CEL Question...

[getarz4u15ster]

So... I put a cam in my car 3 weeks ago.. took it, had it tuned, no CEL's when i left and everything feels great on the car. Randomly Saturday the car thew a CEL. So i hooked up my scanner to it and it reported "No codes can be found" BUT the check engine light was on.... So i chose the clear option anyway, and whadaya know it goes out... I'M ALL HAPPY now that it went out, and guess what it comes back on again the next day, BUT this time it went back off by it's self the following day not to be seen again until This morning 4 days later.

It's really weird, it shows me no codes when i plug my scanner into it, CAR RUNS GREAT even when the light is on. I called the tuner and he said that ECU is going to have to re learn everything again, and that sometimes if the ECu doesn't see enough switching signals it will throw the light on only to go off later on. .I think that one of the O2 sensors is getting a false reading or possibly from the rear 02's (i have shorties with orginal mid pipes). Maybe a Map code error... I thought that the tuner would have turned the rear 02's off in order to pass readiness checks later for emissions. Anyone ever seen this after a tune and cam??? Just curious...

[06MonteSS]

Originally Posted by getarz4u15ster

I thought that the tuner would have turned the rear 02's off in order to pass readiness checks later for emissions.

if you disable/turn off the rear O2 codes, you will not pass emissions readiness tests...

because the rear O2's are used to determine how your CAT's are functioning... and if they're disabled, then they can't "report" on the cat functionality/efficiency...

[DSteck]

Originally Posted by 06MonteSS

if you disable/turn off the rear O2 codes, you will not pass emissions readiness tests...

because the rear O2's are used to determine how your CAT's are functioning... and if they're disabled, then they can't "report" on the cat functionality/efficiency...

That's not true. I have no rear O2 sensors in my Z06, and it passes every single readiness check. The 2010 Camaro I've been doing a lot with lately that is cammed has the rear O2s turned off as well, and it passes all readiness checks just the same.



To the OP, I find it very odd that you're not pulling up any codes. Are you sure that your code reader is capable of reading CAN-based OBD-II? A tune should never have to learn ANYTHING if it's done right. The only thing that will always adapt are your fuel trims, but that's not going to impact you getting a check engine light. Depending on the size of the cam, I'd say there's a good chance you're either seeing P0300 for misfire or P0106 for map sensor performance.

Did you add any other parts when you did the cam?... Were the headers there before the cam? Headers would cause an insufficient switching code on your front sensors because some designs don't have proper scavenging at low rpm, low load. Will the check engine light trip if you just let the car sit and idle?

[getarz4u15ster]

Originally Posted by DSteck

That's not true. I have no rear O2 sensors in my Z06, and it passes every single readiness check. The 2010 Camaro I've been doing a lot with lately that is cammed has the rear O2s turned off as well, and it passes all readiness checks just the same.



To the OP, I find it very odd that you're not pulling up any codes. Are you sure that your code reader is capable of reading CAN-based OBD-II? A tune should never have to learn ANYTHING if it's done right. The only thing that will always adapt are your fuel trims, but that's not going to impact you getting a check engine light. Depending on the size of the cam, I'd say there's a good chance you're either seeing P0300 for misfire or P0106 for map sensor performance.

Did you add any other parts when you did the cam?... Were the headers there before the cam? Headers would cause an insufficient switching code on your front sensors because some designs don't have proper scavenging at low rpm, low load. Will the check engine light trip if you just let the car sit and idle?

Ya know what... that's when i notice it.. everytime i let the car sit and idle for 2 or 3 minutes at a cold start, is when i notice it happens... I thought there was a coincidenece there, but i wanted to try it one more time to see if there was a pattern developing there as well. I did have the headers on before the cam. So at this point it's intake,shorty headers, exhaust, and the cam. What you are saying about the P0106 for the map i've heard will do this same type of thing as well. What can be done about the misfire and map codes? Tune them out completely or what?

Ohh and as far as the code reader... im not really sure it's my Pops. It's brand new for OBD2 vehicles.. but who knows, i'll have to ask him.

[DSteck]

There's OBD-II, and then there's CAN-based OBD-II. CAN-based readers can work with standard OBD-II, but standard readers can't handle CAN-based.

I it possible you're getting either P1133 or P1153 for insufficient switching on a front sensor, but I have a hard time believing shorties (even with a cam) would do that.

Try this. Start your engine, and let it warm up to temperature. Once it's hot, shut it off, disconnect your battery for about a minute, and then reconnect it. This will clear any codes (just to make sure... because who knows what your reader is doing). Start the car again and just let it idle for a while... maybe 20 minutes. After that, go drive it around a bit. If a code comes on while just idling, it's likely insufficient switching or P0106 for the map sensor. If a code doesn't come on until the next time you drive it, it's probably misfire. There are tables you can adjust to tweak the threshold of setting the misfire code, but something tells me it's not misfire. I'd bank on P0106. This is all just speculation though. Find somebody with EFI Live or HP Tuners, plug in the scanner, and pull the codes.

[getarz4u15ster]

Originally Posted by DSteck

There's OBD-II, and then there's CAN-based OBD-II. CAN-based readers can work with standard OBD-II, but standard readers can't handle CAN-based.

I it possible you're getting either P1133 or P1153 for insufficient switching on a front sensor, but I have a hard time believing shorties (even with a cam) would do that.

Try this. Start your engine, and let it warm up to temperature. Once it's hot, shut it off, disconnect your battery for about a minute, and then reconnect it. This will clear any codes (just to make sure... because who knows what your reader is doing). Start the car again and just let it idle for a while... maybe 20 minutes. After that, go drive it around a bit. If a code comes on while just idling, it's likely insufficient switching or P0106 for the map sensor. If a code doesn't come on until the next time you drive it, it's probably misfire. There are tables you can adjust to tweak the threshold of setting the misfire code, but something tells me it's not misfire. I'd bank on P0106. This is all just speculation though. Find somebody with EFI Live or HP Tuners, plug in the scanner, and pull the codes.

Okay.. I'll try that tonight and see what happens. Hopefully i'll get some type of result. Thanks for the help I appreciate it! I'm glad you responded. From what i can tell on other posts you've made here...you know your stuff and it's good to have that knowledge here!

[06MonteSS]

Originally Posted by DSteck

That's not true. I have no rear O2 sensors in my Z06, and it passes every single readiness check. The 2010 Camaro I've been doing a lot with lately that is cammed has the rear O2s turned off as well, and it passes all readiness checks just the same.

so are you using a custom OS that reports no rear o2s equipped then??

[DSteck]

Originally Posted by 06MonteSS

so are you using a custom OS that reports no rear o2s equipped then??

My Z06 has an enhanced operating system, but I did it just the same on the original operating system as well. The 2010 Camaro has a factory operating system, a couple of my friends with C6s that I've done have factory operating systems, and every other car I've ever done all have factory operating systems, and they still complete every readiness check despite having the rear O2 sensors totally disabled.

[Genevieve]

I have used onstar to check my CEL's before. They will just check the car while the light is on and tell you what it is right there. This might help ya if your scanner wont.

X2 on a true tune not needing a learning period after a tune.

my .02

[DSteck]

To the OP... have you had a chance to play with it? I checked the factory code settings for P0106 and and P1133/P1153, and they all trip on the second error. It will probably take two drive cycles to throw the code.

What are the cam specs?

[Dr Jkel]

What kind of tuner did you use?

[getarz4u15ster]

OKAY!!! I was finally able to pull the codes, haven't been to the tuner yet, but this is what it said..

P0300 - Misfire (I'm guessing they are going to have to tune the misfire table here..??
P0121 - Throttle Position Sensor/Switch A Circuit Range/Performance Problem (which is result of my throttle body being ported) i do know that.... So they are going to have to tune that out..

[getarz4u15ster]

Originally Posted by DSteck

To the OP... have you had a chance to play with it? I checked the factory code settings for P0106 and and P1133/P1153, and they all trip on the second error. It will probably take two drive cycles to throw the code.

What are the cam specs?

Cam specs are 227/243 @.50 .614/.624 113LSA

Car runs great other than the idiot light on the dash anoyying me to death...

[DSteck]

P0300 can be caused by a few things. Just tweaking the set criteria alone is not the proper way to deal with that.

As far as P0121, your throttle body being ported doesn't really cause that... It's just a result of moving a lot more air than the PCM thinks it should be seeing. It's easy to deal with.