2002 4l80e 4wd wiring questions

strange1

strange1

Well-Known Member
Joined
Mar 31, 2005
Location
Elkin
I have an ‘02 1500hd that has not had reverse lights, and will not shift into 4lo, for as long as I have owned it (4-5 years maybe). Last week I decided to replace the position switch on the side of the transmission thinking that was most likely the problem, since the taillights and the connector under the bed are new. Some previous owner did a terrible hack job on the wiring, and the new switch did not change anything. After looking online I decided the 7-wire connector was missing a ground wire, so I ordered new pigtails and spent some time replacing them today. Still no change. Where else do I need to look? I’m thinking the 4-wire connector must be wired correctly as the truck will only start in park and neutral.

For the 4WD, it will shift between auto, 2wd, and 4hi just fine. But will not go from 4hi to 4lo. You can hear it clicking as if it’s trying to do something, but no grinding or jerking. Just noises that sound like the shift motor is trying to get lined up. Then it kicks back to the previous position.

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I'm not entirely sure, but I feel like they're separate issues.

I'd probably service the transfer case and make sure there's not any glitter sauce (or chunks) in there. Fresh fluid couldn't hurt either way. I'm not overly familiar with the 246 AutoTrac cases, but they're pretty similar the the 263s. There's the actuator on the front diff and an encoder (shift) motor on the side of the transfer case. Assuming the internals are good, none of the fuses are blown, and there's no TCCM codes, I'd have to lean towards the encoder motor. I'd check for codes first. You'd need a pretty decent scanner to see the codes. Off the top of my head, they'd probably be "U" codes. Similar to BCM fault codes, they usually point toward communication errors.

As for the backup lights... does the dash display properly when you shift through the gears? No blown fuse? (LP/BU and Veh BU) Bulbs good? All the other functions of the tail lights work? You can likely find the pinout for the NSBU plugs and check for power there. It may be in the wiring between the pigtails/NSBU and the reverse light socket itself. If I remember right, that wiring bundle is ground to the same crossmember as the spare tire hoist. The ground could be rough.
 
Croatan_Kid said:
I'm not entirely sure, but I feel like they're separate issues.

I'd probably service the transfer case and make sure there's not any glitter sauce (or chunks) in there. Fresh fluid couldn't hurt either way. I'm not overly familiar with the 246 AutoTrac cases, but they're pretty similar the the 263s. There's the actuator on the front diff and an encoder (shift) motor on the side of the transfer case. Assuming the internals are good, none of the fuses are blown, and there's no TCCM codes, I'd have to lean towards the encoder motor. I'd check for codes first. You'd need a pretty decent scanner to see the codes. Off the top of my head, they'd probably be "U" codes. Similar to BCM fault codes, they usually point toward communication errors.

As for the backup lights... does the dash display properly when you shift through the gears? No blown fuse? (LP/BU and Veh BU) Bulbs good? All the other functions of the tail lights work? You can likely find the pinout for the NSBU plugs and check for power there. It may be in the wiring between the pigtails/NSBU and the reverse light socket itself. If I remember right, that wiring bundle is ground to the same crossmember as the spare tire hoist. The ground could be rough.
Click to expand...
I jumped the 12v input to the reverse light input and they came (and stayed on) with tre ignition switch. I’m leaning towards the new switch being no good. The dash display does show the proper position. Will dig into the t-case at a later date.
 
It IS possible that it just needs minor adjustment. I've fought with some of them before to get them juuuuust right so it would read properly on the dash and trigger the backup lights. I'd probably play with it a little first :lol:
 
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