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Voltage Issues

I decided to have my engine built over the winter. My car went in running. Took everything out, assembled the engine, car won't start. Car has codes which make zero

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Old 10-17-2019, 04:33 PM   #1 (permalink)
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Default Voltage Issues

I decided to have my engine built over the winter. My car went in running. Took everything out, assembled the engine, car won't start.

Car has codes which make zero sense, as the app harness was never touched (see screen shot below). Now here is the weirdest part, the ECU is showing 20v! Below is the troubleshooting we have done:

-Continuity tests on all sensors.
-Checked all grounds.
-Removed all aftermarket accessories.
-Took my ECU to Edconoline (thanks Ed). Plugged in his car, normal voltage and the car started.
-Took Edconolines IPDM, hooked it up. No change.

To state the obvious, there is no 2nd battery hooked in series (or second battery period lol). There is no step up. This is just not possible!

We are going to check voltage to each pin just to confirm that somehow the car is not sending 24v (we assume the ecu pegs out at 20v).

If anyone has any insight into this, it would be greatly appreciated!

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Old 10-17-2019, 07:40 PM   #2 (permalink)
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... -Took my ECU to Edconoline (thanks Ed). Plugged in his car, normal voltage and the car started. ...
That tells me that the problem is in your car. Bad connector, pinched wire, floating ground, etc.

The 20V is weird - I'm guessing you have a power problem to the ECM or a wiring problem and the ECM is giving more or less random readings.

FSM (link in sig) may have some troubleshooting tips.
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Old 10-17-2019, 10:30 PM   #3 (permalink)
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I have no pointers, Just a car bro bra. I too have issues and want you to know you aren’t alone.

You WILL figure this out and it WILL be something ******* stupid.
Speaking from experience

Ps swap the alternator maybe the voltage regulator is shot
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Old 10-17-2019, 10:35 PM   #4 (permalink)
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Originally Posted by SouthArk370Z View Post
That tells me that the problem is in your car. Bad connector, pinched wire, floating ground, etc.

The 20V is weird - I'm guessing you have a power problem to the ECM or a wiring problem and the ECM is giving more or less random readings.

FSM (link in sig) may have some troubleshooting tips.
Thanks for your help. I Think I traced the 20v issue to M107 connector on the ECU. Pulled back the cover and found some exposed wired. Not sure how that would have happened.

I got excited because the aps sensor which I am assuming is for the app is on the same harness. There was no change there. The throttle voltage is sitting at .05v and there is no response. Here is the interesting thing, if I push sideways on the connector I get .695v and the thottle voltage responds. I am thinking this might just be a fluke though, maybe forcing two pins to touch. I also tried a different pedal, no change.

To make things more interesting on the throttle body connector bank 1, I have two lines with ~5v. On bank 2 I only have one at ~5v. Neither of the throttle servos are actuating when I turn the ignition on.

I have been dissecting the FSM, which is where I am heading now. If anyone can save me some reading, that would be awesome lol.
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Old 10-17-2019, 11:20 PM   #5 (permalink)
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... I have been dissecting the FSM, which is where I am heading now. If anyone can save me some reading, that would be awesome lol.
Many PDF readers have a search-all-PDFs-in-a-folder function. Put all the FSM PDFs in a folder and have your reader search that folder to search the entire FSM. If you get a lot of extra junk, use the "-" operator to exclude terms. Good luck.
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Old 10-18-2019, 07:46 AM   #6 (permalink)
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Start by fixing the M107 connector. Make sure the pins in the connector haven't been pushed back or bent and can mate with ECU socket OK. When was ECU removed? before or after problem showed up?

Sometimes there are plugs between engine and harness which are the same size and near each other and you have them the wrong way. This will cause short circuits and fault codes like the ones you are seeing.
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