ABS light on Codes indicate a faulty valve, Pump or Control Unit?????

[Evan Evans - LNS]

ABS light comes on in my '95 M3 w/ 72K on it. I read the codes and it says faulty valve. I take it to the dealer and they say faulty valve, BUT want to put a new control unit in first ($950) my cost plus labor. How often does a ABS control unit go bad?

Now I'm getting info that the pump is the problem. Another list member said he had the same problem and took the pump out, put it on a bench found out there was a bad connection at one point on the board. He resoldered it and Viola, end of problem. One would think that if you have a faulty valve code that it has a real good chance of being in the pump somewhere. I know that's not a sure thing, but if I fix the friggin' control unit and it doesn't fix my problem guess what's next. So do you have any source for a pump in good condition or confirmation that the above experience w/ the pump is on target?

TIA

Evan

[romabimmer]

Which control unit? There's the hydraulic control unit (HCU) and the electronic control unit (ECU).

The HCU has the valves. 99.9% of the time the OEM (BMW in this case) will only sell the entire sub-system, be it the HCU, or ECU or pump and will not allow the dealer service dept to repair, just replace.

Sometimes they only allow the entire ICU (which is HCU, pump and ECU) to be replaced. They do this out of fear that some one will screw up a repair and cause an accident.

[Evan Evans - LNS]

In answer to which pump? It's the hydraulic pump under the hood. My mechanic thinks that the solenoid has been damaged and the driver's side rear valve is faulty in the open position. Now I need a good source for a donor pump. Any suggestions?

TIA

Evan

[romabimmer]

Best bet is to replace the entire ABS unit with a rebuit unit. Get the Bosch (pretty sure it's Bosch) part number off the ABS unit in your car. I say get the Bosch number because I can promise you that same ABS unit is on many different cars, not all BMWs.

Then go to some auto parts stores and see if they have or can get a rebuilt unit. It's the cheapest way because there's a good amount of labor in rebuilding the unit and your mechanic will charger for it.


Only thing you'll need from the old one is the ECU, that black box the with the connector.

Once you have a rebuilt unit it's just a matter of bolting the thing in and refilling the system with brake fluid.

[romabimmer]

Other option:

This is more labor intensive and requires care. Order a new "dressed valve block", that means it has all parts and seals. Then take off the pump and ECU and mount those to the new valve block (HCU).

Only thing is that the pump mounting surface needs to be clean to make it seals well or it will leak.

FYI: With ABS cars (and espcially traction control cars) you MUST bleed the brakes every 2 years or 24,000 miles or the valves go bad.

[Evan Evans - LNS]

I've been calling around looking for a used pump and no one so far has one. I would expect that there aren't many laying around.
I thought I might find one off a racer's car that has taken off the ABS. Do you have any suggestions where else I might look for a '95 BMW M3, I've been told that the pump is unique for this model.

[romabimmer]

I doubt it's that unique. It may be unique to BMW, but it's somewhere else.

The only other option is salvage yards. Cars get wrecked and then taken apart and sold as parts.

Otherwise you'll have to go to buy new.

Also, go here and post in the want to buy sections some one may have race preped their car and have an ABS unit for sale:

http://www.bmwplanet.com/

http://www.dtmpower.net/forum/