SERVICE ENGINE SOON LIGHT WITH A CODE 44 OR 48 STORED

VEHICLES AFFECTED: SOME 1988 "C, E, H" MODELS EQUIPPED WITH 3800 ENGINES (VIN CODE C)

Some 1988 Models equipped with 3800 engines may experience an intermittent "Service Engine Soon" light with a stored Code 44 or 48, but without exhibiting a malfunction or driveability problem.

A new Mem-Cal has been developed which addresses both of these concerns as follows:

CODE 44 (LEAN EXHAUST INDICATED)

One of the criteria for setting a Code 44 is having the oxygen sensor signal voltage on circuit 412 remain below .2 volts for sixty (60) seconds or more. Since the sensor produces no voltage when it is below approximately 360 degrees C. (600 deg. F.), road moisture (water, slush) splashing on the sensor can cool it enough to temporarily turn on the "Service Engine Soon" light and set the code.

To alleviate this condition, the time factor for low voltage has been extended. This will allow the sensor the time to "dry off" and regain operating temperature without setting a Code 44.

CODE 48 (MISFIRE DIAGNOSIS)

Code 48 is sensitive to the tolerances of the basic engine, fuel system and ignition system, and may be stored on occasion, even though there is no malfunction or driveability problem exhibited. In order to avoid an intermittent "Service Engine Soon" light, the new Mem-Cal is calibrated to store the code, but not turn on the light. This will allow the code to still be used as a "diagnostic aid".

If a vehicle displays a Code 48, the vehicle should be examined to determine whether or not there is a malfunction setting this code. If a poor driveability condition exits, refer to the diagnostic *chart in the applicable 1988 Chassis Service Manual. If no malfunction or driveability problem exists, install the new Mem-Cal and erase the code prior to releasing the vehicle. Axle Sales Code Model I.D. (Located On Serv. Scanner Application Axle Deck Lid Decal) Pt No. Mem-Cal I.D. ----------- ---- --------------- ------ ------------- C and H 2.73 FP3 16122516 2494

C and H 2.97 F79 16122521 2504

except Pontiac Bonneville SSE

* Pontiac Bonneville 2.97 F79 16122526 2514 SSE only

E 2.84 F17 16122530 2524

E 2.97 F79 16122536 2534

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.