# No codes....But reduced engine power



## troutslayer (Feb 7, 2006)

Ok....got a 07 duramax....H&S mini max....4" from turbo out

No problems for over a yr...this weekend I was going to the movies with the family and the dash stated Reduced Engine Power....but no check engine light...
stopped the truck and turned it off and turned the key on and went through the mini max to check for codes...

1 code.....did not pay much attention to it....The only thing I remember was it was 2 words..second word was "key".....I hit the erase button and it was gone

cranked back up and left....no engine power.....yesterday...I took the cables off of the battery for about 30 min and put back on ....but did not fix

Any ideas???

I need to change the fuel filter and will do that tonight....


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## mchildress (Jul 11, 2009)

Might throw an air filter at it also.


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## czbrian (Aug 16, 2011)

Can you hear the turbo spool up and sound normal? Not sure if it threw a code or not, but the loss of engine power was the first thing my uncle noticed when the turbo on his Duramax went out. It is a 2005, and I'm not sure exactly what happened to it but it had to be replaced and was pretty pricey. Hopefully your issue is something much simpler.


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## sfwhaler (Dec 31, 2012)

If it is 08 09 10 ford Diesel there are two theomostates I dont know which one it will be one of them could be stuck


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## j4577 (Feb 11, 2013)

Throttle position sensor goes bad and can cause this problem on the gas trucks and I've been told that diesels have same problem.


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## surf_ox (Jul 8, 2008)

Was this it???
P0633 Immobilizer Key Not Programmed â€" ECM/PCM

Read more at: http://www.obd-codes.com/trouble_codes/
Copyright Â© OBD-Codes.com


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## surf_ox (Jul 8, 2008)

Interesting read

http://www.justanswer.com/chevy/372ro-relearn-key-2008-6-6l-silverado-truck.html


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## troutslayer (Feb 7, 2006)

surf_ox said:


> Was this it???
> P0633 Immobilizer Key Not Programmed â€" ECM/PCM
> 
> Read more at: http://www.obd-codes.com/trouble_codes/
> Copyright Â© OBD-Codes.com


I think that was it...now what?


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## DSL_PWR (Jul 22, 2009)

Truck will need to go to dealer for reprogram most likely.

Make sure that *08142A - ECM EEPROM* was done as it was a recall on the 07-08 dmax trucks.


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## troutslayer (Feb 7, 2006)

Do I need to take off my Minimax when I go to the dealer?


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## DSL_PWR (Jul 22, 2009)

troutslayer said:


> Do I need to take off my Minimax when I go to the dealer?


I would advise it.

Not sure what warranty you have left but wouldn't chance it if you still have any left.


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## surf_ox (Jul 8, 2008)

07 prob no warranty left.

any shop be able to do the reprogram??


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## BIG PAPPA (Apr 1, 2008)

*Doesn't matter*

It doesn't matter if you remove the program on GM trucks these days or not. They can tell merely by pulling PCM History and it gives them the last 10 programs down loaded into the pcm/ecm. They won't pull that info "UNLESS" you have a detrimental failure of a Major component while Under Warranty. All programs have a Part Number, and the part numbers are check by GM Technical Assistance for "Non-GM" software's. If you have a Non Recognized Part number, You Have Just been Tattoo'd against ALL Powertrain Warranty. This part number check has Nothing to do with the Dealers. It is done By GM and the okay or Denied Warranty is passed back to the dealer so they can either proceed with repairs under warranty or NOT.


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## baystlth22 (Aug 12, 2008)

my first thoughts are fuel filter and cam position sensor


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## troutslayer (Feb 7, 2006)

Well......I dont know.....I think my batteries need to be replaced...

1 is 12.1 volts
1 is 12.3 volts

replace tomorrow and see if that has anything to do with it....

Max at Maxxed in Baytown ...who originally set up the programmer and exhaust stated tat it sounds like it is in "Vallet mode"

I am going to google that now


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## surf_ox (Jul 8, 2008)

would valet key cause valet mode???


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## troutslayer (Feb 7, 2006)

Don't know.......I aint got one......


going to get batteries now


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## Tall1 (Aug 3, 2009)

I have heard of a dirty fuel filter causing the "Reduced Power" condition. I was told when I bought my 07 Duramax (new) to not let the fuel filter get below 40% life remaining, or I might wind up on the side of the road. I change mine when the life is around45% left, and knock on wood, haven't had any problems so far.


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## troutslayer (Feb 7, 2006)

Well.....after replacing both batteries......fuel filter....air filter....and reseting the computer....

Same issues.......cranks up fine......just does not have any power.....you can get it up to freeway speed....just takes a little while.....and if you push it...the display will say "Reduced Enigine Power"......and shut it down to 2000 RPM......

No fix as of yet......might just have to bite the bullet and take to a shop

Dealer tech stated that since I had a aftermarket programmer on it that he could not figure it out either...stated that the programmer wont let him read the truck computer....I think he is full of chit.....But what do I know


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## j4577 (Feb 11, 2013)

Will your programmer give you the P code?


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## goodwood (Mar 30, 2009)

maybe one of the techs at hd could help you out. theyre pretty helpful.


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## DSL_PWR (Jul 22, 2009)

troutslayer said:


> Well.....after replacing both batteries......fuel filter....air filter....and reseting the computer....
> 
> Same issues.......cranks up fine......just does not have any power.....you can get it up to freeway speed....just takes a little while.....and if you push it...the display will say "Reduced Enigine Power"......and shut it down to 2000 RPM......
> 
> ...


Put the entire truck back to stock. Take it to the dealer and have the ECM reflashed and then have the theft deterrent system reset (if the ECM reflash does not solve it). Should solve problem. The issue is with the pass lock system/key.


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## troutslayer (Feb 7, 2006)

Would have to replace the exhaust to go back to stock.......hopefully I dont have to do that


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## troutslayer (Feb 7, 2006)

goodwood said:


> maybe one of the techs at hd could help you out. theyre pretty helpful.


What is hd?


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## surf_ox (Jul 8, 2008)

hey could try this

http://my.cardone.com/techdocs/pt 77-0011.pdf


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## goodwood (Mar 30, 2009)

troutslayer said:


> What is hd?


Sorry typo. Meant to say call H&S Performance.


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## DSL_PWR (Jul 22, 2009)

troutslayer said:


> Would have to replace the exhaust to go back to stock.......hopefully I dont have to do that


Well here is another option for you.

Take truck to dealer. Make sure to take your tuner with you as you will need it right then. Return truck to the stock tune. It will immediately throw codes because of the exhaust dpf missing. Have them reflash your truck to clear the passkey faults and reset that system. Reload your tuning and see if that clears it. If not then you have other issues with either your theft deterrent system or ECM.


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## surf_ox (Jul 8, 2008)

DSL_PWR said:


> Well here is another option for you.
> 
> Take truck to dealer. Make sure to take your tuner with you as you will need it right then. Return truck to the stock tune. It will immediately throw codes because of the exhaust dpf missing. Have them reflash your truck to clear the passkey faults and reset that system. Reload your tuning and see if that clears it. If not then you have other issues with either your theft deterrent system or ECM.


I thnik this would work also...i'm sure this isnt the first time


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## ibtbone (Oct 7, 2013)

if it says reduced engine power than there has to be a dtc. possibly the programmer is not capable of reading it, do what the other guy said, go to dealer and return to stock, then drive until reduced eng power comes back


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## surf_ox (Jul 8, 2008)

there was code but he deleted it...

stuck at 2k rpm max now


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## troutslayer (Feb 7, 2006)

its kinda strange......when you first get in....it will allow it to go to 3k RPM.....but after a few minutes...the reduce engine power comes on and back down to a little over 2k

how do I return the truck back to stock?

also I did try to releard the key....but the instructions for mine says turn key on and security light will stay on....for 10 minutes....mine goes off within 10 secs



Im lost


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## ibtbone (Oct 7, 2013)

my bully dog programmer has that option, return to stock, that is only the program, not hard parts that you have deleted, if the reduced engine power message is on than there is a code stored or a bad computer. you have to start witct the code stored to diagnose the reduced engine power, that has nothing to do with the key or security system, it could be any number of things wrong.


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## troutslayer (Feb 7, 2006)

So far none of the scanners I have used show a code


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## Muleman (Dec 6, 2011)

My 06 did the same thing and it had reduced fuel pressure , changed fuel filter and solved problem


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## troutslayer (Feb 7, 2006)

I have had that code before...and like you said ....easy fix.....this is different


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## Pocketfisherman (May 30, 2005)

When my jeep diesel behaved the same way, cleaning the MAF and MAP sensors in the intake manifold fixed it. They make cleaner specifically save for those parts and both were crudded up from the PVC valve feeding back into the intake combined with soot from the EGR. Ran like a scalded ape after that 15 minute cleaning effort.


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## Redfish Chevy (Feb 6, 2011)

Not too sure about the 2007 but on my 2011 dmax when I tuned it and changed the exhaust from the down pipe back it only too about an hour. I couldn't imagine it taking too much longer if any on the 07. It would be well worth it to have it back to stock then take to the dealer for a computer flash .


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## sureshot840 (Mar 3, 2009)

I have EFI Live tuner & tunes for LMM & LBZ - I can reflash your truck if you are near Dallas or Beaumont - take about 15 minutes.


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## troutslayer (Feb 7, 2006)

Im near Beaumont.....about 45 min West of there...


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## ibtbone (Oct 7, 2013)

what kind of programmer do you have, most will not allow a reprogram with the aftermarket program in it,


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## troutslayer (Feb 7, 2006)

its an H&S Minimax



weird update........I read online about resetting by key on engine off pump the gas pedal 10 times........cranked up took her for a spin......

Holy Toledo!!!!! it worked!!!........drove about 1 mile....turned around....and here comes the reduced engine light....killed it ...key on...pumped the gas pedal....cranked up.....and wallah....shes back again...get into the neighborhood...same thing...reduce engine power.....

so the step works....but I must have a hard code that aint going anywhere soon....

lost again...but ti was nice to feel the ponies again...lol


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## ibtbone (Oct 7, 2013)

did you install the program in the truck or was it done as part of a kit done by someone else?, i only ask to find out if you are fimilar with the functions, there has to be a return to stock setting. i would do that, then drive it until the reduced engine power message comes back, read codes then, do not shut the truck off. i think you said earlier that you have changed the fuel and air filter. there are a number of failures that can cause this message, low fuel pressure on the high side, low supply side fuel pressure, accelerator pedal sensor ... etc, need a code to isolate issue


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## troutslayer (Feb 7, 2006)

I did not do the install.....it was done by Maxxed in Baytown........it does have a no power setting.......but I don't know if that returns it to stock

You cant read the codes w/out shutting the truck off
and when I try...there are no codes to read....or at least the Minimax aint showing them


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## DSL_PWR (Jul 22, 2009)

Most likley a tuning issue. You need to remove the tuner and update it and then re-install it. 

Have you talked to H&S?


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## troutslayer (Feb 7, 2006)

no...have not


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## DSL_PWR (Jul 22, 2009)

Call and talk to H&S and see what updates are available for your truck/tuner and then go from there. Has to be a tuning error in coding and I am sure they can fix it.


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## ibtbone (Oct 7, 2013)

i do not think that the stock setting with the programmer is back to stock, i think the tune or the tuner is keeping you from getting the codes or the program is the cause of the reduced engine power. that being said, get with the installer or uninstall the program, not just unplug, and retest as said by the prev post


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## troutslayer (Feb 7, 2006)

ok....spoke with H&S.....went through programmer and uninstalled the unit........back to stock..........took it for a drive......

same chit


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## DSL_PWR (Jul 22, 2009)

Well without installing the stock exhaust and hooking it all back up you will still set codes since the dpf is not installed. 

I would say return truck to stock completely and take to dealer for a full stock ECM reflash. Reset theft deterrent system and then start over.


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## ibtbone (Oct 7, 2013)

see if you can read codes with your programmer, if not take to auto zone and have them scan it, not all codes will set the reduced engine power message, now that it does not have the programmer in it i think you will get codes


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## snapperlicious (Aug 11, 2009)

I didn't see it anywhere, but is this a 2007 classic or a 2007.5?


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## troutslayer (Feb 7, 2006)

2007.5

no chance on putting the DPF back on....ill torch it first


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## offshorefanatic (Jan 13, 2011)

Call east fork performance on Cleveland. He's a d max guru.


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## ibtbone (Oct 7, 2013)

update your programmer, usb connection to computer, then reinstall in truck, see what happends. if it still goes reduced and will not read codes you will need to put stock exhaust on. without dpf and with factory program you will get reduced engine power, and that may not be the same problem causing your orginal problem, but if you can only temp install the factory exhaust and test it you can start from scratch.


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## troutslayer (Feb 7, 2006)

reinstalled program.......same ****.........


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## ibtbone (Oct 7, 2013)

were there any updates?, call h &s back, tell them ruduced engine power message but no codes, has to be a programming issue, any chance of temp installing factory exhaust?


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## snapperlicious (Aug 11, 2009)

Try unplugging sensors from the dpf delete and plugging them back in. Then reset everything. You may have to take it somewhere and see how much fuel pressure your getting also.


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## troutslayer (Feb 7, 2006)

the only chance of installing factory exhaust would be if the installer still had one laying around


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## crocket (Feb 12, 2007)

I just had this happen to my truck, I have a 2011 gmc sierra 1500 and I'm pretty sure they have most of the same sensors. I got an engine light though, a friend told me to clean out the trottle body, I tried it a couple of times and, it didn't work, since I had just bought the truck I called the dealership and they told me to take it in and they would pick up the bill, anyways I ask them what was wrong with it and they said it was the PPG ( petal position sensor ) a sensor that is hooked up to ur petal, I don't think it's that expensive, try taking it off one of ur friends truck, and give it a try.
Hope this helps, cause I was breaking my head like u as well


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## DSL_PWR (Jul 22, 2009)

troutslayer said:


> the only chance of installing factory exhaust would be if the installer still had one laying around


You didn't keep all the factory stuff?









The dealership needs to reflash the ECM. Until you have that done you are wasting your time.


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## surf_ox (Jul 8, 2008)

Read this on another forum. When the lly duramax ecms locks me out I pull both positive and negative cables off both batteries. To drain all the juice touch positive and negative. After that and waiting 30min usually I can get them to flash. May or may not work on the 6.4 ecms


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## troutslayer (Feb 7, 2006)

kinda of a weord update....the truck cranks up and runs fine until it reaches 145 degrees.....then on comes the "Reduced Engine Power"......

Ive checked it several times....each time at 145 degrees......or within a degree or 2


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## DSL_PWR (Jul 22, 2009)

Your ECM is fried. It will die soon. Trust me, been there.


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## snapperlicious (Aug 11, 2009)

Did you ever clean your mass air sensor? If not grab you a bottle of mas cleaner and try that.


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## goodwood (Mar 30, 2009)

any progress?


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## Copano/Aransas (Dec 18, 2011)

Not to hijack your thread Troutslayer but, we've got an 08' GMC Sierra CC 1500 and it has 69K and some change on it. It's been to 3 different dealers since around 38K for Reduced engine power, service stabile-track & check engine light on. Between the three dealers they've replaced the gas petal, EMC, fuel pump and a wire in the harness. Going down the HWY set on 75mph throws all the codes out of the blue with no warning at all !!! It's very frustrating none of them have been able to pin point the problem, matter of fact it's at the dealer right now for this problem. Took it yesterday morning and he said they can't figure it out are you kidding me !!! They can keep it, probably going to buy a Ford. I understand your frustration don't know if if these two problems or related or not. Maybe it's a GM thing.


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## ibtbone (Oct 7, 2013)

Copano/Aransas said:


> Not to hijack your thread Troutslayer but, we've got an 08' GMC Sierra CC 1500 and it has 69K and some change on it. It's been to 3 different dealers since around 38K for Reduced engine power, service stabile-track & check engine light on. Between the three dealers they've replaced the gas petal, EMC, fuel pump and a wire in the harness. Going down the HWY set on 75mph throws all the codes out of the blue with no warning at all !!! It's very frustrating none of them have been able to pin point the problem, matter of fact it's at the dealer right now for this problem. Took it yesterday morning and he said they can't figure it out are you kidding me !!! They can keep it, probably going to buy a Ford. I understand your frustration don't know if if these two problems or related or not. Maybe it's a GM thing.


not related to his problems, but will help yours, if the code is a 2138 then we build a new 6 wire harness and eliniminate 2 pass through connectors, takes away potential voltage drop,wire it between the ecm and the accel pedal, some what connom for those trucks.


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## troutslayer (Feb 7, 2006)

No updates as of yet....same ole chit


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## goodwood (Mar 30, 2009)

i was dealing with trouble codes recently with my 64 powerstroke. one day the truck shut down completely. long story short it turned out to be a bad hdmi cable on the mini max. might be worth a shot to change out. apparently its common for the hdmi cables to go out and cause all kinds of problems.


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## troutslayer (Feb 7, 2006)

Well.....update

Had to replace the mass air sensor...and the fuel pump regulator

About $850 in parts and the problem is solved.......

evidently the parts were bad enough to throw into limp mode but not enough to throw a code if that makes any sense......

BTW...this is what the shop stated.....I might have been BSed.....but the problem is solved non the less


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## snapperlicious (Aug 11, 2009)

Glad you got it figured out


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