Hello every one and happy holidays!!

Im trying to pass inspection with my 1999 Trailblazer but I keep getting the good ol p0135 Malfunction I replaced the sensor in the spring and have not had problems until the last 2 months. It comes right back when it goes through the cycles there fore I dont have enough readings to pass the crazy pennsylvania emisson test! The vehicle runs great the engine was replaced last fall.

One thing i did notice reading through the other threads is people mentioning using AC Delco AFS105 not botch which is what i have in there now. One more thing ive noticed is the old sensor DID have a ground splice going from the ground wire directly to a grounding screw that is located in the floor of the vehicle. Should I reground it? I had some minor corosion to the one connector pin but i cleaned it off when i put the new sensor on in the spring of this year.. I cleaned it out again today and got a p0131 low voltage today thats why i ask about the ground splice.

In a nut shell I have an 02 problem and i need just a little help please


Neal

 

P0135 - HO2S Heater Circuit Bank 1 Sensor 1

This code could be caused by a faulty ground. That would be where I would start. You should look at getting it grounded to a really good source and protect all of the wiring. Put some dielectric grease on the ground location before you tighten things down as well to protect the connection. Check over all of the connections for corrosion as this can open up clearances in the connection causing an intermittent loss of connection.

 

Thank you for the advice on the sensor I replaced it and the truck is running great!...

and there is always a but!! I have 3 things in the obdII that i need to have change from incl stattus to ok...

Ive driven over 40 miles hoping stuff would register but i have the following 3 things

* evap
* sec air
* oxygen htd
Ive tried the sequences noted in the obdII gm computer cycle guide including letting my truck run well over 5 min with the ac on and rear defrosters on..

i just need one of these three things to pass to be able to pass state emissions here in PA.. any suggestions?

 

You must complete at least 2 GM drive cycles before the emissions status will update for those items, but it could take more... Check out www.obdii.com for the GM drive cycle requirements.

 

Thanks again for the information..

Now Unfortunatly i was trying to hurry and get this emissions thing over with and nobody locally carried acdelco sensors so i grabbed another bosch..

The oxygen heated sensor is doing its part on the oxygen sensor side but when i do the cold start up cycle test as per the gm cycle manual..

Im getting the p0135 again... I want to meter this connection out but i need a diagram of what is what and what voltages im looking for..

Bosch site states white and white are heater circuit and black is sensor and grey is ground.. should I pigtail grey to my chassy and what else should check.. Is there a fuse anywhere for this particular circuit?

Neal

 

The diagram is provided in the DTC link above. The heater gets battery voltage and ground and that is it.

 

Ok are you ready for the curveball? Its snowing like crazy here in pittsburgh so i have not had the chance to meter out the system for that sensor. I still have the p0135 light on the dash but the I/M Stattus now says OK LOL Im guessing that its working now? IM gonna clear the codes and see what happens

 

You could try swapping the sensor side to side to see if the code follows the sensor over to B2S1 (P0155). Hopefully you get lucky... Problem is, once you reset the codes, the emissions monitors will reset as well so you'll have to go through the whole drive cycle thing again.

 

OK I THINK THIS MAY TOTALLY BE MY MISTAKE. So My last question.. When grounding my heated oxygen sensor. which wire am I supposed to ground> I have crap bosch in there now.. its a bran new sensor. I have been reading through wiring diagrams and everything now I know the conector is labeled A B C D ..

AM i supposed to have the heater circuit grounded to the chassy> (meaning using the two white wires and grounding the second one in) is that how its supposed to be?

 

I had A grounded because bosch said that was the ground!! after reading schematics n diagrams i belive its supposed to be C grounded.. I moved it .. jeez i hope im right LOL heck i do electroncs for a living and i cant figure out one 4 wire o2 sensor LOL HA Let me know if i got the right one grounded please and thanks alot for all the help!!