K 2500 Truck 4WD V6-262 4.3L VIN Z (1992)
PROM - Programmable Read Only Memory: All Technical Service Bulletins
A/T - Lack of Power At Highway Speeds, 4L80E in Hot Mode
Number:
92-236-6E
Section:
6E
Date:
JULY 1992
Corporate Bulletin No.:
236509R
ASE No.:
A1, A8
Subject:
LACK OF POWER/TRANSMISSION HOT MODE
Model and Year:
1991-92 C/K, RV, G AND P TRUCKS WITH 4.3L, 5.7L, AND 7.4L ENGINES
Condition:
Some owners of 1991-92 trucks with 4.3/5.7/7.4L engines and 4-speed automatic transmission (4L80E) may comment on the following conditions:
4.3L (RPO L84 with MT1 transmission)
5.7L (RPO L05 with MT1 transmission)
1.
Transmission converter clutch (TCC) is locking too early in 2nd, 3rd, and 4th gears and may be perceived as lack of power at highway
speeds.
7.4L (RPO L19 with MT1 transmission)
1.
Transmission converter clutch (TCC) is locking too early in 2nd, 3rd, and 4th gears and may be perceived as lack of power at highway
speeds.
2.
Tach needle flutters on decelerations.
3.
Catalytic converter odor.
Cause:
4.3/5.7L with MT1 transmission
1.
Transmission hot mode, which causes TCC lock-up in 2nd, 3rd, and 4th gears, entry temperature is too low.
2.
Thermac door in air cleaner may not be fully opening. This may cause the engine to operate on warm air, lowering power.
7.4L with MT1 transmission
1.
Transmission hot mode, which causes TCC lock-up in 2nd, 3rd, and 4th gear, entry temperature is too low.
2.
Engine fuel calibration is not optimal.
3.
At idle, the engine goes into an open loop condition which does not provide precise fuel control, possibly leading to catalytic converter odor.
4.
Thermac door in air cleaner may not be fully opening. This may cause the engine to operate on warm air, lowering power.
Correction:
4.3/5.7L with MT1 transmission
