P0040 CEL Code
 

This one is going to be a brain teaser as several people I’ve talked to are stumped. My 09 was throwing three CEL codes, P0153, P0133 and P0040 after the header/exhaust (iPE brand) installation. Codes P0153, P0133 have been fixed after installing 4 new 02 sensors. I would have thought P0040 would have been fixed also.



The message on P0040 is “O2 Sensor Signals Swapped Bank 1 Sensor 1/Bank 2 Sensor 1” So we swapped the connectors, still same code.


Seeing how the harness is not clearly marked (driver/passenger), except for a white stripe on two of the harness plugs, does anyone know how to tell which side is which?



The exhaust installer suggested that I use a “bungs" on the primary sensor ports. Would this help?



Has anyone seen this code caused by something upstream?



Any advice would be appreciated.


-Chris:smash:

Bungs did not seem to help :-(

Did u clear it after swapping?

Yes sir.

After I cleared the code, I must have pulled the OBD Tester out without taking the key out of position 2 b/c when I drove away, the car was acting like it was running on 3 cylinders. Pulled it over, shut the car down and started it back up and it was normal again.

Have you confirmed you have all the O2s plugged into the correct sockets??

I believe they are. We actually swapped them around to see if that was the cause. The only visible markings in the harness is a white stripe on two of the sensors.

I am wondering if there is some sort of short in the harness which not enough voltage to/from the sensor.

Try your old sensors.

i have your same problem but i havernt pulled the trigger to buy the o2 sensors as yet

let me know how you go

OK will do and I'm glad it's not just me who has seen this, albeit, it sucks. I have an appointment with a MB care center on the 6th. Hopefully they can sort it out.

Sadly, I think these are tossed by now.

im also checking with IPE to see if they know anything about our issues

does your new exhaust still use cats? did you drop or roughly set the oxygen sensors somewhere, they can be pretty fragile. I can give you the pins outs for the ecu to the oxygen sensors but you'll need to know how to use a digital multia meter/dmm or ohm-meter.

I'm still using cats

No cats on mine. Extended bungs on the primary sensors. My original set of O2 sensors I think got damaged during the install. The new set I picked up from rockauto.com were handled with care. I don't have an ohm-meter but I'm sure I could get one albeit, I would have no clue what to look for..lol

Just throwing this out, the front o2 sensor is fed back to the computer to establish air/fuel/throttle position/power output and so forth. When you remove the cats then the secondary o2 sensors now is reading what the first o2 is reading so is it possible that the computer is thinking that the sensors are mixed up. I always thought when you remove the cats then you take out the secondary o2 out of the circuit by the tune. As it is now both are reading the same, and this is on both banks.

That is a good point. I will ask my tuner.

Pretty good after only one coffee, ha ha Hope it works for you.

Extensions should be on the down streams not the primaries.

See bold

I'll swap them tonight. And will give it a try. These bungs don't have filter elements in them.

how did you go???

Same result, same code.

i wouldnt extend the bungs on the front primary o2's thats going to make the fuel control read improperly.

yeah - I moved them to the back.

Does anyone know if there is fuse that could control any part of the O2 sensor. If so, what number would it be?

there is a fuse for the heater circuit of the oxygen sensor. looks like fuse 22 15amp if i looked it up correctly. You'd have a whole lot of other faults as this fuse is shared with multiple other components airpump switch over valve, thermostat thermostat, intake switch over valve to name a few.
here the wiring diagram. G3/4 is the right upstream, G3/3 is the left upstream, G3/6 is the right downstream, G3/6 is the left down stream. keep in mind left is the driver's side, right is the passenger. Hope that helps

http://imageshack.us/a/img841/3149/byv1.jpg
http://imageshack.us/a/img132/7586/ejbx.jpg