O2 Sensor Heater Problem

[ack2000blazer]

what is the fuse called for the O2 sensor? I cant find it?

[old_master]

Welcome to Automotive Forums!

What year, model, and engine do you have?

[ack2000blazer]

its a 2000 4wd 4.3 4 doors,
i have replaced 2 o2 sensors bank 1 sens 1 and the one before the cat.
and still getting error 0135

thanks for your help

Alex

[MT-2500]

Originally Posted by ack2000blazer

its a 2000 4wd 4.3 4 doors,
i have replaced 2 o2 sensors bank 1 sens 1 and the one before the cat.
and still getting error 0135

thanks for your help

Alex

Fuse is ECMI underhood fuse box.
But if it was bad it also feeds injectors and engine would not run.

On left side engine front sensor.
Check for 4.5 volts on heater circuit to that sensor.
Post back voltage reading.

[Tech II]

This code usually means a problem with the heater circuit, not the O2 sensor circuit......

Should be reading BAT voltage on the heater circuit......

[ack2000blazer]

ok i might be misunderstanding but is the heater circuit complete different from O2 sensor and if so where is it and how do i find it to test it. I am getting code 1035

thanks.

Alex

[old_master]

P0135 is the driver side sensor, closest to the engine, heater malfunction. The heater is part of the oxygen sensor. The electrical connector has 4 wires, 2 for the sensor and 2 for the heater. As mentioned, make sure you have battery voltage and ground at the harness connector. Black wire must be less than 5 ohms resistance to ground, and the pink wire must show battery voltage with the ignition in the RUN position. After repairing the problem, clear the DTC's and perform a drive cycle to verify the repair was successful. http://www.obdii.com/drivecycle.html

[ack2000blazer]

Ok so i did the test as you asked.
The bat voltage was 12v
on the wire harness i test the pink/red to ground and got 11v
for the ohms i got nothing i checked all wires to ground with ohms on and got nothing.
So what does that tell us, I read the article you included however i cleared the codes after i put the new O2 sens in is that the same type of clearing as in that article.


Thanks for all your help.

Alex

[ack2000blazer]

Yes one more thing where does the other side of the harness end terminate in the engine compartment.

Alex

[old_master]

The black wire is the ground for the heater in the sensor. You found it has an open circuit, that's what is causing the P0135. You can either trace it back until you find the break in the wire*, or you can solder on a new piece of wire and attach it to a good, clean, chassis ground. Problem solved! Good job!

* The original ground for the heater is to a bolt in the rear of the driver side cylinder head.

Clearing the DTC's will remove all DTC's from memory. Performing the drive cycle "forces" the ECM to run and complete the monitors. If all of the monitors run and complete their tests, and they all pass, the SES light will remain off.

[ack2000blazer]

Ok i got it. Just duno how i am going to get in there to cut it so dam tight.
Once i do they i can use an OBDII scanner to clear it and hopefully never see the check engine light come on.

[old_master]

You can get right at the harness connector at the sensor, there's plenty of room. First make sure the crimp connection at the black wire terminal in the vehicle harness connector is good. Then move up the vehicle harness, a couple of inches away from the connector, and solder on a new piece of wire. Solder on an eyelet connector and attach it to ground.

[ack2000blazer]

ok just want to be clear on which black wire to cut i dont think it matters but i rather ask first then cut once.

I am going to cut the black wire between the o2 sensor and its connector.
then run that to ground and plug the harness back in.
then using an OBDII scanner clear the code.

Thanks

Alex

[old_master]

In the vehicle harness connector to the sensor, there is only one black wire. Follow that wire through the connector and into the sensor. Remove about a half inch of insulation, (don't cut the wire) between the O2 sensor and its connector. Solder on a piece of wire and run it to ground. IF the crimp is the problem, doing it this way will bypass the crimp. This will also make it more difficult to replace the sensor in the future if necessary, but it eliminates a connection as a possible problem. It's very important to solder the connection and insulate it, DO NOT use a crimp connector.

[ack2000blazer]

ok so i finally had time to get back in to this projected. I added the new ground wire it looks good i will have a friend with a code scaner clear the code for me and see if it comes back. I found many other issues with this truck that leads me to believe the did stuff to it to pass smog. I found the main air in take and the rear vacuum line not attached. I have bolted it down and re attached the removed vacuum line. I dont need it to pass smog for aleast a year but as i work on it i find more things that make me go hummmm.

Thanks for your help i will let you know if the code comes back.