Engine Controls - Intermittent Code 44/False Code 48
88buick02Bulletin 88-6E-8
Date MAR. '88
Ref. No. 88-074-6E
Corp. Ref. No. 806503
SUBJECT: INTERMITTENT "SERVICE ENGINE SOON" LIGHT WITH A CODE 44 (LEAN EXHAUST INDICATED) OR FALSE CODE 48 (MISFIRE DIAGNOSIS)
MODELS AFFECTED: SOME 1988 LESABRES, ELECTRAS AND RIVIERAS EQUIPPED WITH 3800 ENGINES (VIN CODE C)
Some 1988 LeSabres, Electras and Rivieras 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 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 exists, refer to the diagnostic chart in the 1988 Buick Chassis Service Manual. If no malfunction or driveability problem exists, install the new Men-Cal and erase the code prior to releasing the vehicle.
These Mem-Cals are currently available through General Motors Service Parts. Operation (GMSPO) under the following part numbers:
Axle Sales Code Scanner Mem-Cal
Model I.D. Located On I.D. If This Mem- Service
Application Axle Deck Lid Decal Cal is Installed Part No.
Electra/Park Avenue 2.73 FP3 2494 16122516
and LeSabre
Electra/Park Avenue 2.97 F79 2504 16122521
and LeSabre
Riviera 2.84 F17 2524 16122530
Riviera 2.97 F79 2534 16122536