NO DOWNSHIFT AT 80% THROTTLE INSTALL REV. CABLE/PEDAL ASSY.

SUBJECT: NO TRANS DOWNSHIFT AND/OR 80-85% THROTTLE (INSTALL REVISED ACCEL. CABLE AND/OR PEDAL ASSEMBLY)

VEHICLES AFFECTED: 1991-1992 S/T W/4.3L, A/T

Owners of some 1991 and 1992 S/T vehicles equipped with an automatic transmission and a 4.3L (LB4) engine may comment that their vehicle exhibits some-of the following symptoms:

-Poor performance -Lack of power -Sluggishness -No downshift

Important: THE SYMPTOMS FEEL LIKE TRANSMISSION FAILURE (LACK OF RESPONSE) BUT TRANSMISSION REPLACEMENT IS NOT NECESSARY.

These symptoms may be due to the accelerator cable being too long and/or the accelerator pedal having incorrect geometry. When one or both of these conditions are present, full throttle is not achieved. To correct this condition, replacement of accelerator pedal and/or cable with revised units is necessary for the 4.3L (LB4) engine.

VEHICLES INVOLVED

Involved are certain S/T vehicles with 4.3L (LB4) engines and automatic transmissions built before the following VIN Breakpoints:

FOR THE ACCELERATOR CABLE

MODEL MODEL YEAR PLANT FROM TO ----- ---------- ----- ---- -- GMC 1991-92 Pontiac SOP 91 1GKCS18Z0N0504057 CHEV 1991-92 Pontiac SOP 91 1GNCS18Z7N0110865 GMC 1991-92 Shreveport SOP 91 1GCTS19Z1N8505990 CHEV 1991-92 Shreveport SOP 91 1GCCS19ZXN8127815 GMC 1991-92 Moraine SOP 91 1GKDT13Z8N2506457 CHEV 1991-92 Moraine SOP 91 1GCCS19Z7N2122624 OLDS 1991-92 Moraine SOP 91 1GHDT13Z9N2701859

FOR THE PEDAL/LEVER ASSEMBLY ---------------------------- MODEL MODEL YEAR PLANT FROM TO ----- ---------- ----- ---- -- GMC 1991-92 Pontiac SOP 91 1GTCS19Z0N0506093 CHEV 1991-92 Pontiac SOP 91 1GNCS18Z4N0119040 GMC 1991-92 Shreveport SOP 91 1GTDT19Z5N8509235 CHEV 1991-92 Shreveport SOP 91 1GCCS14Z0N8144551 GMC 1991-92 Moraine SOP 91 1GTDT19ZXN2506480 CHEV 1991-92 Moraine SOP 91 1GNDT13Z0N2121994 OLDS 1991-92 Moraine SOP 91 1GHDT13Z4N2701798

SERVICE

1. Before replacing the accelerator cable and/or pedal assembly, connect TECH 1 or similar testing device to get a throttle position sensor (TPS) voltage reading. TPS voltage at idle should be less than 1.0 volts (approximately 0.6 volts). With the engine off and the accelerator pedal depressed to wide open throttle, the TPS voltage should read about 4.6 volts for the 4.3L (LB4) engine.

When the accelerator pedal is depressed and voltage readings are less than the previously mentioned voltage specifications, replace the pedal assembly with a redesigned pedal assembly (P/N 15679725).

Important: Make sure during pedal assembly installation that the insulation mat does not get trapped between the pedal assembly and dash panel Refer to Figure 1.

Refer to the 1992 Light Duty Truck Fuel and Emissions Service Manual X-9236, page 4-90, 4-91 for proper accelerator pedal removal and installation.

2. Retest the TPS voltage. If the voltage readings for 4.3L (LB4) vehicles are still below the specified voltages, replace the accelerator cable with a redesigned cable (P/N 15693481).

Refer to 1992 Light Duty Truck Fuel and Emissions Service Manual X-9236, page 4-90 for proper accelerator cable removal and installation.

SERVICE PARTS INFORMATION

Part Number Description Application Ouantity ----------- ----------- ----------- -------- 15693481 Accelerator Control Cable S/T 1 (LB4 engine)

15679725 Accelerator Pedal Lever Asm. S/T 1

WARRANTY INFORMATION

For vehicles repaired under warranty use:

Description Labour Operation Labour Time ----------- ---------------- ----------- Pedal, Accelerator - Replace J5350 0.3 hrs.

Cable, Accelerator Control J5330 0.4 hrs. (Pedal to Lever) - Replace

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.