Brakes: ABS/TRACS Fault

[richmac]

Hi,

Does anyone have experience/ knowledge of the following, please?

97/98 V70 2.5T

ABS + TRACS lights on with Code 443, which won't clear. Live data also indicates no signal from the front left accelerometer. All other readings normal.
The wiring and insulation all look in good condition.
Brake are otherwise fine although I was starting to suspect an internal MC leak due to slightly changng pedal pressure/position. I've bled the ABS but it was fine.

1. Where is the accelerometer?
2. Anything else I can check before I remove the whole unit and send it off to an expert.

BR,

Rich.

[Luxobarge]

"Accelerometer" is almost certainly another (confusing) word for the ABS sensor. I'd suspect your fault is either that sensor has gone faulty or it's the usual dry solder joints in the ABS ECU itself - both are pretty easy to rectify yourself, in the case of re-soldering the ECU it's a pretty much free fix too. Extremely unlikely that the ECU has gone faulty for any other reason, they're very reliable apart from the bad solder joints, which is a very common fault on these, especially on V70 models.

[volvo again]

As Luxobarge says, plus it may be worth checking the reluctor ring(s)

[richmac]

Thanks. Are the P1 V70 ABS sensors multi-channel? I have good live data signals from the speed and wheel channels. The P2 V70s seem to have sensors under the seats as well.

[SteveSarre]

Hi Richmac,

The 2 reluctor rings are the toothed metal rings on the fat part of the CV joints. They sometime get so rusted or scraped or cracked that they don't trigger the ABS sensor (which sits in the wheel spindle just below the front shock). Have a look at your reluctor rings.

The reluctor rings are cheap, but to replace it you have to disconnect the CV from the hub, remove the old ring and then sweat (heat) the new ring on. Almost easier sometimes to replace the whole CV joint (after market joints are cheap and will include a new reluctor ring).

The ABS sensor also sometimes fails. it is held in by a 10mm bolt, but the sensor is in a plastic housing which sometimes get well stuck in its hole, so be gentle if you pull it out.

Not sure how much a new sensor costs, but worth finding out.

HTH
Steve

[SteveSarre]

Hi Richmac

Skandix don't ship to UK but they are a useful source of information


https://www.skandix.de/en/spare-part...-axle/1010522/

Your ABS sensor Volvo part number is probably 6849311


Steve

[richmac]

Thanks Steve. My rings are all good thankfully and I'm getting strong, equal readings from my sensors in the 'normal' channels. It's the acceleromter feed that's missing from the front left so I'm trying to figure out where the module gets this signal from - ABS sensor or something like a yaw sensor. I'll give the ABS sensor a good clean anyway and see what happens.

[SteveSarre]

Hi Richmac,

What reader are you using? Do you use that to both read codes and to read live data?

In 97/98 V70 2.5T I haven't heard of any accelerometer.

HTH
Steve

[richmac]

Hi Steve,

I didn't think TRACS had them either but I'm getting a real time ACC reading for each wheel in 'g' as well as a total.

I use an iCarsoft unit.

BR,

Rich.

[SteveSarre]

Grasping at straws.

Has iCarsoft correctly detected the car (make model year etc)?

HTH
Steve