Truck runs great but P0252 P0253

[20016speed]

Good morning everyone! Here’s the story, might be a little long but I want to give every detail so it makes it easier, bought an 01 24valve auto off a used car lot not running dirt cheap. Guy didn’t seem to understand these trucks. 
Only mods are a fass DDRP, nothing else truck has 140k, and a new reman trans, very carefully inspected truck and no prior meatball repairs or hacked wiring. 
upon first arriving at the lot here’s what I did.
- trucks battery terminals were beat/ corroded, managed to get them tight and partially clean
-found fuel relay missing out of fuse box under hood, swapped with horn relay and truck fired, ram very poorly but was enough to get on the trailer. 
 

Arrived home

- first things first, replaced all battery terminals with HD bolt on style, replaced all terminals ends soldered and crimped

- removed what looked to be a capacitor tied between the orange wire black strip by PCM, to ground 

-truck would start, but cranked, threw communication code for vp (1689), hot wired VP it ran, (originally wired it backwards by accident) found all grounds under D side battery rotted off, and all grounds in poor shape 

- Redid all grounds, solder and crimped, cleaned all surfaces very well, I’m very detail conscious 

-truck fires up, as it’s running it is intermittently losing power to vp and coming back, truck would sputtter but would catch itself never stalling, as I’m by the fuse box the fuel system relay had a poor connection as I would touch it and the truck would shut down, I just barely bent the taps out on the relay, pushed it back in and now has a solid connection, all sputtering issues are gone, vp is no longer loosing power, 

Things I noticed,

-ecm leaves the lift pump on all the time, swapped in a spare I had and solved that problem, but I did however swap the ecm back and put the lift pump on a key on power source as I’m still diagnosing this truck and don’t wanna fry a good spare ecm. 

 
So here’s the issue left the CEL is on, I’ve tried clearing the codes but they come back immediately after the truck starts , P0252, P0253, truck seems to run great, I’m wondering if the issue is because the ecm is keeping power on at the lift pump, I’ll swap the good ecm and test again, just wanted to get some insights, thank you guys and enjoy the holidays 

 

Edited November 24, 2023 by 20016speed

[Tractorman]

From my 2002 FSM - no P0252 code shown.  Can you confirm that you are seeing a P0252 code?

 

- John

 

9 hours ago, 20016speed said:

So here’s the issue left the CEL is on, I’ve tried clearing the codes but they come back immediately after the truck starts , P0252, P0253, truck seems to run great,

 

When you say "truck seems to run great", does that mean you have driven the truck and the engine performs normal?

 

- John

Edited November 24, 2023 by Tractorman

[Mopar1973Man]

PSG on the VP44 is shot. Most likely AC noise issues.

[20016speed]

1 hour ago, Tractorman said:

From my 2002 FSM - no P0252 code shown.  Can you confirm that you are seeing a P0252 code?

 

- John

 

 

When you say "truck seems to run great", does that mean you have driven the truck and the engine performs normal?

 

- John

Yes, I’ve driven the truck on the road and feels like a stock 24V, I will check for A/C voltage when I get home from work