FORScan forum

boosted_diesel wrote: Tue Nov 04, 2025 8:15 pm Have you considered just reflashing the pcm with the standard software again to see if the problem goes away?
You could always reflash the tune again after.

I've tried that. On the stock tune, it will start and run for about 5 seconds, then it shuts down. I can start it again and same thing, it runs for about 5 seconds and shuts down. After that, it doesn't even turn over when I turn the key. I have to flash it back to one of their tunes in order for it to even turn over again. It's like it goes into some sort of protection mode... With all the sensors unplugged, I get tons of codes so I'm guessing something is putting it into limp mode almost immediately.

It sound like when you flash the tune it upsets the immobiliser.
When you program it back to stock you'll have to reprogram the keys and do the pats initialisation. That's why it cuts out I would guess.

boosted_diesel wrote: Tue Nov 04, 2025 9:45 pm It sound like when you flash the tune it upsets the immobiliser.
When you program it back to stock you'll have to reprogram the keys and do the pats initialisation. That's why it cuts out I would guess.

Thanks for that info. I'm new to FORScan, so I'll research and try doing that. I just don't want to mess anything up.

I'm wondering if there's a way in FORScan that I can prevent the P1556 code from popping up and throwing a check engine light? I know, that's not the best practice - I'm just tired of seeing the check engine light.

petem wrote: Wed Nov 05, 2025 12:52 pm

boosted_diesel wrote: Tue Nov 04, 2025 9:45 pm It sound like when you flash the tune it upsets the immobiliser.
When you program it back to stock you'll have to reprogram the keys and do the pats initialisation. That's why it cuts out I would guess.

Thanks for that info. I'm new to FORScan, so I'll research and try doing that. I just don't want to mess anything up.

I'm wondering if there's a way in FORScan that I can prevent the P1556 code from popping up and throwing a check engine light? I know, that's not the best practice - I'm just tired of seeing the check engine light.

I know what you mean. If you check that forscan can do what you want on your car first, then read all the how to stickies, ypu should be fine to do it matey.

Sometimes you can fool them into putting the light off, but not often with a circuit code. As it will always detect the issue and log the fault unless it's repaired.

lol this is why I drive old cars, you can delete egr's and warning lights don't even come on as it was never programmed to monitor that in the first place.

boosted_diesel wrote: Wed Nov 05, 2025 2:37 pm

petem wrote: Wed Nov 05, 2025 12:52 pm

boosted_diesel wrote: Tue Nov 04, 2025 9:45 pm It sound like when you flash the tune it upsets the immobiliser.
When you program it back to stock you'll have to reprogram the keys and do the pats initialisation. That's why it cuts out I would guess.

Thanks for that info. I'm new to FORScan, so I'll research and try doing that. I just don't want to mess anything up.

I'm wondering if there's a way in FORScan that I can prevent the P1556 code from popping up and throwing a check engine light? I know, that's not the best practice - I'm just tired of seeing the check engine light.

I know what you mean. If you check that forscan can do what you want on your car first, then read all the how to stickies, ypu should be fine to do it matey.

Sometimes you can fool them into putting the light off, but not often with a circuit code. As it will always detect the issue and log the fault unless it's repaired.

lol this is why I drive old cars, you can delete egr's and warning lights don't even come on as it was never programmed to monitor that in the first place.

Yeah, I agree. This is the newest truck I have ever owned and I'm new to owning a diesel truck. I like it - it runs great and tons of power, but I had no idea that diesels were so expensive to do anything with! EGR and DPF delete with the tuner, CCV bypass kit, S&S disaster prevention kit and new cold side pipe and I'm over $3000 just in parts. I am blessed enough with a brother in law who was a diesel mechanic and helped me install it all. That's why this code has really gotten to me I think. All the mechanics I've talked to about it tell me they don't see anything wrong with the truck and to "just run it" but I'd really like to get the issue resolved - or at least LOOK like the issue is resolved so I don't see that light on anymore. My brother in law and another mechanic really think it's something in the tune, but I contacted EZ LYNK and they don't believe that, so I'm kinda stuck in limbo.

Thanks again for the replies and assistance! It is greatly appreciated.

Yeah I know how you feel. You've put a lot into it and it's driving you up the wall instead of down the road with a dashboard warning light free lol.

There are steps you can still take to figure out other things. Which may in turn help you arrive at the answer.
Take the bad injector out (one that gets the code) and also a good one, swap them round and see if the problem moves from one cylinder to another or if it stays on that cylinder.
That will narrow down whether it's an injector or if the issue is pcm/tune/wiring to cylinder 6.

If the problem follow the injector to the new cylinder then it's the injector.

Just make sure you have new seals (usually copper) ready for the injectors when you swap them.

Sometimes it's easier to prove what it isn't until your left with only one option rather than to try and prove what it is.

boosted_diesel wrote: Wed Nov 05, 2025 6:23 pm Yeah I know how you feel. You've put a lot into it and it's driving you up the wall instead of down the road with a dashboard warning light free lol.

There are steps you can still take to figure out other things. Which may in turn help you arrive at the answer.
Take the bad injector out (one that gets the code) and also a good one, swap them round and see if the problem moves from one cylinder to another or if it stays on that cylinder.
That will narrow down whether it's an injector or if the issue is pcm/tune/wiring to cylinder 6.

If the problem follow the injector to the new cylinder then it's the injector.

Just make sure you have new seals (usually copper) ready for the injectors when you swap them.

Sometimes it's easier to prove what it isn't until your left with only one option rather than to try and prove what it is.

Thanks! I thought about doing this, I just didn't know if I needed to reprogram the injectors first, then swap them, then reprogram them to swap them back or if a "quick swap" didn't require programming.

For them to function correctly yea they should be coded in.
It would probably run without the coding but not properly and at this point we don't want to introduce new problems. That's why we also change the seals to make sure there isn't a combustion leak created. Also you don't need to swap them back, you'll have learned what you need to after the first swap and there will be no further meed to swap anything unless you conclude the injector is actually faulty.

boosted_diesel wrote: Wed Nov 05, 2025 10:35 pm For them to function correctly yea they should be coded in.
It would probably run without the coding but not properly and at this point we don't want to introduce new problems. That's why we also change the seals to make sure there isn't a combustion leak created. Also you don't need to swap them back, you'll have learned what you need to after the first swap and there will be no further meed to swap anything unless you conclude the injector is actually faulty.

Good point - no need to swap them back. Either the code will move with the injector, indicating the injector is the fault or it will stay with cylinder 6, indicating a wiring issue. I'll try to get some new copper washers this weekend and if I can get my hands on them, I'll swap them out and let you know the outcome.

Thanks again for all your help and assistance. It is truly appreciated.

petem wrote: Thu Nov 06, 2025 12:51 pm

boosted_diesel wrote: Wed Nov 05, 2025 10:35 pm For them to function correctly yea they should be coded in.
It would probably run without the coding but not properly and at this point we don't want to introduce new problems. That's why we also change the seals to make sure there isn't a combustion leak created. Also you don't need to swap them back, you'll have learned what you need to after the first swap and there will be no further meed to swap anything unless you conclude the injector is actually faulty.

Good point - no need to swap them back. Either the code will move with the injector, indicating the injector is the fault or it will stay with cylinder 6, indicating a wiring issue. I'll try to get some new copper washers this weekend and if I can get my hands on them, I'll swap them out and let you know the outcome.

Thanks again for all your help and assistance. It is truly appreciated.

No worries, just bear in mind that if the code stays on that cylinder after swapping injectors then it is wiring OR pcm, as pcm is part of the circuit and is also the source. If it had a bad injector driver on the pcm pcb then it could do the same.