ABS light comes on for a while after starting

[Volvo3000]

I'd really appreciate some help on this because we recently had a lot of welding and some paint done to keep this car on the road.

It's a 1992 940 2 litre manual automatic estate. When the engine is started (after not being run for a number of days) the ABS warning light is on for about 5-10 minutes. If it has been started recently then it comes on for a shorter time. Does anyone have any idea what could be causing this?

I looked online and found it can be related to a differential sensor etc.
Over the last few months the speedometer was jumping occasionally and I have got a repaired one (the same thing happened on my other 1992 940). The supposedly repaired one when installed is showing 80mph when the car is stopped. The thing is, I had one repaired before for my other 940 (common on 1992 940) and it didn't work properly so had to send it back to be repaired again. So now I can't say if there's a fault with the speedometer as well or the repair place has done a bad job again.

What is giving doubts about it being a sensor is that it only comes on for a certain amount of time.

[Forrest]

Does your car have the diagnostic A and B boxes under the bonnet? If so, put the probe into box A position 3 and read the codes for a clue as to what is triggering the fault.

https://www.volvoclub.org.uk/faq/Bra...cCodeRetrieval

If you have been having dash problems there may not actually be a fault. It could be due to a short on the PCB. Also, there is a small possibility if the diagnostics pinpoint a sensor that it is not the sensor but the controller that is faulty.

[J liddy]

I pin pointed the fault with the test you mentioned forrest open circuit . I can't remember the actual code reading when I irreplaceable my drivers side ABS sensor . If you are a bit handy with tools it's not a bad job .DISC .WHEEL BEARING will need to be removed then easy access to the ABS sensor which will need to be drilled out as it will be rusted solid into the hub there is a small bolt with allen key fitting spray that regularly with WD 40 or similar mine came off OK with gental easing .it's a job for a nice dry day if you do it on the drive like I do .if you require further advice let us know!

[Rversteeg]

The ABS system uses the same speed sensor signal from the rear axle speed sensor as the speedometer. So these problems could very well be related.

[jpliddy]

Originally Posted by Volvo3000

I'd really appreciate some help on this because we recently had a lot of welding and some paint done to keep this car on the road.

It's a 1992 940 2 litre manual automatic estate. When the engine is started (after not being run for a number of days) the ABS warning light is on for about 5-10 minutes. If it has been started recently then it comes on for a shorter time. Does anyone have any idea what could be causing this?

I looked online and found it can be related to a differential sensor etc.
Over the last few months the speedometer was jumping occasionally and I have got a repaired one (the same thing happened on my other 1992 940). The supposedly repaired one when installed is showing 80mph when the car is stopped. The thing is, I had one repaired before for my other 940 (common on 1992 940) and it didn't work properly so had to send it back to be repaired again. So now I can't say if there's a fault with the speedometer as well or the repair place has done a bad job again.

What is giving doubts about it being a sensor is that it only comes on for a certain amount of time.

ah yes reading your comments it may be not the front sensors although i come across the front sensors failures here , its quite a simple check if your car has the 2 black boxes fault finders the sensors are on ebay less than £28 now mine been on 3 years and is fine don't waste money on expensive ones

[Volvo3000]

Thanks for the advice.

The car has the single diagnostic box with 6 positions - with position 2 for fuel and 6 for ignition. I tried both pin 2 and 6 and there were no faults as it was reading 1-1-1 for both. I tried pin 3 but it doesn't do anything.

[Volvo3000]

The light was on and off intermittently for a bit, and now it comes on all the time.

Something I thought about is that - a few months ago we had some welding done not far from where the ABS unit is mounted. I was wondering if the heat from welding could have caused damage to the unit.

Any suggestions of what to do next would be helpful.

[griston64]

try cleaning the front wheel sensor magnet

other info here https://www.volvoclub.org.uk/faq/FAQ.../BrakesABS.pdf