Brake light will not reset.

6Inarowmakesitgo! · 08-11-2019, 02:20 AM

So I did my brakes and installed new sensors, was able to reset the service interval in the cluster relatively easily.
Yay! Nice smooth brakes and no annoying red light.

Cue 3000 miles of driving and it pops back on. WTH.
The mileage counter in the service menu is stating -9000 miles for my front brakes and will NOT reset. Tried the paper clip method, still no change. Tried with my foxwell, no change. For giggles, I put another new sensor on, nope, no luck there. Traced wiring and verified no damage to the harness or water ingress inside connections, all is well there.

Checked rear brake sensor, that is Ohk and I can reset the interval for the rear axle.

I am out of ideas.

Any thoughts?

PhaseP · 08-11-2019, 01:01 PM

My guess is some where in the connector or wiring between the ABS control unit and the sensor there is either a high resistance or disconnect occurred.
The new sensor is short circuit, and resetting the brake wear light requires new sensor, i.e. short circuit on the leads.

The connectors and wiring can look intact but you cannot be sure unless you really measure them.

IF you have dsc_90 module, the ABS connector pin 29 an pin 10 will be for front brake pad wear sensor.
This is the wiring diagram IF you have dsc_90, most likely you have but you should double check:

https://www.newtis.info/tisv2/a/en/e...system/rDCfB4e

The best bet would be verify if the above linked wiring diagram matches your car's build and build date. Then turn off of the car, disconnect the batter negative terminal, put some rag on the trunk lock latch to prevent accidental closure of the trunk so you won't be locked out with battery disconnected.

Then disconnect the ABS connector at the ABS module near the brake booster. Find the pins on the connector at the wiring harness side, (not on the module) that is for front brake pad wear sensor from the wiring diagram for your car. Short circuit the other end, or put that brand new sensor you have on the wheel side. Measure the resistance from the other end on the, you should measure something below 1 ohm. If you measure high resistance you have a either a frayed wire or corroded connection problem somewhere along between sensor and ABS connector.

This is a very good video from a professional auto mechanic which shows how he finds a hidden corroded connector point inside a wheel speed sensor. Different car, different sensor, but troubleshooting method and location of the sensors would be same:

08-11-2019, 02:20 AM	#1
6Inarowmakesitgo! Private First Class 22 Rep 111 Posts Drives: 2006 330xi Join Date: Jan 2019 Location: Wisconsin iTrader: (0)	Brake light will not reset. So I did my brakes and installed new sensors, was able to reset the service interval in the cluster relatively easily. Yay! Nice smooth brakes and no annoying red light. Cue 3000 miles of driving and it pops back on. WTH. The mileage counter in the service menu is stating -9000 miles for my front brakes and will NOT reset. Tried the paper clip method, still no change. Tried with my foxwell, no change. For giggles, I put another new sensor on, nope, no luck there. Traced wiring and verified no damage to the harness or water ingress inside connections, all is well there. Checked rear brake sensor, that is Ohk and I can reset the interval for the rear axle. I am out of ideas. Any thoughts? __________________ Buckle up, Its the ride of your life.
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08-11-2019, 01:01 PM	#2
PhaseP Colonel 1007 Rep 2,108 Posts Drives: 325XI Join Date: May 2010 Location: Earth iTrader: (0)	My guess is some where in the connector or wiring between the ABS control unit and the sensor there is either a high resistance or disconnect occurred. The new sensor is short circuit, and resetting the brake wear light requires new sensor, i.e. short circuit on the leads. The connectors and wiring can look intact but you cannot be sure unless you really measure them. IF you have dsc_90 module, the ABS connector pin 29 an pin 10 will be for front brake pad wear sensor. This is the wiring diagram IF you have dsc_90, most likely you have but you should double check: https://www.newtis.info/tisv2/a/en/e...system/rDCfB4e The best bet would be verify if the above linked wiring diagram matches your car's build and build date. Then turn off of the car, disconnect the batter negative terminal, put some rag on the trunk lock latch to prevent accidental closure of the trunk so you won't be locked out with battery disconnected. Then disconnect the ABS connector at the ABS module near the brake booster. Find the pins on the connector at the wiring harness side, (not on the module) that is for front brake pad wear sensor from the wiring diagram for your car. Short circuit the other end, or put that brand new sensor you have on the wheel side. Measure the resistance from the other end on the, you should measure something below 1 ohm. If you measure high resistance you have a either a frayed wire or corroded connection problem somewhere along between sensor and ABS connector. This is a very good video from a professional auto mechanic which shows how he finds a hidden corroded connector point inside a wheel speed sensor. Different car, different sensor, but troubleshooting method and location of the sensors would be same:
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