'97 Picnic Abs Light Stays On

[Surv1v0r]

So far as I can tell (braking hard on gravel) my ABS is working fine. However, the ABS light stays on all the time. Any suggestions as to what the problem might be, whether I can resolve it myself or what a dealer is likely to charge to fix it?

TVM

[Richard KM]

So far as I can tell (braking hard on gravel) my ABS is working fine. However, the ABS light stays on all the time. Any suggestions as to what the problem might be, whether I can resolve it myself or what a dealer is likely to charge to fix it?

TVM

The best way is to jump on the brakes on the road, as ABS doesn't work as well on gravel. If you get a few chirps as the wheels lock up and then unlock, it's ok. If you get a long screech, the brakes are staying locked up. Usually if the ABS light is on, the ABS does not work. The brakes still slow you down, just will not stop the wheels from locking up. Probably one of the front wheel speed sensors, you would need to get it checked though, have replaced an ABS ECU before in a Picnic.

[Surv1v0r]

The best way is to jump on the brakes on the road, as ABS doesn't work as well on gravel. If you get a few chirps as the wheels lock up and then unlock, it's ok. If you get a long screech, the brakes are staying locked up. Usually if the ABS light is on, the ABS does not work. The brakes still slow you down, just will not stop the wheels from locking up. Probably one of the front wheel speed sensors, you would need to get it checked though, have replaced an ABS ECU before in a Picnic.

Many Thanks for that Richard. You seem to be right; on further testing, I don't believe that the ABS is active at all although the brakes still seem to work fine.

I have now contacted two Toyota main dealers to ask for quotes to fix this problem:

• Toyota Dealer A said that they would charge me £123 just to diagnose the problem without doing any other work. Replacement ABS Speed Sensor about £104.
  
• Toyota Dealer B said that they would charge me £57 to diagnose the problem. Replacement ABS Speed Sensor again about £104. Thy said that replacing a front sensor would cost about £290 in total unless they had problems removing it (it is a press fit) in which case the labour charge would increase. They also said that the rear speed sensor is not supplied with a wire and if that is required the charge would increase by about £45.

Googling around, I get the impression that diagnosing an ABS fault consists of plugging the ECU into a diagnostic set and looking up the resulting fault code - why this would cost £57, let alone £123 is a mystery to me???

The vehicle is a 1997 Toyota Picnic 2.0 GL Automatic with just under 100,000 miles on the clock; I had the OSF ABS Speed Sensor replaced three and a half years ago as part of a routine annual service and prior to its MOT.

Edited: Just 'phoned a local independent dealer who was actually MUCH more helpful that either of the main dealers. I have previously used them for MOTs but never to have work done on my car which I have always taken to a main dealer in the past.

He said that he would start by checking underneath the car to see if there was any obvious mechanical problem. If this didn't show up anything, he would then use a diagnostic system (at £55) to check out the ECU OBD codes. This would include a road test to ensure that all four sensors were reporting the same speed.

He confirmed (as suggested above) that the most likely cause of the problem was a faulty sensor but did warn me that diagnosis could be more involved and could potentially even involve replacement of the ECU, costing very much more.

Why aren't ALL dealers this helpful?

[Richard KM]

Many Thanks for that Richard. You seem to be right; on further testing, I don't believe that the ABS is active at all although the brakes still seem to work fine.

I have now contacted two Toyota main dealers to ask for quotes to fix this problem:

• Toyota Dealer A said that they would charge me £123 just to diagnose the problem without doing any other work. Replacement ABS Speed Sensor about £104.
  
• Toyota Dealer B said that they would charge me £57 to diagnose the problem. Replacement ABS Speed Sensor again about £104. Thy said that replacing a front sensor would cost about £290 in total unless they had problems removing it (it is a press fit) in which case the labour charge would increase. They also said that the rear speed sensor is not supplied with a wire and if that is required the charge would increase by about £45.

Googling around, I get the impression that diagnosing an ABS fault consists of plugging the ECU into a diagnostic set and looking up the resulting fault code - why this would cost £57, let alone £123 is a mystery to me???

The vehicle is a 1997 Toyota Picnic 2.0 GL Automatic with just under 100,000 miles on the clock; I had the OSF ABS Speed Sensor replaced three and a half years ago as part of a routine annual service and prior to its MOT.

Edited: Just 'phoned a local independent dealer who was actually MUCH more helpful that either of the main dealers. I have previously used them for MOTs but never to have work done on my car which I have always taken to a main dealer in the past.

He said that he would start by checking underneath the car to see if there was any obvious mechanical problem. If this didn't show up anything, he would then use a diagnostic system (at £55) to check out the ECU OBD codes. This would include a road test to ensure that all four sensors were reporting the same speed.

He confirmed (as suggested above) that the most likely cause of the problem was a faulty sensor but did warn me that diagnosis could be more involved and could potentially even involve replacement of the ECU, costing very much more.

Why aren't ALL dealers this helpful?

Basically they have to hook up to the scanner and read the codes, here in New Zealand, the Snap-On scanner is something like $10-14,000. So there would be a charge to help pay for the machine. They should clear the code and road test, and see what code returns. If a wheel speed sensor code has returned, they should then check the resistance of the sensor to confirm that it is faulty, usually 1000-1300 ohms. If it's open circuit, the sensor needs replacing, if it's ok, they'd have to check the wiring back to the ECU, if that's ok, the ECU might be faulty. The last thing they want is to check the codes, have it tell them that a wheel speed sensor is faulty, when it might be the ECU. They'd probably replace the sensor, then eventually replace the ECU, and have to charge you for both. Best to spend a bit more time and be sure that you get the correct part replaced.