Jay_WRX05

Hi all bit of an explanation to start,

I have recently bought a 2005 Wrx in bits as it had a melted piston,
car is know rebuilt but is coming up with this P0031 BANK 1 HEATER CIRCUIT LOW code,this same code comes up whether sensor is plugged in or unplugged,car will vertually run on 2 cylinders with all sensors plugged in,when I unplug the maf it puts car into safe mode and runs perfectly fine other than obvious lack of power,

Things I have done so far,

*New Battery
*New 02 sensor pre cat
*New Maf sensor
*checked sensor with multi meter/all ok
*checked loom back to car(between ecu & sensor plug) all ok
*Diagnostic check which is showing sensor in list but showing no output
*Smoke test on inlet track to check for air leaks

Mods are as follows
*Full Prodrive kit & Remap
*3" straight through exhaust
*All uprated hard pipes incuding filter/maf pipe
*FMIC
*Dump valve

All I can think of know is the ecu is shot?really am stuck here guys just throwing money at it guessing know please help!!!

Athame1

iTrader: (2)

Sounds like lambda sensor (O2) has failed

Jay_WRX05

Thanks for reply, I have already replaced lambda and is resistance across heater element is fine

Athame1

iTrader: (2)

Genuine one?

ALi-B

iTrader: (1)

Was it a genuine o2 sensor or a cheapy universal?

I wouldn't use anything other than Bosch, Denso or NGK. Anything else causes headaches.

Jay_WRX05

genuine second hand from midland scooby breakers

ALi-B

iTrader: (1)

My advice: Don't use second hand sensors unless you can test it and prove it to be working yourself on another car. That goes for any engine sensor.

O2 sensors can be damaged if they are dropped or had a impact. Sometimes if they are seized in tight just unscrewing them from a rusted boss can **** them (been there, done that ). I've even had two fail on a BMW after using an air chisel on rusty exhaust flange bolts on the back box (vibrations killed them).

Jay_WRX05

I no what your saying Ali but I have checked sensor with multi meter and has low resistance across heater eliment?

Athame1

iTrader: (2)

Wiring and connectors ok?

Read you have. Has it run with out this fault, with 02 sensor fitted?

Jay_WRX05

Wiring and connections all test ok only thing I havnt tested for is a short not sure how to do that?

STI8Dave

Has the rear o2 sensor been looked into yet? If you have removed cats you will need to have this sensor switched off as it will throw the cel up until you do.

Jay_WRX05

Hi Dave rear sensor is working ok no fault codes there,I have a straight through could the rear sensor affect the front,Im not sure whether that is directly linked to my issue as the fault refers to the heater element but I have no reading what so ever on front lambda?

Jay_WRX05

Sorry Athame1 yes it used to run with just a lean burn on bank 1 fault took it to a specialist and came back with this fault had to heat lambda cherry red to get a voltage out of it so I replaced it but no luck

STI8Dave

I don't know whether they can be linked or not but probably not. I only mention this because mine was playing up when I removed the cats but can't actually remember the fault code!

Athame1

iTrader: (2)

Who mapped it for you. Have a chat with them probably help you with next move.

But could still be the new'ish' O2 sensor.

Jay_WRX05

It was mapped by Prodrive/Subaru from new and I phoned them the other day and they have no intorest or expertise in the subaru field anymore from what they were telling me which is great!lol

Dave the rear sensor is a P0037 code i think

STI8Dave

I was close then lol

Athame1

iTrader: (2)

Need new map for mods added.

Jay_WRX05

Yes u were lol

Jay_WRX05

Sorry for late reply having problems with account login,I agree it will need a re tune but I can't get it tuned in limp mode lol I am going to re check wiring harness again tomorrow if I get chance to see if i can pick up a short