I have a 2009 DB9 throwing P0161. Bank 2 Sensor 2 Heater circuit malfunction. On the 07EE ECU. So this is the right hand bank, downstream, inner O2 sensor.

I figured the original sensors were old enough that replacing them wouldn't be a bad idea so I replaced both downstream sensors. Cleared the codes and it came back.

Is there any tribal knowledge on how to fix this? Otherwise my plan is to start doing continuity tests back to the ECU on the heater circuit.

 

FWIW, I was surprised by how my wiring loom hangs below the ECU. Puts a bit of strain on the wiring/connectors. I "pushed" the wires back into the connector blocks, reseated the connector blocks and they used zipties and wiring tape (the cloth stuff) to support the harness in lieu of the connectors. My random electrical issues disappeared (knocking on wood). YMMV...

 

Using a regular DC voltmeter, I'm getting a steady 12v across the two heater wires at the o2 sensor plug. What now?

 

Are you sure you're working on the correct side of the engine? P0161 can be generated in either PCM. Bank1 is the passenger side and bank 2 is the driver side for left-hand cars.

 

07EE is the primary ECU. Right hand side. I'm on Step 9 there

 

If you're seeing 12v across pins 1 & 2 of the vehicle side O2 sensor connector (vs pin 1 and the chassis ground) and are sure you're on the right side then I'm not sure. It's a pain to get to the PCM, but it might be good to check continuity between o2 connector pin 2 and the PCM connector. Move things around while you're there and see if the resistance changes or is intermittent. Like @AM4884 says, the harness is heavy at the PCM and needs to be supported. My 2007 has fir tree zip ties to support the harness to the PCM mounting bracket, but it was clear someone took it apart in the past and they were all broken and needed replaced.

It also wouldn't hurt to check sensor 2-2 on the other side just in case.

 

So I was on the wrong side. It was the LHD inner downstream sensor that was faulty. Open circuit on the heater. Replacing that one seems to have solved it.

What I dont get is, on a generic scanner, you see two ECUs, 07E8 and 07EE on the powertrain port. I thought 07EE is the primary ECU because when I unplugged a RHD (pass side US car) O2 sensor, it immediately picked it up. And I had no codes on 07E8. So I thought 07EE means RHD bank. But it appears that 07EE can't differentiate between left and right. Because my fault was on the LHD and it shows up on the 07EE ECU.

 

If you're using a truly generic OBD scanner it probably can't properly distinguish between the two PCMs. The Foxwell NT530 seems to do reasonably well in my experience as you can explicitly choose which side to pull codes from.

At the end of the day you found and fixed the issue. Always a good feeling!

 

Can you show me what that looks like? On the scanner screen I mean.

 

Not much to see here. But you can see the tool knows about the two PCMs and lets you select the one you want to look at.