dimma man

Hello, I have a problem on my 964 c4 from 89. Last week as I was driving I had the abs/ traction control lights come on the dash. When I scan the abs/traction control system with scantool it shows no fault codes. I tried bleeding the accumulator and dual solenoid valve block, But that didn't do anything.

When I test drove it the other day the abs/traction control lights went on and of while driving. The beeping noise and "!" also work.

Thanks

Mikke_Possu

Will abs works?

Did you try clean accelerometer?

dimma man

car drives normally, I didn't brake hard enough to test the abs.

I bridged relais 34 that didn't help.
cleaned the ground on the battery but looked good
sprayed contact spray on the pdas control unit plug

Goughary

With the car off, pump the brake pedal until it goes dead hard. Get a timer. Turn the key on, and time the pressurization of the accumulator. It should take approx one minute to pressurize the accumulator. If it takes over 1.5 mins, you need to think about changing that.

Once it's pressured, still with the key on, pump the brakes, every few pumps your pressure pump should turn on and it should run for a short time to pressurize the system. If the beeping occurs on your dash while you are doing this, you'll know it has something to do with pressurization. But you'll also be able to determine by listening and timing , whether that's the issue. If all well, move on to the next...

dimma man

cleaned out the accelerometers and measured them both seem ok. pin 1 and 3, 5v pin 2 should be around 2.7v I measured 2.5v so I think thats OK. no short circuit

dimma man

@Goughary All seems well the pressurization takes a little more then 1 min, but certainly not more then 1,5 mins. If its pressurized and I press the brakes 3-4 times it pressurizes again for a short while. So that would be OK.

Thanks for the help so far everybody

Goughary

Next up check your grounds. There are many.

Then look into the abs relays and abs sensors. Take the wheel speed sensors out and clean them.

The accelerometers aren't likely causing the issue but cleaning them is always a good idea if it hasn't been done.

Just hit one thing at a time. And continually try to replicate the problem. Post here after each so we can see what tracked it down and help as we can along the way.

dimma man

Thanks, tomorrow I will take it for a test drive. And will start checking Grounds.

dlpalumbo

Could an intermittent wheel sensor cause this behavior?

dimma man

cleaned the grounds in the luggage compartment, no improval. Now a different question, My problem started after doing some maintenance, oil change, new seals on the lower valve covers. So offcourse I also removed the spark plug wires. Can the problem be a faulty spark plug wire??? does anybody know the resistance for the spark plug wires.

JasonAndreas

Did you set the spark plug wires back in the plastic clips on the valve cover? So that the wires are not directly touching the engine?

dimma man

yes they are in they are in the plastic clips.

dimma man

Today I finished bleeding the pdas cilinders on the gearbox. some air and dirt came out, must have been a long time. Went for a drive and problem still isn't solved. Then I used scantool again to scan the abs/pdas I now have faultcode:

15: Control unit defective
34: Valve relay(is this relay r34)

any suggestions?

Goughary

Take the plug out of the PDAs controller and look at the pins. Some have gotten water and subsequent corrosion in there. Make are thats all clean.

Test your relays. There is a diy on rennlist somewhere for testing them.
The relays get expensive - so test them before replacing- since they either work or they don't. No need to replace if they function.

dimma man

cleaned another ground(passenger side at the firewall). checked the pdas plug, no visible corrosion, looks clean.

going to look for the relay test now