Throttle Position Sensor on a Diesel truck

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slantflat

slantflat

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Hi everyone.

Here's yet another question about a diesel truck. I've looked over the truck forums and they are not as helpful as FABO. Imagine that.

Anyway, 98 Dodge 2500 24 valve truck that's close to me I want to look at, the guy says it needs a throttle position sensor. He doesn't say why he knows this. Is this a straight forward repair, easy or tough, expensive? It's priced cheap, probably will be sold before I call him. I just wanted to get a heads up on what a TPS entails.

Anything else I should look out for? Is the 24 valve engine a good one generally? Thanks everyone.
 
Diesels don't have throttles or throttle bodies (at least that I've seen), which is where you'd find a throttle position sensor (TPS). They accelerate when fuel is added via auto ignition based on high compression, this is why you need glow plugs to start them and they don't have spark plugs or distributors and have a lower RPM band then gas engines.

What he might mean is a throttle pedal sensor. I'm not sure if the 98' had them but I know newer trucks do and its a common-ish issue. So better ask what they are exactly talking about.
 
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Thanks Dano. I know the diesel doesn't have a carb but these days, who knows what has electronic stuff tacked on. And this wouldn't be the first time I've run into someone who didn't know what they were looking at. Hm, like me, but that's why I asked...

I did email him and ask why he thought it was the throttle position sensor and if the truck ran okay otherwise. I'm waiting to hear back.
 
I had a 98.5 24 valve (the switch from 12v to 24V was mid-year), still kicking myself for selling it. Anyway.....

The TPS (if they are talking about a throttle position sensor )on a 24 valve is on the engine above the injection pump. It's easy to get to.
The biggest thing to look out for on a 24 valve is the lift pump and injection pump (VP44). The stock lift pumps are notorious for failing, causing fuel starvation and failure of the injection pump. If you look around the interwebs you will notice a lot of people offering fuel pump warning lights (5 psi) switches to warn you of a pump failure.
If you get this pickup, I would suggest getting a FASS or air dog fuel pump. It's worth the money to not have to worry about smoking injection pumps.
 
^^^^^^^^^^^^^^ This is correct ^^^^^^^^^^^^ I'm going to bet it needs a fuel injection pump because it never got the lift pump mod done. Still a great truck but look it over good. Also look in the drivers side fender well real good. That is where the wiring and connector are known to rot and cause problems. Still not a bad fix if it's not a rot bucket.
 
zakimodo said:
I had a 98.5 24 valve (the switch from 12v to 24V was mid-year), still kicking myself for selling it. Anyway.....

The TPS (if they are talking about a throttle position sensor )on a 24 valve is on the engine above the injection pump. It's easy to get to.
The biggest thing to look out for on a 24 valve is the lift pump and injection pump (VP44). The stock lift pumps are notorious for failing, causing fuel starvation and failure of the injection pump. If you look around the interwebs you will notice a lot of people offering fuel pump warning lights (5 psi) switches to warn you of a pump failure.
If you get this pickup, I would suggest getting a FASS or air dog fuel pump. It's worth the money to not have to worry about smoking injection pumps.
Click to expand...
Pretty much exactly everything stated above. I had a 98.5 and went through 6 lift pumps before I got a FASS pump that mounted where the lift pump went. There used to be a guy (TIMBO)who sold the TPS’s at a real good price, used one in mine when the stock one went out at about 150K, Genoa carry’s them now, link below. I mounted a Westtach gauge in my truck so I could keep an eye on fuel pressure.

Dodge Cummins Throttle Position Sensor, 98.5-04
 
Yep.

2 factory lift pump's then an upgraded Aftermarket lift pump. I ran pre and post filter fuel PSI sensors.

"The VP44 killer is low pressure from the lift pump"!

The sensor "TPS" is not hard to replace and calibrate!

Never lost the VP44 in 270K miles! Before upgrading to my 2015 6.7 HO.
 
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I agree with most of the above. I will add one more thing to check- do this before putting any money into a throttle position sensor, lift pump, etc (though, it very well may need those). Isolate the alternator field wire from the main harness. Sounds crazy, but I vaguely remember this being a service bulletin, whereby EMI from the field wire would mess with the TPS readings. Maybe do some digging on that, but I remember doing it, on several trucks. All you had to do was isolate the section from the alternator, to the cowl / firewall; and it's just a matter of pulling that wire out of the plastic loom.
 
Great info everyone, thanks so much. Haven't heard back from the guy, we'll see what he says.
 
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