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1999 Chevy Silverado O2 sensors

Tiny
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  • 1999 CHEVROLET SILVERADO
  • V8
  • 4WD
  • AUTOMATIC
  • 15,400 MILES
Engine light came on and the codes are p1133(o2 sensoe insufficiant switching left bank before converter, just changed and still there?), Po175 fuel trim system rich at upstream o2 sensor right bank, and po172 fuel trim system rich at upsteam o2 sensor left bank(just changed). Should I change them all or do I have a vaccum leak somewhere? If so how do I find it?
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Monday, March 30th, 2009 AT 11:25 PM

16 Replies

Tiny
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I would suspect since its rich on both banks that the issue is possibly a dirty MAF sensor. Clean it up and see how it goes.

If that doesnt clean up the codes you might want to check the intake air temp sensors, and engien coolant temp sensor.
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Tuesday, March 31st, 2009 AT 8:50 AM
Tiny
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I started my truck today and the check light was off? Should I spray everything with some MAF cleaner?
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Tuesday, March 31st, 2009 AT 6:39 PM
Tiny
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Just the wires on the MAF sensor. Dont soak everything! And dont touch the wires.
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Tuesday, March 31st, 2009 AT 7:40 PM
Tiny
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So the engine light came back on today. It is coming off and on latley.
What could it be? I cleaned the MAF.
Thanks for your help.
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Friday, April 3rd, 2009 AT 6:47 PM
Tiny
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Maf sensors wires could be damaged.

Check the intake air temp sensor and coolant temp sensor. Make sure their resistance values on cold engine are the same.

You replaced all the o2 sensors? Make sure the sensors were hooked up proper and the wirings arent damaged, sometimes if oil runs down the engine on the harness can gum them up and ruin the connections causing problems due to the very precise measurements of the system
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Saturday, April 4th, 2009 AT 2:05 PM
Tiny
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No I only replaced the driver side above the catylic o2 sensor. I'll check those other things out
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Saturday, April 4th, 2009 AT 5:47 PM
Tiny
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Let me know what you find.

The p1133 is what has me suspecting damage in the circuit since its not detecting the rich to lean to rich switches in the circuit.

The o2 sensor signal could be shorted to a pcm ground.

Check the top on the o2 sensors and make sure they are not plugged or the wires damaged. The o2 sensor takes outside air to compare the mixed air to determine the ratio. No air coming in. It shows really rich.

If you cant find it by this you will have to have a scan tool or ashop look at it to check the o2 sensors with freeze frame.
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Saturday, April 4th, 2009 AT 9:03 PM
Tiny
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Where can I find the PCM ground at?
-thanks
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Sunday, April 5th, 2009 AT 9:37 AM
Tiny
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It isnt really teh pcm ground thats shorting. Could be the pcm internally or the harness shorting to a ground.

Its quite a bit of work to do. Thats why I suggest taking it in for them to test it.
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Sunday, April 5th, 2009 AT 9:51 AM
Tiny
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Ok ill check if its clogged up first. Should any shop be able to do this?
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Sunday, April 5th, 2009 AT 10:32 AM
Tiny
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Anyshop should be able to do it.
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Sunday, April 5th, 2009 AT 11:00 AM
Tiny
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Could these codes be appearing because of a small exhaust leak? I have a small leak on the passenger side at the flange that ive been meening to fix.
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Wednesday, April 8th, 2009 AT 8:58 PM
Tiny
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It could but unlikely.

How big of a leak?

It shoudl throw a lean code on that bank. Not both banks. But it is possible if they refrence eachother to throw the insufficent switching code.
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Wednesday, April 8th, 2009 AT 9:05 PM
Tiny
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Its preety small, after the engine warms its barley noticable.
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Wednesday, April 8th, 2009 AT 9:08 PM
Tiny
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Possible but highly unlikely.

Check it out and fix it that way it dont come back to bite you.

It is a possibility
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Wednesday, April 8th, 2009 AT 10:03 PM
Tiny
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His has all happened after I put on aftermarket headers. If this helps at all?
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Monday, May 4th, 2009 AT 12:25 AM

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