Red Brake warning light & chime - periodic problem

richardnewton

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The red "brake" dashboard light & chime periodically are warning us.

This happened about 10 times in the last week. Sometimes happens when we hit a bump but other times when just cruising in a straight line.

Once the light & chime begin, pumping the brakes or depressing/releasing the parking brake does not help. However, turning off engine and restarting clears red warning light & chime.

Brake fluid level is near top. All 4 disks & rotors were changed by mechanic last year and have little mileage.

I had fixed the ABS/traction-control warning lights last year by repairing the wire from the passenger-front hub. However those warnings have been on for the past few months.

Local mechanic looked at car and sees 3 wheel sensors not communicating but no other codes or issues.

Any ideas?

2003 Buick Rendezvous CX AWD.
 

richardnewton

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Personally, I "speculate" the wheel sensors are unrelated to the red "Brake" dash warning light. The mechanic thinks they may be related and one idea was to replace the three wheel hubs.

A few ideas popped up in internet search:

- Parking brake switch bad.

---> Parking brake seems to work fine and pressing the pedal did nothing to change the red "Brake" dash warning light.


---> WILL DISCONNECT

- The juncture box underneath the driver's seat is corroded or wet.
---> Popular failure area. It was cleaned two years ago and packed with dielectric grease. I removed cables again and it looked perfect; cleaned and packed with dielectric grease..

---> WILL CLEAN AND RECONNECT

- 3 long ABS sensor wires failed.
---> A few of the hubs are rather new; no humming.
--->

the long ABS wires are popular failure items on the Rendezvous (passenger front side was repaired last year)
---> Previously, failed ABS sensor wires never caused red "Brake" dash warning light

---> CONCERNED ABOUT RED "BRAKE" LIGHT SO MAY IGNORE THIS FOR NOW

- Bad EBCM
---> modulemaster in Moscow (Idaho) sells rebuilts for $150?
'02 LeSabre ABS Problem
http://modulemaster.com/rebuilds/instructions/ABS/Buick_Rendezvous_ABS.pdf

---> NOT SURE THIS COULD BE RELATED AND DON'T WANT TO BE THROWING PARTS AT THIS. WILL ASK MECHANIC IF ANY RELATED CODES (E.G. C1214)

- Check no calipers or the parking brake is binding.

- Check brake fluid level sensor
______________________________
 
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richardnewton

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Mechanic did a full review of brake system and several test drives and said car was fine to drive. He said 3 wheel sensors trigger codes indicating bad hub sensors or related wiring and might be cause of red "brake" light:

c0036 left rear
c0051 right rear
c0040 right front

At least one person cleared
"brake" warning with a new hub on the Rendezvous/Aztec/Montana/etc. forums. Several replaced EBCM.

So today, we checked the C305 connectors. There are three connectors: Big, Small white, Small black. It was a bit gritty inside and a few male & female pins were a bit tarnished. All grounds tested fine.

The small white 4-pin c305 connector is for the 2 REAR wheel speed sensors (AC signal & low reference pins for each wheel). One male pin was bent and one female was a bit corroded and oversized. The ABS sensors should read about 1000ohm and show increasing AC voltage with rotating wheels; they read nothing at c305.

-- After cleaning the c305 contacts with a toothbrush and contact cleaner, the left rear sensor tested fine at 1000ohms at c305.

-- I found two connectors going from the c305 to the right rear wheel. The intermediate connector was easy to reach and in perfect condition. The hub connector was in good condition but one contact was a bit green on both the male & female side; after cleaning that a few times, the right rear sensor also showed about 1000ohms at c305.

Ran out of daylight. So tomorrow, we will check the right front sensor; we patched about 2 feet of that wire a few years ago.
Will then check the wheel sensor readings at the EBCM.

Status
c0036 left rear (now reads correctly to c305)
c0051 right rear (now reads correctly to c305)
c0040 right front (to do)
Check ohms readings for all speed sensors at EBCM (to do)
Confirm all speed sensor codes, ABS light, red brake light cleared (to do)

c305 wiring
for similar Aztek:

c305 DIY photos repair of connectors and soldiering all connections similar Aztek:
C305-Ectomy (Lots of pics)

ABS module wiring (EBCM) for similar Aztek:
01 Aztek Looking for a ABS pinout and wire colors
 
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