ABS, ASC lights on and speedometer quit- Why? [Archive] - Bimmerfest - BMW Forums

: ABS, ASC lights on and speedometer quit- Why?

12-15-2004, 08:48 AM
'99 528i 5 speed. I'm having intermittent problems where ABS, ASC lights are on and the speedometer quits. When it goes out, it stays out for the rest of that trip. Sometimes all works fine when I start it next and sometimes it does not. Sometimes it comes on during a short drive and sometimes not. I checked the fuses and there are two that share function with the ABS and ASC but both fuses are fine. I know that my front brake liniings are worn and considered this could affect some sort of sensor for the ABS and ASC but that wouldn't explain the speedometer. Any ideas before I take it to the stealer? :confused:

12-16-2004, 01:09 PM
You need to check your abs sensors. There are 4 per car. (one for each wheel). The speedo picks up vehicle speed off of one of those sensors. If it goes bad, the car has no idea how fast it is going. I don't know if they are 2 or 3 wire sensors. If the connector that goes to the abs sensor has 2 wires, just check it with an ohmmeter at the connector. Compare all 4 on the car and will probably find one that is open circuit. It is either a bad sensor, or a bad connection.

Good luck.

(I make vehicle sensors for a living, ABS, Camshaft, Crankshaft, transmission, etc)


12-20-2004, 08:29 AM
actually ,there are 2

one in the front passenger wheel, and one on the driver rear wheel

sometimes referred to as Vehicle speed sensors... which would cause the speedo to malfunction

if not these two sensors... then something else is wrong

SInce the sppedo is wrong, I would bank on one of these two sensors.... if not then your ABS control module is BAD (would not affect the speedo) and is $$$ to replace

12-21-2004, 11:31 AM
Ok, as I've asked about this elsewhere, I've been told it is most likely the drivers rear wheel sensor because it runs the speedometer. Do you have any reason to believe that it might be the passeneger front wheel instead of the drivers rear wheel?