Code P24C4

[Jesse1975]

Hello, I just re-flashed the ECM back to stock from the mild Kennedy tune (which I love) in hopes of passing the new annual inspection here in MA. I'm getting this P24C4 code and it appears to be a bad value from an EGR valve position sensor. I'd appreciate any input and I will be emailing Kennedy Diesel later on tomorrow. Any one in MA with full delete and success at the inspection station please let me know. They are serious here now about it. They plug into the OBD port with their state computer, multiple pics of VIN and plate. If you're in a state with little or no emissions inspections, be grateful. It's a disaster here.
Thanks in advance and Happy St Patricks Day.
Jesse

2015 2500 Sierra 135k, did the tune at 95k, truck ran perfect, still does, just can't pass this emissions BS stuff.

[Jesse1975]

I'm going to update this as well and hopefully it will just continue to improve. It threw 3 more codes, engine light came on and I reset them. I was hoping they were all due to the ECM now running it's stock programming and a bunch of items that have been asleep for a while getting used again. It appears that is the case and none of those codes have come back yet. I did get the P21DD DEF heater resistance code, but I've had that one once before and I'll deal with it if it doesn't go away.

So for now I'm good.

One other interesting thing is watching the ignition timing on the Edge. It was always a positive number, between 0-15 maybe depending on how hard I was on the throttle, now it spends a fair amount of time below zero, it ranges from -7 to 7 or so with no real rhyme or reason. Once it's warm, and at highway speeds, it seems to be almost always above zero, with being at zero or 1 at idle. Any input on why it is injecting fuel after top dead center would be welcome. It was more drastic right after the ECM flash and seems to be trending in the right direction, but I thought I'd ask here. I've only seen the negative/post TDC injection timing during regens before this.

And I can also see the mileage reduction after taking out KD tune :(
Is there any harm or is it unwise to annually flash and reflash the ECM? I miss the tune...

Thanks
Jesse

[Yukon6.2]

I'm going to update this as well and hopefully it will just continue to improve. It threw 3 more codes, engine light came on and I reset them. I was hoping they were all due to the ECM now running it's stock programming and a bunch of items that have been asleep for a while getting used again. It appears that is the case and none of those codes have come back yet. I did get the P21DD DEF heater resistance code, but I've had that one once before and I'll deal with it if it doesn't go away.

So for now I'm good.

One other interesting thing is watching the ignition timing on the Edge. It was always a positive number, between 0-15 maybe depending on how hard I was on the throttle, now it spends a fair amount of time below zero, it ranges from -7 to 7 or so with no real rhyme or reason. Once it's warm, and at highway speeds, it seems to be almost always above zero, with being at zero or 1 at idle. Any input on why it is injecting fuel after top dead center would be welcome. It was more drastic right after the ECM flash and seems to be trending in the right direction, but I thought I'd ask here. I've only seen the negative/post TDC injection timing during regens before this.

And I can also see the mileage reduction after taking out KD tune :(
Is there any harm or is it unwise to annually flash and reflash the ECM? I miss the tune...

Thanks
Jesse
Get a spare ECM for your KD tune.Emissions time put in the stock one.the rest of the 364 days run the KD one.

[Kennedy]

The ECM swap is not quite as practical on the LML. I also had a guy who does rebuilders tell me that he heard from GM that it would not work at all on the 2015-16 models but I have not verified this.

[Jesse1975]

So EGR problems corrected themselves and all was well for a short time. P21DD, bad resistance reading in DEF heater came back and wouldn't clear, then P20B9 showed up, so it really meant business. The heaters were back ordered at the factory according to local Chevy dealer so I ran it for a week or so waiting for it. The countdown started yesterday and today it went in and had the heater replaced, OEM one. Local shop did the work that I like. The codes cleared upon start up but the countdown continued. It was low (20%) on DEF so I added 2 gallons and drove it about 25 miles to hopefully clear the countdown BS. About 5 miles into the drive a regen started, with only about 10g of soot on the meter. Regen continuing, I am home now, with about 10 miles to go before limit to 55, then 75 miles until 4MPH limit = tow truck. There are NO codes on the truck, check engine light is not on, no P21DD or anything, after several starts and stops, including several ignition cycles.
Does anyone have any ideas? Off to dealer tomorrow if not.