I too have a bosch sensor installed in my '95 that was throwing the p0135 code. My FSM says that means there is too little or too high a current (I think if it's less than 0.2A it throws the code and if it's greater than 2.0A it throws the code) flowing through the heater circuit on bank 1 sensor 1. So you check the resistance on the heater and it should be between 11 an 16 ohms.
Mine was 3.8 ohms. From reading the various o2 sensor posts on mud here, I believe this is one of the (if not "thee") primary reason that the bosch sensors don't work in our vehicles: the heater resistance is not correct.
Since I couldn't return the sensor, I did some quick math and checked my local Radio Shack for a suitable resistor. I grabbed a beefy 8 ohm 20-watt resistor for $3. (The FSM says it can put over 2 amps into that circuit, so using some online Ohm's law calculator figured that it should be about 20-30 Watts on that circuit. That was just some ballpark figure, so someone should do a real calculation if you want the real rating.)
I wired it up inline on the heater circuit (to give me a base 11.8 ohms resistance) where the o2 sensor plugs into the wiring harness and cleared my p0135 code. It usually pops up after 2-3 starts, but I've done at least 8 starts without the code coming back!
Now, the caveats:
1) since the heater is no longer getting the full current, it may not be getting up to the right temp, thus causing the O2 sensor reading to be off. In my case, I'm seeing voltage readings between 0 and 1.25 V Using my obdii reader. I have no idea what it should be - anyone out there have a stock sensor that can post their voltage range?
2) again, the wattage of the resistor may be inadequate, so it may burn up at some point and the code will be back. I'll keep you posted if mine does.
. Anybody have a similar experience? Suggestions?
