From another forum https://frenchcarforum.co.uk/forum/...uld be ABS related.,it would be working again.
"Could be ABS related. Intermittent wheel speed sensors have been known to cause momentary complete loss of braking at very slow speeds around 5-10 mph. It usually only lasts for a fraction of a second so by the time you released the pedal and pressed again it would be working again.
I'm not so sure about whether it could happen at 70 mph though. Have you ever had the ABS system read for fault codes ? If it happens very rarely it could be a challenge to pin it down."
"The wheel sensors just generate a certain number of pulses per revolution which the ECU counts to determine the wheel speed.
The road speed is determined by the wheel(s) with the greatest rotational speed at a given instant, and any wheels deemed to be turning drastically slower than the fastest wheels (or not turning at all) when braking are assumed to be locking up and the brake for that wheel is momentarily released, with the ECU watching to make sure the rotational speed of the wheel increases again. (Consistency checks) Some cars tie the operation of the rear wheels together for ABS, but front is always independent.
So what happens if a wire to one of the sensors goes open circuit due to suspension movement flexing a broken cable ? As far as the ECU is concerned that wheel has just suddenly locked up as its no longer receiving pulses from it, so it will release the brake on that wheel.
However if after a certain time the wheel speed doesn't increase then the ECU will know that the lack of wheel speed signal is bogus because if the other wheels are doing 50mph and it released the brake on the wheel and it still says 0 mph half a second later it knows something is wrong and most likely the fault light will appear and it will start ignoring that wheel sensor.
There are a ton of consistency checks that the ECU does so they're not easily fooled, but a brief intermittent loss of connection to or short on the sensors triggered by suspension/cable movement can confuse the ECU momentarily.
On my previous Xantia every time the rear wheels went over a large enough judder bump at a slow speed of around 5-10mph if I had my foot on the brake as it hit the bump I could feel the pedal rapidly pulsate due to the ABS kicking in. (It never lit a fault light) I never did fix that but it was probably a broken wire to one of the rear sensors. My current Xantia doesn't do this"
ECM is related to the gearbox/transmission module isn't it, which had the error code?
One of the items on the invoice for repair was for a new front wear wire - is this related?
"Could be ABS related. Intermittent wheel speed sensors have been known to cause momentary complete loss of braking at very slow speeds around 5-10 mph. It usually only lasts for a fraction of a second so by the time you released the pedal and pressed again it would be working again.
I'm not so sure about whether it could happen at 70 mph though. Have you ever had the ABS system read for fault codes ? If it happens very rarely it could be a challenge to pin it down."
"The wheel sensors just generate a certain number of pulses per revolution which the ECU counts to determine the wheel speed.
The road speed is determined by the wheel(s) with the greatest rotational speed at a given instant, and any wheels deemed to be turning drastically slower than the fastest wheels (or not turning at all) when braking are assumed to be locking up and the brake for that wheel is momentarily released, with the ECU watching to make sure the rotational speed of the wheel increases again. (Consistency checks) Some cars tie the operation of the rear wheels together for ABS, but front is always independent.
So what happens if a wire to one of the sensors goes open circuit due to suspension movement flexing a broken cable ? As far as the ECU is concerned that wheel has just suddenly locked up as its no longer receiving pulses from it, so it will release the brake on that wheel.
However if after a certain time the wheel speed doesn't increase then the ECU will know that the lack of wheel speed signal is bogus because if the other wheels are doing 50mph and it released the brake on the wheel and it still says 0 mph half a second later it knows something is wrong and most likely the fault light will appear and it will start ignoring that wheel sensor.
There are a ton of consistency checks that the ECU does so they're not easily fooled, but a brief intermittent loss of connection to or short on the sensors triggered by suspension/cable movement can confuse the ECU momentarily.
On my previous Xantia every time the rear wheels went over a large enough judder bump at a slow speed of around 5-10mph if I had my foot on the brake as it hit the bump I could feel the pedal rapidly pulsate due to the ABS kicking in. (It never lit a fault light) I never did fix that but it was probably a broken wire to one of the rear sensors. My current Xantia doesn't do this"
ECM is related to the gearbox/transmission module isn't it, which had the error code?
One of the items on the invoice for repair was for a new front wear wire - is this related?
