Reject Smog Test. Need help with the issue Please.

[mookiex4]

I brought my truck in for smog. I have no check engine light illuminated and no codes listed on the computer when I ran the codes. The smog was rejected for three sensors it could not read, (OBD CATALYST, OXY SNSR and OXY SNSR HEAT.). I cannot imagine why it would not read these sensors and I have no codes on my computer and no check engine light. I DID NOT unhook the battery nor did I clear the codes, because I know the new smog machines will fail it and I had no reason to figure that I wouldn't pass. Can someone give me some helpful guidance?

Mookiex4
Reno, NV

 

[dodge dude94]

Lets start with the basics: why would it throw those codes?

How long has it been since you replaced the spark plugs, wires, and cap and rotor? Are the wires routed correctly?

How long has it been since you replaced your O2 sensors? Is your plenum fixed? Cat original or recently replaced?


I've not heard of a vehicle failing like that, usually it's a code or the sniffer test fail.

 

[mookiex4]

Lets start with the basics: why would it throw those codes?

How long has it been since you replaced the spark plugs, wires, and cap and rotor? Are the wires routed correctly?

How long has it been since you replaced your O2 sensors? Is your plenum fixed? Cat original or recently replaced?


I've not heard of a vehicle failing like that, usually it's a code or the sniffer test fail.

The computer is not throwing codes. The Smog machine rejected the test because it could not read those sensors. It is not the sniffer test. It was plugged into the computer terminal under the dash and the truck was started.

The machine rejected because it could not complete the test on those three sensors. The smog guy asked me if I cleared the computer codes or unhooked the battery. I did neither. It used to be that you could beat the smog test by clearing the coes, not anymore so there is no reason to do it.

 

[mookiex4]

Lets start with the basics: why would it throw those codes?

How long has it been since you replaced the spark plugs, wires, and cap and rotor? Are the wires routed correctly?

How long has it been since you replaced your O2 sensors? Is your plenum fixed? Cat original or recently replaced?


I've not heard of a vehicle failing like that, usually it's a code or the sniffer test fail.

I just bought the truck in Arizona and brought it to Reno NV where I live. I do not have previous replacement information.

 

[dodge dude94]

The computer is not throwing codes. The Smog machine rejected the test because it could not read those sensors. It is not the sniffer test. It was plugged into the computer terminal under the dash and the truck was started.

The machine rejected because it could not complete the test on those three sensors. The smog guy asked me if I cleared the computer codes or unhooked the battery. I did neither. It used to be that you could beat the smog test by clearing the coes, not anymore so there is no reason to do it.

Okay. There is a Oxygen Sensor Heating circuit, but I don't know how that would be directly related to the sensor.


Wait for someone elses input as well, but I would be replacing my sensors if I hadn't in a long time. They're supposed to be replaced every 60-75k mi.

 

[mookiex4]

Thanks. I should do it anyway. It has 122,000 miles on it and not sure if the O2 Sensors are original or not. If one or all were bad wouldn't the check engine light be on telling me there is an O2 Sensor issue? I know my 97 Expedition threw a code for the Upstream Bank 1 Sensor.

 

[dodge dude94]

The PCMs on these trucks are really lax about letting you know something is wrong. lol It could be that they are in spec to the PCM but the smog scanner thinks otherwise.



Get NTK sensors as well.

 

[mookiex4]

The PCMs on these trucks are really lax about letting you know something is wrong. lol It could be that they are in spec to the PCM but the smog scanner thinks otherwise.



Get NTK sensors as well.

Thanks. I will do it. I think I should take the Reject paperwork and have a mechanic do a diagnosis. I think since I have a 90 day permit I can wait until next year and I am then allowed 3 codes and still pass the test.

 

[WhiteExpress]

that's fairly interesting. I wonder if they turned off your rear O2 sensor with a tuner.
If you do a quick visual inspection, do you still have a cat under there?

 

[mookiex4]

that's fairly interesting. I wonder if they turned off your rear O2 sensor with a tuner.
If you do a quick visual inspection, do you still have a cat under there?

Whoa White Express. You scared me! I had to go look. HAHA. The Cat is there. I have on O2 Sensor just before and just after the cat, (Downstream). I assume without looking, that I have 2 upstream O2 sensors. Up high near the exhaust manifolds. So all is good with that. I will have to roll it in the garage tomorrow and see if any of them are unpluged or have damaged wires. Right now it is 9 outside and I am not that anxious right now.

I went ahead and ordered the 2 Upstream and 2 Downstream sensors form RockAuto Parts Catalog and will install those when they arrive. Hopefully DMV here says I can have three smog codes come January 2014 and all of this won't matter. I would still like to correct it and figure it out.

 

[Bigtman07]

My truck I believe only has 2 sensors one pre cat and one post cat. Check the wires on the O2 sensors maybe one is shorting therefor kicking it for the tester and not the PCM.

 

[mookiex4]

My truck I believe only has 2 sensors one pre cat and one post cat. Check the wires on the O2 sensors maybe one is shorting therefor kicking it for the tester and not the PCM.

Thanks,

I never looked under the hood. I was going to do that tonight. I have one Pre and post Cat. Perhaps that is all there is. Hopefully, then i can send one of each back to Rock Auto.

 

[mookiex4]

Thanks all for oyur help and guidance. A new set of O2 Sensors did the trick and about that time the cheap plastic pulley on the tension arm for the serpentine belt disintegrated. They may have helped as well.