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Discussion Starter · #1 ·
I have been fighting my 2003 525i Sedan for weeks. As post title says I have a RED brake light, DSC light, and SEL. The DSC light is intermittent on 80% of the time, and always comes on when I get in a situation traction control should come on. I do not have the ABS light on and have never seen it. I also see the "check brake lining" message. I have cleared the code and brake light and they come right back. I have checked the brake pads and wear sensors including using volt meter and they check out and are working. I seem to have ABS (can feel it pumping upon hard braking, however still burned a bit of rubber). Traction control is not semingly working and its definitely not the DSC button. Everything else is working: speedo, cruise... Note the rear brake pads and sensor replaced around the start of issues but like I said I checked the sensor. I checked the pressure sensor on back of ABS and saw normal voltage also. I did notice the ABS module seems to have a weird pin looking thing that's shorter (see photo). When I check what codes the cars throwing I am seeing Pre Charging Pump (no other ABS related codes, however, there are a few codes for exhaust system). Going to check the tire speed sensor and try checking the pre charge pump today (however I've been told pre charge is almost never and issue and codes can be inaccurate). Really looking for some answers and insight. Need to get traction control working before winter.

_a2_
 

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You mentioned that when you replaced the pad sensor, the problem arise. Well, I read some forum that when they replaced with aftermarket (sensor) parts then their problem arise . Pad sensor is like a close loop wire that when the tip of the sensor worn out by rotor, the loop wire open then brake light illuminate. I am just wondering what kind of sensor you have. Also, scan the CEL and get back with the failure code.

Also check this site about the -40F display.
https://www.youtube.com/watch?v=Wsms8PiCIjE
 

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Discussion Starter · #3 ·
These are all my updates since my post.

The rear brake pads were changed less than a month ago along with the brake pad wear sensor wire made by JL Germany 34 35 1 163 066. Afterwards I turned the key to the on position until the red brake light went out. Then drove the car to the end of the driveway and the red brake light returned. I also used a multimeter to check the resistance of both rear and front brake pad wear sensor wires, both showed a resistance. Then I used a mutimeter to check for voltage on the car side of the brake pad wear sensor connector and found 11-12volts on both the rear and front. I used http://www.matcotools.com/catalog/pr...AX2/reviews/1/ scanner to check for error codes on the car the only thing that came up was (58) 88 Pre Charging Pump Fault Code. Today I removed both front wheel speed sensors and used the multimeter on diode setting between the two pins and found open circuit both ways. Then I did the same test measuring resistance this time and found resistances that jumped significantly between 0.3Mohms-1.1Mohms when swapping the leads. Also when leaving one or two of the speed sensors unplugged and starting the car the ABS light turned on. Once plugged back in and restarted ABS turned off.

- - - Updated - - -

Update: used the INPA software tonight and again cleared all my codes. The SEL light went off and stayed off for the duration of my drive. Will recheck tomorrow. The brake light turned yellow for a bit, but quickly returned to red.

My newest discovery is a voltage issue. While running the car and driving it on the max voltage I could get was 13.81 volts (that with no radio, a/c...) when off it read 12.4 through INPA. I have not had a battery light or dead battery issues, I would assume this is an alternator issue. I am curious if my voltage issues play into these other issues or is a separate issue.

From what I understand the battery should be a minimum of 13.8v when driving/running. I am averaging around 13.2v. The 13.8v was only read when all the extras were turned off (a/c, radio, cruise, phone charger). The battery testing was all done using INPA.
I used INPA and there are no response from control unit so I'm unable to read that module.
 

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Discussion Starter · #4 ·
Ok so I found my other cord for talking to the car with INPA (was having issues talking to the car due to using the newer K line plus decan that is missing some k line).
On INPA I discovered all my speed sensors are most definitely working, I was able to see the speed of each tire while driving and they work. I rechecked all codes the only codes I am seeing is the Pre Charge Pump and Secondary Cat Bank 1 & 2 (something like that).

I again cleared all the codes and had every light off. I then drove and ABS did not work this time when I hard braked. I also was having the Red "Brake" light flash on and then would go off and then would return a bit later. It then eventually stayed on solid. My battery again was reading in the 13.2v range while driving. I am really starting to wonder if I just need a new alternator. I'm wondering if the low voltage is whats causing the abs module to not have enough power. I will be ordering a refurbished alternator in the next two weeks and will keep everyone updated. There is a chance the ABS module has failed, but I would like to rule out lack of voltage (and I need one anyways, so why not just throw money at it lol)


Thanks for the tip on -40 ordeal, however I already discovered that the harness and all got ripped off so I had wires hanging. I did purchase a temp sensor prior to this discovery and haven't had enough motivation to buy the harness to get my temp sensor again. It seems pretty accurate in this MN climate to read the -40 for 6/12 months of the year lol.
 
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