02A7F/09 R55 Mini Clubman/No Resistance on Downstream Sensor/Sensor Not Ready

I have an 09 R55 Mini Clubman with intermittent Downstream H2OS issues. I replaced the Downstream sensor a year ago and it started showing P0136 again.


Experience: I have a background in electronics and auto repair. I used to repair motherboards and consoles. I own an oscilloscope/dmm/probe tool.
Troubleshooting: (What did I do? What have I tested? What have I replaced.)

I started trying to go the 'don't buy anything new route' but I just had the car in the shop for the timing chain. I need my inspection and the shops trying to bankrupt me for being too busy at work to DIY(i.e. The lazy tax.)

• The codes were reset by the shop and I drove 50 miles and P0136 came back.
• I made sure the connectors weren't damaged. Also the blue connector is as expensive as a water pump.
• I checked the fuses and relays to see if any were damaged or missing. I replaced the two green relays to resolve a fan issue.
• I bought an aftermarket downstream sensor and tested again and it failed after 30 miles
• I went and raided the forums for info but all of them said changing the O2 sensor solved their problem. (I am aware ohms may be an issue.)
• I dug around looking for diagrams showing the entire layout in Solera Identifix. I found that there was only one post about wiring damage. I went through every O2 related diagram and found no fuses or relays linked to the DS sensor. I downloaded block diagrams and found it doesn't reference any specific relays so I searched online some more and found the BMW Advanced Troubleshooting PDF and tried to verify that the power line for the DsO2 was connected to a specific relay but the info was missing.
• I removed the connectors and cleaned then with electrical contact cleaner on the sensor end and on the ECU/DME connector end
• I reconnected everything and took it for a test drive and started getting the electrical error 02A7F.
• Just in case there was an issue with the aftermarket O2 sensor purchased 2 new NTK Up/Downstream sensors. Went for a ride and the error came back. Same error.

At this point the only thing I didn't try was testing the sensors but I tested with a sensor from another Mini and it also didn't work.

Once I ohm out all 4 wires in the harness what else is left to check? It's raining so I couldn't troubleshoot today.

Am I missing something basic? Is the DME bad?

What relays are the H2OS lines connected to on the A6000?


From what I understand the DME will use .45v as a test and if the resistance is too high it will fail to put the sensor in MIL Ready status. The Upstream sensor has no issues at all and I tried 3 sensors there as well. (I was waiting to try ultrasonic cleaning the old one but Vevor delayed my shipment.)

I already prepared for the worse and found another wiring harness, a spare DME, and ordered a KTAG because I have a 2011 Hardtop that has issues as well but I am working on that next.

Hello going through the same issue did you find out what the cause was?