ed_pettus

I'm looking for some guidance, I have an intermittent check engine light that has a code P0031 (HO2S heater control circuit low). I've changed both O2 sensors on bank 1 with no joy. Then I replaced the wire from the ECU to O2 sensor (B19 - A4) with the same results. The next step in my troubleshooting is to check A3 of the O2 senor to A4 of the Bridge plug, but I have no idea where this thing is located. I can't seem to find anything on the internet. Has anyone encountered this before?

T10Chris

Haven't had your issue, but I know where the bridge plugs are. They are in relay box above the rear seat, same area as the ECU, except behind the driver seat instead of behind passenger seat. BS21/1 is one of the ones in position 6, theres 4 or 6 bridge plugs in that same side of the relay box so be sure you are checking the correct one. Hope that helps.

ed_pettus

Thanks bud, I found them right where you said they were. A bit of a pain in the butt to get them connectors loose, but that just comes with the territory of working on these cars.

De Jeeper

Did u just replace the wires or did u change the pins in the ecu connector? On my car i had to replace all the o2 pins because at some point a tech spead the teeth and it was loosing the signals intermitantly. I alway back pin the ecu plug with a paperclip to avoid this issue.

ed_pettus

I had not replaced any wires on the ECU. I see what your talking about possibly spreading the pins out to much. Back pinning is a good way about doing that.

ed_pettus

Update:
I disconnected both O2 sensors on each bank and got a fault on bank 2 (P0050 no signal) and still got (P0031 low circuit) on bank 1. So, I hooked bank 2 back up. Then I took it a step further, I removed the pins from B19,B15,B9 to isolate the engine harness from the computer. I still got the P0031 code instead of P0030 which would indicate an open circuit in the heater control circuit of the O2 sensor. At this moment, my troubleshooting is pointing me towards an issue with the ECU (engine computer). Hoping that a reflash will help get rid of this fault code because that would problably cost me $150 at the local dealership, versus $4700 for a new computer.

T10Chris

I think I've got a spare OEM ECU somewhere if it comes down to needing that. I'm not sure what all is involved in swapping an OEM ecu for one from another car and if it requires any programming though

vtec_

I would give Ecudoctors a call and see what they can do

Specialized ECU Repair, Replacement Testing of Electronic Control Unit (ecudoctors.com)

theprf

It's unlikely a reflash will fix this. I would guess there is a failed transistor in the ECU. The failure reason could be a short in the wiring harness so that needs to be checked.
To put a foreign ECU in the car I have been told it needs to be VIN matched. ECU doctors among others can do this. It might be possible with PIWIS as well. ECU doctors might be able to diagnose & fix a bad transistor.

Oh, if you put a manual ECU in a tip car or a Tip ECU in a manual car the car will run in limp mode.