BikeRack Posted August 30, 2009 Share Posted August 30, 2009 I attempted the $5 mechanical fix, and apparently broke the O2 sensor (the housing got twisted and bent). Now, both the sensor and heater lines ohm out to infinity. Prior to my ham-fisted efforts, the computer was throwing the code for reduced catalytic converter efficiency. Now it's issuing a P0037 (heater control circuit low bank 1 sensor 2), which is understandable. Also understandable, and very annoying, is the fact that this code is issued again immediately upon a second start-up, after clearing the codes with a battery disconnect and pump of the brakes. At least the catalytic code was delayed by a 100 miles or so. To beat the P0037, I've tried bridging the heater supply lines (the black wires) with various resistances, starting with 4.7K. The code stopped issuing when I got down to 330 Ohms, and the voltage across that resistor in-circuit was pulsed (didn't haul out my O-scope to the car yet). My reading concerning O2 sensor heaters indicate a cold resistance of 3 to 7 Ohms is typical, and that the resistance increases as heater temperature increases. I measured the resistance across the sensor and heater lines of a universal O2 sensor at the auto parts store, and found 3.4 Ohms for the heater, and an immeasurably high resistance across the sensor lines. The later surprised me, but I suppose an unheated sensor could present such a high resistance. My question is this: What resistances are optimal to bypass the O2 sensor? Can I fool the ECU with constant resistances across both the heater and sensor lines? If not, does anyone here with a Tactrix OpenPort live in my neck of the woods (Dayton, Ohio)? If I understand correctly, one may selectively "mute" selected codes with an OpenPort and EcuFlash, preventing them from causing a CEL fault, and forcing limp-home mode. Any and all advice is appreciated and welcome! Link to comment Share on other sites More sharing options...
EVOthis Posted August 30, 2009 Share Posted August 30, 2009 You said it threw a code for reduced cat. conv. efficiency..P0420? I would be taking the car back to the dealer for a warranty repair for that one...Those cats are warrantied for something like 8 yrs/80k miles, Or if your vehicle is an 06' It might still be under the manufacturers warranty of 3 yrs/ 36k miles....This is what I would be checking into first.... I do have a Tactrix cable for my WRX which is obviously tuned by Romraider OS..I'm all the way over by Philadelphia PA though.. Link to comment Share on other sites More sharing options...
BikeRack Posted August 30, 2009 Author Share Posted August 30, 2009 Bummer is, the Forester is at 84k miles. Convenient, huh? Yeah, I drive alot. Link to comment Share on other sites More sharing options...
Log1call Posted August 31, 2009 Share Posted August 31, 2009 No a resistor won't fool the ecu. It is expecting the rear sensor reading to fluctuate, at a slower rate than the front sensor, but it must fluctuate. Why not just get a new sensor? Link to comment Share on other sites More sharing options...
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