99 v70xc p0036 p0136

[tcbrady]

As much as i love my v70 i'm about ready to put a brick on the gas peddle and send it over a cliff. Just to give a little background, I did an engine swap (to a 2.3 with a 16t turbo) about 6 months ago after blowing a head gasket. 2 months after I did that the transmission BLEW up (kaboom). Unfortunately it blew up 1000 miles from home so for the first time in my life I had to pay a mechanic to do the dirty work for me.

Since the transmission was replaced I had not only one code but two. Since I bought the car it has had a p0422 catalyst below threshold code (it appears the cat has been replaced and temp readings suggest functionality). When I did the engine swap I put a new rear O2 sensor in and it didn't help. I finally remedied that with IPD's O2 CES BOSS (Great Product btw). When I was putting the spacer I realized that I'm getting a front 02 sensor code because the guys that did the transmission didn't plug in the front 02 sensor! I plugged it in hoping that my code would go away but it didn't. The p0422 went away but I still have a front 02 sensor code so I replaced the front O2 sensor. With both 02 sensors replaced recently I still have a p0036 and a p0136 CEL code.

Any idea's what could cause this?

[Ozark Lee]

You aren't getting heater voltage to the rear O2 sensor. Start at the connector and look for battery voltage there. You can also check for resistance across the heater which is the two white wires on the sensor side of the connector. Without the heater you aren't getting a proper reading form the rear sensor but that problem goes back to the open heater circuit.

...Lee

[tcbrady]

Thanks for the tip lee. Is 2.2 ohm the magic number for resistance on the two white wires? When is this circuit going to be "hot", any time the ignition is on? I was under the impression that neither the front O2 or the rear O2 has a functional heater circuit is that not true?

[Ozark Lee]

I will need to look up the heater resistance values in VADIS, 2.2 ohms sounds reasonable. Both the front and the rear sensors do indeed have heater circuits and they must be functional to get an accurate reading from the sensor. The heaters are on when the ECU tells them to be on but it is most of the time. You should have constant battery voltage on the green wires from the harness any time the key is on.

...Lee

[tcbrady]

i checked the impedance on the two white wires all i could get is .009 ohms. is that bad? i never could get the probes connected for voltage... i hate those tight spaces.