1.26 Volts at PCM to CNK Sensor

[123pugsy]

Custom 496 BBC build with 0411 PCM.

Fresh rebuild screwing it up with turning over and no start.
PCM output at pin C1 #2 is 1.26 volts.
Maybe PCM is toast by having some wires hooked up incorrectly before?
Some extra grounds and what else, can't remember.

EFI Connection Gen 1 crank sensor, set up wrong maybe?
Tried to get it dead center of crank sensor.
I tried a 12 volt jumper directly to the crank sensor also.
No spark.

Tune is from the repository, 2001 C2500, 6.0, 4L80e

Using diagrams from All Data.
They show DBW for some reason.
I have a drive by cable throttle body.

36 LB GTP injectors.
Data from a Frost tune, copied.

I'm pretty much a newb still because everything I've learned years back has been forgotten.

[blindsquirrel]

Is C1 #2 still less-than-12v with the sensor not plugged in?

I believe the 12v 'reference' pins on these are not a true reference voltage the same way the 5v is, it's not regulated, it's just a pass-thru from one of the IGN rails inside the PCM. (this means double check all your BAT/IGN feeds to the PCM)

Trucks were DBW if they were built with traction control, DBC if built without. Most all diagrams show all the possible options. There should also be diagrams for an IAC which no DBW will ever have.

[blindsquirrel]

I tried a 12 volt jumper directly to the crank sensor also.
No spark.

Oh JFC, just saw that part. Don't do that.

[123pugsy]

Is C1 #2 still less-than-12v with the sensor not plugged in?

I believe the 12v 'reference' pins on these are not a true reference voltage the same way the 5v is, it's not regulated, it's just a pass-thru from one of the IGN rails inside the PCM. (this means double check all your BAT/IGN feeds to the PCM)

Trucks were DBW if they were built with traction control, DBC if built without. Most all diagrams show all the possible options. There should also be diagrams for an IAC which no DBW will ever have.

Yes, same with sensor unplugged.
I just went thru the whole harness, redid all my 12 volts into the PCM.
Double checked all grounds and soldered them all to a nice fat wire directly to the battery.

IAC and TPS are on the drawing. Also shows the TAC wiring on the same drawing.
Just use one or the other?

If it was a traction control tune wired up for drive by cable, would it cause weird issues?

[123pugsy]

IAT was whacked as well. It showed 87 Celcius.
It's the one piece later model with MAF and IAT together.

[blindsquirrel]

Well I don't think it would be a good idea to flip a coin for choosing diagrams/which parts of the diagrams, if the donor was DBC then it uses DBC diagrams. It's also possible that Alldata just has shit diagrams. If multiple options are shown in the same diagram they should be marked out for which is which. GM does it by the RPO codes ('with XYZ" / "except XYZ").

If it was a traction control tune wired up for drive by cable, would it cause weird issues?

No idea, you didn't post your files.

[123pugsy]

Thanks.

Tried to upload it last night and I got an error.
Try again later when I get home.

[123pugsy]

Current tune.

TOMBSTONE 6 - INJ DATA.hpt

[123pugsy]

The attached states (With electronic throttle control) for the TAC module.
But it also has DBC stuff.
My wiring is currently like this. Except the O2's. I have them disco'd currently because I found some info about Canadian O's being different. For now, I need to fire this engine off. Fresh rebuild.

Attachment 160156

[123pugsy]

I have an unknown 4896 PCM in stock.
I'm wondering if I should try that.

Should I make up a data only harness to read it?

[blindsquirrel]

Preeeety sure you can just plug it in and check voltage at the CKP connector, even if it has some different calibration in it. I don't think anything will explode.

[123pugsy]

Thank you. I'll check it out later and report back.

[123pugsy]

OK, the new used PCM is a 2000 gmc sierra K2500, 6.0 L.

I got just under 12 volts at CNK sensor, key on

Fuel pump primed right away.

I had forgot to plug in the cam sensor after oil priming the engine, and when i did, the fuel pump started.
These all seem like good signs.

[123pugsy]

OK, I guess now it's time to spend more credits and flash my tune?

[123pugsy]

I didn't check crank voltage after plugging the cam sensor back in.
Assumed it would be good.

Then, I wrote entire on new PCM and same thing. Voltage is low until unplugging the cam sensor, then it goes up.

I found this:

I don't remember where I got the info from but somehow the cam and crank sensors are connected internaly in the ecm (run off the same drivers) , I think on their 12v ref signal but there's not diagrams to reflect this. Once I disconnected the cam sensor I had no more issues on the crank sensor side and the 12v reference stays there .

[123pugsy]

With key off, if I ohm test the 12 volt pin at crank sensor to ground, it shows continuity to ground. WTF? Cam sensor same.

[123pugsy]

I swapped A and C wires on crank sensor and scanner is now showing RPM's.

[123pugsy]

It barked once and then stopped. P0122 TP low, circuit A, +5V
Also:
0405, EGR, gotta turn this off.
0713, Trans fluid circuit high, no tranny hooked up currently.
1637 and 1638 L and F from Gen. Not hooked up because I have an alt from March in my kit. I got the pigtail to fit, but don't know what wires go where.

I don't have my O2 wires hooked up.
I have some 2003 O2's, and wondering if I can wire them to work.
Would that make a no start?

[123pugsy]

I got it running for about ten seconds throttling by hand.

So, I believe VATS is not in play, correct?

[blindsquirrel]

Is the CMP pinned correctly? Still rear mount/Gen3 style or a front sensor conversion?