2012 C/C No start No crank, Is this a bad ECM or maybe a bad ground?

[Motor Mike]

So my truck won't start and won't crank. It ran fine when I last parked it. Now the tach doesn't move when i jump the starter relay, it doesn't display a wait to start message and i can't connect to the ECM with my scan tool. And no 5v ref at the MAF or EGR temp sensor. So maybe its a bad ECM

I do have 12v on pin 3 and 5 on the ECM, and a good ground on pin 2 and 4. My diagram says there should also be a ground on pin 6, but my voltage gauge shows that is open. Anyone have any idea where the pin 6 ground goes?

Any other suggestions on diagnosing a bad ECM before I roll the dice buying one at the dealer. TIA

 

[Turbo Terry]

I think I would take a good look at the condition of your battery’s first thing

 

[Timd32]

What size truck is this on 3500, 4500, 5500.

See attached pdf for the general starting system tests for 3500 basically same for others...

for the ground question..... I only see a PCM listed, but no hands on here just shuffling some paper and screen shots.


For example what I can see on a 5500 the pin 6 is G114 and its listed as part of the Transmission Harness. G114 comes up the same on 3500 but different picture.

Not the best shot here for either one.
3500

5500

I also found this listed from another repair again this is under 5500.

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After Installing Engine, No Crank, No Communication
TECH-ASSIST08/24/2018 | 14:54:41
After installing a replacement engine, now the engine will not crank. Found that there is no communication with the PCM.

Mileage Symptoms Test Performed
None Indicated

Does Not Crank

No Communication

None Indicated
Systems DTC Codes Keywords
Computers and Control Systems

None Indicated

None Indicated Comment(1)
Check power and ground to the PCM to make sure that everything went back together correctly. There are 3 fuses in the Totally Integrated Power Module (TIPM) that feed power to the Powertrain Control Module (PCM). Fuse J03 (40 Amp) to pins B3 & B5 at the PCM, fuse M28 (15 Amp) to pin B7 at the PCM and fuse M33 (10 Amp) to pin B71 at the PCM, . Also make sure that PCM pins B4, B6 & D have ground

 

[Motor Mike]

I think I would take a good look at the condition of your battery’s first thing

Batteries are good, if i jump the starter relay it cranks strong like normal, still won't start tho, thanks for the suggestion

 

[Motor Mike]

"Check power and ground to the PCM to make sure that everything went back together correctly. There are 3 fuses in the Totally Integrated Power Module (TIPM) that feed power to the Powertrain Control Module (PCM). Fuse J03 (40 Amp) to pins B3 & B5 at the PCM, fuse M28 (15 Amp) to pin B7 at the PCM and fuse M33 (10 Amp) to pin B71 at the PCM, . Also make sure that PCM pins B4, B6 & D have ground "

Hey thanks for the diagrams. The truck is a 5500. I checked the fuses and relays in the fuse panel and they all checked out. I haven't traced b7 back to the pcm yet, I'll try that and let you know what I find. Makes sense that pin 6 goes to the trans harness. Still not sure why pcm still isn't doing any pcm stuff even when it has power, my guess is it's shot.

 

[p-Bar]

Try disconnecting batteries let it sit a few minutes and rehook up. maybe computer needs a reboot.

 

[Ozymandias]

Did you check the fuses for continuity or just a visual inspection?
I just ha a tractor in the shop which had a 40A fuse broken - not melted - which looked great but had intermittent connection issues.

 

[Tuesdak]

Does it just display "Key in Ignition" with the driver door open or do you get radio and other accessory items powering on in ACC? (This may be for newer like mine IDK.) The ignition switch device would be my suspect with this question. I have heard the term "run relay" as well but IDK anything about it.

Any lights on dash, any other MISSING lights during the bulb check or start sequence? Radio/ headlights work? (You mentioned no WTS.)

 

[PRS]

Any sign the ignition switch is on?