Limp Mode

[TimHamlin]

I have a 2004 1/2 Ram 2500 Diesel and I had a new 5" MBRP exhaust from the turbo back installed 2/12. I pull a 39ft 5th wheel and the first time I tried to pull a steep pull the truck went into limp mode in tow/haul mode. The check engine light came on and then off the next day. I tried to do this pull again later and I had no problems at all. I was going up this same road earlier this week with no load and once again it went into limp mode. The only thing I notice was this happen after I had been in tow/haul mode and then pressing the button on the gearshift lever going back to normal mode it again went into limp mode but, if I went back to tow/haul mode it was fine. The check engine light came on and then went out with no other issues. Does anyone know what is going on? I bought the truck new 9/04 and this is the first problem I have experienced with pulling or driving.



Thanks,

Tim

 

[Prairie Dog]

I remember this coming up in the very beginning of the third gens on stock trucks. Something about the 5" breathing so well that it builds boost too quick or over boosts? I can't remember exactly but because of this, an early stock 3rd gen may perform better with a 4" pipe than a 5".

Hopefully somebody with a better memory will pipe up.

 

[SierraRam]

Gotta pull the code to even venture a decent guess. I suspect it is a transmission issue. On your 04 you should be able to cycle key on/off/on/off/on without starting and the code will display on the odometer.

 

[TimHamlin]

I went and cycled the key on/off and the code came up as P2121. ???

 

[6speed]

I had that code and it is the APPS. I have a manual but P2121 is APPS. With your auto it might clear it temporarily.

 

[Bob4x4]

usually internal apps but it can also be wiring or ecm

 

[TimHamlin]

Thanks everybody... This is the same code as before. Is this something easily fixed or would the dealership have to repair it?

 

[6speed]

Yeah its easy. On mine its under the driver side battery. If I remember correctly (CRS has started) I disconnected the batteries, pulled the inner fender liner out, there is actually a cable from the pedal to the APPS, replaced it, and it is a little pricey part, I believe the service manual gives a procedure to teach the ECM there is new electrical part. Something like turn on the key, don't start, depress the accelerator 3 times, turn key off, then everyting should be back to normal. Don't forget the fender liner.

 

[cerberusiam]

Thanks everybody... This is the same code as before. Is this something easily fixed or would the dealership have to repair it?

Yes, on yours it is simple and easy to source. Go here http://www.dodgecumminsapps.com/index.html

 

[TCDiesel]

Cerb, it looks like He's out of stock for the Under battery,But I think the OP has APPS in cab, he will have to check. At the shop when We disconnect Batteries we NOW want the Tech to turn key on and step on the pedal 100% down to floor or carpet 3 times GAS/DIESEL Always. This fly by wire is touchy,If th OP is not using 100% of the throttle form time to time it seems to cause mis-communications form time to time.

 

[cerberusiam]

Cerb, it looks like He's out of stock for the Under battery,But I think the OP has APPS in cab, he will have to check.

The OP has an auto trans so the APPS is on the front of the engine not under the battery. The Timbo APPS should work. Don't think Timbo ever did the manual APPS under the battery cuz they are a one off pain in the rear. An 04. 5 will have the APPS on the engine not inside the cab.

The APPS under the battery is a unique item to these trucks and is a pain to get new lately.

 

[TCDiesel]

I hear Ya,I don't Know. I know this I would install the BD noise reducer before I replaced the TPS/APPS on 03-04. 5. I install several to eliminate the Lockup problems on 03-04. 5

 

[S.Morris]

Timbo's a APPS will work if on engine. Have used it on 04. 5.

 

[cerberusiam]

Timbo's a APPS will work if on engine. Have used it on 04. 5.

Only if it the correct APPS. APPS on the engine does not guarantee it is the correct one.