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Re: brake warning lights and pressure monitor switch Posted by Ari [Email] (#2847) [Profile/Gallery] (more from Ari) on Fri, 9 Oct 2009 06:48:52 In Reply to: brake warning lights and pressure monitor switch, weston, Wed, 7 Oct 2009 09:45:40 Members do not see ads below this line. - Help Keep This Site Online - Signup |
With a TCS car, the TCS light will be on if the ABS light is on. So troubleshoot the ABS light, and TCS will (hopefully) take care of itself.
You say the ABS light is on, but you didn't mention the Brake Fluid light. Low pressure is signaled by having BOTH the ABS and Brake fluid lights on; just the ABS light indicates a different problem.
Having the pump cycle after 4-5 pumps isn't the sign of a bad accumulator - it'll start running when the pressure starts to drop. Start the car and let the pump finish running. Then pump the brake pedal, hard and fast, until both the ABS and Brake Fluid lights come one. If the ABS is already on, see how many stabs to get the Brake Fluid light on. Over about 12 pumps before the Brake Fluid light comes on, the accumulator is just fine. 7-12 - weak. 6 or less - bad. Those thresholds are pretty arbitrary - 15 is great, 4 is bad, in the middle, is, well, in the middle.
So let's say that (1) you start the car, and just sit there. The ABS light stays on, but the Brake Fluid light flickers out after about 10 seconds or so. Normal. That implies you're reaching pressure. If the ABS light comes on when you first start the car and doesn't go off WITHOUT THE CAR MOVING, then the ABS is failing one of its start-up tests. There are a bunch, and without reading out the faults, it'll be hard to figure.
But a very common one is a bad ABS sensor. When the ABS first powers up, it check the resistance of all of the wheel sensors. If one is out of spec, the light stays on. The sensors should be all around 1100 ohms. I'm not sure what the fail limit is, but I'd take a meter, and at the connector up by the ABS unit, check the resistance of each sensor. If one is way out from the others, suspect that one.
If the ABS light comes on after the car starts moving, that means it isn't getting speed pulses - for that, check that metallic gunk hasn't built up in the shutter wheel teeth (gear) the sensors read.
I suspect you probably have a bad wheel sensor.
posted by 192.249.47...
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