ABS ETS BAS 4ETS Problem DIY Repair Instructions for Mercedes Benz

Diagnostic code C1401: High-pressure return pump circuit open or shorted, or pump will not shut off.

Difficulty Level:  6 – Medium
Time:2 to 3 hours
Repair Cost: DIY Cost – Less than $20 

Parts You’ll Need:

• ML ABS Bearing
• 12mm x 5 mm x 5 mm Carbon Brushes

Your ABS/ETS/BAS lights just came on your Mercedes-Benz, and you almost had a panic attack. Don’t panic. There are a few reasons why you see these lights, and you can do some of those repairs yourself.

Possible causes for ABS, ETS, and BAS lights are:

• Faulty brake light switch
• Faulty wheel speed sensor
• Failed K25 relay
• Bad ABS Motor (4ESP)

This DIY article will focus on repairing the ABS motor (4ESP). This repair could cost around $3,000 at the dealer or around $2,000 at an auto repair shop. If you have DIY repair skills, you are looking at about $20. That’s right, $20.

This is a very common problem on ML W163. A couple of years ago, I posted this solution on a Mercedes Benz forum, and I am glad to see that it has helped many people. Even though other models are not affected as much, this fix applies to any other Mercedes Benz model. Even to others makes, for that matter.

Diagnostic Steps:

1. 1. Locate the ABS pump on your Mercedes Benz. On the ML, it is located on the front left behind the driver’s side headlight, next to the washer fluid reservoir.
      View the Location of the ABS Pump on W163
   2. Find the relay that runs the ABS pump. If you look at your fuse box, it will be marked ABS Pump or ABS Motor or 4EPS.
      On the W163 shown here, relay K25 is in the underhood fuse box on the left side.
      
   3. Manually get the ABS motor to run by jumping the wires on the ABS Relay socket.

1. If the ABS motor doesn’t run when you jump the relay, move to the next section.

DIY – ABS Motor Repair Steps

1. Disconnect the negative battery cable.
2. Remove the driver-side front wheel and wheel liner for access on the ML. Alternatively, remove the washer fluid reservoir for additional access
   
3. Unscrew the bolts that hold the pump to the ABS control valve unit—two T25 Torx bolts on each side of the motor in the ML. Be careful not to strip them. They strip easily; don’t ask how I know.
   
4. Pull the ABS motor straight out. An O-shaped “cap” metal ring is at the center of the ABS module. Be careful not to pull that out with the ABS motor. If you pull the ABS motor about ½ inch out, put a long screwdriver in the gap pointing toward the shaft. This helps prevent the cap from coming out with the motor.
5. Remove the rotor from the motor housing. Use one of these methods:
   1. Use a flathead screwdriver to remove the black plastic from the metal motor housing. Once the central piece is loose, you must pull hard to remove it. The magnet inside will want to hold the rotor in place.
   2. Put the shaft on vice, and make sure you do not damage the shaft by over-tightening it. Pull on the motor.
      
6. Use a puller to remove the bearing on the ABS motor. I reused mine. If you need one, you can use NAPA 6001-2RSJ or 6001ZZE Nachi Bearing Shielded C3 from Amazon.
   You can rent this puller from Advance Auto Parts or AutoZone, or be creative when removing the bearing. Or you could also purchase one on Amazon.
7. Inspect the brushes and replace if necessary. Remove the old brushes. Cut the copper braid flush with the surface of the old brush. The old brush will pop out. Cut the other end of the copper braid around 1/4″ from the support molded into the plastic cover on each side. The brushes shown are completely worn.
   
8. Install new brushes.
9. Reinstall in reverse order.
10. Last step: Start the car and turn the steering wheel fully from lock to lock to reset the lights.

Conclusion

The repair is very straightforward but requires a certain level of experience. If you feel uncomfortable doing this repair, consider just removing the ABS motor and sending it in for repair to any of the Mercedes-Benz ABS pump repair services

Tips:

• • You can rent the following bearing puller in the picture from AutoZone.
  • The magnetic field will pull the rotor back to the housing. Try not to damage the rubber seal, which insulates the rotor and the housing.
  • Can the vehicle be driven while the ABS pump motor is removed? Though we strongly would NOT recommend this, you can drive the truck without the pump. At your own risk!
  • What are the part numbers of the brushes, and where can I get them?
  • Possible ABS unit part numbers include A 163 545 97 32 and A 163 431 07 12. Verify the correct unit by VIN.

Troubleshooting Mercedes-Benz ABS, ETS, BAS, & 4ETS Problem

Before replacing the ABS pump motor, scan the ABS and ESP modules with the YOUCANIC UCAN-II Pro. It can read fault codes and live data and run supported bidirectional tests to help distinguish a failed motor from a relay, wiring, sensor, or control module problem. It includes full AI Diagnosis, built-in TPMS sensor programming, a rear VIN scanning camera, coverage for 140+ makes, 3,500+ active tests, and 1,000+ special functions, with no subscription or AutoAuth required.