BMW E53 X5 4.6i 2004 - ABS / rotation sensor problem - Fixed #
Posted by Sean Murphy on August 1, 2012, 8:21 pm
Year of Manufacture *: 2004
Hi All, After a bit of advice before i go insane!!
The X5 above came in with an intermittent ABS/DSC warning on the dash which Autologic reported as a "wheel speed sensor, rear right". When left overnight this would clear on its own!
long-story-short there was a thermal problem inside the Bosch 5.7 ABS ecu that turned off the supply to the speed sensor at the rear wheel (confirmed by scoping the outputs from the ecu whilst wafting a hair drier on the ecu!). Aparently this is a fairly common fault with this unit. We removed it and sent it off to be repaired by a specialist (ECUtesting.com.
After [eventually] getting the unit back we refitted it but the abs/dsc warning lights were still on and cannot be reset. Autologic now reports a fault with the "rotation rate sensor, line" (the original speed sensor fault has gone). The car didnt even turn a wheel in the time the ECU was away for repair. Our supect was that the ECU was somehow affected by the repair. We then checked out the continuity between each ECU pin to the RPM sensor and all was OK so the wiring should be fine. We checked for voltages on the RPM sensor and have battery voltage between pins 1-6, 2.5v between 3-6 and 2.39v between 4-6. These all appear to be with the BMW specs.
We pulled the ABS ecu again and returned it for a warranty check but again it was returned as OK, no faults found. We sourced a used RPM sensor (new ones are well over £400) and swapped it out but still the same fault appears and cannot be cleared. A battery reset also failed to have any effect. We are now thinking that the ABS ecu is somehow not 'seeing' the sensor values? The RPM sensor value in autologic is shown as -68.29 and does not change, and is the same as with the original RPM sensor.
We have recoded the ABS unit with no effect on the fault. Interestingly, trying to reprogram the DSC unit fails with a "cannot communicate with unit" message.
Before we shell out on a new ABS unit, has anyone seen this before or have any ideas?
Had similar code description recently on an E46 similar age,with that one they were hard codes and would not clear,after checking all lives and earths at yaw sensor bit the bullet and bought new genuine at £350 plus VAT, as soon as plugged in DSC light cleared with no coding required,looks to me as though you have a double fault that was partially fixed with the ECU repair but for whatever reason it has now thrown up the yaw sensor?
After constant ear-ache from the owner and dealer that sold it to him, hours of second-guessing my self and going around in circles the car is now fixed!
Turns out our "repaired" ABS ECU came back with a fault it didnt go with free of charge (even though we sent it back for further testing under warranty)! Renewed the ABS ECU with a brand new unit and faults instantly cleared even with the original rotation sensor fitted.
Important lesson learned and the last time i'll try and do a used-car dealer a favour by having an ECU "repaired" and saving him a few quid - its new unit or no unit from now on!!
Re: Fixed #
Posted by Rob Nicholson on August 10, 2012, 9:26 pm, in reply to "Fixed #"
Hi Sean,
"Important lesson learned and the last time i'll try and do a used-car dealer a favour by having an ECU "repaired" and saving him a few quid - its new unit or no unit from now on!!"
I couldn't agree more but I'm sure we are all guilty of this at some point!