CEL mystery

bascars · **Joined:** Mon Jun 24, 2019 11:18 pm **Posts:** 23

Had p0401 on and off for the first year that I had my CRD. I just recently completed EGR/FCV delete. Had custom tune built and installed. CEL turned off but then came back a day or two later. I checked with both of my scanners, both of which stated no stored DTCs (one even had a CEL status that said “off”). I disconnected the battery overnight and still no change. All that work and money to get the light to shut off and now it is lit without any reason (and will need to be off when I have to register the vehicle again). I am baffled. Has anyone had or heard of an issue like this?

WWDiesel · **Posted:** Sun Apr 26, 2020 10:13 pm

bascars wrote:

Had p0401 on and off for the first year that I had my CRD. I just recently completed EGR/FCV delete. Had custom tune built and installed. CEL turned off but then came back a day or two later. I checked with both of my scanners, both of which stated no stored DTCs (one even had a CEL status that said “off”). I disconnected the battery overnight and still no change. All that work and money to get the light to shut off and now it is lit without any reason (and will need to be off when I have to register the vehicle again). I am baffled. Has anyone had or heard of an issue like this?

Where did you get the tune?
What version software is yours?
If you installed a true EGR/FCV delete tune you should not have any DTC's for them.

bascars · **Joined:** Mon Jun 24, 2019 11:18 pm **Posts:** 23

Yeti custom file.
521 - although seems odd as I was not finding that software in the EGR software delete thread from others.
I do not show any DTCs, but CEL is on (although scanning tools shows the MIL status off)

I've got to figure out how to post a picture but here is what is on my Autel MaxiCheck screen
System Status
MIL Status=OFF
Codes Found=0
Monitors N/A=9
Monitors OK=1
Monitors INC=0

Jay ne Ohio · **Joined:** Sun Dec 12, 2010 5:49 pm **Posts:** 216

You might try a different scanner. I have a cheap Harbor Freight scanner and also a ICARSCAN that works by bluetooth on my phone. The HF scanner does not show all the codes where the ICARSCAN seems to probe deeper and find codes even when there is no CEL.

Mountainman · **Posted:** Tue Apr 28, 2020 12:54 pm

I've seen this before. Other than the not being able to see the code.
Swap the MAP, MAF, and then the turbo solenoid (the one that's by the fender, in that order. You can get a GM MAP sensor for much less $. And, if you can get a junkyard airbox lid, or borrow someone's for a minute, that also gets you a MAF and an absolute pressure sensor swapped in 2 minutes, but I dont think its that one.
Basically it's one of the engine sensors (or their wire).
That's what I love about the GDE tunes. The MAF and APS are gonzo, so makes troubleshooting these faults much easier. Hopefully he can get back to selling them soon!

WWDiesel · **Posted:** Tue Apr 28, 2020 1:18 pm

I believe you need a better scanner.
One that will show stored codes as well as active codes.
If your CEL is on, there should be an active DTC that is turning it on.
:shock:

bascars · **Joined:** Mon Jun 24, 2019 11:18 pm **Posts:** 23

I believe both of my scanners are quality with high functionality, not just cheap readers
Autel MaxiCheck Pro
Innova 3160e

That is what has me so confused. It makes no sense that there are no stored codes in the vehicle. I guess I'll give it a couple weeks and see if it self clears.

WWDiesel · **Posted:** Wed Apr 29, 2020 3:46 pm

bascars wrote:

I believe both of my scanners are quality with high functionality, not just cheap readers
Autel MaxiCheck Pro
Innova 3160e
That is what has me so confused. It makes no sense that there are no stored codes in the vehicle. I guess I'll give it a couple weeks and see if it self clears.

Just for giggles, have you tried the old disconnect negative battery cable for 24 hours trick?
Does not make any sense that neither of your scanners is telling you what the offending code is. :shock:

Know anyone that has a Snap On Verus Pro that can scan it for you?

rankom · **Posted:** Wed Apr 29, 2020 7:56 pm

I had lots of mysteries with my jeep when I purchased it in 2013 and then I took my ECU to greendiesel engineering in michigan. and they fixed all the issues.

bascars · **Joined:** Mon Jun 24, 2019 11:18 pm **Posts:** 23

I disconnected overnight, but I'll disconnect longer and see what happens

If that doesn't work maybe greendiesel is an option since I am in Cleveland area.

Mountainman · **Posted:** Fri May 01, 2020 11:21 am

well, it's not necessarily a matter of how good the scanner, it's just that very few are able to "talk" fully with these strange vehicles. Try pulling the codes at an autozone, NAPA, oreileys, etc...
The code reader/tune loader GDE sells works great.

Or you migh just have sticky turbo veins that aren't throwing a code. I have one like that right now

PZKW108 · **Joined:** Sun Apr 06, 2014 5:23 pm **Posts:** 461

bascars wrote:

I disconnected overnight, but I'll disconnect longer and see what happens

If that doesn't work maybe greendiesel is an option since I am in Cleveland area.

Disconnect and join the wires together !

bascars · **Joined:** Mon Jun 24, 2019 11:18 pm **Posts:** 23

Update-but unfortunately not a positive update.
I did disconnect the battery (and connect the posts) for nearly 3 days. CEL still on with no stored DTCs.
I unplugged MAF and no change.
I verified the new file only deletes p0101, p0102, p0401, p0402, p0403, and p1140
I reinstalled the new file through mpps and no change.
I reinstalled the original file through mpps and no change. This is where I should absolutely see a difference. The system said the file uploaded successfully. But if that was the case it should throw codes as the EGR is no longer there. So potentially one of two issues. Either the software for MPPS is not working or ECU is damaged/malfunctioning, however the Jeep runs fine-no issues.

Any suggestions? I'm at wits end after so much time and money.

Mountainman · **Posted:** Fri May 08, 2020 2:03 pm

Read my previous post. It's most likely not the ecu. Check for your 5v at the various sensors. And unplugging the MAF wont do anything, but swapping it will. I'm pretty sure only GDE tunes eliminate the MAF and APS sensors. Usually it's the MAP, with the MAF being the 2nd most failure I see.

WWDiesel · **Posted:** Fri May 08, 2020 2:59 pm

I still believe you should have it scanned with a "high end" scanner like a Snapon or DRBIII.
With not knowing exactly what is setting the offending DTC, any sensor you change or action you take is pure speculation. :5SHOTS:

Guessing can get very expensive and still not solve the issue... :dizzy:

bascars · **Joined:** Mon Jun 24, 2019 11:18 pm **Posts:** 23

Mountainman wrote:

I've seen this before. Other than the not being able to see the code.
Swap the MAP, MAF, and then the turbo solenoid (the one that's by the fender, in that order. You can get a GM MAP sensor for much less $. And, if you can get a junkyard airbox lid, or borrow someone's for a minute, that also gets you a MAF and an absolute pressure sensor swapped in 2 minutes, but I dont think its that one.
Basically it's one of the engine sensors (or their wire).
That's what I love about the GDE tunes. The MAF and APS are gonzo, so makes troubleshooting these faults much easier. Hopefully he can get back to selling them soon!

What is the “GM MAP” that works?

I’ll take it to an auto parts store tomorrow and see if they can see any codes.

bascars · **Joined:** Mon Jun 24, 2019 11:18 pm **Posts:** 23

Mountainman wrote:

I've seen this before. Other than the not being able to see the code.
Swap the MAP, MAF, and then the turbo solenoid (the one that's by the fender, in that order. You can get a GM MAP sensor for much less $. And, if you can get a junkyard airbox lid, or borrow someone's for a minute, that also gets you a MAF and an absolute pressure sensor swapped in 2 minutes, but I dont think its that one.
Basically it's one of the engine sensors (or their wire).
That's what I love about the GDE tunes. The MAF and APS are gonzo, so makes troubleshooting these faults much easier. Hopefully he can get back to selling them soon!

What is the “GM MAP” that works?

I’ll take it to an auto parts store tomorrow and see if they can see any codes.

bascars · **Joined:** Mon Jun 24, 2019 11:18 pm **Posts:** 23

Mountainman wrote:

I've seen this before. Other than the not being able to see the code.
Swap the MAP, MAF, and then the turbo solenoid (the one that's by the fender, in that order. You can get a GM MAP sensor for much less $. And, if you can get a junkyard airbox lid, or borrow someone's for a minute, that also gets you a MAF and an absolute pressure sensor swapped in 2 minutes, but I dont think its that one.
Basically it's one of the engine sensors (or their wire).
That's what I love about the GDE tunes. The MAF and APS are gonzo, so makes troubleshooting these faults much easier. Hopefully he can get back to selling them soon!

What is the “GM MAP” that works?

I’ll take it to an auto parts store tomorrow and see if they can see any codes.

WWDiesel · **Posted:** Tue May 12, 2020 11:31 pm

bascars wrote:

What is the “GM MAP” that works?
I’ll take it to an auto parts store tomorrow and see if they can see any codes.

GM PN: 55206797 :google:

it.
Plenty available online.

bascars · **Joined:** Mon Jun 24, 2019 11:18 pm **Posts:** 23

I'm going to bring this one back to the group. As a recap, my CEL is on and there are no stored codes. Tried 2 other scanners, including a Scan Gauge II, from a forum member. He stated he also had the same issue with his 05 but never fixed it before selling. Just wondering if any others had similar problems and if there is something to correct the apparent glitch.

CEL mystery

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