At 70 mph on the highway, the rear diff lock indicator and ABS indicator both came on in my '99. The diff lock light went out and was intermittent for a while but is now on all the time. The ABS never went out. A quick spin in tight circles in a paved parking lot confirms that the rear diff is not locked. I'm on the road and have no choice but to press on. I'll be near a dealership soon (2 hours). Any suggestions?
ABS and Rear Diff Lock Lights
- Thread starter FAMAJ
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Cranked up to head to the dealer this morning. Rear diff is now locked. Switch is off. Great. 20 careful miles of paved road later, I'm waiting on diagnosis. Fingers crossed for a malfunctioning switch or relay and not something more expensive...
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- #3
Interesting finding. An exhaust leak at the muffler (previously unknown by me) was pointed right at the wiring harness. The harness is good and melted causing screwed up functions. I would have never thought of this. Keep in mind when you're chasing mystery gremlins. Seems to be a good dealer here in Panama City by the way.
Wow, that makes sense though. I can't remember each wire right now, but if the wire in charge of locking the diff were to get 12v then that would bypass all safety steps; (less than 5 mph, 4LO etc). Scary!
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- #5
But wait, there's more.
Dealer repairs the wiring harness. Rear diff is not locked. ABS light is not illuminated. All good? Nope. Within 10 feet of driving when I picked it up, I noticed that the center diff is locked - light is illuminated in dash and tires squeal when turning on pavement. Switch is in off position and no manipulation and driving back and forth will unlock the diff. Dealer said that they found "low voltage at the 4 wheel drive ECU" that is likely the culprit. I'm confused. Any help on these two would've appreciated:
1. I thought the center diff lock has a relay and the rear diff lock has a separate ECU. Can one affect the other?
2. Can I pull the center diff relay and disable the system and wind up in unlocked mode?
I tried searching and came up with a few threads on 80s but not on 100s. Thanks in advance.
Dealer repairs the wiring harness. Rear diff is not locked. ABS light is not illuminated. All good? Nope. Within 10 feet of driving when I picked it up, I noticed that the center diff is locked - light is illuminated in dash and tires squeal when turning on pavement. Switch is in off position and no manipulation and driving back and forth will unlock the diff. Dealer said that they found "low voltage at the 4 wheel drive ECU" that is likely the culprit. I'm confused. Any help on these two would've appreciated:
1. I thought the center diff lock has a relay and the rear diff lock has a separate ECU. Can one affect the other?
2. Can I pull the center diff relay and disable the system and wind up in unlocked mode?
I tried searching and came up with a few threads on 80s but not on 100s. Thanks in advance.
If you could get the center unlocked you could then disconnect it at the t-case and not have to worry about it re-engaging.
If you are forced you could disengage the center with a wiring diagram and some test leads (make connections to disengage the t-case and leave the connector un-plugged)
Seems odd that the center got involved but it sounds like the truck 'thinks' it is in LO and therefore is locking up the center and allowing the rear to lock as well? On a 99 you can't un-lock the center when in LO, only when in HI does it respect the dash button (unless pin 7 mod is done). Could it be that the LO interlock or signal circuit is common to both lock systems and is the common problem?
Also, the ABS light is lit when in LO.
If you are forced you could disengage the center with a wiring diagram and some test leads (make connections to disengage the t-case and leave the connector un-plugged)
Seems odd that the center got involved but it sounds like the truck 'thinks' it is in LO and therefore is locking up the center and allowing the rear to lock as well? On a 99 you can't un-lock the center when in LO, only when in HI does it respect the dash button (unless pin 7 mod is done). Could it be that the LO interlock or signal circuit is common to both lock systems and is the common problem?
Also, the ABS light is lit when in LO.
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- #7
ABS light is off. It still could think it is in low range though.
Test leads are a great suggestion. I'll see what I can manage. Famous last words: how much worse could I make it?
I may just have to park it until I have either more time to investigate or more funds for quality time at the dealer.
Test leads are a great suggestion. I'll see what I can manage. Famous last words: how much worse could I make it?
I may just have to park it until I have either more time to investigate or more funds for quality time at the dealer.
Really funny because this exact thing has now happened to me...
Does anyone know what part number this harness is??