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ABS ASC Module Replacement
 
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Pelican Technical Article:

ABS ASC Module Replacement

Kerry Jonsson

Time:

3 hours3 hrs

Tab:

$100

Talent:

***

Tools:

T20 Torx bit, flat head screwdriver, Digital Meter

Applicable Models:

BMW E39 5-Series (1997-03)

Parts Required:

Brake ABS ASC Module, fasteners

Hot Tip:

Make sure the Torx bit is fully seated in the fastener so you don't strip it.

Performance Gain:

Replace failed module keeping the ABS ASC warning light on.

Complementary Modification:

Replace the brake pressure switch.

If you have an ABS/ASC warning light on in your instrument cluster you have a problem with the ABS/ASC system and you do not have the use of your anti-lock brake function or traction control. This can lead to unsafe driving situations. If you have the codes pulled in the braking system and you get a code for the brake pressure switch voltage being low it may not be the pressure switch that is the problem. Sometimes the module fails to put out the 5 volt reference and therefore the signal voltage drops out. The ABS/ASC module sees this as a failure of the switch and not the module 5 volt reference. You can send the module out to companies like Module Masters and they can sometimes repair your unit. If your unit goes back in the car there is no need to code the unit. If you purchase a new one and install it you will have to take it to an automotive repair shop that has the equipment to program or code the modules for you.

ABS/ASC Module Removal:

Make sure the ignition key is off. If the key is on you will cause diagnostic trouble codes to set in other modules that will need to be cleared by someone with the equipment to do so.

This photo illustrates under the hood on the right side looking at the ABS/ASC module.
Figure 1

This photo illustrates under the hood on the right side looking at the ABS/ASC module.

With a flathead screwdriver lever on the slide lock in the direction of the blue arrow that holds the connector to the module.
Figure 2

With a flathead screwdriver lever on the slide lock in the direction of the blue arrow that holds the connector to the module. Once you have moved the slide lock all the way to the end pull straight up on the connector to unplug the unit.

Facing the ABS/ASC module locate the six T20 Torx fasteners (green arrows) that mount the module to the hydraulic unit.
Figure 3

Facing the ABS/ASC module locate the six T20 Torx fasteners (green arrows) that mount the module to the hydraulic unit.

Remove the six T20 Torx module fasteners.
Figure 4

Remove the six T20 Torx module fasteners. Make sure the Torx bit is fully seated in the fastener head. You donÂ't want to strip any of these screws as they are difficult to get to.

Pull the module away from the hydraulic unit in the direction of the blue arrow.
Figure 5

Pull the module away from the hydraulic unit in the direction of the blue arrow.

Do not leave this area exposed to the elements.
Figure 6

Do not leave this area exposed to the elements. If you are sending the module out to be repaired or remanufactured cover the hydraulic unit with a plastic bag to reduce the exposure to moisture.

ABS/ASC Module/Brake Pressure Switch Testing: Make sure the ignition key is on during your testing. If you are going to have the key on for awhile you may want to install a battery charger to prevent the battery from going dead. These cars draw a lot of amperage and can drain a battery anywhere over 15 minutes depending on the condition of your battery.
Locate the brake pressure switch (green arrow) on the backside of the ABS/ASC hydraulic unit.
Figure 7

Locate the brake pressure switch (green arrow) on the backside of the ABS/ASC hydraulic unit. The brake pressure switch is a three wire sensor. Wire colors may vary with your year but look on the electrical connector or inside the brake switch and locate the pin numbers.

Our 1997 BMW 540i followed these wire colors.
Figure 8

Our 1997 BMW 540i followed these wire colors. Pin #1, white wire with blue tracer (green arrow) is the ground wire. Pin #2, blue wire with black tracer (red arrow) is the signal wire. Pin #3, black wire with violet tracer (yellow arrow) is the 5 volt reference.

Connect the red test lead to pin#3 and the black test lead to pin# 1 and turn the ignition switch on.
Figure 9

Connect the red test lead to pin#3 and the black test lead to pin# 1 and turn the ignition switch on. Be careful not to allow the two terminals to touch otherwise the 5 volt reference will be pulled to ground and you will set a code in the ABS/ASC system that will have to be cleared with a capable scan tool.

Turn on the ignition switch and you should read 5 volts on the meter.
Figure 10

Turn on the ignition switch and you should read 5 volts on the meter. You may want to shut off the ignition switch to change the test lead location. When you are done turn the ignition switch back on.

Move the red test lead to pin# 2 and keep the black test lead in pin# 1 for the ground.
Figure 11

Move the red test lead to pin# 2 and keep the black test lead in pin# 1 for the ground.

With little residual pressure in the brake hydraulic system your meter should only read approximately 0.
Figure 12

With little residual pressure in the brake hydraulic system your meter should only read approximately 0.50 volts (here our meter reads 0.59 which is okay). Either use long test leads so you can look in the meter while you are applying the brake pedal or have someone help you and step on the brake pedal gradually.

Have someone inside the car and apply the brake pedal with the ignition key on but the engine off.
Figure 13

Have someone inside the car and apply the brake pedal with the ignition key on but the engine off.

As the brakes are applied the brake pressure sensor signal voltage will increase to approximately 1.
Figure 14

As the brakes are applied the brake pressure sensor signal voltage will increase to approximately 1.7 volts. The harder the brakes are pressed the higher the signal voltage.

Start the engine and apply the brake pedal.
Figure 15

Start the engine and apply the brake pedal. Be careful to keep test leads and body parts away from the front of the engine so you and they are not struck by moving parts.

The meter should read approximately 2.
Figure 16

The meter should read approximately 2.8 volts. The increase in brake pressure is from the vacuum booster adding additional force with the engine running. The problem these modules suffer is the 5 volt reference drops out. This may be momentary so you would have to be watching your meter when it happens or have more sophisticated electrical equipment to capture the drop in voltage. Test the brake switch and if the brake switch works properly then you should look into getting your brake module serviced or replaced.

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Comments and Suggestions:
Ala Comments: Excellent papa good
December 7, 2016
elevmech Comments: ABS problem no 5 volts at pressure sensor does this voltage come from module?
November 19, 2016
  Followup from the Pelican Staff: ABS sensor, Yes. - Nick at Pelican Parts  
TPK Comments: Last year in August I got the trifecta ABS,DSC, BRAKE lights on dash. Replaced the ABS module with a new unit from BMW and had the unit coded. Just yesterday I got the trifecta again. What gives??? 1200$ part only lasts 1 year? So frustrating.
September 27, 2016
  Followup from the Pelican Staff: Was it new or reman? Could be a defective part of something else. Before blaming the module, check the fault codes. - Nick at Pelican Parts  
Shabonian Comments: One of the small pins on the abs module where the plug connects on to is twisted and pushed down slightly. Could this cause a problem? And if so is this normally repaired when sent to do a refurbish?
July 26, 2016
  Followup from the Pelican Staff: Yes, that is a problem. It may be repaired by someone, you'll have to check with them. If not, you'll need a new one. - Nick at Pelican Parts  
Shaw Comments: Bmw 528i se 1999.speedometer not working . Works when cold weather, works with acknowledge sound on take of, from 1/2 a mile to 1 1/2 miles. Then stops working. Has worked briefly in two chilly summer mornings. I've changed sensor and same, so not sensor.ive bridged from wheel sensor to glove box. Still not work. ?
July 25, 2016
  Followup from the Pelican Staff: Issue could be in the cluster. Best bet is to check for fault codes. If there isn't one stored for speed signal in cluster, it is likely the cluster. - Nick at Pelican Parts  
Chris Comments: I'm pulling a fault code 70 can failure, as well as 06 and 07 front wheel sensors, I cleared the codes to see if they came back. Now the car won't accelerate. I can't push it past 500 revs.
1999 528i touring
March 2, 2016
  Followup from the Pelican Staff: What module are the faults from? Did you check the DME for fault codes as well? You may have to issues. Wheel speed faults will not prevent acceleration. - Nick at Pelican Parts  
wanttolearn Comments: Forgot to clariy, the car is a 2001 bmw 740il
January 22, 2016
  Followup from the Pelican Staff: Thanks, got it. - Nick at Pelican Parts  
wanttolearn Comments: Intermittantly the Brake, ABS and Traction lights comes on...and loses power steering help. The Speedometor and MPG scale stop working as well. When we restart the car all is ok.. Not sure what's going on...what to replace. really appreciate any help. Love the car but it's killing us financially.
January 22, 2016
  Followup from the Pelican Staff: Sounds like a wheel speed sensor. I would start by checking the vehicle for fault codes. The code will identify the sensor. - Nick at Pelican Parts  
a h k Comments: I just changed the wheel abs sensor that was broken but the ABS & ASC lights didn't turn off and it was just fine before the sensor broken
how do I rest it by my self ?
December 10, 2015
  Followup from the Pelican Staff: With a BMW scan tool. I would suggest checking if additional fault codes are stored. - Nick at Pelican Parts  
mack50 Comments: trans-safe program fail comes on with abs connected. disconnect abs no trans-fail but other gauges erratic, replaced abs module still same symptoms, checked wheel sensors, replace brake pedal sensor, no luck. possibly a faulty wire or connection, any thoughts
November 6, 2015
  Followup from the Pelican Staff: Start by checking for fault codes. It could be a data line error or shared signal that is faulty. - Nick at Pelican Parts  
Nick Comments: Hello, first time 528i owner 4th bmw with m52 motor here with a goofy abs / voltage issue. Quick history: I purchased the car in limp mode with an almost trifecta, but the brake light was red! The spedometer didn't work and there were 12 codes thrown. All fixed using the improperly, already installed parts on it. Literally all lights are off, but the abs is making springy noises and killing altornator output by a few Volta with every occurance. In one minute, the abs will go nuts 10 times.

I suspect the rear sensor I knew didn't work in the left wheel that's now in the right wheel more than I would the module. Your thoughts would be super helpful in terms of my next steps, thanks in advance!
September 15, 2015
  Followup from the Pelican Staff: First be sure charging system voltage and current are OK. If so, you will have to find the wheel that is causing the issue. Monitor wheel speed sensor readings and look for one that doesn't match. - Nick at Pelican Parts  
JH Comments: Hi. I got 2001 bmw 525i and stuck in trouble with ABS signal, traction signal and transmission. Both ABS and traction signal had no problem with driving but tranny is used to sutck at the 4th gear or drive gear is not workingrpm is up but won't go forward. Is this happening possible to related with ABS control module? Or is there something other issues with tranny?
September 12, 2015
  Followup from the Pelican Staff: It could be. You may have speed signal issues, causing fault all around. i would check the vehicle for fault codes to begin. - Nick at Pelican Parts  
Donna Comments: Nick - yes, found out that a faulty abs module can make quite a few things go haywire. Car wasn't overheating, especially since it was a cold start in 19* weather. There was a fault code for the module.
November 21, 2014
  Followup from the Pelican Staff: What was the fault code? On BMW models, a faulty ABS module doesn't cause the same issues of other makes. I would think your car has a communication issue. - Nick at Pelican Parts  
Donna Comments: Trifecta lights on, temp gauge pegged right, fan constantly running, tach/speedo gauges not working. Could all of this be caused by a failing abs module?
November 21, 2014
  Followup from the Pelican Staff: I haven't seen that. Is the engine actually overheating? If there is a communication problem with the DME, all those things could happen. I would check for fault codes. - Nick at Pelican Parts  
Shane Comments: Can the module prevent speedo/fuel gauge not to work. Abs and ask lights are also on. If car is very cold it works ok for a short while. Thanks in advance.
July 12, 2014
  Followup from the Pelican Staff: Not the fuel gauge. So if both are out on your vehicle, I would suspect the cluster or data to the cluster. - Nick at Pelican Parts  

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Page last updated: Fri 12/9/2016 02:05:36 AM