastegate control valve failure.

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.