E38 stand alone harness --During scanning, starter shuts off scanner

[Lakegoat]

I have a swap vehicle with a 2012 E38 computer, service number and OS are compatible. I have power hooked directly to the computer and starter. Computer is powered all the time. I have a 4 pole starter switch with only the battery and starter poles attached. I can turn ON the switch, start scanning, and as soon as I switch to start, the scanner shuts off. Motor spins just fine. This is a new build and cannot attempt to start at this time. I was checking everything to see if I had oil pressure and all other functions. Spark plugs are out and fuel pump is turned off. I was concerned that I was not getting RPM signal, but I guess if the scanner shuts off at start, I won't be getting RPM's. I have the dreaded 158mph reading---changed the speedo to Serial, but above problem has me stumped.

[blindsquirrel]

1300 posts and no tune file? Seriously? Come on.

Where does DLC pin 16 get its power from? Is it from a circuit that's hot only in RUN, or RUN & CRANK?

Constant 158MPH - is this an auto trans OS with no more auto trans? POST TUNE FILE. NOT OPTIONAL!

[edcmat-l1]

1300 posts and no tune file? Seriously? Come on.

Where does DLC pin 16 get its power from? Is it from a circuit that's hot only in RUN, or RUN & CRANK?

Constant 158MPH - is this an auto trans OS with no more auto trans? POST TUNE FILE. NOT OPTIONAL!

Yeah 11-year member, he deserves the callout. C'mon man! LOL

[danmw2003]

This is typically normal behavior for modern vehicles. It does this because there is a massive load put on the electrical system during cranking. The modules shut off during this momentary start situation to prevent the frying of delicate electronics from a power surge.

[Lakegoat]

LOL---I am red faced
This was so screwed up, I didn't think anybody would reply.
Anyway, here is the tune and a short scan. The blower is not on this car yet so there is no firing the engine.
The -40 ECT was because the temp sensor was not plugged in.

It would really be nice if this was normal.

I have to look up pin 16. Auto OS with 4L80. Good question about pin 16. I would have to peel back some tape to see where it originates. Just like above, I applied direct battery power to the two power wires at the starter and the red wire marked run and start . As soon as I plugged in the OBD plug, the green light on the HPT box comes on and stays on.
Service # is 12633238
TCM OS 24235341
ACCelerator pedal 19417903

[Lakegoat]

I just looked at a guys CTSV scan, and it shows cranking rpm. All of my sensors are plugged in including the throttle body. I am waiting on my rotor pack to get repaired. Might be this cheap wiring harness ??? Wake up you guys, get some coffee and look at this.

[blindsquirrel]

I think you should not be so concerned with the labels on the ends of the wires, and rather where those wires go. I don't have 2012 Sierra diagrams, mine stop at '09, so I'd hate to give you something that turned out to be wrong.

Go through it at the ECM connectors and make sure all the powers and grounds are at the places they should be both in run and in crank (disconnect trigger wire at starter). Make sure #16 at the DLC has power at both run and in crank. Don't overlook the secret hidden power feed into the ECM (X1 #18), they call it 'Accessory Wakeup Serial Data' and is found in the Data Communications diagrams and not in ECM power/ground where you'd logically think to look. It originally passed through the BCM but is just another power feed - also goes to the TCM (#11).

[blindsquirrel]

I don't think your TCM OS is compatible with a post-'09 ECM, even though you said you were double super extra sure it was. 24235341 was from 2007 Suburban, and pre-'09 and post-'09 do not work together. If your ECM was '08 or early '09 it would work. I don't think this is the cause of your scanner or no-RPM thing though, just something you will need to figure out sooner or later.

There are Express van 80E TCM OSes that will work with your 2012 ECM. Should be 24243356. When you're looking for compatible files, check the injector flow rate limit. If it's 63lb it's a pre-'09, 127lb is post-'09.

edit: OK, that's Not Nice. Your log file shows a different TCM OS than what is in the tune file you posted. So, was the log made with some tune file other than the one you posted? Which one should I believe, the tune file or the log file? Or neither?

[Lakegoat]

I'm sorry blindsquirrel, The 24243356 is the T42 that is the one that is correct. The other 2007 one is one that I had previously. I replaced it with the newer one and forgot to change the number in my notes.

[Alvin]

Quite often cars I run into will not stay connected during a start.

I figured it's likely how the car is wired.. For instance.. is the DLC staying powered up during "START" what is powered up in start, run, and ACC are all different.

[blindsquirrel]

Actually... DLC #16 should be B+ (via a fuse, not IGN switch), hot at all times no matter what. Even if it's connected to a B+ source that doesn't mean there isn't a flaky connection somewhere, and voltage drop during cranking is enough to shut down/glitch the MPVI.

The 'Details' tab in the log file has the TCM as 24235341. So that was the one plugged in when that log was recorded.

[Alvin]

Its a swap vehicle.. How it should be and how it is could be very different.

[Lakegoat]

Yes, that is correct on the log file. That is the only log that I kept. It was after, that I found out the newer T42 was needed.
You are very thorough! The tune file shows the newer T42.
And thanks for all the info on things to check.
I am going to see if I can run down that #16 wire and see where it goes. I will get another short log and post it.
Thanks

[Lakegoat]

I cut apart the harness and pin 16 comes from the fuse box 12 volt run and start source. I kept the battery charger hooked up so I wouldn't have a large voltage drop.
Key on, Start Scan---orange light comes on HPT. Switch to start, orange light goes off and channels go blank. Saved log. Start scan---all numbers come back on channels. Switch to start, same as last time. Save log.
Key on voltage shows 13.4 volts on voltmeter. As soon as switch to start, voltage drops to 9.5 to 10 volts. The computer is being fed direct from two -4 cables (new, with new ends). Nothing else is running. Fuel pump off, no gauges, air, no residual wiring harness in the car. I guess that I will wait until the rotor pack comes back, get it assembled and see if it will start. I will check the #18 wire and see what results I get with that. Is it supposed to be 12V ? on #18

[blindsquirrel]

Are you trying to do this without your own wiring diagrams? If so, brave. I guess.

Are you monitoring voltage for real, or relying on something in the scanner? What kind of meter? Are you watching it or using min/max hold? Do you just have a battery made from old garbage? 10 volts cranking with the plugs out?

[blindsquirrel]

Why are the logs recorded today, just two hours ago as I type this, still showing the '07 TCM OS, 24235341?

screenshot.19-09-2023 14.31.26.png

Why is the crank position sensor not working? Have you checked power/ground/signal back to ECM at the CKP connector? Is the CKP sensor installed into the side of the engine? Is there a trigger wheel on the crankshaft? Is the crankshaft turning during those logs?

[Lakegoat]

This is a stand alone swap harness. They have no wiring diagrams---came from the big C, I think.
I monitored the voltage with a digital voltmeter, Southwire multimeter. Watching voltage.
Battery is brand new. Maybe I should take it and get it load tested. New ones can be bad.

[Lakegoat]

The rpm reading is what started this to begin with. I replaced the sensor, and probed the two outside pins for voltage while cranking. The 5 volt reference voltage was there, and on the other outside pin there was .1 to .2 volts on my meter. Center was grounded. Yep, sensor is bolted to the block, trigger wheel on the crank and the crank is turning.
Now--- I don't get the TCM OS problem. I open scanner and start scanning. Maybe I need to clear it before.
Back to the hot box

[Lakegoat]

OK, got the T42 OS changed. Good news---no more 158mph. Bad news, no cam counts and no rpm.

[blindsquirrel]

At the CKP, unplugged, there should be two wires with voltage. One is the 5vref. The other one is signal back to the ECM. My diagrams show a pullup resistor inside the ECM on the signal wire pin (but it does not specify the voltage) so, open circuit, it should not be reading .1-.2, which is basically just stray noise from a wire acting as an antenna. I believe CKP signal goes from 'A' at the sensor, to ECM X2 68. In the factory harness that's a white with black stripe.

I think you should diagnose it as if it was setting a P0335, that's where the 'Engine cranks but does not run' diag sends you if there's no RPM on the scan tool, even if that code is not current.

edit: OK, P0335 diag says you should have the same 4.8-5.2v on CKP 'A' (signal) when open circuit (sensor unplugged).