EXPERTEC TSB (91C23)
Reference number: 91C23
4.3L/5.7L/7.4L ENG: TPS LOW OUTPUT VOLTAGE
EMISSION RECALL BULLETIN
THROTTLE POSITION SENSOR (TPS) - EMISSIONS RECALL 91C23
Model 1991 Chevrolet C/K, R/V, P Trucks, G Vans
Recall No. 91C23
Date September, 1991
Number of Affected Vehicles: 65,966
DEFECT INFORMATION REPORT
1: MANUFACTURER:
General Motors Corporation
2: Description of the Defect:
A deposit buildup on the throttle position senor (TPS) opening element may cause a "Service Engine Soon" (Code 22 - TPS signal low) light to appear. The loss of TPS signal is caused by loss of wiper contact with the sensing element at certain locations near the idle point. For affected vehicles with electronic automatic transmission, the setting of Code 22 will put the transmission in a default mode until the next key-up occurrence. In this default mode, the customer will experience harsh shifts, and no torque converter clutch lockup or overdrive.
3: CLASS OR CATEGORY OF VEHICLES POTENTIALLY AFFECTED:
The 1991 model year vehicles affected are the following engine families:
4.1: NUMBER OF VEHICLES ESTIMATED TO HAVE THE DEFECT:
The following are the 1991 production volumes of the involved vehicles:
4.2: PRODUCTION PLANTS:
General Motors Corporation Truck & Bus Group Janesville Assembly 1000 Industrial Ave. Janesville WI 53546-2531
General Motors Corporation Truck & Bus Group Flint Assembly Van Slyke at Atherton Roads Flint MI 48551
General Motors Corporation Lordstown Assembly PO Box 1406 Warren OH 44482
General Motors Corporation Truck & Bus Group Pontiac E 31 Judson St. Pontiac MI 48058
General Motors Corporation Truck & Bus Group Detroit Assembly 601 Piquette Detroit MI 48202
General Motors Corporation Truck & Bus Group Fort Wayne Assembly 12200 Lafayette Ctr Road Fort Wayne IN 46783
GM of Oshawa Assembly Plant General Motors of Canada Ltd. Park Rd S MC 7033 Oshawa ON Canada L1J 5Z3
General Motors of Canada Ltd. Scarborough Assembly Plant 1901 Englington Ave E Scarborough ON Canada M1L 2L8
5: EVALUATION OF EMISSIONS AND DRIVEABILITY OF THE DEFECT:
The affected vehicles with electronic automatic transmission will exhibit an overt indicator to the customer of degraded drive ability (i.e., harsh shifts, no torque converter lockup overdrive). The resultant emission impact will be insignificant, since the condition is intermittent and the customer will seek repair of the vehicle. The affected vehicles without electronic automatic transmission will exhibit only a brief "Service Engine Soon" light (Code 22). There will be no driveability problem or impact on emissions on those vehicles.
6: AVAILABLE EMISSIONS DATA:
There is no available emission data relative to this specific problem.
7: ANTICIPATED FOLLOW-UP ACTION:
A voluntary campaign will be conducted to replace the throttle position sensor (TPS) on 1991 Chevrolet and GMC trucks equipped with 4.3L, 5.7L and 7.4L engines and with electronic automatic transmissions. The new TPS will utilize a different internal lubricant that will not allow the formation of the deposit buildup. Although this campaign will be conducted on emission related components, General Motors does not consider this an emission-compliance concern, the campaign will be conducted to avoid customer dissatisfaction potential from a temporary harsh driveability condition. A dealer service bulletin will be issued for other affected vehicles that only set brief "Service Engine Soon" light. The bulletin will instruct replacement of TPS with the new TPS part number.
ATTACHMENT I VOLUNTARY EMISSION RECALL CAMPAIGN
1: DESCRIPTION OF SUBJECT VEHICLES TO BE RECALLED:
The following are the 1991 production volumes of the involved vehicles with electronic automatic transmissions:
2: DESCRIPTION OF THE MODIFICATION:
A voluntary emission recall campaign will be conducted to replace the throttle position sensor (TPS) on 1991 Chevrolet and GMC trucks equipped with 4.3L, 5.7L, and 7.4L engines with electronic automatic transmissions. The new TPS will utilize a different internal lubricant that will not allow the formation of the deposit buildup. A dealer service bulletin applies to approximately 10,883 manual transmission-equipped vehicles that may experience a brief "Service Engine Soon" Light. The bulletin requires replacement of the TPS with the new TPS part number.
3: IDENTIFICATION AND NOTIFICATION OF VEHICLE OWNERS:
The specific vehicles involved in this campaign have been identified by Vehicle Identification Number Computer Listings. These listings are furnished to all involved dealers with the campaign bulletin.
4: CONDITIONS OF ELIGIBILITY FOR REPAIR UNDER REMEDIAL PLAN:
Dealers are to service all vehicles subject to this campaign at no charge to owners, regardless of mileage, age of vehicle, or ownership from this time forward. Dealers are to correct all affected vehicles in new and used vehicle stock prior to their sale.
5: PROCEDURE TO BE FOLLOWED BY VEHICLE OWNERS TO OBTAIN CORRECTION:
The letters being sent to the affected owners will include an owner reply card which identifies their vehicle. The Owner Letter contains necessary information concerning owner participation in the campaign. Presentation of this card to the dealer will assist in making the necessary correction to the vehicle.
6: CLASS OF PERSONS OTHER THAN DEALERS WHO WILL REMEDY THE DEFECT:
Only Chevrolet and GMC dealers and in-shop fleet warranty accounts are authorized to provide this remedy.
7: OWNER LETTER
See Attachment III below.
8: SYSTEM TO ASSURE AVAILABILITY OF ADEQUATE PARTS SUPPLY:
Parts ordering information is provided in the Bulletin. Parts are to be obtained from General Motors Service Parts Operation (GMSPO).
9: NECESSARY INSTRUCTIONS TO PERSONS WHO ARE TO PERFORM REPAIRS:
See Recall Bulletin (Attachment II).
10: IMPACT OF THE PROPOSED CHANGES ON FUEL CONSUMPTION, DRIVEABILITY AND SAFETY:
No impact on fuel consumption, driveability and safety.
11: SAMPLE OF ANY LABEL TO BE APPLIED TO VEHICLES OR ENGINES WHICH PARTICIPATE IN THE VOLUNTARY RECALL CAMPAIGN
A description of the label and instructions on the use and application of the label is provided in the Bulletin.
ATTACHMENT II RECALL CAMPAIGN BULLETIN - 91C23 THROTTLE POSITION SENSOR
Chevrolet 91C23 August, 1991
Model: 1991 C/K, R/V & P TRUCKS AND G VANS
General Motors has determined that certain 1991 Chevrolet C/K, R/V and P trucks and G vans with 4.3L, 5.7L or 7.4L fuel-injected gasoline engines, couple with Hydra-Matic 4L80 electronic transmissions (MT1), may have a Throttle Position Sensor (TPS) which exhibits intermittent low output voltage. This condition may cause the transmissions in these vehicles to have no upshift to 4th gear, no TCC, or harsh transmission shifts. To correct this condition, dealers are to inspect and, if necessary, replace the TPS switch.
VEHICLES INVOLVED
Involved are certain 1991 Chevrolet C/K, R/V & P trucks and G vans with 4.3L, 5.7L or 7.4L fuel-injected gasoline engines, coupled with Hydra-Matic 4L80 electronic transmissions (MT1) built within the following VIN breakpoints:
Involved vehicles have been identified by Vehicle Identification Number Computer Listings. Computer listings contain the complete Vehicle Identification Number, owner name and address data, and are furnished to involved dealers with the campaign bulletin. Owner name and address data furnished will enable dealers to follow-up with owners involved in this campaign. These listings may contain owner names and addresses obtained from State Motor Vehicle Registration Records. The use of such motor vehicle registration data for any other purpose is a violation of law in several states. Accordingly, you are urged to limit the use of this listing to the follow-up necessary to complete this campaign. Any dealer not receiving a computer listing with the campaign bulletin has no involved vehicles currently assigned.
OWNER NOTIFICATION
Owners will be notified of this campaign on their vehicles by Chevrolet Motor Division (see copy of owner letter included with this bulletin).
DEALER CAMPAIGN RESPONSIBILITY
Dealers are to service all vehicles subject to this campaign at no charge to owners, regardless of mileage, age of vehicle, or ownership, from this time forward. Whenever a vehicle subject to this campaign is taken into your new or used vehicle inventory, or it is in your dealership for service in the future, you should take the steps necessary to be sure the campaign correction has been made before reselling or releasing the vehicle. Owners of vehicles recently sold from your new vehicle inventory are to be contacted by the dealer, and arrangements made to make the required correction according to instructions contained in this bulletin.
PARTS INFORMATION
Parts required to complete this campaign are to be obtained from General Motors Service Parts operations (GMSPO). To ensure these parts will be obtained as soon as possible, they should be ordered from GMSPO on a "C.I.O." order with no special instruction code, but on an advise code (2).
| Part Description | Part Number | Qty. |
|---|---|---|
| Throttle Position Sensor (TPS) Kit | 17112679 | 1 |
SERVICE PROCEDURE
- Remove air cleaner (if necessary).
- Inspect vehicle's TPS for yellow dot. If the TPS has a yellow dot at the connector area, skip to step 4 below.
- If the TPS does not have a yellow dot, replace the TPS with the new TPS kit per the Fuel And Emissions Section of the appropriate service manual.
- Install Campaign Identification Label.
CAMPAIGN IDENTIFICATION LABEL
Each vehicle corrected in accordance with the instructions outlined in this bulletin will require a "Campaign Identification Label". Each label provides a space to include the five (5) digit dealer code of the dealer performing the campaign service. This information may be inserted with a typewriter or a ball point pen.
Each "Campaign Identification Label" is to be located on the radiator core support in an area which will be visible when the vehicle is brought in for periodic servicing by the owner. Apply "Campaign Identification Label" only on a clean, dry surface.
CLAIM INFORMATION
Submit a Product Campaign Claim with the information indicated below:
ATTACHMENT III NOTIFICATION LETTER
September 12, 1991
Dear Chevrolet Owner:
This notice is sent to inform you that Chevrolet Motor Division is conducting an emission recall campaign that includes your vehicle.
REASON FOR THIS RECALL
General Motors has determined that the throttle position sensor (TPS) on your 1991 truck/van may exhibit an intermittent low-output voltage. This condition may cause your transmission to have no overdrive and/or harsh transmission shifts.
WHAT WE WILL DO
To correct this condition, the existing TPS in your vehicle will be replaced with a new updated part. This service will be performed for you at no charge.
WHAT YOU SHOULD DO
Please contact your Chevrolet dealer as soon as possible to arrange a service date. Instructions for making this correction have been sent to your dealer. Please ask your dealer if you wish to know how much time will be needed to schedule, process and repair your ve.
The enclosed owner reply card identifies your vehicle. Presentation of this card to your dealer will assist in making the necessary correction in the shortest possible time. If you have sold or traded your vehicle, please let us know by completing the postage paid reply card and returning it to us. Should your dealer not schedule a service date within a reasonable time, you should contact the Chevrolet Customer Assistance Center by calling 1-800-222-1020.
If your dealer and the Customer Assistance Center are unable to remedy this condition within a reasonable time, you may wish to advise the Environmental Protection Agency, at the following address: Director, Manufacturer's Operations Division (EN-340F), United States Environmental Protection Agency, 401 M Street. S.W., Washington, D.C. 20460.
To ensure your full protection under the emission warranty made applicable to your vehicle by Federal Law, and your right to participate in future recalls, it is recommended that you have your vehicle serviced as soon as possible. Failure to do so could legally be determined to be lack of proper maintenance of your vehicle. Also, your vehicle may fail a state or local emission inspection test if this recall work is not accomplished.
We are sorry to cause you this inconvenience; however, we have taken this action in the interest of your continued satisfaction with our products.
Chevrolet Motor Division GENERAL MOTORS CORPORATION