Need help with 2001 GMC 2500HD

[LaneKornn]

Recently got a 2001 GMC 2500HD with the 6.0. When the truck is cold started and drives after cooling down it runs perfectly and has no issues driving or power related issues at all. After its warm and you re start it though it wants to die right away. You can keep it running but not happily and barely at that rate. Has some codes I got off my scanner and recently has had an EGR valve replaced. When I bought it, they gave me some top-of-the-line coil packs and plug wires with it but the coil packs on there now have been replaced in the last 6 months. I was told by a friend it could either be coil packs gone bad, or possibly a bad coolant temp sensor. Not sure if starting with the temp sensor or coil packs and wires is a good place to start or if I have a different issue I'm looking at. The current codes I have ar as follows:


 

PO121 Throttle/Pedal Position Sensor/Switch “A” Circuit
PO122 Throttle/Pedal Position Sensor/Switch “A” Circuit Low

PO300 Random/Multiple Cylinder Misfire Detected

PO327 Knock Sensor (Manifold Absolute Pressure (MAP) sensor “A,” turbocharger (TC) system low input

PO404 Exhaust Gas Recirculation Circuit Range/Performance Problem
PO405 Exhaust Gas Recirculation Sensor "A" Circuit Low
P1404 B Circuit Malfunction/ Exhaust Gas Recirculation Closed Position Performance
 

Only get these codes after the truck has been warmed up as far as I'm aware, ordered a OBD scanner with live feed today and won't be 100% sure on the accuracy of that until it arrives. If anyone has experienced this or has suggestions, please let me know. Thanks, Lane.

Edited July 22, 2024 by Digital Abis
update codes

[richard wysong]

Welcome to the Forum! ALWAYS post the definitions along with the codes, There are over 18000 possible codes, no one remembers them all and most folks will skip over your post rather than look them up, myself included

[diyer2]

This ^^^^

[LaneKornn]

11 hours ago, richard wysong said:

Welcome to the Forum! ALWAYS post the definitions along with the codes, There are over 18000 possible codes, no one remembers them all and most folks will skip over your post rather than look them up, myself included

 

11 hours ago, diyer2 said:

This ^^^^

Updated! Thanks for the tip, honestly this is the first time I've ever gone to the internet seeking advice on forums, I had a friend who did it all the time and figured I'd take a shot at it, updated now!

[richard wysong]

With all the circuit malfunction codes a wiring diagram may help you determine what these circuits have in common, a common ground or 5v reference. Get yourself a FACTORY service manual or subscribe to AlldataDIY and follow the diagnostic tree for those codes. The misfire code may be unrelated