Code uo109 Lost communication with fpcm

P1686 is a Transmission Control Module issue. You need an auto-electrician with a pro grade scan tool computer do diagnose why these codes are coming up?

Chevrolet Codes - TroubleCodes.net

https://www.troublecodes.net > chevroletcodes
OBDII Chevrolet Code Definitions. Be sure to double check the codes. ... P1686, Transmission Control Module Power Up Temperature Sensor Circuit High Voltage.

U0109 is a communication code

https://www.google.com/search?q=2012+chevy+traverse+u0109+code

Lost Communication with Fuel Pump Control Module (FPCM)

https://www.obd-codes.com > u0109
If you can access codes from the FPCM module, then the U0109 code is either intermittent or a memory code. If unable to communicate with the GPCM module, then ..

I suggest you read the pages at the links below...

https://www.obd-codes.com/u0109

https://www.autocodes.com/u0109_chevrolet.html

Why ? You won't fix it , take it to a qualified repair shop before mess it up.This vehicle has a fuel pump driver module (computer) that controls the fuel pump .
Fuel Pump Flow Control Module (FPCM)
The fuel pump flow control module (FPCM) is a serviceable GMLAN module. The FPCM receives the desired fuel pressure message from the engine control module (ECM) and controls the fuel pump located within the fuel tank to achieve the desired fuel pressure. The FPCM sends a 25 KHZ PWM signal to the fuel pump, and pump speed is changed by varying the duty cycle of this signal. Maximum current supplied to the fuel pump is 15 amps. A liquid fuel pressure sensor provides fuel pressure feedback to the FPCM.
Electronic Returnless Fuel System (ERFS)
The electronic returnless fuel system is a microprocessor controlled fuel delivery system which transports fuel from the tank to the fuel rails. It functions as an electronic replacement for a traditional, mechanical fuel pressure regulator. A pressure vent valve within the fuel tank provides an added measure of fuel pump flow control module (FPCM). Desired fuel pressure is commanded by the engine control module (ECM), and transmitted to the FPCM via a GMLAN serial data message. A liquid fuel pressure sensor provides the feedback the FPCM requires for Closed Loop fuel pressure control.

This is a generic communication system diagnostic trouble code that applies to most vehicle makes and models, including but not limited to Dodge, Ram, Chevrolet, Ford, GMC, and VW. This code means that the Fuel Pump Control Module (FPCM) and other control modules on the vehicle are not communicating with each other.

Read more at: https://www.obd-codes.com/u0109
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year, make, model?

(50-60 psi). Is your fuel system with or without (FPCM ) fuel pump control module ?
The engine control module (ECM) supplies voltage to the fuel pump control module (FPCM) when the ECM detects that the ignition is ON. The voltage from the ECM to the FPCM remains active for 2 seconds, unless the engine is in Crank or Run. While this voltage is being received, the FPCM closes the ground switch of the fuel pump and also supplies a varying voltage to the fuel tank pump module in order to maintain the desired fuel rail pressure

Follow the link to read about this code and what causes it. U0109 Lost Communication with Fuel Pump Control Module FPCM eval ez write...

DTC P025A: Fuel Pump Flow Control Module Enable Circuit
The engine control module (ECM) supplies voltage to the fuel pump flow control module (FPCM) when the ECM detects that the ignition is on. The voltage from the ECM to the FPCM remains active for 2 seconds, unless the engine is in crank or run. While this voltage is being received, the FPCM closes the ground switch of the fuel pump and also supplies a varying voltage to the fuel tank pump module in order to maintain the desired fuel rail pressure.
Circuit/System Testing

1. Ignition OFF, disconnect the harness connector at the FPCM.
2. Ignition OFF, install a test lamp between the control circuit terminal 13 and ground.
3. Ignition ON, verify that a test lamp illuminates for 2 seconds.
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If the test lamp does not illuminate, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the ECM.

4. If all circuits test normal, replace the FPCM.

Relay for what ? Which engine do you have LY6 or non LY6

drop the fuel tank and remove the circle lock. Youll see it when you take the cover off.

{: ) Yes, if the vehicle is equipped with a Fuel Pump Flow Control Module (FPCM). The FPCM is located underneath the vehicle, left side chassis, near the Electronic Brake Control Module. Sometimes, when you check fuse and relays at the underhood fuseblock, you can still see labels and alloted space for the fuel pump fuse and relay. But the circuit is actually internally omitted or modified inside the fuseblock if the vehicle is using FPCM. An FPCM controlled fuel systems doesn't have fuel pump relay at the fuseblock, and instead you may find a FSCM fuse 20amp which gives battery power to the FPCM.