1.26 Volts at PCM to CNK Sensor

7.4 CKP sensor
A = 12v
B = lo ref
C = signal

LS CKP sensor
A = signal
B = lo ref
C = 12v

My pigtail is the left style.

Attachment 160336

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Originally Posted by 123pugsy

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

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Let me qualify this. They match the AllData 5 page color drawing they supply.
2001 C2500 2WD 6.0L VIN U

Drawing seems nice unless they labeled the low ref wrong.

Which sensor is it?

7.4 1998 in the dizzy.

New CMP sensor and about the same.
I did find a short between two pins of the CMP sensor, zero resistance.
Sending juice right back into the PCM I would imagine.??

So I totally changed the fuel to stock 6.0L numbers and she stayed running longer.
The code for A on the CMP didn't appear on the latest log.
Funny, no O2 codes came up even though I don't have any hooked up.
They will be arriving Wednesday. I better stop playing until I got those installed, wired, and monitoring things.



Thanks you.

CKP. Crankshaft.
CMP. Camshaft.

Quote:

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Originally Posted by blindsquirrel

CKP. Crankshaft.
CMP. Camshaft.

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Got it, thanks.

Cam sensor changed today.

Quote:

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Originally Posted by blindsquirrel

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

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I'm asking, because the two crank position sensors have different pinning, and mis-wired at either CMP or CKP can take down the 12vref for the other one. The original 1998 7.4 wasn't like that, the 12vrefs didn't come from the PCM they came from fuses.

You've been messin' with both of them what seems like randomly without being real clear about what you have and so makes it hard to nail down whether you have any wires crossed or not.

I have the 7.4 crank sensor.
I had to swap the wires around from the 01 pin outs to get it to fire as they were as you mentioned, where, when I plugged in the cam sensor, 1.26 volts instead of 12V was at the crank sensor.

So, 7.4 CKP is wired:
A is 12Volts from PCM, C1-2,
B is Low ref, C1-21,
C is signal, C1-12

I have a C6 Vette MAF/IAT combo sensor also.

Quote:

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Originally Posted by 123pugsy

I have the 7.4 crank sensor.

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Actually, no, I don't. It's not the same as what's listed on Rock Auto at all.
I will have to find out what it's from.
It uses the same pigtail as the Vortec CMP sensor.

I assumed only, because I wondered, what other sensor is going to fit this cover.

Well, how about that. It's from a 2000 Chevrolet C7500 Kodiak. I'm sure there are all kind of wiring diagrams floating around for this, ha.....

Because the fellers that started selling the kit discovered the 24X reluctor on this motor and the light bulb went off for them.
I remembered this story is what got me to track it down. Big 5 ton truck or something.

2000 medium duty truck 7.4L

Attachment 160404 Attachment 160405

edit: Now I don't know and am not going to go look up if that uses the same PCM as a 6.0L LD truck, so don't use those references on the PCM side as anything but '12vref goes to this pin at the sensor' type stuff.

Quote:

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Originally Posted by blindsquirrel

2000 medium duty truck 7.4L

Attachment 160404 Attachment 160405

edit: Now I don't know and am not going to go look up if that uses the same PCM as a 6.0L LD truck, so don't use those references on the PCM side as anything but '12vref goes to this pin at the sensor' type stuff.

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Thanks. Only problem is I have no clue how to read the symbols, ha.......
I'll search for that I guess.

Attachment 160407

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Originally Posted by blindsquirrel

Attachment 160407

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Thanks.

I couldn't find those.
From left to right on each looks like 12v, signal, ground.

The ground symbol in the PCM should be easily identifiable, the clue to which is the signal is up in the picture of the sensor(s), so there's only one thing the third one can be.

Thanks.

I'm certain the wires are fine.

I gotta get the new O2's installed next and do some scanning.

Then, make some changes to the tune so that it will stay running?
It ran about 30 seconds today without touching the throttle.
Good sign.

1.26 volts has been solved, but how to keep the 8.1L motor running is the next concern.
I can rev with the throttle blade to keep it going but that's revving too high and up and down in RPM's, but that eventually dies and combustion temps are way too high.
Ceramic coated headers are starting to smoke.

I will have to start a new thread for that I guess.
It seems like this idea was too stupid, shoulda never went here.

Timing too low will make the exhaust glow, but actually give cooler temps in the chamber (since the fuel isn't completely burned by the time the valve opens). Are you sure-sure it's got high chamber temps? Or just speculating? Based on what?

And if there's a question around spark timing not doing what it should, have you checked actual mechanical TDC versus what the PCM thinks it is? Do you have a timing pointer and a mark on the balancer, and a dial-back timing light?

Thanks.

I wrote in a stock 6.0L tune and it stayed running long enough to show 20? on my balancer. (It's got the graduations)
It hunts quite badly, but settled at 20 every time before it stalled after about 40 seconds.

Any idea what I need to change to smooth it out?

I have 36 LB white injectors, Bosch? I found some data by Frost, but if I plug that data in, it stalls after a few seconds.

Also, when I log, the fuel trims are not showing up on VCM.

Did I mention?:
10.47:1 with a 212/218 @115 LSA camshaft .552/.552 lift.
Aluminum GM Performance heads.
Pro Flo XX intake


Attachment 160623

IAC not allowing enough air in?
Sounds like it's gasping for air.

Were you manually commanding a fixed timing of 20* when you checked it? That's what you need to do, command 20* and measure 20* means there's zero offset.

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Originally Posted by 123pugsy

IAC not allowing enough air in?
Sounds like it's gasping for air.

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Yes, it was.

I removed the IAC, covered the hole with masking tape, and she fires up and stays running.

High cylinder temps though. Ceramic coating is smoking.
I gotta add fuel, using the data by Frost or WS6.

Quote:

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Originally Posted by blindsquirrel

Were you manually commanding a fixed timing of 20* when you checked it? That's what you need to do, command 20* and measure 20* means there's zero offset.

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I have no idea how to manually command timing.

I'm a rookie at at this stuff even though I managed to set my fuel trims in my 5.3 nicely. That was about 5 years ago and I forgot everything, pretty much.

I think you're just using the wrong terminology. You can't tell anything about the temperature inside the cylinder from exhaust temps, in fact they go opposite of each other. If the timing is late and the burn isn't completed by the time the exhaust valve opens, EGT will skyrocket (because actual fire) and in-cylinder temps will fall, because the fuel is being burned somewhere that isn't the cylinder.

There are manual controls in the scanner.

Quote:

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Originally Posted by blindsquirrel

There are manual controls in the scanner.

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Thanks.

Quote:

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Originally Posted by blindsquirrel

I think you're just using the wrong terminology. You can't tell anything about the temperature inside the cylinder from exhaust temps, in fact they go opposite of each other. If the timing is late and the burn isn't completed by the time the exhaust valve opens, EGT will skyrocket (because actual fire) and in-cylinder temps will fall, because the fuel is being burned somewhere that isn't the cylinder.

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Thanks.

Wrong terminology, me? Probably.
I'm not proud.

Just trying to describe anything I feel is not right.
I had a 160 thermostat in the intake. I pulled that out to get some coolant flowing immediately upon start up.

I'm gonna add fuel injector data next and try another start after I find the settings in the scanner.
Hopefully, the ceramic coating stops smoking.

I've made two other sets of stainless headers for other engines, had em coated, and never had a tiniest poof of smoke.

Without the IAC in the hole, it's running between 1300 and 1700 RPM's. 20 degrees still?
Can't buy one today, holiday.

Scanner wasn't showing any STFT's or KR.

It did show O2's in the red at 400's mv. I understand red is bad.

Color can be set to whatever you want it to be. Don't rely on color to tell you good or bad. Learn to read the actual data.

Below 450mV is leaner than stoich, higher than 450 is rich. Fuel trims aren't active until it goes to closed loop which is usually around 130*F.