Engine/Transmission (1998.5 - 2002) P0122 Fault Code--Accelerator Pedal Position Sensor (APPS); Throttle Position Sensor

[MAYoung]

Gentlemen:



Yesterday, my 1998. 5 displayed a P0122 fault code which indicates a low voltage reading to the Accelerator Pedal/Throttle Position Sensor. This is the first time that I have seen this truck display this code after 232,000 miles. I have reviewed the other posts on this code but I am inclined to invest in a new APPS since that is the easiest to replace. (This assumes that I can find the part at the dealer tomorrow. )



I understand that there could be other sources for this failure from weak batteries, poor connenctions or even a failing VP44. The VP44 has about 70,000 miles on the unit and I monitor the fuel pressure and I have replaced the factory lift pump with a FASS direct replacement pump. The truck maintains about 14-15 psi throughout all phases of throttle positions. Batteries are good. The only symptom has been a hard start after the engine has warmed up. It will go from a touch start when cold to a full 3 or 4 seconds worth of cranking when hot. Cranking speed is normal and brisk. The engine runs normally once it has started.



Does anyone have any additional insights into this repair? (I do understand that there is a kit to be purchased from Geno's to effect repairs to the APPS but I cannot wait for the transit time. ) If a new APPS fixes the problem, how confident should I be in the repair? Should I stay local for several hundred miles before I undertake a 500+ mile trip to San Diego?



Thank you in advance,



M. Young

 

[JR]

If you purchase an apps through a dealer, as far as i know you will have to buy the entire belle assembly which costs several hundred dollars versus an aftermarket sensor for about 160 bucks (if i remember right). The sensor is the only part that goes wrong, no need to replace the entire belle crank assembly. You may even be able to over night or next day ship if you order online. Not sure of your situation when you say you cant wait, but for several hundred dollars difference it would have to be a pretty big deal for me not to wait the extra day or 2. When my apps went out, that was the code I received as well. It could be a battery issue or bad connection, but if youve eliminated those issues its probably safe to say you have an apps going bad. As far as your hard start issues it may be due to high lift pump pressure or early signs of v. p. starting to go south. Either problem will give you a hard start issue. Good luck in getting everything fixed,
JR

Just noticed you stated 15 psi lift pump pressure that shouldnt be too high i actually run closer to 18 at idle so it could be early signs of vp issue. When was the last time you changed your filter? Im assuming you moniter your fuel pressure after the filter?

 

[JLandry]

I agree that the hard starting could be an early sign of VP44 wear.



How many miles on the injectors? If original, they're undoubtedly very worn and the tips probably leak a little.



John L.

 

[MAYoung]

Gentlemen:



The new APPS/TPS is installed. Truck has been test driven and power and starting appear to be normal. The problem seems to be solved for now.



I had no real big problems with the removal and installation of the sensor. The plastic cover has those two funky "screw pegs" to figure out. I was most concerned with pulling out the throttle and cruise control cable from the hold down bracket. At 14 years, the plastic retainers tend to be brittle so I have to handle them with patience.



I understand that there are cheaper alternatives to the original Dodge part. If I had time, I would have tried the part from Geno's that seems to be a much cheaper fix. The APPS was $521. 31 out the door from our local Dodge dealer in Folsom, CA. Ouch. Still, it was an origianal part and this is the first time that I replaced the part at 231,548 miles.



I am in a rush since the truck is scheduled to haul my daughter, her horse trailer and her horse to San Diego tomorrow. It will be a 525 mile, 11-12 hour trip at 55 miles per hour so I had to be confident that the repair was more than adequate. CA-99, I-5, I-210, and I-15 are not user friendly roads through the Central Valley and Los Angeles Basin. I am always concerned about the Grapevine pull. The truck has no problem with the grade but if you have a weakness iin your truck, it will find it.



Thanks for your assistance.



M. Young

Fair Oaks, CA

 

[MAYoung]

BTW, after I deliver my daughter and her cargo to San Diego, the truck is going into my garage for some heavy maintenance. I will look at the injectors. Every leak is going to be fixed. I am going to work on the front end. I'm trying to get it ready for the next 230,000 miles.



M. Young