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Wacky 3 channel/4 channel issue

This is a discussion on Wacky 3 channel/4 channel issue within the General Help forums, part of the LSx Technical Help Section category; Working on my buddies 99 Z28. The "original" job was for me to build him a 4 channel 10 bolt ...

  1. #1
    TunedByFrost supporter rel3rd's Avatar
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    Cranberry Red
    1971 Chevelle SS 402

    Question Wacky 3 channel/4 channel issue

    Working on my buddies 99 Z28. The "original" job was for me to build him a 4 channel 10 bolt rear and swap it for his 3 channel presently in the car...(he assumed that since the car has the ASR button, it had simply gotten the wrong rear installed sometime before he owned it)


    He has 3 channel rear in the car. Wiring harness has just the one wire going to the differential, plugging into the factory 3 channel ABS sensor. There's only the two brakelines going to each caliper, and where the wiring connector comes through the driver's side rear floorboard, it looks like it's all original and un-touched.

    Here lies the problem...

    Car has an ASR button on the dashboard, above the radio, where they usually are.
    Car has all the brake related warning lights illuminated.
    ASR, ABS INOP, BRAKE

    Owner of car checked codes and code said faulty left rear abs sensor...

    Now I KNOW that only 4 channel cars (ASR/TCS) have 4 wheel sensors.
    I also know that only 4 channel cars should have the ASR button.

    Like I said, code says LR sensor is bad, but the car definitely has a 3 channel rear in it right now, and it looks like it's been there forever...

    On my old 2000 SS, I am 99% sure that I had more wiring and brakelines than this car has, so what the heck is going on here?

    Does anyone have a picture of the 4 channel wiring/plumbing under the rear of the car? I strongly feel that this car's wiring/plumbing looks different than my old 2000 Camaro did.

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    Veteran Blackbird WS6's Avatar
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    does it have the ASR/TCS unit in the engine bay??

  3. #3
    TunedByFrost supporter rel3rd's Avatar
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    Cranberry Red
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    Quote Originally Posted by Blackbird-WS6 View Post
    does it have the ASR/TCS unit in the engine bay??
    You mean the motor or whatever it's called, on the passenger side strut tower?

    If this is what you mean, do you know how many hard lines are (or should be) connected to it?

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    Quote Originally Posted by rel3rd View Post
    You mean the motor or whatever it's called, on the passenger side strut tower?

    If this is what you mean, do you know how many hard lines are (or should be) connected to it?
    yea...

    you can see it in this thread with pics

    Official Show Your Engine Bay Pics!

  5. #5
    TunedByFrost supporter rel3rd's Avatar
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    It looks like every pic on that first linked page has THREE cables coming from it.

    The car in my driveway has TWO cables coming from it and the one hooked to throttle body looks to go in towards the firewall, NOT to the motor thing like the three cabled ones do.

    This car is supposed to be a B4C or whatever the code is for police type vehicle. If that makes any difference?

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    Veteran Blackbird WS6's Avatar
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    mines a 99 and i have 3 lines...one going to the TB and 2 going to the driveside firewall

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    Quote Originally Posted by rel3rd View Post
    It looks like every pic on that first linked page has THREE cables coming from it.

    The car in my driveway has TWO cables coming from it and the one hooked to throttle body looks to go in towards the firewall, NOT to the motor thing like the three cabled ones do.

    This car is supposed to be a B4C or whatever the code is for police type vehicle. If that makes any difference?
    yea i dont think that car has TCS in it

  8. #8
    TunedByFrost supporter rel3rd's Avatar
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    Quote Originally Posted by Blackbird-WS6 View Post
    mines a 99 and i have 3 lines...one going to the TB and 2 going to the driveside firewall
    Yours is 4 channel, I take it?

    Quote Originally Posted by Blackbird-WS6 View Post
    yea i dont think that car has TCS in it
    That's my thoughts as well....BUT, it does indeed have the ASR button, which is very weird. I know the dashlights (that are all lit up) aren't a great diagnostic tool, since I guarantee that they don't use different clusters for 3 channel vs. 4 channel cars...maybe it's some fluke, I'm dumbfounded....and kinda pissed that I totally rebuilt this guy a nice 4 channel rear (even welded the axle tubes to the center section) that is no good to him now...

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    Quote Originally Posted by rel3rd View Post
    Yours is 4 channel, I take it?



    That's my thoughts as well....BUT, it does indeed have the ASR button, which is very weird. I know the dashlights (that are all lit up) aren't a great diagnostic tool, since I guarantee that they don't use different clusters for 3 channel vs. 4 channel cars...maybe it's some fluke, I'm dumbfounded....and kinda pissed that I totally rebuilt this guy a nice 4 channel rear (even welded the axle tubes to the center section) that is no good to him now...
    yea mine has TCS and it works lol

    what was done to the rearend? just a stock rebuilt??

  10. #10
    TunedByFrost supporter rel3rd's Avatar
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    Quote Originally Posted by Blackbird-WS6 View Post
    yea mine has TCS and it works lol

    what was done to the rearend? just a stock rebuilt??
    TCS/ASR/ABS/4 channel/3 channel, blah LOL...

    Yes, stock, complete rebuild. Drivetrain rebuilding is what I do for a living, this was just a side job for my buddy.
    Started with low mileage (45K) housing and axles, cleaned and painted, welded axle tubes, new axle bearings and seals, new carrier bearings, new pinion bearings, solid adjustable pinion spacer, new pinion seal, gears are low mile 373's, and it is low mileage Torsen differential. He told me to sell it to cover what I have done so far, but I wouldn't even know what to ask if I did that...

    and it's VERY WEIRD that he gets a LEFT REAR WHEEL SENSOR code
    Last edited by rel3rd; 01-03-2011 at 05:05 PM.

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    Quote Originally Posted by rel3rd View Post
    TCS/ASR/ABS/4 channel/3 channel, blah LOL...

    Yes, stock, complete rebuild. Drivetrain rebuilding is what I do for a living, this was just a side job for my buddy.
    Started with low mileage (45K) housing and axles, cleaned and painted, welded axle tubes, new axle bearings and seals, new carrier bearings, new pinion bearings, solid adjustable pinion spacer, new pinion seal, gears are low mile 373's, and it is low mileage Torsen differential. He told me to sell it to cover what I have done so far, but I wouldn't even know what to ask if I did that...
    honestly yourl be lucky to see $300 for it (give or take)

  12. #12
    TunedByFrost supporter rel3rd's Avatar
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    Quote Originally Posted by Blackbird-WS6 View Post
    honestly yourl be lucky to see $300 for it (give or take)
    I know...

    The housing and axles were mine, bought as a complete 4 channel rear (minus backing plates), with a brand new Eaton differential, 342 gears, and an LPW girdle, for 150 bucks...

    I had the housing and axles laying around for 2 years and gave them to the guy, then he asked me about building him a rear....and here we are...

    I still have no clue why he is getting a bad LR wheel sensor code...

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    Quote Originally Posted by rel3rd View Post
    I know...

    The housing and axles were mine, bought as a complete 4 channel rear (minus backing plates), with a brand new Eaton differential, 342 gears, and an LPW girdle, for 150 bucks...

    I had the housing and axles laying around for 2 years and gave them to the guy, then he asked me about building him a rear....and here we are...

    I still have no clue why he is getting a bad LR wheel sensor code...
    hmmm...he was getting that code on the rearend you built OR the one he has in there now?

  14. #14
    TunedByFrost supporter rel3rd's Avatar
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    Quote Originally Posted by Blackbird-WS6 View Post
    hmmm...he was getting that code on the rearend you built OR the one he has in there now?
    well....That's how this whole episode started...

    He "thought" the car was a 4 channel and that someone had put a 3 channel rear in, sometime in the past, mainly due to the code he's getting, and knowing it doesn't have any rear wheel sensors at the moment. He bought all the bearings, seals, paint, etc., even the wheel speed sensors, and figured he'd just get me to build him a nice 4 channel rear to swap back in, but it doesn't look like (to me) that this car has ever been a 4 channel car.

    Why it has the ASR button, or why it's getting a faulty L.R. sensor code, is a mystery at this point.

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    Quote Originally Posted by rel3rd View Post
    well....That's how this whole episode started...

    He "thought" the car was a 4 channel and that someone had put a 3 channel rear in, sometime in the past, mainly due to the code he's getting, and knowing it doesn't have any rear wheel sensors at the moment. He bought all the bearings, seals, paint, etc., even the wheel speed sensors, and figured he'd just get me to build him a nice 4 channel rear to swap back in, but it doesn't look like (to me) that this car has ever been a 4 channel car.

    Why it has the ASR button, or why it's getting a faulty L.R. sensor code, is a mystery at this point.
    yea something doesnt make sense there OR we are missing something

  16. #16
    TunedByFrost supporter rel3rd's Avatar
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    Quote Originally Posted by Blackbird-WS6 View Post
    yea something doesnt make sense there OR we are missing something
    I think there is more to the story...all I know is what I see and what he's told me...unfortunately, the two versions don't jive together.

    What sucks is that I got the car all jacked up on stands, got some tools out, got the compressor all pumped up, hose unrolled, tires off, and then come to a standstill...not as bad if it wasn't 30 degrees outside, where I am working on it...

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    the car might have had TCS and then someone wanted to delete it and got a diff rearend and cable setup for the engine bay to they could delete the unit itself???

    does it look like it had a unit on the pass fender at some point???

  18. #18
    TunedByFrost supporter rel3rd's Avatar
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    Quote Originally Posted by Blackbird-WS6 View Post
    the car might have had TCS and then someone wanted to delete it and got a diff rearend and cable setup for the engine bay to they could delete the unit itself???

    does it look like it had a unit on the pass fender at some point???
    I guess thats possible. Just has that motor thingie, with the 2 cables.

    I think he wants me to just go ahead and swap the rears, then he'll worry about how to make it all work again...Thank GOD!

  19. #19
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    Quote Originally Posted by rel3rd View Post
    I guess thats possible. Just has that motor thingie, with the 2 cables.

    I think he wants me to just go ahead and swap the rears, then he'll worry about how to make it all work again...Thank GOD!
    so it has that unit on the fender?

    i think you should just install it and be done with it and out of your way

  20. #20
    TunedByFrost supporter rel3rd's Avatar
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    Quote Originally Posted by Blackbird-WS6 View Post
    so it has that unit on the fender?

    i think you should just install it and be done with it and out of your way
    I agree.

    Yes, it has the motor on the passenger side, but it has only TWO cables coming out of it. Cable to throttle body does NOT go to the motor, but looks to go right back to firewall...

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