SERVICE ENGINE SOON LIGHT (CODE 22) DIAG./PROC. (TPS)

SUBJECT: SERVICE ENGINE SOON LIGHT (CODE 22 (PROCEDURE/DIAGNOSTICS REPLACE TPS)

VEHICLES AFFECTED: 1991-92 B/D/F CARS, C/K/R/V/P/S/T/G/M L AND U

THIS BULLETIN HAS BEEN REVISED TO ADD: (1) THE 2.8L ENGINE TO THE LIST OF ENGINES FOR LIGHT DUTY TRUCKS. (2) CLARIFY AFFECTED S/T TRUCKS WITH 4.3L ENGINE

THIS BULLETIN CANCELS AND REPLACES BULLETINS #91-650-101 and 91-6-118.

This bulletin pertains to the 5.0L and 5.7L engine for passenger cars and 2.8L, 4.3L/3.1L, 5.0L/5.7L and 7.4L engines for light duty trucks.

NOTE: This Bulletin is NOT applicable to 1991 S/T Trucks equipped with the 4.3L engine and built prior to the VIN breaks listed below.

PLANT MAKE VIN BREAKPOINT ----------- ------ ----------------- SHREVEPORT GMC 1GTCS19R9M8521806 CHEVY 1GCCS14ZLM8177329

MORAINE GMC 1GKDT13Z6M2530285 CHEVY 1GNCS13ZLM2211006

PONTIAC GMC 1GTCS14Z5M0514776 CHEVY 1GCCT14Z5M0149156

Condition:

----------- Some owners of the above vehicles may comment on a Service Engine Soon Light - Code 22 - Throttle Position Sensor low. Additional comments may include no upshift to 4th gear, no TCC, harsh transmission shifts, or poor idle quality. These conditions may be more prevalent after initial startup.

Cause:

------ The above concerns may result from an intermittent electrical contact inside the Throttle Position Sensor (TPS).

Correction:

------------ If any of the subject conditions are found, complete the following procedure:

1. Perform the normal diagnostics per Section 6E of the Service Manual. 2. Check TPS/ECM connectors per Product Service Bulletin #91-8-135. 3. If no problems are found using the normal 6E diagnostics or the bulletin, replace the TPS with a new TPS kit, P/N 17112679 per the procedure in Section 6E of the Service Manual. The new TPS will have a yellow dot at the connector area for easier identification.

Part is currently available from CANSPO.

Note: The lack of 4th gear, no TCC and harsh transmission shift concerns are only associated on truck applications with the HYDRA-MATIC 4L80-E (4 speed automatic) electronic transmission.

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.