1950 GMC on an s10 frame with a 2004 4.8 DBW getting Code UO107 on shutdown..

[suburban99]

Got a 4.8/4L60E swapped into my 1950 GMC.
Truck runs and drives although not completed yet. I am getting a UO107 when I shut the truck off.
If I clear the UO107 truck will start and run well, until I shut it off. After about 5 secs I here a click from the area of the throttle body.
Truck will start again but no throttle control. Sets UO107 code. I read somewhere that the ECM and the TAC must get power from same source.
Also to note my ECM to TAC connections are not shielded..Thanks in advance

[blindsquirrel]

You will get better answers if people can see the file and from that, the year/make/model, the specific OS, whether there are any revisions posted at GM TIS that might have footnotes that call out a specific solution, etc. So this is based on a guess as to what we're working on.

Also, in a swap, nobody but whoever built/modified the harness knows what the wiring config is now, so offering specifics is kinda impossible. Having a diagram, even if it's hand-drawn, is really important to know how things are connected together so that when something weird happens you can look and see if there's been a change from the original layout might be a potential root cause.

Diagnostic Aids

Important: Reprogramming the PCM may cause a communication error between the PCM and the TAC. If the PCM detects a communication error, DTC U0107 sets. Clear any DTCs from the memory that may have been set by Reprogramming.
• DTC U0107 sets if the battery voltage is low. If the customer's concern is slow cranking or no crank because battery voltage is low, ignore DTC U0107. Clear any DTCs from memory that may have set from the low battery voltage condition.
• DTC U0107 sets when there is a short to B+ on the TAC module ground circuit. Inspect the fuses for the circuits that are in the TAC module harness--i.e. cruise, brake. An inspection of the fuses may lead you to the circuit that is shorted to the TAC module ground circuit.
• DTC U0107 sets if the TAC module ignition feed circuit is shorted to a B+ supply circuit. The TAC module stays powered-up when the ignition switch is turned OFF. When the ignition switch is turned ON, the TAC module is powered-up before the PCM. DTC U0107 sets because no communication is detected by the TAC module from the PCM. Inspect related circuits for being shorted to a B+ supply circuit.
• Inspect the TAC module power and ground circuits and the TAC module/PCM serial data circuits for intermittent connections.
• Inspect the TAC module connectors for signs of water intrusion. If water intrusion occurs, multiple DTCs may set without any circuit or component conditions found during diagnostic testing.
• When the TAC module detects a problem within the TAC system, more than one TAC system related DTC may set. This is due to the many redundant tests run continuously on this system. Locating and repairing an individual condition may correct more than one DTC. Remember this if you review the stored information in Capture Info.
• For an intermittent condition, refer to Intermittent Conditions .

[Alvin]

Got a 4.8/4L60E swapped into my 1950 GMC.
Truck runs and drives although not completed yet. I am getting a UO107 when I shut the truck off.
If I clear the UO107 truck will start and run well, until I shut it off. After about 5 secs I here a click from the area of the throttle body.
Truck will start again but no throttle control. Sets UO107 code. I read somewhere that the ECM and the TAC must get power from same source.
Also to note my ECM to TAC connections are not shielded..Thanks in advance

I'll bet the TAC is staying alive while the ECM is shut down. Especially since you can hear the throttle body long after the engine is off. I assume you haven't verified the power source? Do you have schematics for the 04 4.8? I'd make sure IGN and BAT pins for both are working exactly like OEM.

[suburban99]

Thanks guys, no I have not verified power source for TAC and ECM.
All wiring was as per LT1swap.com harness modifierd by me.
This is the 4th one I have done, but first one with a DBW...all rest were DBC.
Thanks.

[suburban99]

I'll bet the TAC is staying alive while the ECM is shut down. Especially since you can hear the throttle body long after the engine is off. I assume you haven't verified the power source? Do you have schematics for the 04 4.8? I'd make sure IGN and BAT pins for both are working exactly like OEM.

Thanks Alvin... That was it. TAC was staying powered up after Key-off. All good for now.

[Alvin]

Great news! awesome!