I purchased at 2011 Z4 35i a little over a year ago from a local BMW dealership. Since the weather has started to warm, I've been having issues with power steering. Randomly as you are driving down the road the car will display "Steering Assistance Malfunction" . Initially this would flicker on and then go back off, and you could continue to drive. It progressed to flickering, coming back on, and then staying off until the car was restarted. Relatively annoying and a safety issue (should it drop out while in a curve for instance). Last week it stopped working 20-30 minutes into a drive. This week it doesn't work at startup.
The error being thrown is "D507 PT-CAN communication error". This error and the symptoms of a restart to fix match an EPS related voluntary recall campaigns that BMW NA had for 2011 1-Series and 2012 Z4's (12V302000 (BMW Recall Campaign 12V-302). This included an extremely small subset of vehicles. The vehicles that were included were based on manufacturing records related to some lot/lots of defective capacitors.
In the notice from BMW to NHTSA for 12V302000 (attached) it states the exact symptoms I'm seeing:
I scoped the PT-CAN line on the EPS computer when it was working properly:
And when it was malfunctioning:
If you disconnect the EPS computer from the harness while the issue is occurring, the waveform returns to normal. There don't seem to be any issues with the transceiver on either side (normal looking ohm readings between PT-CAN lines from the harness as well as directly on the EPS computer). It looks like the voltage on both lines (which are slightly different and show no indication of short) drops and slowly rebuilds before dropping again.
Snippets of data from the EPS:
D507 PT-CAN communication error (FC 13)
Error frequency: 54
Environmental data at the first occurrence of the error:
Mileage 5456.00 km
So it looks like this has been happening since ~3300 miles, when the car was brand new and still under lease. I've only seen the error maybe 10-15 times (very intermittent) so it means that the dealerships have been clearing this error during service and pre-prep vs addressing. I have the full service history from each dealer that took care of the car throughout it's life, no mentions of the rack at all. After lease turn-in this car was flipped a couple of times before the factory warranty had expired.
I know this car was manufactured about a year prior to the recall lot/window, but the issue seems identical. I've engaged BMW Customer Relations to see if I can get any traction to have it included in the recall, or have them goodwill a portion/all of it. I dropped it off yesterday. The dealership has confirmed the issue and I'm waiting to hear back from them or customer relations.
If it doesn't work out (not holding my breath) then I have an aftermarket warranty I can lean on for the repair. Plan C is either to refurbish my existing unit, or replace the motor/ecu (or entire rack) with a used unit. There is a company that will refurb in the UK as well. Cost wise - ~$1k for a used rack, $400-500 for a motor+ecu, $400-500 to ship off for refurb, or <$20 in ceramic capacitors (and the same work that would be needed for a used motor or ship-off refurb). Things would be a lot easier if the EPS computer wasn't attached to the motor on the rack itself.
Has anyone else had an EPS rack failure? Specifically 2011 models?
The error being thrown is "D507 PT-CAN communication error". This error and the symptoms of a restart to fix match an EPS related voluntary recall campaigns that BMW NA had for 2011 1-Series and 2012 Z4's (12V302000 (BMW Recall Campaign 12V-302). This included an extremely small subset of vehicles. The vehicles that were included were based on manufacturing records related to some lot/lots of defective capacitors.
In the notice from BMW to NHTSA for 12V302000 (attached) it states the exact symptoms I'm seeing:
If a loss of power steering assist occurred, the driver would be alerted by the illumination of a warning symbol in the instrument cluster and also by the activation of an audible warning. At the next vehicle (ignition) start, the EPS unit could function properly (the warning symbol in the instrument cluster would not appear, the audible warning would not be activated). However, the condition may occur again.
On the control module's circuit board, the ceramic material of a capacitor was manufactured incorrectly. As a result, the capacitor's isolation resistance is out of specification. This can cause variations in the electric current. Variations in the electric current can result in a sudden loss of power steering assist.
I scoped the PT-CAN line on the EPS computer when it was working properly:
And when it was malfunctioning:
If you disconnect the EPS computer from the harness while the issue is occurring, the waveform returns to normal. There don't seem to be any issues with the transceiver on either side (normal looking ohm readings between PT-CAN lines from the harness as well as directly on the EPS computer). It looks like the voltage on both lines (which are slightly different and show no indication of short) drops and slowly rebuilds before dropping again.
Snippets of data from the EPS:
D507 PT-CAN communication error (FC 13)
Error frequency: 54
Environmental data at the first occurrence of the error:
Mileage 5456.00 km
So it looks like this has been happening since ~3300 miles, when the car was brand new and still under lease. I've only seen the error maybe 10-15 times (very intermittent) so it means that the dealerships have been clearing this error during service and pre-prep vs addressing. I have the full service history from each dealer that took care of the car throughout it's life, no mentions of the rack at all. After lease turn-in this car was flipped a couple of times before the factory warranty had expired.
I know this car was manufactured about a year prior to the recall lot/window, but the issue seems identical. I've engaged BMW Customer Relations to see if I can get any traction to have it included in the recall, or have them goodwill a portion/all of it. I dropped it off yesterday. The dealership has confirmed the issue and I'm waiting to hear back from them or customer relations.
If it doesn't work out (not holding my breath) then I have an aftermarket warranty I can lean on for the repair. Plan C is either to refurbish my existing unit, or replace the motor/ecu (or entire rack) with a used unit. There is a company that will refurb in the UK as well. Cost wise - ~$1k for a used rack, $400-500 for a motor+ecu, $400-500 to ship off for refurb, or <$20 in ceramic capacitors (and the same work that would be needed for a used motor or ship-off refurb). Things would be a lot easier if the EPS computer wasn't attached to the motor on the rack itself.
Has anyone else had an EPS rack failure? Specifically 2011 models?