Engine Controls - Improved Driveability/False MIL Lamp

87chevy11

GMC NUMBER: 88-T-25


GROUP: 6E - Engine Emissions

DATE: July, 1987

CORPORATE
NUMBER: 836501
SUBJECT: REVISED PROMS - TO IMPROVE DRIVEABILITY AND ELIMINATE FALSE "SERVICE

ENGINE SOON" LIGHTS

MODELS: 1987 R/V, G AND 1988 C/K MODELS WITH 5.0L (VIN CODE H) AND 5.7L (VIN CODE K) ENGINES AND LIGHT DUTY EMISSIONS
Some 1987-88 R/V, C/K and G models with TBI engines may experience one or more of the following driveability conditions and/or false codes. If these conditions are experienced, they can be repaired by replacing the PROMS. The new PROMs went into production in mid June, 1987.

DRIVEABILITY CONDITIONS - 5.0L (LO3) TBI ENGINE

1. Rolling, hunting or surging idles
2. False Code 54 - Fuel pump circuit (low voltage)
3. False Code 43 - ESC fault
DRIVEABILITY CONDITIONS - 5.7L (LO5) TBI ENGINE

1. Rolling, hunting or surging idles.
Notice: In addition to the PROM change, it will be necessary to reset minimum idle speed, per the procedures on PG 4-22 of the Driveability and Emissions Book.
A. Automatic (Drive) 425 plus or minus 25 RPM
B. Manual (Neutral) 500 plus or minus 25 RPM
2. Low speed road load surge
3. Detonation and weak acceleration during warm-up
4. Poor cold starting at minus 20 degrees Fahrenheit
5. False Code 24 - Vss circuit fault when using 4 wheel drive low lock.
To repair the above conditions install PROMS per the following charts.


L03 (5.0L) ENGINE


BODY STYLE SERIES TRANSMISSION EMISSION SYSTEM PROM NO.

Pickup 10/1500 3 Spd. Auto (M40) Fed. (NA5) 16073446
Pickup 10/1500 3 Spd. Auto (M40) Alt. (NA6) 16073245
Pickup 10/1500 4 Spd. Auto (MD8) Fed. (NA5) 16073430
Pickup 10/1500 4 Spd. Auto (MD8) Alt. (NA6) 16073250
Pickup 10/1500 4 Spd. Auto (MD8) Calif. (NB2) 16073417
Pickup 10/1500 4 Spd. Man (MY6/M20) Fed/Alt (NA5/NA6) 16073460
Suburban 10/1500 4 Spd. Auto (MD8) Fed/Alt (NA5/NA6) 16073395
Suburban 10/1500 4 Spd. Auto (MD8) Calif. (NB2) 16073399
Pickup 20/2500 4 Spd. Man (M20) Fed/Alt (NA5/NA6) 16073352
Pickup 20/2500 3 Spd. Auto (M40) Fed/Alt (NA5/NA6) 16073347
Blazer/Jimmy 10/1500 3 Spd. Auto (M40) Fed/Alt (NA5/NA6) 16073347
Pickup 4WD 10/1500 3 Spd. Auto (M40) Fed/Alt (NA5/NA6) 16073347
Pickup 20/2500 4 Spd. Auto (MD8) Fed/Alt (NA5/NA6) 16073442
Blazer/Jimmy 10/1500 4 Spd. Auto (MD8) Fed/Alt (NA5/NA6) 16073442
Pickup 4WD 10/1500 4 Spd. Auto (MD8) Fed/Alt (NA5/NA6) 16073442
Pickup 20/2500 4 Spd. Auto (MD8) Calif. (NB2) 16073435
Blazer/Jimmy 10/1500 4 Spd. Auto (MD8) Calif. (NB2) 16073435
Pickup 4WD 10/1500 4 Spd. Auto (MD8) Calif. (NB2) 16073435
Blazer/Jimmy 10/1500 4 Spd. Man (MY6/M20) Fed/Alt (NA5/NA6) 16073334
Pickup 4WD 10/1500 4 Spd. Man (MY6/M20) Fed/Alt (NA5/NA6) 16073334
Chevy Van/
GMC Vandura 10/1500 3-4 Spd. Man (M62/MY6) Fed/Alt (NA5/NA6) 16073376
Chevy Van/
GMC Vandura 20/2500 3-4 Spd. Man (M62/MY6) Fed/Alt (NA5/NA6) 16073376
Chevy Van/
GMC Vandura 10/1500 4 Spd. Auto (MD8) Fed/Alt (NA5/NA6) 16073386
Chevy Van/
GMC Vandura 20/2500 4 Spd. Auto (MD8) Fed/Alt (NA5/NA6) 16073386
Chevy Van/
GMC Vandura 10/1500 4 Spd. Auto (MD8) Calif. (NB2) 16073390
Chevy Van/
GMC Vandura 20/2500 4 Spd. Auto (MD8) Calif. (NB2) 16073390
Chevy Van/
GMC Vandura 10/1500 3 Spd. Auto (M40) Fed/Alt (NA5/NA6) 16073380
Chevy Van/
GMC Vandura 20/2500 3 Spd. Auto (M40) Fed/Aft (NA5/NA6) 16073380
LO5 (5.7L) ENGINE


BODY STYLE SERIES TRANSMISSION EMISSION SYSTEM PROM NO.

Pickup 10/1500 4 Spd. Auto (MD8) Fed/Alt (NA5/NA6) 16081140
Chevy Van/
10/1500 4 Spd. Auto (MD8) Fed/Alt (NA5/NA6) 16081140
GMC Vandura Chevy Van/
GMC Vandura 20/2500 4 Spd. Auto (MD8) Fed/Alt (NA5/NA6) 16081140
Suburban 10/1500 4 Spd. Auto (MD8) Fed/Alt (NA5/NA6) 16081146
Pickup 4WD 10/1500 4 Spd. Auto (MD8) Fed/Alt (NA5/NA6) 16081146
Pickup 20/2500 4 Spd. Auto (MD8) Fed/Alt (NA5/NA6) 16081146
GMC Rally/
Chevy Sportvan 30/3500 4 Spd. Auto (MD8) Fed/Alt (NA5/NA6) 16081146
Pickup 10/1500 4 Spd. Auto (MD8) Calif. (NB2) 16081152
Chevy Van/
GMC Vandura 20/2500 4 Spd. Auto (MD8) Calif. (NB2) 16081152
Suburban 10/1500 4 Spd. Auto (MD8) Calif. (NB2) 16081157
Pickup 4WD 10/1500 4 Spd. Auto (MD8) Calif. (NB2) 16081157
Pickup 20/2500 4 Spd. Auto (MD8) Calif. (NB2) 16081157
GMC Rally/
Chevy Sportvan 30/3500 4 Spd. Auto (MD8) Calif. (NB2) 16081157
Pickup 10/1500 4 Spd. Man (M20) Fed/Alt (NA5/NA6) 16081163
Blazer/Jimmy 10/1500 4 Spd. Man (M20) Fed/Alt (NA5/NA6) 16081163
Pickup 10/1500 5 Spd. Man (MG5) Fed/Alt (NA5/NA6) 16081185
Suburban 4WD 10/1500 4 Spd. Man (M20) Fed/Alt (NA5/NA6) 16081168
Pickup 4WD 10/1500 4 Spd. Man (M20) Fed/Alt (NA5/NA6) 16081168
Pickup 20/2500 4 Spd. Man (M20) Fed/Alt (NA5/NA6) 16081168
Pickup 4WD 10/1500 5 Spd. Man (MG5) Fed/Alt (NA5/NA6) 16081190
Pickup 20/2500 5 Spd. Man (MG5) Fed/Alt (NA5/NA6) 16081190
Pickup 10/1500 4 Spd. Auto (MD8) Export 16081174
Pickup 20/2500 4 Spd. Auto (MD8) Export 16081174
Chevy Van/
GMC Vandura 10/1500 4 Spd. Auto (MD8) Export 16081174
Chevy Van/
GMC Vandura 20/2500 4 Spd. Auto (MD8) Export 16081174
Chevy Van/
GMC Vandura 30/3500 4 Spd. Auto (MD8) Export 16081174
Pickup 10/1500 4 Spd. Man (M20) Export 16081180
Pickup 20/2500 4 Spd. Man (M20) Export 16081180
Suburban 10/1500 4 Spd. Man (M20) Export 16081180
Suburban 20/2500 4 Spd. Man (M20) Export 16081180


Use applicable Labor time and Operation number.