1.26 Volts at PCM to CNK Sensor

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.

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.

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

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

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Originally Posted by 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.

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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?

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

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").

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

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No idea, you didn't post your files.

Thanks.

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

Current tune.

Attachment 160155

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

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?

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.

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

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.

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

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:

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Originally Posted by mccarthy69

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 .

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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.

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

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?

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

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

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

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Originally Posted by blindsquirrel

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

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Oh, totally forgot the '496' part of this. But then, what is the cam sensor with that setup?

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Originally Posted by blindsquirrel

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

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It's a 1998 Vortec Gen VI BBC motor with dizzy cam sensor.

It's pinned correctly, just the ABC could be different?
I swapped A and C on both crank and cam sensors and got it running. I use the term running loosely.

I need to order the correct O2 sensors I think.
I mistakenly thought I could use an 03 tune, and ordered the wrong sensors.
Unless I can wire them in somehow?

I have CMP code for A circuit low currently when scanned and started.
All other codes up for tranny and stuff, so non issue.
It won't stay running.

Oh shoot, I have to check the fuel pressure. That will be a chore with the Edelbrock fuel rails.

Attachment 160312

Attachment 160313

Your tune file has Crank Lo Res, in System Options, as '0'. That means 'not lo res/4x'. Needs that changed to '1' if you have the 1998 4x crank reluctor.

Attachment 160314 Attachment 160315

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Originally Posted by blindsquirrel

Your tune file has Crank Lo Res, in System Options, as '0'. That means 'not lo res/4x'. Needs that changed to '1' if you have the 1998 4x crank reluctor.

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Thanks.

I have a 24X crank reluctor.

The engine didn't come that way though, right? How is the wheel indexed, so that whatever the wheel's TDC is lines up with the piston's TDC?

Just read this in the instructions.
No idea what they're talking about. My regulator is built in to the fuel pump bucket assembly.
(they recommend using the express van 0411 PCM)

- Set {B4001} Injector Flow Rate (a constant for vacuum operated regulators)
- Change {B3704} Injection Bank Assignments to match the 2001-2002 Express Van calibration (for closed loop operation)

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Originally Posted by blindsquirrel

The engine didn't come that way though, right? How is the wheel indexed, so that whatever the wheel's TDC is lines up with the piston's TDC?

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Keyway in the crank, and pressed tight in place with the balancer.

Attachment 160317

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Originally Posted by 123pugsy

Just read this in the instructions.
No idea what they're talking about. My regulator is built in to the fuel pump bucket assembly.
(they recommend using the express van 0411 PCM)

- Set {B4001} Injector Flow Rate (a constant for vacuum operated regulators)
- Change {B3704} Injection Bank Assignments to match the 2001-2002 Express Van calibration (for closed loop operation)

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They don't know what they are talking about - the Offset vs Volts vs VAC table also has to change when the fuel system type/regulator changes. For a returnless/static rail pressure you do not change either the flow rate or offset table to one single number all the way across. You do that when the regulator is referenced to manifold.

Injector bank assignment is just so that each bank's O2 readings get applied to the correct injectors, it does not affect the ignition firing order. What that needs to be depends on the firing order according to the camshaft. 1-8-4-3-6-5-7-2 translates to 0-1-1-0-1-0-0-1 (odd numbers are bank 1/left/0, even numbers are bank 2/right/1).

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Originally Posted by blindsquirrel

They don't know what they are talking about - the Offset vs Volts vs VAC table also has to change when the fuel system type/regulator changes. For a returnless/static rail pressure you do not change either the flow rate or offset table to one single number all the way across. You do that when the regulator is referenced to manifold.

Injector bank assignment is just so that each bank's O2 readings get applied to the correct injectors, it does not affect the ignition firing order. What that needs to be depends on the firing order according to the camshaft. 1-8-4-3-6-5-7-2 translates to 0-1-1-0-1-0-0-1 (odd numbers are bank 1/left/0, even numbers are bank 2/right/1).

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Thanks.

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Originally Posted by blindsquirrel

Attachment 160314 Attachment 160315

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I put the CMP wires back to factory as shown on this drawing, plug it in, and that's when the voltage at crank drops to 1.2X.
Fuel pump also starts up when I plug into the cam sensor key on.

And then it won't crank of course.

This is an unknown CMP sensor as it came with the engine.
Is that the reason they scrapped the truck and sold off the parts perhaps? No start, bad sensor?

Wires are all correct to the PCM.
Checked twice with the OHM meter.

I ordered the correct O2's and pigtails from Rock Auto last night.
I've got enough mad scientist shi.....shtuff going on with this project.
Will be nice to have all the correct wiring on one drawing.

Well... that's half of one diagram correct and the other half correct on the other one.

CMP
A to C1 61
B to C1 73
C to C2 39

Do you have a LS type crank sensor, or the 7.4?

I have A and B reversed.
C correct.

My diagram is for the 2001, and my CMP sensor is 98, so I see some confusion.
Especially since it is a dizzy.
Should I swap those two wires?

Will it hurt anything to try it?