2002 Chevy Silverado O2 light on

Tiny
RTAYLOR128
  • MEMBER
  • 2002 CHEVROLET SILVERADO
  • V8
  • 4WD
  • AUTOMATIC
  • 120,000 MILES
I have a 02 Silverado and the check engine light will come on stay on for several days and then go off. It will stay off for several days then comes back on. I have had the codes checked. The first time they said both o2 sensors on bank 1 were bad. Unhooked the battery to clear the codes. When it came back on the codes said number 1 sensor on both banks were bad. I could use any help as the light drives me batty. Thanks in advance for the help.
Sunday, March 23rd, 2008 AT 12:19 AM

9 Replies

Tiny
RHALL77
  • MECHANIC
  • 3,361 POSTS
Did you replace the sensors? What codes are you getting?
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Monday, March 24th, 2008 AT 7:43 AM
Tiny
RTAYLOR128
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  • 6 POSTS
I have not replaced the sensors as of yet because of the conflicting codes. As for the codes, I don't know as I had them checked at a parts store. I don't know if I should trust them or take it to the dealer.
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Tuesday, March 25th, 2008 AT 2:47 AM
Tiny
RHALL77
  • MECHANIC
  • 3,361 POSTS
Can you tell me what codes you are geting
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Tuesday, March 25th, 2008 AT 7:07 AM
Tiny
RTAYLOR128
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  • 6 POSTS
Accord to the code reader the codes are 171 and 174. The codes say to lean on upstream sensors. Is it possible that both sensors have gone bad at the same time. As of yet I have not replaced anythhing.
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Wednesday, March 26th, 2008 AT 9:04 AM
Tiny
RHALL77
  • MECHANIC
  • 3,361 POSTS
I worked for a GM dealer for years, I personally dont think you need O2 sensors. I think, and it sounds like you have a vacuum leak. Which 90% of the time it is an upper intake gasket. You will need a code scanner to read the fuel trim under a load to verify. When the fuel trim reads -10 or more that will tell you that you have a vacuum leak.
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Wednesday, March 26th, 2008 AT 9:51 AM
Tiny
RTAYLOR128
  • MEMBER
  • 6 POSTS
Thanks for your advice, but I was wondering if it is a vacuum leak why would the light come on for a few days and then go off. It seams if it were a vacuum leak the light would stay on all the time.
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Wednesday, March 26th, 2008 AT 12:39 PM
Tiny
RHALL77
  • MECHANIC
  • 3,361 POSTS
A friend of mine had one do the same thing yours is but when we cleared the light it never came back on. But still had a performance problem.
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Wednesday, March 26th, 2008 AT 12:48 PM
Tiny
RTAYLOR128
  • MEMBER
  • 6 POSTS
I have cleared the light several times but it still does the same thing. Guess I will have to put in the shop for them to check it. If it is a vacuum problem at the intake I have no way of checking it. Thanks for all your help and advice.
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Wednesday, March 26th, 2008 AT 2:05 PM
Tiny
RTAYLOR128
  • MEMBER
  • 6 POSTS
I know this doesn't make sence, but I replaced the K&N air filter with a Fram and reset the check engine light and it hasn't come back on. It has now be about 3 weeks. Next week I am going to put the K&N filter back in and see what happens.
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Tuesday, April 29th, 2008 AT 12:02 AM

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