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'05 Rendezvous, ABS/TRAC warning lights...
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mdevour
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Oct 27, 2015, 8:19 AM
Post #1 of 8
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'05 Rendezvous, ABS/TRAC warning lights...
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Hi all,
2004 Buick Rendezvous, 3.4 liter, FWD, ABS, Traction Control... I'm working on my brother's truck, trying to get the SES, ABS, TRAC, and Low Tire Pressure warnings to stop. One time recently while I was test-driving it for other work, it started up just fine and all the lights stayed off. After a few minutes of driving around, the ABS spiked for no reason while I was braking gently and the traction and ABS lights came on again... So it looks like things CAN work, occasionally. 
The first thing I'd like to do is check out the c305 connector in the floor pan behind the driver's seat, which seems to be notorious for causing things like this. I took the two connectors off from below and the terminals are clean and shiny. Treated them with contact cleaner and added some dielectric grease and re-sealed. No change in symptoms.
My first question: Is this connector a two-sided thing that the harnesses plug into from each side, or do the harnesses plug directly into each other through the body of this connector?
I just want to avoid taking apart the interior only to find the already greased connections I took care of from below.
If servicing that connector doesn't fix anything, I'll move on to probing the harnesses from the wheel sensors, but one thing at a time.
Thank you,
Mike D.
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Discretesignals
Ultimate Carjunky
/ Moderator
Oct 27, 2015, 8:47 AM
Post #2 of 8
(1342 views)
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Re: '05 Rendezvous, ABS/TRAC warning lights...
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Have you scanned the ABS module to see what trouble codes are being stored? You should do that before ripping the vehicle apart.
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
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kev2
Veteran
Oct 27, 2015, 9:00 AM
Post #3 of 8
(1340 views)
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Re: '05 Rendezvous, ABS/TRAC warning lights...
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remove seats, cleaning connectors, checking harnesses - before that I suggest you
1) get ALL codes.
2) check for TSB's
3) list anything that is NOT stock, remote start, alarm. any added BS...
more likely
" it looks like things DON'T work, occasionally.  " "the ABS spiked for A reason"
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mdevour
User
Oct 28, 2015, 4:14 AM
Post #4 of 8
(1316 views)
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Re: '05 Rendezvous, ABS/TRAC warning lights...
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Thank you for the replies, Jon, Kevin.
Have you scanned the ABS module to see what trouble codes are being stored? You should do that before ripping the vehicle apart.
You're exposing a weakness in my toolbox. My Actron 9575 doesn't do ABS, as far as I can tell.
I see there are adapters like the OBDLink products, and they offer add-on software to do the proprietary PID's. The budget is tight, so what's the cheapest combination of hardware/software that'll let me read ABS codes, given that I have access to a windows laptop and a couple of android smartphones?
2) check for TSB's
3) list anything that is NOT stock, remote start, alarm. any added BS...
Can I read service bulletins online somewhere? There are about 107 TSB's for this model to be seen at safercar.gov, but only summaries.
I have seen no sign of anything after-market or other than stock.
more likely " it looks like things DON'T work, occasionally. " "the ABS spiked for A reason"
No, really it almost never works. 
The usual mode is the warning lights come on within the first few seconds of driving.
Just now I tested it some. It looks like steering input might be the trigger. With it in park and the engine running, the warning lights turned on at near left lock, and after stopping and restarting, at part-way right... suggesting to me that at least the front wheel sensor harness(es) have problems.
Okay, that's new information.
Before I took on the repairs, another family member replaced the left front bearing/hub, and I didn't much like the way they routed the sensor wiring. I've since replaced the RF as well, and I thought I did okay with it, but it's definitely not how I'd design things.
If I wanted to probe the harnesses from the front wheel sensors at the firewall or inside, where would I be able to get at them?
Keep in mind that my time is cheap. If probing connectors with a multimeter will eventually tell me what a scan tool would, it's all the same to me.
Thanks,
Mike D.
(This post was edited by mdevour on Oct 28, 2015, 4:25 AM)
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Tom Greenleaf
Ultimate Carjunky
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Oct 28, 2015, 4:50 AM
Post #5 of 8
(1310 views)
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Re: '05 Rendezvous, ABS/TRAC warning lights...
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Quote:>>
Just now I tested it some. It looks like steering input might be the trigger. With it in park and the engine running, the warning lights turned on at near left lock, and after stopping and restarting, at part-way right... suggesting to me that at least the front wheel sensor harness(es) have problems.
Okay, that's new information.
Before I took on the repairs, another family member replaced the left front bearing/hub, and I didn't much like the way they routed the sensor wiring. I've since replaced the RF as well, and I thought I did okay with it, but it's definitely not how I'd design things.
If I wanted to probe the harnesses from the front wheel sensors at the firewall or inside, where would I be able to get at them? <<"
_______________________
I think that answers a lot of possible issues at once. Not sure of tire pressure warning but it's just colder in most places so possibly normal and needs air.
Now the key question is what the heck with parts not fitting exactly properly including wiring (was that moved?) and another working on it having a problem?
Vehicles with either or both ABS and traction controls are watching the speed of each wheel and deciding what to do for you. If it thinks a wheel is locked or spinning faster than another it will make what it thinks is appropriate action but wrong info in is wrong action happening. It gets confused and really should quit trying to help and just light up warnings of a system that's not right.
Example with ABS. Just slam on brakes on wildly slippery surface (safe area) and all wheels stop so it thinks vehicle isn't moving and doesn't need to do a thing if abrupt enough. You could still be sliding away at whatever speed it's sliding at.
Same if proper and one is skidding and others not acts on that one.
All this calculating is IMO confused by that one job you didn't do with that messed up by part or how installed and would be looking there.
Is that bearing even any good even if recent? IDK if an entire wrong one would fit at all but star wheels might not be right for that wheel first?
Just thoughts on this,
T
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mdevour
User
Oct 28, 2015, 9:40 AM
Post #6 of 8
(1299 views)
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Re: '05 Rendezvous, ABS/TRAC warning lights...
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Hi Tom,
Thanks for your thoughts...
Not sure of tire pressure warning but it's just colder in most places so possibly normal and needs air.
The first time I saw that, I checked the tires and topped them up. It doesn't seem temperature related. However, since there's no absolute pressures displayed, I think this system infers the pressure from the wheel speed stuff. So a dead or flaky sensor might do it?
Now the key question is what the heck with parts not fitting exactly properly including wiring (was that moved?) and another working on it having a problem? ... Is that bearing even any good even if recent? IDK if an entire wrong one would fit at all but star wheels might not be right for that wheel first?
I've seen Rendezvous/Aztec forum comments that complain about the design of these wiring harnesses. They're simply a couple of inches too short, and allow strain on the connectors and wires that no sane engineer should have accepted, apart from being vulnerable to snagging and road damage. They sell replacement harnesses, since they apparently go bad or get damaged so often.
I'm reasonably sure the hub unit I installed is the correct one. The other one looks right, but I don't know. What I'm more concerned with is if there's a wire broken inside its insulation or at a connector or hub. Once I can get an ohm-meter on the other end of the harnesses I can see if there's a wire opening up, and whether the coil resistances are right.
However, it's raining hard today and I don't have a garage to work in.  I'll get to it tomorrow! 
I'll have to trace the harnesses from the wheels to the firewall, unless somebody who's been in there before can tip me off as to where they end? I don't know if they'll be accessible at all, or from above or below?
Thank you,
Mike D.
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Oct 28, 2015, 10:10 AM
Post #7 of 8
(1295 views)
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Re: '05 Rendezvous, ABS/TRAC warning lights...
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! You said it already - wires too short! NO - that's "a" problem if not "the" problem. When something replaced isn't just as you replacing except not worn and new it should match exactly. How hard is it to check a new one and measure wires for you? Bet it's all wrong for some reason maybe nobody's fault.
Just to beat on it with techno info: Air as in tires and what we breathe. For each 10F change in temp you get 1PSI change in pressure up or down commensurately - exactly! When driven a tire warms up actually quite a bit. Read suggested pressure on door jam and put it to the max. Tires leak some over time by themselves thru good rubber even and should tolerate the added heat of lots of driving especially on highway.
They all say max pressure when COLD if you noticed.
Check out that wire,
Tom
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kev2
Veteran
Oct 28, 2015, 10:34 AM
Post #8 of 8
(1291 views)
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Re: '05 Rendezvous, ABS/TRAC warning lights...
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did a Quick TSB search with issue and your concern about c305 likely this is where the gossip concerning the connector originated.
your friendly dealer can help with TSB text... basically water maybe from HVAC, And connector corrosion BUT without a scanner to ID the codes its just a guess.
TSB # 01-01-38-009A
TSB # 01-08-45-005E
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