Here's a PI that is sort of funny. I wonder how they figured this out?
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#PIP4431: Intermittent SES Light Due To A P0442 With No EVAP Leaks - keywords BQMI - (Jun 26, 2008)


Subject: Intermittent SES Light due to a P0442 DTC with No EVAP Leaks


Models: 2005-2007 Chevrolet Cobalt SS
2005-2007 Saturn Ion Redline
with 2.0L Engine (RPO LSJ)
2006 Chevrolet Cobalt
2006 Chevrolet HHR
2004-2006 Chevrolet Malibu
2006 Saturn Ion
with 2.2L Engine (RPO L61)
2004-2007 Chevrolet Colorado
2004-2007 GMC Canyon
2006-2007 Hummer H3
with 2.8L, 2.9L, 3.5L, or 3.7L Engine (RPO LK5, LLV, L52, or LLR)
2006-2007 Buick Rainier
2006-2007 Chevrolet Trail Blazer
2006-2007 GMC Envoy
2006-2007 Saab 97x
with 4.2L Engine (RPO LL8)
2005 Chevrolet Trail Blazer
2005 GMC Envoy
with 5.3L Engine (RPO LH6)
2005 Chevrolet SSR
2005 Chevrolet Corvette
with 6.0L Engine (RPO LS2)
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The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.

Condition/Concern:
On rare occasions, an intermittent SES light may be experienced due to a P0442 DTC even though no EVAP leaks are present. This DTC may be induced when the key is turned to the accessory position to turn the engine off, rather than the off position.

Here is an example of a common scenario that may induce this DTC: The customer drops somebody off at a store, parks their vehicle, turns the key to accessory (without turning the key to off first) to turn their engine off, listens to the radio, and restarts their vehicle once the person in the store returns.

Recommendation/Instructions:
If a P0442 DTC is encountered, perform the related SI diagnosis and any bulletins or PIs that relate to this concern on the vehicle you are working on. If the SI diagnostics did not isolate the cause of this concern, and no bulletins or PIs helped/were found, interview the customer to determine if this may be a result of the key cycle described above. If it is, explain to the customer that they should be able to prevent this concern by avoiding the key cycle described above. They can still use the accessory position but they just need to turn the ignition to the off position before turning it back to the accessory position again. If they turn the key to the off position before using the accessory position, it should prevent this concern from occurring.

 

My '03 Silverado did a similar thing. It would set the SES and when I scanned it the DTC was EVAP. Always thought it was for my gas cap not being tightened properly after a refuel or something. I would clear it or sometimes it the SES would go out on it's own after a few days.

And yeah, wonder how they figured that out.

 

Took someone shopping?

 

Interesting thing happened on Saturday. (read bold red text) After listening to the radio, I went inside. I then started my engine 2 hours later and CEL comes on. Got the code read at the local auto parts store and I got a code P0442. I asked the counter-person if this was related to seal on gas cap. Counter-person answers that it has nothing to do with the gas cap but it is a faulty purge valve PV443. I told the counter-person that I was going to do more research and come back later. Sunday morning, I open my fuel door out of curiosity - the gas cap wasn't even screwed-on!! I filled my tank more than a week prior to this so if I didn't put my cap on properly, CEL would have come on immediately. Someone tamper with my gas cap? LOL How many miles will I have to reach to clear the CEL ? Should I go-ahead and replace the gas cap since it's 10 years old anyway? I filled the tank yesterday,,,

 

A. the counter guy was wrong; it is the VENT valve. PV483
B. sometimes it takes a while for the test to run, it takes some special circumstances including 15%-85% tank of gas. If it is the cap it should clear after the next cold start when the tank is under 85% full and you park it for an hour or so..



To be fair to the AutoZone crew; the part names are very confusing and listed incorrectly in many parts books. Both parts have combinations of "canister", "vent", "purge", "valve". The one under the hood (PV443) is sometimes called "canister purge vent valve", the one near the gas tank is "canister vent purge valve". The one under the hood purges fumes from the canister into the combustion chamber, the vent valve allows air into the tank so that gas can be pumped out of it.

 

UPDATE: After I filled the tank, I gave the gas cap a few extra clicks after it tightened. Once my trip odometer reached 100 miles, the CEL went off. Problem solved; it was probably because my gas cap wasn’t on as I stated in my previous post.

 

Fixed! Enjoy the ride!