Archived Power drop out on cruise

[RNixon]

Need a quick opinion here. Truck is in the shop. '99 Ram 2500 24-valve with 125,000 miles. Was cruising home yesterday in heavy rain. On cruise control at about 50 mph. Suddenly, without warning, power dropped out. Like turning off key. I was trying to get across 2 lanes to right shoulder when power came back. Check Engine light came on at the same time. After power came back, I was able to drive home with no more problems.



Drove to shop this morning, no problems. Mechanic says code indicates throttle position sensor problem (May actually be Accelerator Position Sensor) I didn't get exact code number yet (tomorrow)



Is this right? Sensor costs $350-500 so I want to be sure.



I've been suspciions of the lift pump. Bought a new one 2 weeks ago before 1,000 mile trip. No problems on trip, and had not installed pump. Went ahead and told mechanic to install new pump regardless. Don't have fuel pressure guage. On my list.



Would it make sense to drive with old position sensor to see of new lift pump made a difference?



What is risk of complete failure and getting stuck on road?



Hope this makes some sense. Thanks.

 

[p-Bar]

I would it's nice to figure out what the problem really is. If I owned a 2nd gen I would have a fuel pressure gauge considering that the fuel is the only thing lubricating the injection pump.

 

[RKlaassen]

Ok, here is my quick opinion; I would guess it is probably your APPS and not the lift pump. My lift pump failed at 95k, and I would not have noticed it, if I had not installed a F. P. gauge at about the same time. The truck was still running fine with intermittent fuel pressure between 0 to 10 lbs. My APPS started its demise in about the same way as you are experiencing now. I posted here on the site for help on how long it might last and if it would leave me stuck. most members said it would just get worse over time and be a more common event. I decided to drive it for a few weeks and it did as everyone said it would. Once a week, once every other day and so on. Maybe ten times total. I was always able to work the pedal and eventually get a response, but decided I had pressed my luck long enough. A new APPS was $349. 00 + $10. 00 freight from the Kenworth dealer in Tucson. Anyway, that's how it was for me. Best of luck to you.

 

[RNixon]

Ok, here is my quick opinion; I would guess it is probably your APPS and not the lift pump. My lift pump failed at 95k, and I would not have noticed it, if I had not installed a F. P. gauge at about the same time. The truck was still running fine with intermittent fuel pressure between 0 to 10 lbs. My APPS started its demise in about the same way as you are experiencing now. I posted here on the site for help on how long it might last and if it would leave me stuck. most members said it would just get worse over time and be a more common event. I decided to drive it for a few weeks and it did as everyone said it would. Once a week, once every other day and so on. Maybe ten times total. I was always able to work the pedal and eventually get a response, but decided I had pressed my luck long enough. A new APPS was $349. 00 + $10. 00 freight from the Kenworth dealer in Tucson. Anyway, that's how it was for me. Best of luck to you.

Truck is back home now. Lift pump has been replaced, and my guy tells me it was bad. He didn't get a pressure reading, but he said it wasn't pumping much. Error code was:

P0121

From the message posted here, that is said to mean:

Accelerator Pedal Position Sensor Signal Volts Do Not Agree w/Idle Validation Signal



According to my mechanic, from his high dollar computer reader, that code translates to: Accelerator Pedal Position Sensor Malfunction



What is the APPS sensor voltage compared with? I'm wondering if a brief loss of fuel pressure could cause something with "Idle Validation Signal?



He tested the APPS resistance, and said he did not see any readings to indicate a problem with it. We left it alone for now. If this happens again, with the new lift pump, we will have more data to go on.



I've been planning to install a fuel pressure gage, but found so may different ones out there that I had a hard time picking one. Is there a particular brand / model that the group here recommends?



Thanks, everyone.



Rob

 

[RSimmons]

I have been pleased with the westach brand from Geno's Garage.

 

[RNixon]

Today's trip to work was uneventful. Maybe this problem is solved with the new lift pump. Sure hope so.



I'll check with Geno's on that Westach guage. Thanks.

 

[RNixon]

something odd with forum. I didn't see this message from last night

 

[RNixon]

Has something changed so we see all these "moved" messages?

 

[Bob Cochran]

I can tell you that when my fuel pressure dropped to zero between La Junta Colorado and Taos New Mexico I was one worried guy. The route I was taking was scenic with lots of pulls and elevation changes for about 100 miles and I was pulling a 14,000# 5er. While I tried to be easy on the throttle I can tell you the truck seemed to run fine. I think if I had lost prime I would have never gotton the truck to run. After getting to Taos and before LP change opened fuel filter housing and removed filter. Hit the key to get the pump to run and it barely squirted fuel but some!!!! Then again I have heard others where the truck stopped when the LP went to zero pressure maybe no fuel at all was pumping. At any rate hope this helps. Glad you seem to be running again and the LP was the problem.

 

[DieselLady]

I have been pleased with the westach brand from Geno's Garage.

I second this. The nice thing about the westach is that you done have fuel or any other liquid entering the cab. Just install the sending unit on the filter and run the wire to the gauge. Great unit. Westach makes gauges for aircraft so they are very very reliable and accurate.

 

[the whale dog]

my 98. 5 did the same thing and only on cruise the tps was bad and according to the dealer mechanic it tested fo 0 volts at start up and any way I bought the tps from napa for I am thinking around 150 bucks which was about a third of dealer cost.

I also noted improved performance and a smoother idle with new sensor.

 

[RNixon]

My loss of power problem is baaaaaaaaacccccccccckkkkkkkk



Started happening again last night (3 times, and again this morning) Check engine light comes on at the moment the power drops off. Code set is P0121. Same as before. "Accelerator Pedal Position Sensor Signal Volts Do Not Agree w/Idle Validation Signal" My OBD-2 software calls it "Throttle / Pedal Position A Circuit Range /Performance"



Tried to find a replacement APPS today, but no luck. Does anyone know a good source? I did find one reference to Hoesli Diesel. Part number is 53031575 (stamped on the part) I know from last time Dealer wants $455 for one.



Is there anything else I should check before replacing APPS? Just installed new lift pump last time this happened (less than 1 month ago) New fuel filter installed today. Old one looks normal. No other symptoms or problems noted so far. Truck runs great except for these incidents. '99 model with 130k miles.



Any suggestions??