Question about Volvo 850

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Abs light comes on intermitantly. changed some wiring to wheel sensor on two wheels. still comes on and off. should i change on all wheels to ecu.

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Intermittent ABS lights could be a wheel sensor but more commonly it is a sign your ABS controller is going bad. Eventually it will come on and stay on. If you have TRACS that will also come on and stay on. Eventually your speedometer will quit working. This site provides a rebuild service which is much cheaper than buying a new ECU. http://home.earthlink.net/~vicrocha/Volvo_Parts/Volvo_ABS_removal.htm

Posted on Oct 20, 2009

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Abs/brake light on in my 2004 dodge ram, changed wheel sensors/ speed sensors/ , checked fuses and noticed th a the Abs ignition run fuse circuit has no power flowing through it, fuse is good


The ABS light on Will Have to be deleted From the ECU Stored fault, regardless of any repairs. The fuse in question is only hot when a signal From ECU to ABS module is present.

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1996 toyota celica st202 abs light come on intermitently


While it may be an eletrical issue developing, it may also be internal to the hydraulics of the brake system. If the system was recently flushed, I would look at the wheel sensors first- make sure thery have not picked up debris and sensors are snugly mounted and wiring in good shape.

If the brake system has not been flushed with new fluid, the system should get flushed out next time brakes are serviced. This may mean an expensive repair, but it depands on how comfortable and experienced you are without ABS at all.

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I have toyota sienna 2002 . ABS warning is coming on and off while driving. I checked with the local mechanic. He changed the wheel air pressure censor and changed the connecting wires too. but still the...


The wheel air pressure sensor only records the air pressure, the speed sensor or as its sometimes called abs sensor sends the signal that abs is engaged. When they malfunction it can send a false signal that the wheel is sliding or going slower than the other wheels which can engage the abs system or cause the abs light to eluminate. Have your mech check the speed sensors and abs system.

Mar 22, 2011 | 2002 Toyota Sienna

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I have a 2000 Audi TT Quattro (180). Both my ABS and ESP light were on. I took it to my local garage who replaced a front wheel sensor which eliminated the ABS light. After a 30 mile drive the ESP light...


Check bearing and joint/knuckle on every wheel and even on the drive shafts, if there is lack/knocking, that could cause abs and esp light, because sensor doesnt give right information and ecu only records sensor fault but doesnt say why the infromation is wrong.
They changed the sensor but didnt solve the cause!!!

Feb 17, 2011 | 2005 Audi A3

1 Answer

My anti-lock brakes light on the dash is on....what could be causing this?


Problems with ABS can be frustrating. You have senors on the front wheels, you have wires that run to the sensors, plus you have the ECU mounted to the master cylinder or on the fire wall depends on other options. Now the wheel sensors work like little alternators. Your wheels will have a gear that the senor reads as the wheel turns and then creates an A/C voltage that tells the ECU unit that the wheels are turning. Having a ABS code could mean that wiring to one of the sensors is broken or has fallen off, or is corroded at the plug end. Your ABS system has four major parts the ECU, an ABS hydraulic unit and the wiring harness to the wheel sensors, then last the sensors themselves. You will need to check all the wiring harnesses to each If you have a multi meter you can read the voltage of each wheel sensor at the other end of its wiring harness. Jack up the front end and find the end of each wheel sensor harness and spin the wheels by hand. you should get a reading on the AC voltage scale of about ..45 volts. not quite a half volt. when the wheel stops the meter should go to zero. spin the wheel and the meter should show voltage. That will tell you if the sensor and the wiring is good. The ECU has no trouble shooting it is good or bad.can't help you there. same with the Hydraulic unit. Most times it will be a wire broken or a bad wheel sensor. Good hunting.

Oct 20, 2010 | Oldsmobile Cutlass Ciera Cars & Trucks

2 Answers

What to look for when your ABS light comes on. Is therea sensorthat needsto be replaced. Where are the ABS located on the car. Thanks


Problems with ABS can be frustrating. You have senors on the front wheels, you have wires that run to the sensors, plus you have the ECU mounted to the master cylinder or on the fire wall depends on other options. Now the wheel sensors work like little alternators. Your wheels will have a gear that the senor reads as the wheel turns and then creates an A/C voltage that tells the ECU unit that the wheels are turning. Having a ABS code could mean that wiring to one of the sensors is broken or has fallen off, or is corroded at the plug end. Your ABS system has four major parts the ECU, an ABS hydraulic unit and the wiring harness to the wheel sensors, then last the sensors themselves. Now learn what each part looks like I am posting pictures for you. You will need to check all the wiring harnesses to each part. Then check the sensors. here is the ECU unit --->> e6fbbf8.jpg --->>> Next is the Hydraulic unit.--->>>45dc6de.jpg--->>> Then the wheel sensors. --->>> 3d29687.jpg If you have a multi meter you can read the voltage of each wheel sensor at the other end of its wiring harness. Jack up the front end and find the end of each wheel sensor harness and spin the wheels by hand. you should get a reading on the AC voltage scale of about ..45 volts. not quite a half volt. when the wheel stops the meter should go to zero. spin the wheel and the meter should show voltage. That will tell you if the sensor and the wiring is good. The ECU has no trouble shooting it is good or bad.can't help you there. same with the Hydraulic unit. Most times it will be a wire broken or a bad wheel sensor. Good hunting.

Oct 18, 2010 | 1998 Ford Ranger SuperCab

1 Answer

ABS light stays on sounds like a abs pump is staying on. Is there a pump for the abs system?


There is no seperate pump. The following lines will give you more details

Braking force and the tendency of the wheels to lock up are affected by a combination of factors such as the friction coefficient of the road surface, and the difference between the vehicle speed and the road wheel speed. The ABS prevents the road wheels from locking up during heavy braking by controlling the vehicle's brake system hydraulic pressure.
During normal braking, as the rotational speed of the wheel falls, no electric current flows from the ECU to the hydraulic unit. The solenoid valve is not energized. The brake master cylinder hydraulic pressure is applied to the brake unit, and the ABS is not involved. However, even though the ABS is passive during normal braking, its control module is constantly monitoring for rapid deceleration of any of the wheels.
If a wheel-speed sensor signals severe wheel deceleration - which means the wheel is likely to lock up - the ECU sends a current to the hydraulic unit. This energizes the solenoid valve. The action of the valve isolates the brake circuit from the master cylinder. This stops the braking pressure at that wheel from rising, and keeps it constant.
If the sensors signal the wheel is still decelerating too rapidly, the ECU sends a larger current to the hydraulic unit. The armature moves even further and opens the valve. It opens a passage from the brake circuit. Brake fluid is sent from the brake circuit back to the master cylinder. Pressure in the brake caliper circuit is reduced so that the wheel is braked less heavily.
If the wheel sensors indicate that lowering the brake pressure is letting the wheel accelerate again, the ECU stops sending current to the hydraulic unit and de-energizes the solenoid valve. This lets the pressure increase, so that the wheel is again decelerated.
This cycle repeats itself about four to six times per second.
It is normal in an ABS for the valves in the hydraulic control unit to keep changing position as they change the brake pressure that’s being applied. These changes in position may cause rapid pulsations to be felt through the brake pedal.

Jun 06, 2010 | 2003 Chevrolet Silverado 1500

4 Answers

I have a 1997 Blazer. The ABS light comes on intermittently. When the ABS light is on the power windows and blower motor do not work. When the ABS light is off everything works just fine. Help????


That sounds strange about the power windows and the blower motor not working when the ABS light comes on. I happen to have a 99 Chevy blazer and I had the ABS light come on several times. There are ABS sensors on the two front wheel bearing hubs. If you take off the front wheels you will be able to see a black electrical cable that has 2 wires inside of it. This cable is coming directly from the ABS sensor on the wheel hub and is strapped to a bracket the is on the upper ball joint. From the hub it then goes to a plug connector that is under the protective flap that you lift to change your spark plugs. What I found that is a common problem is that wire tends to corrode or doesn't have enough slack in it when making turns and starts to pull and break. Examine that cable and if you see any breaks in it, that will cause the ABS light to come on. Also if you can get to the plug underneath the flap, unplug it and use a multimeter to see if you are getting any resistance on the two wires. If you aren't getting any resistance then your sensor is bad or you have a broken wire to the sensor. On my vehicle the ABS light kept on coming goin on and off intermitently and I found that wire from the sensor to the plug had a break in it. I stripped the wires back, spliced them together, soldered them and I used heat shrink tubing to cover the connections. The ABS light went out and it has been fine ever since. Hopefully this will solve your problem as well.

Jan 24, 2010 | 1997 Chevrolet Blazer

1 Answer

1998 f150 abs and park light on fluid good, feel no dragging


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1 Answer

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