1997 Chevy Truck Transmission won't shift

BULLWHACKER

MEMBER
1997 CHEVROLET TRUCK

Transmission problem
1997 Chevy Truck Two Wheel Drive Automatic 130000 miles

I just bought a 1997 Chevy C2500 Truck 5.7 engine and auto 4L80? Transmission.

Everything works fine except the trans won't shift out of first gear.
Fluid is fine, fuse? I looked at all of the ones in the fuse box and none were found blown.

I shifts into first/low gear no problem and reverse fine; again it won't shift out of first gear.
Any idea why?
P.S. Where is that trans fuse I've seen mentioned; nothing shown on the fused box door?

1 Reply

DAVE H

MECHANIC
13,384 POSTS

Check fuse 20 in dash fuse box

LIMP-IN MODE
If sensor input signals are missing or inadequate for transmission operation, PCM will output preset operating signals to transmission. This mode will keep vehicle operational and allow it to be driven, with reduced transmission function and performance, to a repair facility. Malfunction Indicator Light (MIL) may light if malfunction occurs. Vehicle should not be driven for extended periods in limp-in mode.

To test electronic control of transmission solenoids, sensors and pressure switch assembly without using self-diagnostics or if self-diagnostics does not function, go to COMPONENT TESTS under ELECTRONIC TESTING. After repairs are made, DTCs should be erased from computer memory. See CLEARING TROUBLE CODES.

NOTE:If no DTCs are present and vehicle is in limp-in mode, check fused power supply circuit to transmission solenoids. Non-related transmission component system failure may cause this circuit fuse to fail. Fuses such as ERLS or SHIFT SOL fuse supply power to non-related transmission components (A/C clutch, EGR, EVAP, or ABS system) which may have caused fuse to fail.

NOTE:Trouble codes will be recorded at various operating times. Some codes require operation of affected sensor or switch for 5 seconds; others may require operation for 5 minutes or longer at normal operating temperature, road speed and load. Therefore, some codes may not set in a service bay operational mode and may require road testing vehicle in order to duplicate condition under which code will set.