Check engine light coming on after long trips

**NYKRINDFW** · 09-27-2012, 03:27 PM

So I took the 'Bird to Dallas from San Antonio in April and when I arrived and gassed up the Check Engine Light came on. All systems seemed to be 'go' so I figured I'd have it checked out when I got back home. A few days after getting back home and doing some city driving the light went off and stayed off. A week ago I had a tune up done and the Chevy dealership did not mention any issues.

It is now September and I took the car out to the El Paso/Big Bend area. I drove 300 miles and stopped for gas. When I started the engine, the Check Engine Light came back on again. I've put 500 + miles on the car since with no change, car is getting 30 highway miles to the gallon and all systems are 'go'.

Any ideas?

TY

NY

**FinZ28** · 09-27-2012, 04:04 PM

Go to some place like Advance and get them to pull your code(s), and report back what you find.

**Knight** · 09-28-2012, 05:29 AM

Agree. See if you can get a code. It may be something simple like a rear O2 sensor, which won't affect performance, but will throw a SES light. If you still have them, that is.

**NYKRINDFW** · 09-28-2012, 07:32 PM

The light went out tonight.

No one else has experienced this?

NY

**az gt eater** · 09-29-2012, 12:21 AM

Here, read this, this will give you an idea of how many different codes there are that could throw the service engine soon light. That is why it is important to get the codes when the light comes on.http://www.ls1.com/forums/f6/sticky-maybe-122570/

**Too Fast** · 09-29-2012, 02:43 AM

Yup gotta see what the code is. A loose gas cap can cause the light to come on like you say, so can O2 sensor heater codes and air pump check valves that are almost clogged.

**428 78T/A** · 10-03-2012, 07:13 PM

Mine comes on every now and again. Isn't on for 99% of the time.

**Redrokit8** · 10-04-2012, 05:51 PM

I had the exact same experience when I installed Kooks Long Tubes with High Flow Cats. I had already had the PCM reprogrammed by Frost, but it had to be tweaked a little more for the headers. Ran a lot better as a result. If it's one thing I have learned from this Forum that most modifications can be felt immediately but you need to retune for maximum benefits.

**mrbvlo** · 10-06-2012, 07:19 AM

I had the same problem with my 2000 formula. Turned out to be the air injection system. It's suppose to inject air into the exhaust manifolds during start up to reduce emissions until the engine warms up. The air pump should run for the first couple minutes during cold starts. It's located under the driver headlight (you'd have to open up the facia underneath to get access). But you should be able to hear the pump running from inside your car. I think the air pump was getting ready to go as it would work sometimes, and not at others. Hence, a code would appear, and then go away a couple days later by itself. Just like the other posts on here, I eventually bought a "scan tool" to narrow it to this system. I replaced the two valves first hoping that would be the easy fix (and cheaper), but ended up replacing the electric motor as well. Paid maybe 70 dollars on Amazon for the replacement electric motor.

**pajeff02** · 10-07-2012, 05:36 PM

^^ I bagged the entire system on our car. If you ever need a replacement pump or other parts for it, let me know.

**35th-ANV-SS** · 10-10-2012, 08:45 PM

I removed my system as well.

**Too Fast** · 10-11-2012, 02:36 AM

Jon, don't you have emissions testing in the Chicago area? Or is it just the ''check for codes/SES on/are all the monitors run and passed'' type of emission check?

**35th-ANV-SS** · 10-12-2012, 05:37 AM

We only have the OBDII plug-in test. So, you are correct with the later part of your statement. I live in Indiana

**johnfin** · 10-12-2012, 06:36 AM

I have a p0430 (cat conv) code that comes on and off frequently. Since the OBDII light isnt suppose to reset by itself and turn the light off I attribute the problem to the computer.

**pajeff02** · 10-12-2012, 06:13 PM

Certain codes will actually disappear after so many starts provided the problem does not reappear during the count. Depends on the specific code and the error reporting setting for it.

**mrbvlo** · 10-13-2012, 02:09 PM

FYI,

P0430: Basically this means that the oxygen sensor downstream of the catalytic converter on bank 2 is detecting that the converter is not working as efficiently as it should be (according to specs). It is part of the vehicle emissions system.

A code P0430 may mean that one or more of the following has happened:

The catalytic converter is no longer functioning properly
An oxygen sensor is not reading (functioning) properly
There is an exhaust leak

Leaks usually aren't intermittent. Since the O2 sensor is a cheaper fix than the converter, I'd try that first. Of course it could just be the wire going to the O2 sensor; may be shorting out on the tranny or the exhaust.

**johnfin** · 10-15-2012, 04:21 AM

I thought the O2 sensors tripped different codes when they were faulty.

**mrbvlo** · 10-15-2012, 11:55 AM

I'll qualify this response with "I'm not an ASE certified mehanic". Just got alot of driveway trouble shooting experience. I hate letting someone else work on my car, cause they'll usually charge you an arm and a leg, and do all the same things.

The O2 sensors help determine the efficiency of the catalytic converter. The powertrain control module does this by comparing the signal of the sensor located at the inlet of the catalytic converter with the signal of the sensor located at the outlet of the converter. Of course other codes would be set if an O2 sensor went completely out, but if the signal was degraded on the downstream sensor for some reason, the computer would interpret that as "the cat not working efficiently". And of course it could be the cat needs replacing. I wouldn't fix anything until the code stayed on permanently or kept you from passing an inspection. But if you do find yourself in that situation, it's just cheaper to replace an O2 sensor than a cat for the backyard mechanic. Of course you could pay "someone" to evaluate the problem and you'd probably get sold a set of O2 sensors and a cat!

**pajeff02** · 10-15-2012, 05:05 PM

My Durango kept tripping the same code for "catalytic efficiency below threshold". The light would come and go, but it never affected my mileage so I wasn't in a big hurry to fix it. I eventually changed out the cat and haven't had a problem since. The cats on our cars are known to go bad - they had an extended factory warranty that is now expired. I have a set of stock replacement cats with around 20,000 miles on them if you decide you need one or both.

**johnfin** · 10-16-2012, 04:07 AM

GM actually said they would fix mine (if there was a problem) but I said no way. I would never have some looser mechanic touch my car. Too many problems in the past.