PeachParts Mercedes-Benz Forum - ML320 Work Done- ABS/ETS Lights Still On

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ML320 Work Done- ABS/ETS Lights Still On

The info that follows is for a 1998 ML320 with 190,166 miles. I am the original owner since new. No prior brake issues.

The ABS/ETS lights came on about two weeks ago. I have done all of the things I could come up with in a progressive trouble shooting procedure (least costly parts first).
1. Checked OBD codes. None stored. (Have a few high mileage cars so bought my own code reading/reset tool a few years ago)
2. Battery is 2 years old (Dec. 2005). Voltage checked with voltmeter and is 12.8 volts
3. Brake pads and rotors have about 10k miles on them. Wear is normal. No perceptible wheel bearing play.
4. Checked all four wheel speed sensors for chafing/damage. All wiring appears OK. Removed all four sensor heads, cleaned pick-ups and reinstalled.
5. Replaced brake pedal switch
6. Replaced ABS Relay K25
7. Applied 12VDC and ground to power and ground pins on ABS hydraulic pump. Runs fine.
8. Removed ABS control module from front of ABS hydraulic pump/manifold assembly. Sent out for professional rebuild. Reinstalled.

ABS/ETS Lights still on.

Any recommendations or further ideas appreciated.

NOTE: I have a service appointment Saturday morning (tomorrow) for a brake fluid flush.

Thanks,
Ken

sounds like the brake light switch.
Search for it and it should give you an idea.

Update- Results of Code Check by Dealer

Code scan by the dealer came back as bad solenoid in ABS hydraulic unit for right rear hydraulic circuit. The ML320 is still at the dealer service department. Action plan not yet defined.

Good example of why a simple diagnostic evaluation by someone with proper tools can save some bucks. While you might be able to fix the circuit involved, a used unit might be a better option. Be sure and get the same number there were about three different numbers used.

Root Cause Found

Just to close out this project I am reporting back with answers to my original questions included below:

Quote:

Originally Posted by kwmccauley (Post 1738181)

Finally discovered the root cause to a problem on my 1998 ML320 (190k miles). The ABS/ETS warning light is on. The trouble code is C1304 which indicates a fault in the left rear HOLD solenoid. The dealer wanted to replace the ABS Hydraulic Unit and Control module @ $2,200. This work was declined and the vehicle was driven home without ABS.

Upon further examination, the actual fault is the pink wire that goes to PIN #10 in the 15 pin connector attached to the ABS Hydraulic Pump/Control Module unit (A7/3). This pink wire is completely abraded to the point that there is no copper conductor remaining. According to the wiring diagram, PIN#10 pink wire does indeed feed the left rear hold solenoid so this checks out with code C1304. Three questions for now related to the wiring repair:

1. What is the recommended splicing procedure, e.g. twist ends & solder then wrap, butt connector, insulation displacement connector, etc. ?
ANSWER: Snipped out about 1/2" of the damaged wire where the copper conductor was gone. Slipped about 3" of 1/8" diameter heat shrink tubing (the type with sealant) over one of the wire ends. Stripped ~ 1/2" of insulation from each of the two wire ends. Pushed the two ends together and made certain of good contact amongst the now interleaved strands. Soldered the wire strands with rosin core solder. When cool, slipped the heat shrink tubing over the repair and heated to shrink the tubing and seal the repair to make it waterproof. Wrapped the wire harness with new friction tape.

2. I may have done some damage to the 15 pin connector….not certain until I reassemble. What tool is used to remove the metallic terminals from the 15 pin connector block?
ANSWER: The original 15 pin connector block was damaged somewhat. A new one was available with MB part number 032-545-18-28 at a price of $14.40. This was FAR superior to buying a new wiring harness which was $600+. The only trick was removing the connector pins from the original block. If you do not have the correct AMP or Molex pin removal tool, one can be made from 3/16" OD aluminum, copper or brass tubing available at most hobby shops. The OD requires some filing (or lathe work if one prefers) to slightly reduce the OD. The ID fits over the connector pins and the OD must fit snugly in the connector block barrel. When the tube is pushed into the connector block, the locking tabs on the connector pins release and the pins can be removed through the rear of the connector. Sounds more complicated than it is. Just take your time and make sure you snap the connector pins into the correct location on the new connector.
2.1 Are replacement connector blocks available or does MBUSA sell a pigtailed replacement and all 15 wires must be spliced?

Thank you,
Ken

Ken,

Thanks for the update. Any idea why or how the wire was damaged?

Jim in Phoenix

After almost 10 years since taking delivery of the vehicle in May 1998, this is the first wire that failed. It appears that the original friction tape wrapping (black, cloth-based tape) of the wire harness was unraveling and some of the wires became exposed to rubbing on sheet metal surfaces behind the left side headlight under the windshield washer reservoir tank.
Ken