O2 voltage and fuel trims issue
Jan 20, 2019, 05:38 PM
#1
O2 voltage and fuel trims issue
Hey guys. I have had this issue with my car for a long time. I mean close to a year long. I had my evo 9 tuned and it was running great. I don't drive it very often so it sat in the garage for a while. I went to drive it one day and it would barely start. I had to give the car gas in order for it to start and it idled like straight crap. As soon as it moved it just wanted to die the whole time. At this point i inspected everything and seen my camshafts had pitting on the intake cam so i decided to upgrade to S3 cams. While doing the timing i noticed my intake cam was 1 tooth off so i reset everything and when i started the car, it started right up. Sounded a little off but it ran a lot better than before.
I ended up hooking up an OBD scanner to it and instantly noticed that my car was running on open loop. Checked my O2 sensor and the voltage is stuck at .8 volts. I replaced the O2 sensor thinking it was dead and nothing changed. I changed my MAP sensor and still nothing. Next i changed my coolant temp sensor and still nothing. I inspected my whole engine harness and no issues at all. I replaced my O2 sensor again and nothing changed. I tested the old O2 and it got good continuity. I have read the repair manual many times and pulled schematics for it and i have replaced everything associated with it except for the tune itself and the ECU. I have gone over the troubleshooting section for the closest thing possible and it tells me to change the ECU. Is there any other tests i can do before going that route.
I bought a tractrix cable and verified on evoscan that the voltage is not moving at all. Also noticed i am not receiving any fuel trims at all at idle. AFR's start rich at idle 11-12 and slowly creep up to 14-15. I am at a loss and don't know where else to look or what to replace. please help.
I ended up hooking up an OBD scanner to it and instantly noticed that my car was running on open loop. Checked my O2 sensor and the voltage is stuck at .8 volts. I replaced the O2 sensor thinking it was dead and nothing changed. I changed my MAP sensor and still nothing. Next i changed my coolant temp sensor and still nothing. I inspected my whole engine harness and no issues at all. I replaced my O2 sensor again and nothing changed. I tested the old O2 and it got good continuity. I have read the repair manual many times and pulled schematics for it and i have replaced everything associated with it except for the tune itself and the ECU. I have gone over the troubleshooting section for the closest thing possible and it tells me to change the ECU. Is there any other tests i can do before going that route.
I bought a tractrix cable and verified on evoscan that the voltage is not moving at all. Also noticed i am not receiving any fuel trims at all at idle. AFR's start rich at idle 11-12 and slowly creep up to 14-15. I am at a loss and don't know where else to look or what to replace. please help.
