2000 Ram 2500, 5.9L Gas

Been poring over the service manual, and can't nail this down.
Brief history...
Probably unrelated, but: several weeks back the coolant bypass hose blew. Engine overheated (quickly shut down, no damage). After overhauling the complete cooling system, I noticed that I was getting fluctuating coolant temp readings, it would suddenly drop to ice cold, then back to operating temp. Checked with IR temp gun and everything was normal so I put this troubleshooting on the back burner for a bit.

Then a couple of days ago the truck suddenly died when stopped at a red light. Was able to restart, drove to the closest parking lot to see if I could find an obvious problem (could not). Re-started the truck and went to exit the parking lot. Truck died again while waiting to pull onto the roadway. Got it home uneventfully, and was unable to replicate the problem in the driveway that day- started and ran normally.

In the process of looking over the engine compartment I went back to the temp problem I mentioned- and found the coolant temp sensor plug had basically crumbled away from age, and likely the heat from the overheat problem previously and this would logically have been the source of the fluctuating temp readings so I replaced the sensor and the connector on the wiring harness.

Truck will not start...nor even cough. Cranks fine, acts as though zero spark or fuel.
Other symptoms

I noticed the gauges "flicker" when key is turned to run position- voltage gauge needle moves- but I noticed the fuel gauge does NOT come off empty. From what I read, the ECM receives data from the senders and transmits to the gauges. If correct, wouldn't this point to a dead ECM?

Blue Driver OBD running live diagnostics when cranking showed "dead"- intake air temp, -40 degrees, engine coolant temp -40 degrees as though sensors were inop.
Error codes after cranking:
P0123
P0118
P0113
P1492

Appreciate and suggestions/diagnoses...thanks in advance.

 

Obviously the PCM is not dead as your code reader can talk to it. The codes are all "circuit high" codes meaning the PCM sees more than 5V on the sensor inputs. Most often that is a wiring issue that allows 12V to get onto the 5V sensor supply.

Edit: Scrap that, the temp sensors don't even use 5V supply. Most if not all sensors share a signal ground to the PCM so something might be wrong on that side.

 

P0123 Throttle Position Sensor #1 Voltage High
P0118 Engine Coolant Temp Sensor Voltage Too High
P0113 Intake Air Temp Sensor Voltage Too High
P1492 Battery Temperature Sensor Voltage Too High
If all these codes where set after "repairing" the harness i would think you got something wrong.

 

^^^
Nope. Simple two wire connection, checked resistance hot/cold. Functioning correctly.
I keep going back to the fact that the gauges are not functioning with key in the "run" position. I believe this- and error codes- are related to the ECM but I am not sure.
I think the temp sensor was just a coincidence, not a cause of the stalling/non-starting problem now.

 

Nope See this thread from just a few days ago: https://dodgeforum.com/forum/2nd-gen...-or-short.html

 

^^^
Different animal in '97 in that there are two temp sensors, only one in 2000.
Simple two wire, non-polarized connection to the sensor- I'm no mechanic but that's too simple for even me to eff up.
I'm not saying "no way" or I wouldn't be asking, but everything else that's going on- including the 3 other codes besides the temp code- still has me thinking it's the ECM- including "battery temperature"...clearly unrelated to anything other than a computer malfunction in my mind.

The fact that the gauges are inop with the key in the run position- while the indicators/dummy lights are working is the biggest red flag to me, the gauges get their input from the computers over the CCD bus.
Service manual has a procedure for an "actuator test" which runs self-diagnostics on the instrument cluster to determine if it is capable of operating correctly, I'm sure all is good there but it's simple to do and I'm going to run it tomorrow.

 

Well, you asked for suggestions but then you argue that they are invalid. Good luck !

 

Have you tried disconnecting the battery(clear codes) then connecting it again? Are the codes still there?

 

Think I would be tempted to check and see what voltages the sensors in question were getting. They all have a common ground, but, signal comes from a different pin on each. Of course, the MAP sensors feeds off of that as well..... but, not seein' a code for that one.

 

I do appreciate the input-really,
I was only saying that I didn't see how the replacement of the coolant temp sensor could be related to other three error codes.

Thanks again to all.