l.chadburn

Hi guys I am a new member to this forum.
I drive a 1992 C4 Cab in Guards Red.
Spent the last 18months restoring a shed basically (will post some pics eventually)

Basically I want to pick any C4 owners brains who have had this problem.

When I start the car all is fine, however when I set off the PDAS and ABS light comes on as well as the warning light and the buzzer sound.

Thanks to Dave who has already gave me some checks to do, but before I look at spending more money just wanted to see what other drivers say about this issue and what were the outcomes.

regards lee

Jim Howley

For me it was a bad clutch slave cyclinder which was leaking.

Rocket Rob

Verify that your brake fluid reservoir is at the max. The C4 system will give faults if its not.

Crystal Cranks

Wheel speed sensor?

Kovic

For me it was water ingress into the ABS unit, had it cleaned and refurbed, seems to only happen to UK cars!

l.chadburn

I thought wheel speed sensor, had it on the computer and all it says is pump return?

I will check the unit for water over the wekend - cheers

boxsey911

One thing to check is that the ABS plug on the controller is seated correctly. I found that if you click it into place it might still be making partial contact. I found to get it to fully seat I had to hold up the silver clip while pushing it home. Sounds silly but caught me out the first time I unplugged mine - I kept getting the buzzer and ABS light (no PDAS because mine is a C2) until I figured it out.

l.chadburn

Cheers will have a look at that at the weekend. It's booked in on Monday to sort a slight hood problem, they did say they would have a quick glance at abs pdas

Scamper

I had this happen a while back, needed a new ECU as no-one was able to repair mine...

I am sure Dave has given you a comprehensive list but these are the things i would check;

ECU pins for corrosion/water ingress
Wheel speed sensors - check and clean - tends to attract duct/crap
Brake fluid level - system is very sensitive!
Earth contacts in front trunk - lots in there quick remove and clean required.

if you know someone else with a C4 see if you can swap ECU's - thats what the garage did to fault find my problem...French or German ebay is the cheapest and probably has the most units for sale....

l.chadburn

Cheers scamper will check the unit for water/corrosion.
Dont really know how to check the wheel sensors - do i just unplug them and clean - is it an easy job?
brake fluid is full.
will also check earth contact on battery and any other i can find.


unfortunately dont know anyone with a c4.

lee

l.chadburn

Just a thought, but if there is a wheel speed sensor not working properly - wouldn't this stop the spoiler lifting automatically?

My spoiler works fine.

lee

Computamedic

Lee,

The speed signal is generated by the wheel sensor on the front left. Any of the other three could be faulty without affecting the speed signal.

Regards

Dave

l.chadburn

Ok, cheers for that. i'll check the other 3.

lee

l.chadburn

Just found a chapter on testing them at the pdas / abs unit with a multimeter.
will do this at the weekend

l.chadburn

Right got impatient - just been in the garage

Removed the pdas / abs unit and blew all the dust out, no water or obvious corrosion marks, then sprayed with electrical cleaner.
whilst off i checked all 4 wheel speed sensors with the multimeter on the plug.
all 4 read around 960 ohms (book says they should be between 600 and 1600), therefore as my spoiler works I am assuming they are all fine due to the readings being similar.

like you say scamper - shame I cant try another unit!