5v reference circuit? Ecu? All of the problems!

[yohon]

Starting this thread to help troubleshoot and document a host of problems  with my father's "new" truck a 2001 24v 3500 dually with a 6 speed.

Problems Truck will start and idle fine but will surge/buck inconsistently with throttle/load

Codes p 1475 p0522 p0122 p 1295 p 0237 p 1488  and the companion code. 

Alternator ac noise seamed good <.03 

No wait to start light but truck has a grid heater delete block on it not shure if it was installed "correctly" 

Probably is ecu but I'm going to check out the 5v system just to check. I did notice temp sensor was spliced thinking wires might be swapped? Grounding out the circuit Truck seamed to behave better when warmed up. 

 

Questions! Does the wait to start light still light up momentarily without grid heaters? Also lift pump cycled for a shorter time then my truck does (2000 vs 2001) both pumps are aftermarket airdog pumps.

Can ecus be repaired/rebuilt? Any new ones on the market? 

Are ecus truck specific? I can't swap a 2000 auto with a 2001 manual? 

Thank yall for reading!

[Tractorman]

Since all of your codes point to a 5 volt supply issue, I would definitely check out the 5 volt supply and ground.  Also, I would check the supply voltage and ground for the ECM and look over the general condition of the electrical system (battery terminals, cross over cable, grounds, etc.)  Splice 165 (a problematic splice) is part of the grounding circuit for the ECM and other sensor grounds of the 5v system. 

 

Auto Computer Specialists (look in the Vendors section on this site) rebuilds ECMs .  New ECMs are not available.

 

Lift pump cycles 1/4 second with key in "run" position, approximately 25 seconds in "bump start" position.  Just round numbers. 

 

- John

 

 

 

Edited September 24 by Tractorman

[yohon]

Great thank you I'll post what I can find!

[yohon]

Finally got a chance to crack into this thing. Wiring looks like a mess (never buy a vehicle at night ) I'm guessing rodents got into it at some point map sensor pig tail is new but connected with wire nuts lift pump wiring had 3 butt splices in it ground wire was hooked on the alternator just a real mess. Thank yall for the help 

[Tractorman]

Sounds like you have your work cut out for you.  Just be patient and correct all of the previous owner's careless wiring.  Chances are that there is nothing wrong with the expensive components - just poor electrical connections to them.

 

Let us know when you get the problem resolved.

 

- John

[yohon]

Does any one know how to tell what pin is what on the map sensor? I have the diagram but can't tell what each pin is on the plug. The truck is reading 28 psi of boost at idle so I think the 5v circuit is wired to the wrong pin shorting the circuit. Did finally get the truck to start the neutral safety switch is wired to a switch up under the dash. Something else to add to the fix list. 

[yohon]

Well I still haven't figured out the MAP sensor wiring yet.  But got the scan tool to read a few more variables and it shows ECM battery voltage tanking whenever the truck cuts out. So I'm guessing this is showing either a bad ecu ground or bad 12v supply?

[Tractorman]

28 minutes ago, yohon said:

So I'm guessing this is showing either a bad ecu ground or bad 12v supply?

 

I think you are on the right path.

 

Something worth checking.  Is the stock engine block-mounted lift pump still being used?  If so, the lift pump will get its power directly from the ECM, not the best decision from an electrical engineering standpoint.   Many people have relayed the lift pump using the ECM to trigger the coil of the relay - a much better operation and the relay greatly reduces the electrical load on the ECM.

 

- John

[yohon]

It does have an aftermarket lift pump on it and uses a relay. Good idea on checking that. Tractorman I know your an 02 not an 01 but any way you can tell me what order your map sensor wires go? Should be an orange Grey red and blue black wire. 

[Tractorman]

Here's the pin out from the 2002 FSM.  Let know if this helps.

 

- John

 

[yohon]

That helps so much thank you! 

[yohon]

Well good news bad news. Map sensor is fixed and finally wired correctly! Thank you tractorman! Bad news is I think the ecm is toast. Voltage across every sensor is fluctuating and crashing out. I checked the common power and grounds at ecm and it was solid. But thank you everyone for you help!

[Tractorman]

Give these folks a call.  They have a good reputation.

 

https://mopar1973man.com/forum/210-auto-computer-specialist/

 

- John