Need a little help with CANBus trouble.

[BattleTank]

Have we gotten codes out of it yet?

 

[Ham-Truck]

Found it!!!
The ABS module was cactus. The fuel pump control module connects to the ECU through it.

What's the spread on the ABS module being out causing the vehicle not to crank?

(Background: the start relay only fires when the ECU is commanded to by a diagnostic test, it will not fire the relay when the key is cycled, and it does properly report the key's status.

 

[Ham-Truck]

Have we gotten codes out of it yet?

Only codes are fuel pump system & EVAP related, see above for the fuel pump & the EVAP is a sticky vent valve.

 

[BattleTank]

Think about the CAN network like your 2 wire phone network in your house. Back in the old days(90's) and we had dial up network and you were trying to watch Mary Jane Rotten Crotch do weird things and your mom downstairs picked up the phone to call someone and interrupted your 'video'. Same thing applies here, if a module takes a dump, it will interfere with other modules trying to chat because they are all daisy chained via the 2 wire 'phone line'.

 

[j91z28d1]

Found it!!!
The ABS module was cactus. The fuel pump control module connects to the ECU through it.

What's the spread on the ABS module being out causing the vehicle not to crank?

(Background: the start relay only fires when the ECU is commanded to by a diagnostic test, it will not fire the relay when the key is cycled, and it does properly report the key's status.

if you have the abs modual pin out. you can unplug it, jump the can in and out pins to complete the circuit and see if your can network comes back it. normal truck should start without the abs module plugged in.

it so, it could be your abs module, or you could also find a bad pin or connection at if while doing it.

 

[BattleTank]

^ What he said!

 

[Ham-Truck]

When i had lights going crazy, it was a ground.

I even had the truck stall once after a long drive home with both the front and rear ac on full blast.
Hours before that i drove through a mud puddle.

I found the mud coated the grounds on the driver side under the driver seat, and the rear seat.

I cleaned everything, and then removed the grounds to inspect.
They looked great, so i cut the wire insulation back.
I found green corrosion!

I cleaned that up with electrical contact spray and soldering flux, then flowed solder into the joint.

All has been great since then.

Thanks, but it's not lights going crazy, it's the ECU not allowing the vehicle to crank. It registers the key turning to Start, and will fire the starter only when commanded to by a scan tool..

 

[j91z28d1]

Thanks, but it's not lights going crazy, it's the ECU not allowing the vehicle to crank. It registers the key turning to Start, and will fire the starter only when commanded to by a scan tool..

on mine that's scary cause everything is involved with enabling power when key is on, but a normal truck, what all can inhibit crank if it's seeing key requests. Immobilizer? neutral safety switch? is your little PRND indicator lit up? I seem to remember that means something in the tranny gear switch won't tell the ecm what gear it's in. so it doesn't start. some new stuff won't start without your foot on the rake but I don't think these do that.


yeah, I don't know. sounds theft related.

 

[Just Fishing]

Just saying, bad grounds make things go fkn nuts.

 

[solli5pack]

So is the CAN down or not? If it is that's why the truck is not starting and you're gonna need wiring diagrams. First step is to check ohm's with a volt meter at the Obd port to see if the CAN is intact. I'm not sure what the correct ohmage should be and what two ports you need to check but you can find it out pretty easily with some research. Pine Hollow Diagnostics on YouTube has some pretty good videos on CAN troubleshooting.