At the fire dept we have a 2007 Ram 3500 with the 6.7. A few months ago the transmission case cracked. We took it to the stealership for a new case. While it was there they said that it needed a new TPS. They put it in, and when we test drove it, it ran fine. Then a few weeks later after we put the truck back in service, it threw about a million codes, and when you would hit the throttle, mainly after a red light, it would shift real harshly to OD then stay there no matter how far you pushed the throttle. We get about 2200rpm and thats it. After a bit driving it like that, it goes back to normal, shifts fine, and runs like a dream. Then itll do it again. If you run the truck in tow haul mode, it seems to do it less often, but it will still do it. Some of the codes it is throwing:

U1400: Implausible TPS signal recieved
P0700: Transmission Control System (MIL Request)
P2059: ECM/PCM Power Input Signal Intermittent
P0121: Throttle Position Sensor/Switch A Circuit Range/Performance Problem

There were a few more but after we reset the computer I lost them from my code reader.

Any suggestions on what to look at first?

 

So it ran fine with the old and with the new that they recc'd it runs funny? Figures.

I'd multimeter the TPS to see if it's within spec. You can get the range value from the service manual in weedahoe's signature or in the FAQ section. it'll prob be somewhere between .5v at idle to 5v at WOT. You don't need the truck running to check those, just key in start psoition to provide power to T/B. idle would be completely closed btw.

I'll move this to the Deisel section, but I also wonder if maybe there's an injector problem even though there are no codes thrown?

 

Definitely sounds like a bad TPS sensor to me.

 

Thanks guys, Ill give that a try.

Also, I forgot to mention, the charging light has been flashing for quite a while. I took the truck and had the batteries tested the other day, and the passenger side tested low (400CCA) and the driver's side was fine (1100CCA)

Had the guy test the alternator. The little tester they use outside maxed out on amps, but gave low voltage. At idle the voltage would be about 14. Then as we reved it up, it went down to 13 at about 1400rpm, then at about 2k was back at 14. I shut the truck off, got everything back together, hopped back in, started it, and no flashing charging system light. Drove it back to the station. It ran fine the whole way. Once we got back, I shut the truck off, let it sit for a few minutes, then re started it to see if it was gonna start flashing again. Started it up, no charging light, and the CEL cleared itself. took and drove it for about an hour and it drove fine the whole time? Bad battery causing funky computer problems, forcing a limp mode of some sort?

 

It is a possibility. Hopefully that fixed it.

 

It was a combination of things. Repaced both batteries, belt, and belt tensioner. Alternator is charging fine, CEL cleared itself, and no electronic throttle light, and voltage is fine. Drove the truck several hours across several days, and it is fine now. Dang computers.

 

Very voltage sensitive for sure. Glad it is working out for ya!