E36 M3 race car ABS issues

[hoki06]

I'm at a loss right now trying to figure out my ABS issues so I'm hoping someone here can provide some insight or help. Here's a rundown of what we did to the car recently:

-Nov 2014: everything works fine during the last track weekend
-Late Nov 2014: we gutted the rest of the interior which involved removing the dash, heater core, door harnesses, speaker wiring, etc.
-Dec 2014 / Jan 2015: front half of the cage is completed, battery drain issue identified which I believe is due to the alarm/EWS searching for door closing signals
-Jan 2015: full suspension overhaul including removing rear subfame
-March 2015: first test day with all the changes, no ABS

Here's where the fun begins... Using an AutoLogic tool on the diagnostic port in the engine bay, I began to diagnose the ABS and immediately there is no communication with the ABS control module. I bought a used module off eBay (same part #) and no change, still no communication. Then I replaced both ABS relays and again, still no communication.

Using this guide (http://www.m3forum.net/m3forum/showthread.php?t=341672) I started further troubleshooting. At the ABS control module, I do NOT have power at pins 3, 16, and 33 however I do have power at pins 35 and 51. Some posts near the end of that thread indicate similar no power issues at the same pins (3, 16, 33) and those people had issues with the ribbon cable in the ABS pump. I found a good deal on a used pump (same part #) and had that installed today and again, still no communication with the control module.

I spent 3 hours chasing wires tonight. Both new relays are good, all fuses are good, and I verified power is at all necessary pins in the distribution box for the ABS relays and fuses.

At this point I'm completely stumped and at the limits of my troubleshooting knowledge. Any help would be great.

[chikinhed]

I had an ABS issue for a while and the fix ended up being dirty pins at the round plug by the ABS pump. It might be something that simple.

Sent from my GTX3582R

[Iverson jr]

Is the abs module grounded? I'm sure it got disconnected when you did the front half of your cage...

[GGray]

Is it a 95 or a 96-99 M3 that makes a difference... ASC comes into play in the later cars and can cause the ABS to not work....

[hoki06]

I had an ABS issue for a while and the fix ended up being dirty pins at the round plug by the ABS pump. It might be something that simple.

Sent from my GTX3582R

I'll check the plug but I wouldn't think that would be our issue since we have never unplugged the pump until this week.

Is the abs module grounded? I'm sure it got disconnected when you did the front half of your cage...

There were 2 tabs cut from the body because they were in the way of the A pillars. I reconnected those grounds to the chassis but I'll double check that is a good connection.

Is it a 95 or a 96-99 M3 that makes a difference... ASC comes into play in the later cars and can cause the ABS to not work....

I should have included that, it is a 96 with ASC. I have removed ASC and installed a 1 watt 10 ohm resistor per the DIYs I found for an ASC delete.

[Franky goes]

I would undelete the ASC to eliminate it as the source of your issue.
Faulty ground is also somthing you want to triple check.
Keep us posted.

[dsp135i]

Maybe check the 10 ohm resistor to see if you burned it out. If so replace with one with a higer watt rating.

[hoki06]

It's fixed! And the cause of my problems was....... a bad ground. I relocated two grounds after the cage install and one of them was not as good as I thought it was. I moved the grounds to another location and everything works like it should now! Thanks for all the suggestions and help!

[Iverson jr]

Winner.

[niemanj]

It's fixed! And the cause of my problems was....... a bad ground. I relocated two grounds after the cage install and one of them was not as good as I thought it was. I moved the grounds to another location and everything works like it should now! Thanks for all the suggestions and help!

I'm going through the same issue as you do and checked all the pins and have no power at 3, 16 and 34. So where were these ground located that you needed to fix? Any pictures? I've been at this for weeks like you and not luck. My car is a 94 without ASC but from my research it should not make much difference.

[hoki06]

I'm going through the same issue as you do and checked all the pins and have no power at 3, 16 and 34. So where were these ground located that you needed to fix? Any pictures? I've been at this for weeks like you and not luck. My car is a 94 without ASC but from my research it should not make much difference.

I no longer have an E36 but it was a group of grounds running to 1 or 2 ring connectors in the passenger footwell near all the modules. If I recall correctly, there is a factory tab near the footwell speaker that the grounds mount to.

[niemanj]

Thanks for responding. Most appreciated. My abs computer is just dangling. I taped it up to me cage. I checked the grounds on the 55 pin connector those seem OK. Not sure the bracket that holds the ABS unit needs a separate ground.

[grahamular]

Thanks for responding. Most appreciated. My abs computer is just dangling. I taped it up to me cage. I checked the grounds on the 55 pin connector those seem OK. Not sure the bracket that holds the ABS unit needs a separate ground.

Were you able to track down the source of your ABS fault? I have nearly identical symptoms and my troubleshooting has not revealed any grounding issues so far (my car is caged as well, so I thought for sure a loose/missing ground would be the fix), but I've replaced nearly every ABS component at least once (pump, module, relays, brake position sensor) and still haven't resolved it.

[BMWManiac]

Were you able to track down the source of your ABS fault? I have nearly identical symptoms and my troubleshooting has not revealed any grounding issues so far (my car is caged as well, so I thought for sure a loose/missing ground would be the fix), but I've replaced nearly every ABS component at least once (pump, module, relays, brake position sensor) and still haven't resolved it.

Did you get this resolved...same boat here!

[dominator293]

This was a post my mate made on Facebook, so you may not understand all of it but here it is verbatim. He stuck a resistor in his ASC plug (from what I understand he removed or replaced the ASC throttle body which caused the issue) and ABS started working again...may not work for everyone but worth a shot.

"Well I am once again back to drop some knowledge on yo asses about ABS.

I’m not claiming this is my solution, or that I did anything other than google the problem, however this may help someone.

So I’ve been trying to diagnose faulty ABS for ages, replaced pump, sensors, wiring etc etc. turns out the issue was the computer didn’t like that I’d removed the ASC throttle body.

Solution - stick a 10ohm resistor across the plug for the motor that controls the ASC, and profit.

Again, not my solution, and not saying it will work for you - but might be worth a try if you can’t fix your Christmas tree!"

[NeilM]

The above is a well established thing. If you remove the ASC throttle body and its actuator motor the ABS will be deactivated.

The solution is either to retain the connected actuator motor by tying it back out of the way, or to substitute a 10 Ohm resistor so that the car thinks the motor is still there. This needs to be a ceramic body power resistor rated 10 watts or so. I bought a lifetime supply on Amazon for $7, see https://www.amazon.com/Tegg-Resistor...s%2C166&sr=8-1

Neil

[grahamular]

Did you get this resolved...same boat here!

Unfortunately, no. And I haven’t deleted ASC yet, so that’s not the culprit either. I just dropped it off at a well-respected shop to look at, so hoping they can figure it out.

[GrifM3]

The above is a well established thing. If you remove the ASC throttle body and its actuator motor the ABS will be deactivated.

The solution is either to retain the connected actuator motor by tying it back out of the way, or to substitute a 10 Ohm resistor so that the car thinks the motor is still there. This needs to be a ceramic body power resistor rated 10 watts or so. I bought a lifetime supply on Amazon for $7, see https://www.amazon.com/Tegg-Resistor...s%2C166&sr=8-1

Neil

Hi Neil, I'm curious about this. I removed ASC from from my 97 M3 over 20 years ago. I did not use any kind of resistor in line to fool ABS and I've never had any ABS issues. Is your comment specific to the 95 and earlier cars? Or any idea why some cars would need the resistor vs not?

I'm helping a friend build a 95 325 into a track car and the plan is to remove ASC. But, I hadn't thought there was a need for the resistor in order to ensure the ABS continued to work. I assumed this was typically done as a way to turn the light off.

Real world experience from others is welcome.

[aeronaut]

95 and earlier (OBD1) don't have ASC, I believe.

These E36 ABS issues are a true PITA. I chased one for a year, and did what many others on here have done; threw replacement parts at it. I convinced myself my fix was to finally use the correct length tip on the end of the brake travel sensor. But thinking that through, I just don't understand. Yet, a new sensor comes with about 4 different tip lengths.

[AJLM34A]

95 and earlier (OBD1) don't have ASC, I believe.

It was an option, my 1994 325i has it with 4 channel ABS(2 brake lines to the rear).

[aeronaut]

No shit! Well then!

[GrifM3]

Yep, I believe some of the later non M3 OBD I cars had it, possibly optional. My friend's 95 does.

[NeilM]

Hi Neil, I'm curious about this. I removed ASC from from my 97 M3 over 20 years ago. I did not use any kind of resistor in line to fool ABS and I've never had any ABS issues. Is your comment specific to the 95 and earlier cars? Or any idea why some cars would need the resistor vs not?

I'm helping a friend build a 95 325 into a track car and the plan is to remove ASC. But, I hadn't thought there was a need for the resistor in order to ensure the ABS continued to work. I assumed this was typically done as a way to turn the light off.

Real world experience from others is welcome.

Mine is a 96MY, but you've got me with that question. This was years ago, but I'm pretty sure I never ran the car with the ASC actuator disconnected and no resistor. For a while I simply kept the actuator connected but tied back out of the way, then a while, err, several years later remembered to buy some resistors and tidy it up.

Neil

[fbirch]

As far as deleting ASC is concerned, you can delete the ASC throttle body without needing to add a resistor and ABS will still work. But if you delete the ASC actuator motor then you need the resistor, or else ABS will be disabled. I chased an intermittent ABS problem for over a year, and it turned out to be a faulty ASC actuator motor that tripped up the ABS system only intermittently. My advice is to get rid of the motor and replace with a resistor just as a precaution. It removes one potential source of trouble from the system.

[BlackHawkRacing]

Can also confirm the ACS actuator was the cause of my own ABS issues. Once I plugged it back it, the issues went away. Other than the actuator, the ACS throttle body and associated wiring has been removed from my car.