LB7: Codeless limp mode

[Mike_S]

Alright guys, im starting to get very frustrated here. I have what appears to be a codless limp mode occuring with mu truck.

Specs are 04 LB7, custom dual lift pumps, 60% injectors, s480 turbo with custom piping, 5" intake tube, LBZ regulator, i dont believe that anything else could be related to the situation.

The truck pulls like a damn freight train, then all of a sudden limits fuel to about 55-65 mm3. No light, no codes, peak boost about 35 PSIG, rail pressure 25K and some change, and its maintaining. I have tried everything i can think of, rescaled the MAF voltage table, disabled the expected airflow test, disabled the 1093 code and diagnostic test, bumped the fuel flow maximum table to 60000. The fuel limit that occures directly coresponds to the stage 1 engine protection mode table. Anyone ever dealt with this? Any pointers where else to start looking? Im beating my head against the wall here...

 

[x MadMAX DIESEL]

What happens if you "clear codes" will it go away

 

[Mike_S]

Nope. If i let out of the throttle for a few hundred feet and then lay into it again it takes off like a rocket, pulls like a mule, and then does the same thing. Doesnt seem to matter if its from a roll or a dig, it does it either way, and how long it takes seems to be random. But its only at WOT.

 

[ocwelder]

I'm no expert, but could it be in the ECM did you try doing a complete re-flash, I am curious to hear if you can go into a limp without throwing a code.

 

[hondarider552]

have you checked table B0732??

 

[x MadMAX DIESEL]

have you checked table B0732??

I want that table

 

[Mike_S]

have you checked table B0732??

Yessir, but the log does not seem to corespond to that table. The engine will still rev past 3000, that table is set to zero fuel above 2200.

The log seems to follow b0733 directly, engine protection stage 1. I just cant figure out whats making it go into engine protection mode.

 

[JoshH]

Have you tried re-enabling your DTCs?

 

[Mike_S]

Have you tried re-enabling your DTCs?

I havent, but that is a good idea i think. Didnt Ben have a similer problem with his LLY when he put his compounds on?

 

[DIESELMAFIAPER.LB7]

I thought you said you were losing rail pressure? As for pulling fuel turn all the dtcs on again see which codes it kicks? Is it boost related sounds like what mine did for turning overboost codes off??

 

[delong_1]

sounds like what mine was doing when i first put compounds on, the maf flow rate just had to be rescaled. mine set no codes also.

 

[Mike_S]

I thought you said you were losing rail pressure? As for pulling fuel turn all the dtcs on again see which codes it kicks? Is it boost related sounds like what mine did for turning overboost codes off??

I thought thats what it was too, but it is not, rail pressure is within +- ~ 1000 PSI, and i have the variation limits set pretty loose. Boost limits are set to 37 PSI, cant remember if the tune in the LB7s are absolute in that table or not though, could be an issue there. Didnt have time to mess with it today, hopefully ill have some more time again this week, we'll see.

 

[Mike_S]

Bringing this thread back...still having this problem. I re-enabled the dtc's that i had disabled. The truck still does the same thing...i did have a boost sensor circuit high code tonight...but it did its thing several times before throwing the code...is there an error time limit that i could max out to get rid of this perhaps? The MAF table has been rescaled, Trent helped me out with that trying to reduce part throttle smoke...anyone got some ideas? :baby:

 

[DIESELMAFIAPER.LB7]

Whats your max boost now?

 

[Mike_S]

Uuuuhhhmmmm....something north of 35 psig. The gauge pegs now...order me up a 50 psig one would ya? Autometer pro comp ultra light.

 

[Mike_S]

Follow up on this, finally got it to code. Boost sensor circuit high voltage. Was sot for 2 trips before the code was set. Evidently weather or not it sets the code it still defaults to engine protection mode. Anyways, disabled this code and the truck pulls like a freight train all the way to the speed limiter now. Thanks for the help fellas!

 

[02dirtymax]

glad you got it figured out, I had the same problem after I put my turbo on. It would just fall flat on its face when it pulled out the fuel for overboost. Never had another problem after disabling that code.

 

[chevyburnout1]

Had the same exact issue as well. Same defuel for a few seconds then full power again. Set the same MAP sensor code. Wish I would have seen this sooner!

 

[DAVe3283]

Bit of a necro-post, but I just wanted to say I ran into the same issue on my brother's truck. LB7, federal emissions OS 15189044. The exact DTC is P0238.

It was set to "B: 2 Trips, Emissions Related". Changed it to "X: Not Reported" and the truck stopped falling on its face.

It completed the CCM system readiness test, so it looks like it should still be good to go to pass CA smog. :roflmao:

 

[THEFERMANATOR]

Bit of a necro-post, but I just wanted to say I ran into the same issue on my brother's truck. LB7, federal emissions OS 15189044. The exact DTC is P0238.

It was set to "B: 2 Trips, Emissions Related". Changed it to "X: Not Reported" and the truck stopped falling on its face.

It completed the CCM system readiness test, so it looks like it should still be good to go to pass CA smog. :roflmao:

Had this code pop on me on about a 5% grade pulling the travel trailer. Pulled off, turned the dtc off, and went back about my way with no more defuel.