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[terry paget]

1999 2 litre petrol manual saloon - new thread

Took my car to friendly Vx dealer with Tech2 and he says Front Right sensor absent. Great, think I. Problem solved. Not quite.

I unplug faulty sensor and plug in spare sensor, and turn on ignition. ABS light stays on. Puzzling. Compare both sensors with meter - both about 700 ohms.

I then attempt to remove front right sensor. Cannot turn allen screw - seems to be 5mm. Seems to be rusted in. New problem. Should I go in heavy, with torch and angle grinder, certainly destroying sensor, and not sure then if it would get out allen screw? Or could there be a break in the circuit somewhere else, and if so, where? Connector somewhere? ABS socket?

Please advise.

[steve6367]

I think the ABS light stays on until cleared by Tech 2 - not sure fixing the fault is enough.

Others who may know better will be along soon I am sure :-)

Steve

[terry paget]

Thanks Steve. That gives me hope. I have just plugged in another spare sensor (a rear one), but again the ABS light stays on. I hope you are right. Still funny the sensor stuck in place is 700 ohms, like the other two.

I see on e-bay I can but a complete hub with ABS sensor for £26. One solution if I cannot get the sensor out.

[Webby the Bear]

From what I've learned about resistance checks is that it could still give the right resistance but have failed from corrosion and stuff.... I think.

[henryd]

Thanks Steve. That gives me hope. I have just plugged in another spare sensor (a rear one), but again the ABS light stays on. I hope you are right. Still funny the sensor stuck in place is 700 ohms, like the other two.

I see on e-bay I can but a complete hub with ABS sensor for £26. One solution if I cannot get the sensor out.

It hasn't got to be the sensor at fault,could well be the wiring from the ecu to that sensor,tech 2 says its absent because maybe it can't "see" that sensor

[terry paget]

Thanks Henryd. Are there any connectors in the circuit between the sensor connector at the wheel and the multipin connector at the ECU? I doubt it's a broken wire. I suppose I could check continuity if I knew which pins or which colour wires  at the multipin connector are from the front right sensor. Does anyone know that?

[henryd]

Pins 4 and 5 at Ecu are front right sensor

[terry paget]

Many thanks, Henryd. Now I can proceed.

[2woody]

I think that once the sensor is changed, the light will stay on until the car has got to 5mph ( all wheels together )

[terry paget]

Thanks 2woody. That rings a vague bell of what happened when I repaired an ABS fault some years ago. My problem now is I cannot get out the original sensor (screw rusted in solid), am not convinced it is faulty (700 ohms resistance, same as all other sensors), and have yet to check continuity of loom from connector at wheel and multiconnector at ECU. Hours of fum yet preparing this car for MOT. Still have to change idler arm and handbrake.

[Andy H]

If the wires inside the ECU going to the pins 4 & 5 are fractured then the ECU will report that the wheel sensor is absent just the same as if the fault is external to the ECU.

[terry paget]

I agree, Andy H. However, I did change the ECU for one which was OK when removed from a scrapped car, and a fault was still present. I presumed the fault would disappear if it lay within the original ECU.