MALFUNCTION INDICATOR LAMP ON/ DIAG. TRBLE CODES 17,18 STORED

SUBJECT: MALFUNCTION INDICATOR LAMP ON/DIAGNOSTIC TROUBLE CODES 17,18 STORED (DIAGNOSE/REPLACE PROM)

VEHICLES AFFECTED: 1993 "W" MODEL WITH 3800 ENGINE (VIN L, RPO L27)

APPLICATION:

----------- 1993 Buick Regal "W" cars equipped with 3800 (VIN L, RPO L27) engines built prior to VIN P1415488.

CONDITION:

--------- Some 1993 "W" cars equipped with 3800 (VIN L, RPO L27) engines built prior to VIN P1415488 may set a diagnostic trouble code (DTC) 17 and 18 and turn the Malfunction Indicator Lamp on. The car may also exhibit a rough running condition that clears up above 1200 RPM.

CAUSE:

----- When the PCM gets hot, around 71 degrees C (160 degrees F), a transistor inside the PCM reacts slower than the software (PROM). This causes the diagnostic for DTC 17 and 18 to set.

CORRECTION:

---------- If this condition exists, follow the diagnostic trouble code charts in the 1993 "W" Service Manual (pages 6E3-A-51 and 6E3-A-53) and repair as necessary. If the chart leads you to replace the PCM , it may be necessary to only replace the PROM.

Prior to PROM replacement, confirm that the PROM will correct this problem by allowing the PCM to become warm. This can be accomplished by bringing the car inside the shop and letting the engine idle with the hood closed for a minimum of one hour OR until the DTC codes reset.

o If DTC 17 and/or 18 reappear within one hour of idling, replace the PROM.

o If DTC 17 and/or 18 do NOT reappear within one hour of idling, replace the PCM.

PARTS INFORMATION:

PROM PROM PROM SERVICE SCANNER BROADCAST YEAR SERIES PART NUMBER I.D. NO. CODE ---- ------ ----------- -------- --------- 1993 Federal 16189642 9644 BDZW

1993 California 16189648 9654 BDZX

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.