Well here is one for you... I would like to know if it is possible for my truck to go into limp mode due to the sensors (for the DPF) getting wet?

This afternoon, I drove into an automatic/brushless carwash under full power. When the wash wash done and I left the parking lot, the reduced power light comes on. Is it possible that water in the open sensors could cause a short of some kind? I went to the store and picked up some carburator cleaner. Sprayed that in the sensors and it was good to go again.

Any opinions or theories?

I think your truck would get wetter in a rain storm than a car wash. But I'll have to say thats a new one. Good luck.

Brier1,
First, pull codes and tell us what year LMM.

Second, as far as your question about the DPF sensors getting wet and thowing a code. I would say no, the connectors are weather pack sealed and don't cause reduced engine power, unless you have a 2008.
Now, if by chance a connector seal was missing, then maybe a MIL.

How about water intrusion at the MAF Sensor or air filter, that would cause a MIL and reduced engine power.

Wow, you guys are fast! Well I have a 2007.5 with the dpf removed and the sensors have not been sealed(I know, get them sealed!) I have also done the airbox mod from PPE so it is possible. I will go out to the truck and get the codes. I wrote them down. be right back.

OK here are the codes my PPE spit out:

2453
244B
0546

Anyone know what these are? I checked the code search but it gave me no info.

"unless you have a 2008"

What is the problem if an 08?

2453 particulate matter trap differential pressure sensor 0546 EGT sensor 1...... i didnt find a 244b but a 244c is catalyst temp is too low during regeneration.....i dont think your ppe is set up correctly to block those codes as they are related to regeration

"unless you have a 2008"

What is the problem if an 08?
There is no problems with an 08 other than DPF temp sensor codes now can put the vehicle in reduced engine power.

Yea I know:damnit1:

2453 particulate matter trap differential pressure sensor 0546 EGT sensor 1...... i didnt find a 244b but a 244c is catalyst temp is too low during regeneration.....i dont think your ppe is set up correctly to block those codes as they are related to regeration

:exactly:Yup, yur right.

P244B is excessive DPF back pressure, or the DPF sensor is disconnected you should have P2455 too.

found 244b...DPF differential pressure too high

I think it is time for EFI live to eliminate the codes

I think it is time for EFI live to eliminate the codes


Brier! I recently had the same EXACT problem. truck is straight piped DPF removed. It did it once to me in the car wash before I cleared the codes with efi live so the engine light was already on. The second time I already had the DPF removal codes cleared and I was idling on a rainy crappy day in my driveway and when i jumped back into the truck and drove away it went into reduced power mode with NO check engine light??? shut the truck off for a couple mine started in back up and it has been fine since. I think the wierd part is I didnt get a light?

dur maxed out have you checked your ecm with efi while the truck is runing ill bet ther are some stored codes in there try it and let me know ill let you know how to fix it if there is

That is strange duramaxedout! After reading some of the comments I am thinking it had to do with the air intake more than anything. I too had the truck running (kids were watching Dora on the DVD - cant interupt that!!). Must have sucked in some water. I am interested to hear if there were any stored codes and what fire 0021 says.

by clearing a DTC code you really only resolve the issue temporarily, u have to set the related codes to mil off , with EFI Live. but then i dont know what you can really do with ppe

lot of car washes do an underbody spray too

my DPF realted codes were all turned off (told not to report) via EFI live and it happened once before and once AFTER they were cleared. Keep on mind these two times were only twice in 11,000 miles. I do not own EFI live I had it done by a guy localy. So it is hard to check for 'stored' codes without efi live sometimes they wont show up on a hand held scanner especialy if you didnt get a CEL like I did.

Brier! I recently had the same EXACT problem. truck is straight piped DPF removed. It did it once to me in the car wash before I cleared the codes with efi live so the engine light was already on. The second time I already had the DPF removal codes cleared and I was idling on a rainy crappy day in my driveway and when i jumped back into the truck and drove away it went into reduced power mode with NO check engine light??? shut the truck off for a couple mine started in back up and it has been fine since. I think the wierd part is I didnt get a light?

I started laughing when I read this, my truck went into reduced power mode only once, (not one since the PPE was put on the truck), when I was sitting in a car wash.

duramaxed yea even thoe the cels are reported to off i almost gurantess there are pending codes ing the ecm. that a code reader wont see. even ppe has stored codes with there programer that there programer cant see. you cant get to thm with out a tec 2 efi or hptuners is the only way i know to get to them . i f you get a chance mabey try to have the guy who tuned ur ecm pull the codes for you.

truck limped twice today right after YES........ a car wash. So I sprayed the plugs that I unplugged and are just dangling there with silicone spray so displace anywater that may be in them which is very likely. I will let you know how this work out. If this solves the problem I am going to put some heat shrink tube around them to keep water and such out incase I need them again.

yea let us know how it goes i have had my truck washed sevral times had some good rains with big pudles and no issues to date. and my plugs are just open and not taped up or any thing so who knows.

ok guys...I just bought an 07 Duramax...and not to sound stupid or anything but how do you know if you have a 2007.5 Duramax???

ok guys...I just bought an 07 Duramax...and not to sound stupid or anything but how do you know if you have a 2007.5 Duramax???
Classic body style or new body style - if it's nbs (same as 08) then it's 2007.5.

I've got the new body style...

I've got the new body style...Then it must be 2007.5 with the LMM engine.

I've got the new body style...
Best thing you could do is have your dealer install all latest updates. And any new and improved parts available. Depending on your relationship with your dealer they should be able to do that for you. Could save lots of aggravation.

yea let us know how it goes i have had my truck washed sevral times had some good rains with big pudles and no issues to date. and my plugs are just open and not taped up or any thing so who knows.
been raining since i posted last. Did it twice before in 20 mins. After the silicone spray not a problem since. I think the mystery is solved. Next I am going to put some shrink tube over the plugs for good measure.

After reading this seems most problems are with people that have removed the DPF? Any problems with people who have not removed the DPF? I was about to get my truck washed at a car wash until I read this. Chris

After reading this seems most problems are with people that have removed the DPF? Any problems with people who have not removed the DPF? I was about to get my truck washed at a car wash until I read this. Chris


the carwash thing is only an issue if you have removed your DPF and have the unplugged connectors dangling there and they get wet.

Best thing you could do is have your dealer install all latest updates. And any new and improved parts available. Depending on your relationship with your dealer they should be able to do that for you. Could save lots of aggravation.

How come we hear about these computer updates, but no one is posting a number for them or what they are for. Shouldn't there be a TSB on them? Sounds fishy to me!

How come we hear about these computer updates, but no one is posting a number for them or what they are for. Shouldn't there be a TSB on them? Sounds fishy to me!
Unless it's something critical (like engine won't run), computer flashes aren't included in TSB's, usually some other bulletin and then ecu flash is applied when the vehicle goes in for regular service. One of the GM techs can probably answer with more detail.

Pretty much right on there Jeff. You usually don't know if there are any updates unless you check. You never really know what all the updates may "fix" either. There is usually very little description with them.

How come we hear about these computer updates, but no one is posting a number for them or what they are for. Shouldn't there be a TSB on them? Sounds fishy to me!
GM is constantly gathering information from service departments all over the world. And when there is consistencies in problems the computer geeks go to work on it. Hence the update. You may never hear of the problem because, if they where to notify everyone with a vehicle that does not have the latest updated, one you would be at the dealer more than the corner store, and two GM could not afford the postage. They will simply wait for you to come to them for some service related thing and slip the updates in. Lets face it people would be freaking out if they got notified every time there was a new update.

I agree some people might freak out if they knew that the ECM software is revised a few times during a new product launch.

I disagree that the dealers will just slip in an update or two under the table. I think that if you were in for some other service the dealer will either tell the customer that an update is highly advised, or more likely, not do anything until the customer complains about the truck's performance.

I've had the same problem with mine. It first happened in the carwash about a month ago. No codes found just reduced power. If I clear the codes even though there isn't any it shuts off temporarely. The only way it will stay off is if I shut the truck off and then start it back up after a few minutes. I though it was the carwash but since then it seems to do it if I leave it idle for very long like it did in the carwash. I think it's more to do with it idleing then getting wet.
Now it seems to do it about everyother day and it's driving me crazy. I was parked watching the dvd player and after about 5 or 10 minutes there it was reduce power. I have no idea whats going on but I hate it. Those of you with problems should try and let it idle and see if it does it. It did it at the car wash for me too but it was also idleing for some time there too.

I've had the same problem with mine. It first happened in the carwash about a month ago. No codes found just reduced power. If I clear the codes even though there isn't any it shuts off temporarely. The only way it will stay off is if I shut the truck off and then start it back up after a few minutes. I though it was the carwash but since then it seems to do it if I leave it idle for very long like it did in the carwash. I think it's more to do with it idleing then getting wet.
Now it seems to do it about everyother day and it's driving me crazy. I was parked watching the dvd player and after about 5 or 10 minutes there it was reduce power. I have no idea whats going on but I hate it. Those of you with problems should try and let it idle and see if it does it. It did it at the car wash for me too but it was also idleing for some time there too.

I recently taped up the plug that went to the black box the the two metal tubes go into. Before I taped it up I also sprayed it wityh silicone spray to displace moisture. I havent had a problem since.

Well I've tried everything. I unlugged the batteries overnight and I cleaned the connectors with brake clean and then sprayed the silicone spray in there. I got 2 new female connectors to plug on the pug to keep it sealed. Started the truck back up and instantly says engine reduce power. Any other suggestions?

are there wires on the tail end of the dummy plugs you installed that might be touching? Also the sensors getting wet may not be your problem. Most of us have only run into this problem on the temporary basis. Dry the plugs off shut the truck down for a few mins and back to normal no problems untill wet again.

Just did the dpf delete today with the quad and sprayed both with silicone spray and taped up one in the rear real good. I had mine idling for about 30-45 min afterward, -15 deg. oustside and didn't have any problems. Sounds like a computer problem. I will post if ever have this problem as well, good luck.

Do they make a closed end heat shrink? I've got a lot of heat shrink, but no closed end heat shrink.

The tail end of the dummy plugs were just cut off so they wouldn't touch. I put some wax on the end so water wouldn't get in there. Maybe the wax is conductive enough to cause the problem I don't know.

The tail end of the dummy plugs were just cut off so they wouldn't touch.
With that said, here's what I would do......Remove the wax and dry the lines REALLY well. Then, get some heat shrink and shrink it around the wires. You will have a small opening left at the end of the heat shrink, get a small dab of JB Weld (get the regular JB Weld, NOT the JB Kwik) and close the hole.

With that setup, there is no way water can get in.

Ok I'll give that a shot. Thanks

I think your wasting your time trying to keep water out of your plugs. Today I was gitin' it through snow drifts and still runs better than new. I think you should get your ecm looked at. Just my .02.

I'm just a little afraid to take it to the stealership to get my ecm loked at since I have everything takin off. I would probably have to explain to them what I had done so they would know what to look at and I don't think that is something that I want to do.

well i would have to agree i dont belive its the plugs i never eaven taped mine up been through some good rain storm car washes ect no problems now on a trip in co -13 degree blowing snow no issues. i however dont think its the ecm in your case i belive its the quad programing not having those sensors peramaters set correctley. if you know some one with efi you could pull the tune and look at it to see im going to be thts the problem

It probably is the quad now I think about it. I had a few problems initially downloading from quads website. The updater from the website is supposed to be v2.1 i think and the first one I down loaded was 1.3 I think. Called them and had a tech email the correct version and uploaded and programmed the truck first try. I would check with quadzilla. Also I called my local chevy dealer that I use and talked to them about what I was going to do with the dpf, programming etc and they didn't have a problem with the mods as long as I told them exactly what I did so they knew what to look for if they had any problems. Never hurts to call, ask a few questions.

yellowdmax, i think BKdespain is on the right track. the problem is with your quadzilla not being set up properly

yellows problem may not be wet plugs but be warned the big rear plug with cause limp if wet. I tested this directly with a pressure washer and made it limp. This may be because i used efi live to tell the codes not to report. Maybe the quad and PPE work differently. I too have been in snow and carwashes before taping and havent had a problem right away. I think this is due to a small amount of lube in the plugs from the factory but after a few washes and wheeling it will wash out. You dont want to be on your back on the side of I 95 in Maine during a snowstorm cleaning and spraying out your plugs with wd and duct tape. Ive been there.

Mine went into "Engine reduced power mode" tonight on I-80! Pulled over and checked codes, none, cleared them with the Insight, still in limp. shut it off and started it. Fine for less than a minute, tripped it again. Pulled over and got my elctric contact cleaner I bought just for this specific reason it ever happened to me and cleaned the plugs. Fired it up and took off and never did it again. Should have checked my soot mass on the insight. I think the quad is overlooking a few parameters or settings. Any one else still having problems with this?

Its not a coincidence that it didnt trip again after you cleaned the plugs.......I could re-start and limp 4 or 5 times in a row,then finally clean the plugs and it is good again untill they get dirty and wet again. Told ya taping up the plugs would do the trick.

I think your right, taped up the one under the truck, not the two on the rails, cleaned those 2 and good to go.

I am trying to think of a better idea than just taping them up tho. There has to be a way to cut power from going to those plugs because I sometimes like to do a little wheeling where the water is upto the door handles and I dont think even a whole roll of tape will help.........Im working on it. So far I think the problem isnt the two smaller plugs on the frame rail. I have narrowed it down to the 1 large plug closer to the rear diff.

I am trying to think of a better idea than just taping them up tho. There has to be a way to cut power from going to those plugs because I sometimes like to do a little wheeling where the water is upto the door handles and I dont think even a whole roll of tape will help.........Im working on it. So far I think the problem isnt the two smaller plugs on the frame rail. I have narrowed it down to the 1 large plug closer to the rear diff.

I've been lurking around here for awhile with only a couple posts. I'll be looking to buy a Duramax 3/4ton maybe late this year or next. Never too early to start the research! Anyway, I am an electrical engineer with a Tier 1 and access to GM electrical architecture. I thought to help you guys out with the DPF related connectors. Here you go...

According to my information, there are 3 sensor connections directly related to the DPF. One "delta pressure sensor" and 2 "temp sensors". One pre and one post DPF. The pressure sensor is a 3 wire device; 5V power feed, gnd, and a signal input into an A/D at the ECM and I think this may be the main culprit.

DPF Delta Pressure sensor (Gold terminals, Delphi Packard connector p/n - 15401052) in the "Chassis Harness"

Pin 1 - ckt #6055 , Gnd, 20Ga, YE/BK (Yellow wire with black stripe) via Chassis Harness, goes to cavity D in a 10-way Delphi Packard connector at the "Inline to Engine Harness". Ckt #6055 continues to ECM via the Engine Harness where it terminates at the "J1" connector, pin 35.

Pin 2 - ckt #6053, Signal, 20Ga, D-BU (Dark Blue wire) via Chassis Harness, goes to pin F in the 10-way "Inline to Engine Harness". Ckt #6053 continues to ECM via Engine Harness where it terminates at the "J1" connector, pin 43. This is an analog signal wire that is converted to digital in the ECM.

Pin 3 - ckt #6054, 5V Pwr Feed, 20Ga, GY (Grey wire) via Chassis Harness, goes to pin C in the 10-way "Inline to Engine Harness". Ckt #6054 continues to ECM via Engine Harness where it terminates at the "J1" connector, pin 14.

PRE-DPF Exhaust Temp Sensor (Pigtail device, 2-way Delphi-Packard Conn p/n - 13510085)

Pin A - ckt #5277, Temp Sensor signal, 20Ga, GY (grey wire in the device pigtail, but changes to D-BU wire in the Engine Harness) goes to ECM via Engine Harness where it terminates at the "J1" connector, pin 69.

Pin B - ckt #6782, Temp Sensor Return, 20ga, WH (white wire in the device pigtail, but changes to BN-brown wire in the Engine Harness) goes to ECM via Engine Harness where it terminates at the "J1" connector, pin 70.

POST-DPF Exhaust Temp Sensor (Pigtail device, 2-way Delphi-Packard Conn p/n - 13533784)

Pin A - ckt #5377, Temp Sensor Signal, 20Ga, GY (grey wire in device pigtail, but changes to L-BU light blue in the Chassis Harness) via Chassis harness (now L-BU) goes to pin K in the 10-way "Inline to Engine Harness". Ckt #5377 continues via Engine Harness to ECM where it terminates at the "J1" connector, pin 93.

Pin B - ckt #6783, temp Sensor Return, 20ga, WH (white wire in device pigtail, but changes to BN/WH brown with white stripe in the Chassis Harness) via Chassis Harness (now BN/WH) goes to pin J in the 10-way "Inline to Engine Harness". Ckt #6783 continues via Engine Harness to ECM where it terminates at the "J1" connector, pin 94.

I'm not sure what connectors are causing the limp, but this way help in diagnosis. Feel free to post up further questions about the connectors/circuits if you want. I should remind you that GM does change things by updating revisions and this data may not be exact. Always inspect the actual parts and reference to the data before making "permanent changes". That's my disclaimer...:D

Thanks for the info! So much for just pulling a fuse hehe :) ill be working on it

I will have to print that and get under there with it in hand! Thanks again.

Mine went into "Engine reduced power mode" tonight on I-80! Pulled over and checked codes, none, cleared them with the Insight, still in limp. shut it off and started it. Fine for less than a minute, tripped it again. Pulled over and got my elctric contact cleaner I bought just for this specific reason it ever happened to me and cleaned the plugs. Fired it up and took off and never did it again. Should have checked my soot mass on the insight. I think the quad is overlooking a few parameters or settings. Any one else still having problems with this?
I installed a 4" turbo back exhaust last week (08 LMM),ran 100 miles with quadzilla stealth2 in economy mode then switched to the 50 hp mode. I was liking the extra power and better mileage towing my snowmobile trailer home sunday (150 miles) (11.6 at 80 mph). Left for work this morning,passed someone at part throttle, truck went into reduced power operation. Limped truck into work,went out at lunch and looked thru owners manual,said reduced power operation was caused by mismatch in info for the electronic throttle,plugged the quad box in and looked at the data,the throttle percentage was going crazy,from 0% to 75% at idle,sorta like a shorted out tps. No code stored. I returned truck back to stock programming then installed the economy/ tow programming again. I am going to seal up the dpf terminals real good but I'm pretty sure the problem was being caused somehow by the quad being it wouldn't go away but as soon as I re-programmed it it cleared up. I drove 25 miles since and its been fine,it was snowing real wet snow this morning but I still don't think that was the cause because 5 hours later it was still doing it but as soon as I returned it to stock and re-loaded the quad it was fine. I think Quadzilla has some work to do,Smitty

If any of you guys know a phone man that works for the local telephone company, ask him for a black jack or a click it. These items are a plastic covering to repair cable after a cut. They are filled with poly bee silicon to keep water out. This may be a good solotion to the water problem on the sensors.

I installed a 4" turbo back exhaust last week (08 LMM),ran 100 miles with quadzilla stealth2 in economy mode then switched to the 50 hp mode. I was liking the extra power and better mileage towing my snowmobile trailer home sunday (150 miles) (11.6 at 80 mph). Left for work this morning,passed someone at part throttle, truck went into reduced power operation. Limped truck into work,went out at lunch and looked thru owners manual,said reduced power operation was caused by mismatch in info for the electronic throttle,plugged the quad box in and looked at the data,the throttle percentage was going crazy,from 0% to 75% at idle,sorta like a shorted out tps. No code stored. I returned truck back to stock programming then installed the economy/ tow programming again. I am going to seal up the dpf terminals real good but I'm pretty sure the problem was being caused somehow by the quad being it wouldn't go away but as soon as I re-programmed it it cleared up. I drove 25 miles since and its been fine,it was snowing real wet snow this morning but I still don't think that was the cause because 5 hours later it was still doing it but as soon as I returned it to stock and re-loaded the quad it was fine. I think Quadzilla has some work to do,Smitty

What you are describing does not sounds liek wet or dirty DPF plugs....prolly a quad problem. But tape em up to be on the safe side anyway

When mine went into limp I checked the plugs immediatley after and they had crap in them. Cleaned them and problem went away. Taped them all up real good and been driving the snow storms and wet roads with salt and dirt and haven't had a problem. Although airfilter froze up for the first time and put me into limp again a few days later! 70 bucks for a new one. Is gm warranting this air filter BS?

When mine went into limp I checked the plugs immediatley after and they had crap in them. Cleaned them and problem went away. Taped them all up real good and been driving the snow storms and wet roads with salt and dirt and haven't had a problem. Although airfilter froze up for the first time and put me into limp again a few days later! 70 bucks for a new one. Is gm warranting this air filter BS?

Im with you BKD but prolly not going to warrante mine after the PPE air box mod :(

Ya, thats what I was thinking, I just about called the dealer, then remembered that I have the PPE mod too. Whoops!