Truck won't start after head unit replacement. *** solved ***

voltage
4 - 14 is 2.42v
6 - 14 is 9.8v

sure glad someone understands this stuff.

 

The red light above your air-conditioning controls.
Blinking stops when the key is inserted into the ignition. If still blinks, the key is not recognized by immobilizer

 

Are you certain you were on the right pins? Those readings don't seem plausible.

 

voltage
4 - 14 is 0.6mV
6 - 14 is 180mV

 

I'm confused, are those key on readings?

 

ah, that light!
Yes, it blinks until I insert the key and then it stops blinking.l

 

I'm confused too....

With key ON:

4 - 14 2.42v
6 - 14 180mv

a mixture of earlier readings.

A hosed ECM? But first test don't guess! Love it.

 

Why are we checking 6 -> 14?
Pin 6 is CAN High, Pin 14 is CAN Low.

Why are we not checking Pin 4 to 6
And Pin 4 to 14

I believe we need to see around 2.5v on each.
A little more on Can H, and a little less for Can L. But around 2.25-3V is "close"

Key in ON position when reading....

 

If true, This puts you close to the 2.5v.
as the difference is 180mv....
2.42+180mv = 2.6ish volts on CAN H.

 

I might have missed it, but with key ON, does the CEL come on?
It should, with key in the ON position.

 

Key ON
4 - 6 2.6v

 

With key ON, there are NO symbols lit on either side. No CEL.

Currently there is no radio installed, just a bunch of wiring harnesses hanging out

 

As expected.

And.....Now we are on to something.

We have issues, major issues.

Kind of like to know what is unplugged.

 

@psvines

Just to be clear.
We have NO lights illuminate on the dash with key turned to the ON position?

 

Yes, NO lights with ON key. (except the middle section showing door ajar and odometer)
Also, fuel gauge doesn't move. Can't recall if it should.
And I installed the OEM radio, get same voltage readings.
4-14 2.42v
6-14 180mv
4-6 2.6v

 

Ok. Just because we can.
Check both sides of the 7.5A METER Fuse.
Let's go from there. As that fuse is tied to another (main fuse).
But lets start simple.

Again check both sides of the 7.5A Meter fuse for 12v.
Key in ON position.

 

So our CAN bus seems to be good, I think we need to go back to fuses.

I'm not at my PC to look at diagrams and get a full list of fuses to check, maybe @TnShooter will in the mean time.

 

If we test the 7.5A Meter fuse, and it has power. We just checked 3 fuses, a relay, a ground and wire integrity, - all at once.
There is a method to my madness.... (sometimes)

 

Key ON.
2.4mv on both sides of METER. Checked many times.
And fuse looks good, continuity works.

 

I like it, I tend to overcomplicate things and go down a rabbit hole sometimes.