For 1990-2009 cars

# SERVICE MANUAL UPDATE-SEC. 8A VEHICLE SPEED SENSOR

#### SUBJECT: SECTION 8A - ELECTRICAL DIAGNOSIS VEHICLES SPEED SENSOR (SPEEDOMETER IS INACCURATE)

#### VEHICLES AFFECTED: 1991-93 "C, H" MODELS

#### APPLICATION:

----------- 1991-93 Oldsmobile Eighty-Eight 1991-93 Oldsmobile Ninety-Eight 1991-93 Pontiac Bonneville SE, SSE, SSEi 1991-93 Cadillac DeVille/Fleetwood 1991-93 Buick Park Avenue/Ultra 1991-93 Buick LeSabre

Diagnosis for Test A "SPEEDOMETER IS INACCURATE" symptom found in the above mentioned service manuals has been revised to avoid any confusion and misdiagnosis.

The following revised text should replace the following given text for proper system diagnosis.

#### OLDSMOBILE

1991-1993 Eighty Eight/Ninety Eight Service Manuals, Page 8A-33-1

#### THE TEXT WHICH STATES:

o If scan tool and Speedometer do not display the same speed, replace the Instrument Cluster (see Section 8C).

#### SHOULD BE REPLACED WITH:

o If scan tool and Speedometer do not display the same speed, do Test B.

#### PONTIAC

1991 Bonneville Service Manual, Page 8A-33-1 1992 Bonneville SE Service Manual, Page 8A-33-1 1992 Bonneville SSE/SSEi Service Manual - Book 2, Page 8A-33-1 1993 Bonneville Service Manual. Page 8A-33-1

#### THE TEXT WHICH STATES:

o If scan tool and Speedometer do not display the same speed, replace the Instrument Cluster (see Section 8C).

#### SHOULD BE REPLACED WITH:

o If scan tool and Speedometer do not display the same speed, do Test B.

#### CADILLAC

In the 1991 Cadillac DeVille/Fleetwood Service Manual, on Page 8A-33-1, located at the center of the page, the text which states:

o If Scan Tool and Speedometer do not display the same speed, check wiring to Instrument Cluster. If wiring OK, replace the Instrument Cluster (see Section 8C).

#### Should be replaced with:

o If Scan Tool and Speedometer do not display the same speed, check wiring to Instrument Cluster. If wiring OK, do Test B.

In the 1992/1993 Cadillac DeVille/Fleetwood Service Manual, on Page 8A-33-1, located at the center of the page, the text which states:

o If FDC display and Speedometer do not display same speed, check wiring to Instrument Cluster and tires for correct size and inflation. Also check all applicable terminals at in-line connectors and at Instrument Cluster connector (see schematic) for proper terminal contact, refer to Section 8A-5 for inspection/repair procedures. If OK, replace the Instrument Cluster (refer to Section 8C).

#### Should be replaced with:

o If FDC display and Speedometer do not display same speed, check wiring to Instrument Cluster and tires for correct size and inflation. Also check all applicable terminals at in-line connectors and at Instrument Cluster connector (see schematic) for proper terminal contact, refer to Section 8A-5 for inspection/repair procedures. If OK, do Test B.

#### BUICK

1991 Park Avenue ESM, Page 78, and 1991 LeSabre ESM, Page 72, "TEST A: VEHICLE SPEED OUTPUT TEST" add the following text to the test:

o If all measurements are correct, do Test B.

1992 Park Avenue ESM, Page 82 1992 LeSabre ESM, Page 80 1993 LeSabre/Park Avenue ESM, Page 185, "SYMPTOM/DIAGNOSIS GUIDE"

#### THE HEADING WHICH STATES:

o If the Speedometer and scan tool display different speeds, replace the Instrument Cluster see 4.

#### SHOULD BE REPLACED WITH:

o If the Speedometer and scan tool display different speeds, do Test A.

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.