Rep Power: 0

Hello,

I am currently in the process of trying to eliminate the p0135 code that the car has been throwing. Its bank 1, sensor one (pre cat) heater circuit malfunction.

2002 Civic DX
D17A1
CAI, Header, Catbackw w/ test pipe

I've replaced the o2 sensor with an OEM NGK sensor, reset the ecu and the mil comes on instantly upon starting the car. I checked fuse #4 under the dash, and its fine.

I tested for voltage on the heater circuit with the car in acc and on, and there is no voltage. So, my question is. Does anyone know where in the ecu the heater circuit feeds from, and how do I perform a continuity test? If the wire has a break can I bypass the main wiring harness and run wire directly to the ecu? Or could it be a bad ground on the circuit?

Any suggestions? I've been chasing this issue for awhile and have had no resolve. I brought the car to a shop and they told me the issue was the secondary o2 and to remove the test pipe and run the o2 sensor directly in. Somehow that doesn't sound right...

 
Rep Power: 518

Secondary (rear) sensor has a whole set of codes all of its very own. Should not be any sort of factor in setting codes for the front sensor. Completely independent other than sharing power for the heater.


Sensor heater circuit ohm test should be 3.0-3.6 ohms.
Looks like it takes the PCM only 5 seconds to recognize the fault.


Get a wiring diagram for yourself...It should show another half-dozen items or so that share the same #4 fuse.

Fuse #4 (10 amp) supplies power directly to BOTH O2 sensors. PCM is not involved in the power side. If you are missing B+ power, you have a wiring issue somewhere.

PCM controls and monitors amperage draw for the ground circuit of each O2 sensor heater, independently of each other.

Anything else?
HTH

 
Rep Power: 0

Thank you very much. You have confirmed what I expected based on my own limited electrical experience. I'll look around for a wiring diagram and hopefully locate the break.