I have had the SES light come on twice. The first time was after I had the belt replaced. The dealer did not attach the hose from the turbo to the intake correctly and it blew off. Corrected this on the road and the light went away. The second time the truck went into a limp mode mode and would not rev over 2K rpm. Limped the truck home. When started the next day all was fine. Light went away on its own later that day. I figured this was a fuel filter so went to dealer to replace filter and get glow plug recall done. When I asked about what codes were stored I got a confused look from service manager and he said no codes were present. Asked mechanic about it and he said they will clear themselves after a predermined number of motor starts. I think the mechanic did not even check for codes. Will they still be present or does the glow plug update delete them. I have been hunting a ticking noise and intermitent miss and was hoping the codes could indicate somthing that is getting progressively worse.

Any techs online. Are the codes stored indefinately or will they clear themselves. Thanks in advance.

The light will go out after 3 or 4 cycles... I think it takes around 10 or so for the codes to completely clear, but they will clear.
The glow plug recall may have cleared stored DTCs.

My CEL came on today. I was showing the wife the cool way that when you have cruise on and in tow haul, it will keep a constant speen going down hill. I was towing a 16 ft car trailer with 2 ATVs. I was going down a slight grade. I was coming to a curve, so I stepped on the brake. Cruise kicked off, enging reved (not much but noticable). Light came on. Do you think it will clear as stated above or do I need to take it in next week? Also I have heard about a tool to clear codes. Any input about that?

The light will go out after 3 or 4 cycles... I think it takes around 10 or so for the codes to completely clear, but they will clear.
The glow plug recall may have cleared stored DTCs.

They stay until cleared, atleast they have in my truck. I have had a few:rolleyes: cel and the only way I got them to go away was with my scanner.

+1 with what haulin-rv says. They stay until cleared, however, I've also read that they clear after one cycle (hence no CEL one cycle after the fault first occurs unless the fault re-occurs) but I'm beginning to think the PCM is selective, keeping codes on some faults but not all.

Maybe this is GM's approach to "fuzzy logic". :secret:

They do eventually clear, but the conditions must be met regarding number of cycles without fault.

I unplugged my EGR and got a light on the 2nd restart.
Plugging it back in cleared the LIGHT on the 2nd restart after that, but I'm sure stored the code.

I got my Bullydog a little over a month later and no codes were stored when I checked before downloading.


For example, the logic could be something like this:

Set code on fault.
Set CEL on 2nd restart with fault.
Clear CEL on 2nd restart after fault cleared.
Clear stored code on 20th restart with no subsequent fault.

IOTW, if the PCM detects a fault on restart #15, it will reset the 20-restart counter, but will not bring up the CEL unless it faults again on restart #16.


And of course, different codes MAY have different logic... like I said, my CEL cleared on the 2nd restart, but a different code may take 4 or 5.

Good info, Rich! I'll try that cycle on my CEL I got after installing a Cold Air Intake!

Glad you are here to pass along the info.

Different codes have different priorities to self clear. Some will take 40+ignition cycles, others will clear as soon as fault conditions are gone. If the glow plug recall required a PCM reflash, all codes will be cleared, as to reflash all "soft" info is removed. Usually the emissions related codes will stay the longest.

good info, benjammin. I'm still struggling with clearing a code on my '06 DMax after installing a Volant cold air intake kit. I got a "MAF Pass/Fail" code at startup. First go 'round I noticed that the install shop didn't insure that the MAF was perpendicular (at a right angle) to the air stream. I re-oriented the MAF and had the dealer read and clear the code. All was good for one cycle but when I started it up again, back comes the CEL. I haven't read this one yet but I expect to get the same code as I realized the MAF was facing the wrong way with the unshrouded sensor opening not facing into the air stream. So, I once again re-oriented the MAF and will have to read and clear the code again. If the same code comes back I guess I'll replace the MAF and go see the shop manager.

What fun!