Evo X Engine Management / Tuning ForumsDiscuss the major engine management systems.
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Hi, I need to replace a faulty stock o2 sensor with a resistor. (I'm not using the sensor, so I'd rather spend 50 cents on a resistor than a hundred on a new sensor)
I've tried 8 ohms and 16 ohms and I get P0031 - Circuit Low.
Does anyone know what the resistance level is supposed to be?
-------************** Editing to add answer**************------------
I was connecting the wrong wires together. On the 2008 Evo X GSR, the real heater circuit is black wire to black wire. I ended up using 16 ohms for the resistance.
The 16 ohm solution I posted does not get rid of the problem codes.
None of the resistor values I tried - 5,6,7,8,16 got rid of the code.
I finally gave in and got a replacement O2 sensor. This also did not get rid of the code. I called the parts guy and he sent me a replacement (nice work Rock Auto) but the replacement had the same problem. Rock Auto told me to get my ECM diagnosed.
I went to the local shop here and they tinkered with it and eventually figured out that the "historical data" needed to be reset in the ECM. This appears to have fixed the codes.
So it may be that the resistor works, but you need to reset the ECM properly to prevent codes?
Now I only wish the shop hadn't put 26 mysterious miles on it...
Last edited by didalos; Apr 13, 2012 at 06:47 AM.
Reason: add answer
That info is for the IX. Does anyone know if it applies to the X?
It says this:
"This ECU circuit requires an ohm load between 1.1 and 80 to keep the CEL from coming on"
So, seems like 8 ohms meets that criteria. I don't have the ability to do step 2 with modifying the ECU, but again, not sure that it applies to the X.
i'm not sure about what translates from evo IX to the X regarding the resistor specs. maybe cross reference the stock o2 part numbers from both models.
i believe the resistor part is for the simulating the o2 heater only. using the resistor should keep the o2 heater code from being thrown.
HOWEVER, if you remove the o2 sensor and do not disable the rear o2 sensor via the ECU, then you will throw a code or two related to a missing rear o2. i assumed you disabled your rear o2 when you said you werent using the sensor.
Not saying your method wouldn't work, just saying I think there are easier ways, like golden's, especially if the OP doesn't have a code reader to reset the CEL, or a rhetostat, or electrical skills, or a bunch of resistors just laying around.
i might test this for you next week, possibly this weekend if i get some time. i would like to know the voltage, resistance, and current of the stock o2 heater as well and i want to compare to the AEM uego's heater.
i can tell you with the sensor out of the car, the resistance is between the two black wires is 6.5 Ohms
are you sure the white wire is heater?? all denso 4 wire o2 sensors seem to be
blue - signal
ground - white
black - heater
black - heater
do you have any plans for your broken o2 sensor?
Last edited by momostallion; Feb 23, 2012 at 08:02 PM.