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ABS/Handbrake warning light - quick, zero-cost fix |
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ChrisW
 
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  Member No: #1335
Location: Surrey |
I know there are a number of threads on this topic but this fix is so weird and effective that I thought it deserved a new thread. A few weeks ago I started to get the ABS - handbrake warning lights. Intermittent at first but getting more frequent until the warnings came on as soon as the car was started and nothing could remove them. The handbrake motor would operate but it would not latch. I was going to take it in for repair when I remembered that I had fixed the same fault about 10 years ago. This is what I had recorded in my logbook: To clear a "faulty handbrake/ABS" warning light 1. Stop car, put into park and put-on handbrake. Turn off engine and remove key. Wait a few seconds and replace key. 2. Turn key to ignition (position 1). Take-off handbrake. 3. Start engine. Drive off. 4. You may need to repeat this a few times to clear the fault. Crazy waste of time, I thought, but I followed the procedure to the letter. This time the handbrake did not latch-on in 1. But it did latch-on after turning key in 2. I released handbrake after starting engine in 3. The first time, nothing changed. Next time, there was a few seconds delay before the lights came on. Next time they came on after a few hundred yards. Next time they remained off permanently and have not come on again during several trips with lots of start-stop and handbrake on/off. I can see no reason for this. But the fix has worked on two separate occasions about 10 years apart. It is real (on my C6, at least)! It has saved me from what might have been a costly repair. The fix might be crazy. But the C6 is crazy in many ways. Why for example, route the ABS wiring above the fuel tank so that the tank has to be dropped to replace the sensor?! |
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MGmike
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   Member No: #3151
Location: South Queensferry |
That's very interesting. Do you know what error codes have been logged for this fault/fix? |
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ChrisW
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Member No: #1335
Location: Surrey |
I don't have a Lexia, so no error codes, I'm afraid. The whole thing is a bit of a mystery. ABS sensors are robust with no moving parts, etc, so why do they appear to fail so often? I assume that the Citroen engineers who designed the C6 were not intentionally evil and routed the wiring over the fuel tank in the expectation that the sensors would seldom, if ever, go wrong. It is perhaps plausible that my fault warnings may have reflected a bug in the ECU that was corrected by my weird procedure in the same way that switching off/on fixes my laptop when it is playing up. |
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C6Dave
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  Member No: #1
Location: Northumberland |
ChrisW wrote ... It is perhaps plausible that my fault warnings may have reflected a bug in the ECU that was corrected by my weird procedure, in the same way that switching off/on fixes my laptop when it is playing up. Basically rebooting the software. Interesting explanation and plausible. |
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cruiserphil
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 Member No: #38
Location: Celbridge |
Hello ChrisW, The beginning of a faulty brake pedal switch perchance?? Best regards, Phil C. |
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ChrisW
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Member No: #1335
Location: Surrey |
Thanks for all your replies. As my weird procedure did not affect any of the hardware in the car, I am inclined to believe that the root cause was a software fault. But I imagine it will be impossible to determine how my fix worked. I hope that someone with an ABS/handbrake fault will try my fix and report back on whether it worked or not. It seems to me that car electronics have become so complex that faults such as this are almost inevitable and very difficult to fix. For example a friend had a hybrid that would repeatedly shut down for no apparent reason when driving along. It couldn't be fixed and he had to get rid of it. Oh for the days of simple cars with no sensors or electronics, when fault diagnosis was easy. |
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