Hi there,

The ABS light on my 02 CL500 has recently lit up. I've also noticed all of the brake lights are also on w/o applying the brake pedal. My initial thought was I had a bad brake light switch so I went ahead & replaced it with a new genuine MB brake light switch, however that wasn't it. I then hooked up a Bosch OBDII scanner & was able to pull code C1011. Surfing the net, the code indicates the following errors:

1. ASR/ETS/ESP Circuit Open or Shorted
2. Power Supply A7/3 - Traction System Hydraulic Unit
3. Valve relay

I do have a new Bosch AGM battery (purchased last year), however my CL isn't my daily driver so the battery could be low even though car started up fine every time. While I'm charging the battery, would like to know if you have any thoughts on this issue. Please advise & thanks for all your help in advance.

 

I was hoping by disconnecting & recharge the battery overnight would cure the problem but found out that would only clear engine error codes. I've also bypassed the brake light switch by removing it out of the circuit but the brake lights remain on. I've just bought an Icarsoft MB II scanner but won't have it until mid-week next week. Does anyone has a schematic on how the brake lights are connected so I can do some troubleshooting while waiting for the scanner? Thanks in advance

 

I'm looking into the ABS wheel speed sensors & noticed there are only 3 of them on my car. The left rear doesn't have 1. Should there be 4? ABS was working fine before. Any idea?

Correction: There are 4 ABS wheel speed sensors & only 3 cables/harnesses for the brake wear indicators.

 

I would stop playing around and find someone with a real scanner, Xentry DAS
with that you will find the real cause within seconds

 

My iCarsoft MB II scanner arrived & I've spent the past few days troubleshooting the problem. The scanner pointed to the Power Supply A7/3 Traction System Hydraulic Unit which is the ABS pump. Initially, I thought the pump went kaput so I was about ready to buy another pump, however upon surfing the net, I've found out whenever the car is turned on, all of these devices i.e. ESP, BAS, ABS, etc.. will also be turned on to run a quick self-test then provided a telemetry signal back to the ECU as part of the health check. I've noticed the pump's motor wasn't running at all so I've decided to manually energize the relay to provide the 12V to the pump & lo & behold it ran so it wasn't the pump. I then back traced starting from the relay & worked my way back & found the problem in the ESP/BAS/ABS module. I've then pulled the module from the car, pried open the module's cover & upon inspection, I've found some of the FET's (Field Effect Transistors) had shorted out & melted some of the pads & traces on the board. Upon closer examination, it was deemed beyond repair as u can see from the attached photos. Guess how much a brand new module cost? $2040. Yes, over $2k, yikes. Luckily, I was able to find a used one on EBay for just under $20, what a deal. Just got the module in the mail this afternoon, dropped it in & voila, all the lights are gone. Hooked up the MB scanner to run a full diagnostic test & cleared all the codes. The ESP/BAS/ABS is now working, all the brake lights in the rear are back to normal & car runs like a champ. The investment on a new scanner has already paid for itself in just 1 fix & you don't need to use a Xentry DAS to diagnose your problem. If I had taken the car to a dealer or even an indy shop, it would have costed me over 2 grands + labor. I'm a happy camper. My years at Purdue to become a EE has finally paid off

Hope this will help others get yours fixed if & when you run into the same problem I had.

Latest investigation:

Today, I took another closer look at the damaged components & areas on the board. Based upon my investigation, the damage appears to be due to water intrusion/moisture which leads to corrosion & causes dendritic growth between un-coated metal i.e. transistor's leads thus caused them to short out. Problem solved.

 

Where is that module located ?

 

driver side engine fuse+module box
it's written on the module, you can't go wrong

 

Where is the location the relay to see if it indeed our pump gone out as well?