L76

Hi Guys,

I had an earlier post on this one... a bit elusive... but wonder if anyone else has had problems with the ABS Modulator (not the EBCM, but the hydraulic pump for the ABS system)? I think this is the source of my problems, wondering what your thought are? Here's my situation (2001 6 Speed Manual):

1. Replaced brake rotors, pads, and wheel hubs (with wheel speed sensors), and shocks on all four wheels.

2. Flushed the brake fluid and bled the brakes the old-fashioned way (one person in car, and me on the bleeders).

3. Car road fine for a week, but then all of a sudden one day the ABS and Active Handling went bananas without any fault codes. ABS activated every time I braked and the active handling came on with such frequency (under normal driving conditions) that I had to turn active handling off to just drive down the road.

4. Sent the EBCM in to be tested - it checked out "fine." Pulled the steering wheel position sensor... and still had ABS issues. After shutting car off I hear an electric pump (which sounds close to the brake booster or somewhere on driver's side) pump for approx 10-15 seconds.

5. Took the car to a local (good) shop and had them bleed brakes (with a Tech 2) and put new tires on car. Still having problems with ABS - and had to unplug the steering wheel position sensor to get the car down the road. Electric pump still runs for 10-15 seconds after I shut the vehicle off.

I am suspecting that the ABS Modulator (the hydraulic pump - not the EBCM) is bad. Are there diaphrams or other parts internally that could have been "blown out" causing the ABS not to pressurize properly and thus the hydraulic pump is working overtime? Anyone else have a similar problems? What was the cause of your problems?

P.S. Anyone know of a service that rebuilds (or sells rebuilt) the ABS Modulators?

Thx,
Dennis

Bill Curlee

NOTHING in that Brake Pressure Modulator Valve, is electronic except the Pump motor. The Pump Motor gets its power from the EBTCM. Something in the EBTCM is commanding the motor to run and fire the solenoids/poppet valves to apply the brakes on what ever wheel/s is/are active.

Either the EBTCM micro processor is corrupt and sending out bad commands to the motor and solenoids,,,, OR ,,,,, you have a sensor issue that is sending signals to the EBTCM and telling it you have the steering wheel pointed in X direction and the car is going in Y direction.

Here is the schematic for the EBTCM power, ground and it shows you how the coils are arranged:



Here is a removed and separated EBTCM and the BPMV. As you can see, the coils operate a mechanical poppet valve that is locates inside a sealed spindle.









Electronic board and coils removed from the EBTCM:



The only other device with wires on a BPMV is the Brake Pressure sensor:







Even if you have an early C5 EBTCM/BPMV, the brains for the module and all of the active electronics is still located in the EBTCM portion of the system:

L76

Thx Bill. I sent the EBCM to ABS fixer - and they said it is operating perfectly. I have new wheel hubs (which include the wheel position sensors). I have disconnected the steering wheel position sensor - and I still have ABS issues and some electronic pump/motor runs every time I shut the car off. I believe this is the hydraulic pump in the abs modulator. I understand what you are saying about the EBCM - and the sensors. Based on what you are saying, I need to either come to grips with a) the abs fixer guys are wrong - and my EBCM is faulty, or b) the brand new wheel hubs (and wheel position sensors therein) are faulty. Unfortunately, I suspect my problem lies elsewhere. E.g. Air in the line (still), or a bad ABS modulator that was damaged by too much air in the line when I drove the car the first week after bleeding it improperly (e.g. Without a tech 2). I do not know enough about the ABS modulator (pump) to know if anything inside the pump can go "bad"... but I am suspicious... am I going down the wrong path? What readings should I get from a voltmeter on the wheel speed sensors?

Dennis

Bill Curlee

Call me pm sent!

Bill Curlee

Here are the pictures and info that we discussed:

WSS Schematic:



EBTCM Plug:



BAD PINS on the right,,,, NEW connector and pins on LEFT!



Inside a front HUB!





REAR and FRONT Hub connectors are DIFFERENT pin orientations:





JUMPER HARNESS:

jackthelad

What versions of the EBTCM and the BPMV are you discussing? There were multiple versions with different functions depending on year.