A few things then:

Why did you replace the O2 sensor? What behavior were you getting with the old sensor?

Which wires did you check for continuity and how did you do this?


George

 

I will help you for as long as you want regardless of your level of knowledge. I am 70 and have been doing this for 55 years.


George

 

Honestly i had a p0420 code for catalyst low efficiency bank 1 so i thought id try a new o2 sensor by the way it is a bosch and i just seen where someone said gm doesn't use bosch for the long run. I unplugged the harness to the vcm with the High signal circuit and Low single circuit and tested continuity and they were good.

 

[QUOTE=GeorgeLG;751816]I will help you for as long as you want regardless of your level of knowledge. I am 70 and have been doing this for 55 years.


I appreciate it more than you know👍

 

P0420 is low catalytic converter efficiency. Normally the precat O2 sensors switch up and down after the truck warms up and goes into closed loop between around 0.1 and 0.9v like a crappy sine wave. Normally the post catalytic O2 sensor slowly drifts around somewhere between 0,5 - 0.7V. If there is something wrong then the rear sensor will start to track the front sensors or peg high or low. The most frequent cause is a spent converter but a bad fuel air ratio or an exhaust leak can also trigger codes. Was the old precat sensor switching properly and did the new code only happen after the replacement? If this is true then your new sensor may be bad, the wrong one or the wiring is wrong. Was it a plug and play sensor or a generic 4 wire and you have to decipher the wiring connections?

0.45v is the bias voltage that the engine computer supplies to the sensor. When the sensor warms up it starts manipulating that voltage and it starts switching.


George

 

Yep it showed up after i put the new bosch 4 wire o2 sensor in and drove it down the rode a few miles. Its a 4wire that you probably have to decipher the wires. Im gonna put the old one back in tomorrow and try that then that will tell me my new one is bad or not. Would you recommend NTK?

 

If the old sensor was switching correctly or you dont know if it was then your best move may be to put the old one back in and we start over diagnosing your problem.

George

 

I also think i have a exhaust leak which im going to check thoroughly tomorrow.

 

There may be nothing wrong with any of your O2 sensors. Lets:

1. Put the old one back in
2. See what the voltages are doing for all three sensors after the truck warms up
3. Clear the codes go for a drive and see what you get
4. Get your 4 fuel trim numbers at idle and 2500
5. Look for exhaust leaks
6. Tap you converter and see if it sounds crunchy inside (not too hard)

George

 

Okay i will and i will let you know whats going on while im working on it