Stubborn Check Engine Light

[welwillie80]

My check engine light has been on for about 2 and a half months now. First, I had no codes but changed my gas cap out: no change. Next, I actually threw codes for idle air intake so I replaced that. Now, I have no codes but the light persists. I have cleaned my air filter, checked all connections, and both o2 sensors are about a year old. My only other guesses, codes or not are, are either a) I need a new MAP sensor or, b) I need to replace my dash cluster. According to the dealership, this is $90 vs $1250, respectively. Any ideas?

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[BaddestCross]

My check engine light has been on for about 2 and a half months now. First, I had no codes but changed my gas cap out: no change. Next, I actually threw codes for idle air intake so I replaced that. Now, I have no codes but the light persists. I have cleaned my air filter, checked all connections, and both o2 sensors are about a year old. My only other guesses, codes or not are, are either a) I need a new MAP sensor or, b) I need to replace my dash cluster. According to the dealership, this is $90 vs $1250, respectively. Any ideas?

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If there's a light on there's a code. Get a better scanner.



--
Build Thread - Adventures of Fiona - https://wayalife.com/showthread.php?t=47407

 

[welwillie80]

I've used a cheap scanner and had a friend use his professional grade scanner. No codes.

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[harrisonsims62]

I've used a cheap scanner and had a friend use his professional grade scanner. No codes.

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There’s gotta be a code, think about it.
Why throw a check engine light if there’s no code.
Does it same anything at the odometer? Like instead on miles does it maybe say “no bus”


Mike honcho himself

 

[welwillie80]

I'm telling yall....there is no code active, pending, or stored. Once I had a check engine light on intermittently because of an electrical component that needed to be replaced in the dash itself.

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[Primo82]

Have you tried clearing codes to remove the light? Does the light come right back or just not go off?

If the lights on it should be throwing up something. Maybe a messed ups witch that controls the check engine light... I'm really curious what you find.

 

[Spazbyt]

Maybe check battery cables. I know the dash lights will do some crazy shit if they are even slightly loose. That's all I got, hope you figure it out soon.

 

[welwillie80]

Have you tried clearing codes to remove the light? Does the light come right back or just not go off?

If the lights on it should be throwing up something. Maybe a messed ups witch that controls the check engine light... I'm really curious what you find.

I've cleared them numerous times. I had a different guy use his scanner and it finally came back as evap. I replaced the purge solenoid and still on. Next step is vapor canister.

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[welwillie80]

Maybe check battery cables. I know the dash lights will do some crazy shit if they are even slightly loose. That's all I got, hope you figure it out soon.

This was an issue a while back. Looking into it.

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[Primo82]

I've cleared them numerous times. I had a different guy use his scanner and it finally came back as evap. I replaced the purge solenoid and still on. Next step is vapor canister.

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Lol, I hate the codes because even if you get a code you're still trying to guess what out of the 15 things in that system tripped the code!

For evap related stuff my goto first fix would be the gas cap. Purge solenoid and vapor canister are also potential offenders so I think you're on the right page. Obviously start chasing hoses and whatnot of none of those are fix it... Good luck man!

 

[sipafz]

Check the evap. hoses! They dry rot and leak over time.

 

[Primo82]

Check the evap. hoses! They dry rot and leak over time.

Yea, I looked at his profile after my last post. Looks like this is happening on a 90s TJ. Dry rot is definitely likely.

 

[welwillie80]

Gas cap was first fix. Obviously didnt work. Thanks for the vote of confidence.

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[Snboarder113]

Key on/off/on/off/on see if the dash will Show you a code.

Smack your gauge cluster inwards, they have crappy connection design.

Unplug and clean harness connections at computer above the battery. Ensure seated properly.


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[welwillie80]

If anyone cares, this was my stepwise process:

1. Idle air module/valve.

2. Purge solenoid valve

3. Vapor canister

4. Had a dry rotted elbow from VC to intake.

At this point, none of the fixes got rid of the light. My last choices were horses (they were all good), MAP sensor, and new PCM.

5. Replaced MAP sensor. Light immediately went off.

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[bigwheel53]

dash lite for vapor

I've cleared them numerous times. I had a different guy use his scanner and it finally came back as evap. I replaced the purge solenoid and still on. Next step is vapor canister.

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I know its a little late but the same thing was driving me crazy. I have a scanner and I would clear the code but down the road it would come on again. Theres a brake line looking thing that goes back to the gas tank that was rusted right off the tank. Replaced the line and light never came on again.

 

[ItayGrubman]

I know its a little late but the same thing was driving me crazy. I have a scanner and I would clear the code but down the road it would come on again. Theres a brake line looking thing that goes back to the gas tank that was rusted right off the tank. Replaced the line and light never came on again.

The first and easiest method for clearing the check engine light is driving and time. ... If the check engine light is still on after three days, your problem may not have been fixed or you may need to try some of the methods below to reset it.

 

[ItayGrubman]

Gas cap was first fix. Obviously didnt work. Thanks for the vote of confidence.

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So first things first, pull over (as soon as it's safe) and make sure your gas cap is on tight. If this was indeed the trigger, your check engine light should go off within 10 or 20 miles once you're back on the road.

 

[cozdude]

The first and easiest method for clearing the check engine light is driving and time. ... If the check engine light is still on after three days, your problem may not have been fixed or you may need to try some of the methods below to reset it.

3 days isn’t enough time. Most check engine lights require 40 engine heat cycles for them to go away once set. This goes for type A and B codes. If the failure doesn’t repeat within those cycles then it will self clear.

 

[monstrousmac]

I've cleared them numerous times. I had a different guy use his scanner and it finally came back as evap. I replaced the purge solenoid and still on. Next step is vapor canister.

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Don't waste your time on the EVAP system I get the code every 2-3 months or Gas Cap Light. I clear the code and it stays off for a few months. It seems to be a problem with Jeep vehicles. The code is P0456. I started to get it when my vehicle was about 2 years old and now it is 10 Years old with 200,000 miles on it. It is the 3.8 Liter. The local dealership mechanic even told me not to waste my time, it is like chasing a rabbit down a rabbit hole.