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Bad Co2 Sensor

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Anonymous Poster

Aug 12, 2008, 6:28 PM

Post #1 of 6 (6219 views)
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Last week I got my chevy 1500 pickup inspected. It didn't pass emissions so the shop performed a tune up (Oil Change, Distributor Cap & Rotor, Plugs & Wires, PCV Valve) The Tune up and Inspections cost me $351.81.

Over the weekend I had to take the truck out of town on the highway, about an hour into the 3 1/2 trip the Service Engine Soon Light came on. After I got back in town I called the shop that did the repair thinking they might have done something wrong, so i took it to them last night and they told me that it was a malfunctioning Co2 Sensor. They charged me $75 for diagnosing the problem and want another $225 to replace the sensor.

My questions are: Is that a fair price? Could they have damaged or not connecting something during the emission test to cause this, or is it just really bad luck? and What does this sensor do?

Thanks in Advanced!

Tom Greenleaf
Ultimate Carjunky / Moderator

Aug 12, 2008, 10:04 PM

Post #2 of 6 (6208 views)
Re: Bad Co2 Sensor [In reply to] Sign In

What year and engine in this?

O2 sensors are a bit pricey and can be a pill to replace. Depending on what year there could be four of these! Did all on my own 97 - all worked but wires were coming loose on an "after the converter" one so didn't impair operation but would have stopped it from an inspection sticker. Replaced all anywho on my own - not so cheap!

I'm a tad surprised they charged you to read the code after just doing the tune-up items and a subsequent SES light which just a highway run might have triggered and may reset.

Is it running well? Did the inspection include saying what was wrong if anything or just that a code was set and wouldn't pass it while a code was set?

More info would help,

Long retired now

Anonymous Poster

Aug 13, 2008, 2:43 PM

Post #3 of 6 (6198 views)
Re: Bad Co2 Sensor [In reply to] Sign In

it's a 95 6cylinder 4.3L. It doesn't seem like it had as much power as it used to. All they told me was that it passed inspection and failed emissions. They said the injectors need cleaned and it would need a tune up.

After they performed this it did pass the emissions test, and the next day it went on the highway and the SES light came on.

How many sensors are on this truck? If there are more than one do they all have to be replaced?

Tom Greenleaf
Ultimate Carjunky / Moderator

Aug 13, 2008, 5:37 PM

Post #4 of 6 (6189 views)
Re: Bad Co2 Sensor [In reply to] Sign In

That's more info than you may want to know on o2 sensors for this vehicle. There could be two types used and not sure how many total. Some are heated and some aren't - it asked when searching for them.

If it itsn't running well it needs the source (probably cleaning injector spider) solved first or a new sensor will also fail soon. This is probably fixed as you passed emissions after the tune up. The dang sensors can pick up some debris and clear later - forever or just a short while - it's hard to know for sure without a real look.

Anything that causes an engine to no run well will be hard on convert(s) and o2 sensors. A sensor sending wrong info to allow for computer adjustments will cause it to run lousy by itself. It's a "chicken and egg" type thing for many vehicles in the guess of which came first.

If you are running well now it might reset - I suggest adding some fuel injector solvent (Chevron's Techron a fav) and give it some time. That and get a code reading as to what it's storing for info now and reset it. If it comes right back it's a hard code problem and probably won't clear out on its own.

I've had these sensors fail by corrosion problems with wiring right at them more than failures inside where it does its sensing.

IMO - poke around town type driving aggrevates these things and as you said a hwy trip set yours off which may or may not reset now. AutoZone and others near me read codes for free. You should know what it's telling you and make a plan based on that and how well it runs right now.

If they won't reset it, it should reset with battery disconnect (neg off for a while) and may or may not come right back on of stay off if all is well.

There's more to these little suckers than just screwing in a new one - beware of that,

Long retired now

Anonymous Poster

Aug 15, 2008, 2:18 AM

Post #5 of 6 (6174 views)
Re: Bad Co2 Sensor [In reply to] Sign In

Ok, Do you think $225 is an appropriate price for this repair?

Tom Greenleaf
Ultimate Carjunky / Moderator

Aug 15, 2008, 8:46 AM

Post #6 of 6 (6168 views)
Re: Bad Co2 Sensor [In reply to] Sign In

Oxygen Sensor Results 1-4 of 4 Product Part No. Price Bosch / Oxygen Sensor
Warranty - 1 YR 15700 $59.99 Application: Sensor located before catalytic converter Note: O.E. type 3 wire; heated, 2 required. Store: Online: Bosch / Oxygen Sensor
Warranty - 1 YR 15726 $69.99 Application: Sensor located before catalytic converter Note: Universal 3 wire; heated, 2 required. Store: Online: Denso / Oxygen Sensor
Warranty - 3 MO 234-3000 $70.99 Application: With 1 wire connector Note: Universal Store: Online: Denso / Oxygen Sensor
Warranty - 3 MO 234-3005 $68.99 Application: With 1 wire connector Note: O.E. type Store: Online: Repair Information for your: 1995 Chevrolet Truck C1500 1/2ton P/U 2WD 4.3L TBI Vehicle Repair Guides: GM Full Size Vans 1987-1997 Repair Guide GM Full-Size Trucks 1988-1998 Repair Information Suzuki Samurai/Sidekick/Tracker 1986-1998 Repair Guide

Not so fast. I think there are four o2 sensors in all in this vehicle. That info wasn't quick to find. There seem to be at least three - two heated jobs before converter.

The questions are........

Is it running well now? If so and it did just legitimately pass inspection then I'd reset the SES and let it go thru a cycle again. Diag should have said which one was at fault for the SES.

In cleaning the throttle body if part of the tune-up or racing the engine for the inspection the sensors could be aggrevated and might just up and get over it. If it's not running well because of this it would be best to act quickly to prevent further problems.

Your quoted price. I can't say what rates are for your area. You can see the parts prices above and there is some legitimate time and testing (paid already) involved. The pipe these screw into can be troublesome at the age now.

Do you have an itemized quote to fix this in hand?

More: You didn't pass the emissions back when to begin with. Was there a warning then with any SES light? Was it running well? What type of emissions test do they do in your area - dyno?


If one of the sensors is truly bad I'll go along with your price. I'm still worried that this may need the others and or more if in fact it was running poorly long enough it could also involve converters and those get real pricey!


Long retired now

Bad Co2 Sensor

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