Hi,

after some slow driving i got a CEL Code today.

My ODB-II Software says:

Category: Powertrain
Name: P0138
Description: O2 Sensor Circuit High Voltage


What does that mean and how can i fix it?

 

BTW: It seems the CEL Code means the 2nd O2 Sensor (in catalytic converter).

Hopefully it does not mean that my cat is defective

 

Most likely it's a bad 02. Does your OBDII software let you monitor the 02's output voltage? If the 02's output Voltage stays above .6V, and doesn't switch from .1-.9V at idle, it's a bad 02.

The sensor is pretty expensive, you could replace the cat with a straight pipe and 02 simulator and spend less than the 02. That is if your emmisions control laws allow that sort of thing. It is illegal here in several states, but emmision checks and reguations vary state to state.

 

I use Digimoto 3.7 and it allows monitor the O2 voltage. I will check this later and tell you what it shows.

Thanks for your helping, Chris

 

I just checked it.

The voltage from the 2nd O2 Sensor stays always on 1.25V and dont go up and down

Could this also be possible because of the vtecfrog harness i have (pins not connected)?

 

If you have a voltage input to the pcm, most likely your wiring is good. Does your PLX tap into the primary or secondary 02?

If you want to check Vtec frog harness, unplug it and re check your 02 volts. Same result, it's a dead 02.

 

The PLX tap into the primary O2 and the primary 02 heater circuit.

Is the primary and the secondary O2 identical?

If so i could install my old primary O2 for the defective secondary O2. Because i use now a Bosch Lambda Sensor for the Primary O2.

 

Can't swap the 02's they have different heater elements.