Visually inspect. Tug them to make sure they're in good shape. Make sure there'* no corrosion.

Okay I'm about to check them now... truck has been down for over a month.. I don't have any bi-directional scanners which makes it more time consuming on top of that my a week after my truck went down I got a phone call my dad was seriously injured in a hit and run while he was on a bicycle..luckily my neighbor saw the desperation in my eyes and let me use her vehicle I had it for a week while I spent the nights and days in ICU...my dad passed away 5 days later...he never came to ...unresponsive ...just about a month and a half ago... June 14 5.20pm he had just turned 60 in January...

Well we were close and him and i were in the middle of a fabrication welding project on our leisurely spare time...my truck broke down the same day I told him "I'll be back tomorrow I'll see you then okay?" I got stuck on troubleshooting and fixing it...that 5 days went by and I never called him..., I was so hell bent and hyperfocused on figuring this problem out. That was the last time I seen him other than the heart crushing, gut wrenching condition he was in when I arrived at the hospital....

so solving this issue with my damned truck has become something more,,, personally for me its become sort of a love Hate kinda troubleshooting...I don't know who I'm trying to prove what to at this point but I'll be able to get passed something mentally as well instead of merely saying " alright, good deal, I figured it out and fixed it and it runs"

Anyway I appreciate the help and advice I was starting to chase the wiring in circles....

I cleaned up all grounds on the frame and engine bay. Still have 121 ohms instead of 60 on CAN Hi and low.
I am also not getting voltage to fuel pump fuse but im getting voltage to FSCM fuse.
when I first turned the key to ACC, once again the cluster was delayed in response. Then the message service theft deterrent system popped up turned key off and back to acc and the message went away but no crank no start

I'm sorry for your loss. Hopefully some justice will be felt by the hit and run driver.

Regarding the truck, I think it'* time to hit the diagnostic trees in the manual: https://charm.li/Chevy%20Truck/2009/...2WD%20V8-4.8L/

Thanks Im doin okay considering but I think I'm just keeping busy is why every so often throughout the day it hits home...reality sinks in...sucks

So here'* what I've got I'm just confused as to what this means exactly .....With battery unhooked
Resistance between. Pin 6 & pin 14 DLC can hi can lo •••••121.1 Ohms
Pin 14 and ground •••••• 9.90kOhms
Pin 6 and ground••••••9.89kOhms

Battery hooked up Can Bus asleep
Voltage between
Pin 6 & pin 14 •••••••• 0.00vdc
Pin 6 and ground •••••••.0.00vdc
Pin 14 and ground•••••••0.00vdc

Continuity between
Pin 6 & ground. OL.
Pin 14 & ground OL

I unplug terminating resistor behind ebcm and resistance is still 121ohms
When I leave the resistor unhooked or plugged back in and disconnect PCM X1 connector it reads infinity. But when I put my multimeter to auto resistance setting I get 20k ohms

When I add the terminating resistors back in and unhook tcm i get 30k ohms what is happening here??

The multimeter I'm using is

Kobalt DMP-32 600-Volt Digital Multimeter

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Home >> Chevy Truck >> 2009 >> Silverado 1500 4WD V8-4.8L >> Repair and Diagnosis >> A L L Diagnostic Trouble Codes ( DTC ) >> Testing and Inspection >> U Code Charts >> U0109

U0109

DTC U0100-U02FF

Diagnostic Instructions

^ Perform the Diagnostic System Check - Diagnostic System Check - Vehicle Vehicle prior to using this diagnostic procedure.
^ Review Strategy Based Diagnosis Strategy Based Diagnosis for an overview of the diagnostic approach.
^ Diagnostic Procedure Instructions Diagnostic Procedure Instructions provides an overview of each diagnostic category.

DTC Descriptor

Refer to Control Module U Code List U Code Charts.

Diagnostic Fault Information






Circuit/System Description

The serial data circuit is the means by which the control modules in the vehicle communicate with each other. Once the scan tool is connected to the serial data circuit through the DLC, the scan tool can be used to monitor each control module for diagnostic purposes and to check for diagnostic trouble codes (DTCs). When the ignition switch is in RUN, each control module communicating on the serial data circuit sends a state of health (SOH) message to ensure that the control module is operating properly. When a control module stops communicating on the serial data circuit, for example if the module loses power or ground, the SOH message it normally sends on the serial data circuit disappears. Other control modules on the serial data circuit, which expect to receive that SOH message, detect its absence; those control modules in turn set a DTC associated with the loss of SOH of the non-communicating control module. The DTC is unique to the control module which is not communicating and one or more control modules may set the same exact code. A loss of serial data communications DTC does not represent a failure of the control modules that contain the stored code.

Conditions for Running the DTC

The system voltage is between 9-16 V.

Conditions for Setting the DTC

A supervised periodic message that includes the transmitter module availability has not been received.

Action Taken When the DTC Sets

^ Specific subsystems will not function.
^ DTC U0100 in the TCM will cause the transmission to go into default gears.
^ Both DTC U0100 in the TCM and DTC U0101 in the ECM will cause the malfunction indicator lamp (MIL) to illuminate.

Conditions for Clearing the DTC

^ The ECM/TCM turns OFF the MIL after 4 consecutive ignition cycles that the diagnostic runs and does not fail.
^ A current DTC clears when the malfunction is no longer present.
^ A history DTC clears when the control module ignition cycle counter reaches the reset threshold of 50, without a repeat of the malfunction.

Diagnostic Aids

^ Sometimes, while diagnosing a specific customer concern or after a repair, you may notice a history U-code present. However, there is no associated current or active status. Loss-of- communication U-codes such as these can set for a variety of reasons. Many times, they are transparent to the vehicle operator and technician, and/or have no associated symptoms. Eventually, they will erase themselves automatically after a number of fault-free ignition cycles. This condition would most likely be attributed to one of these scenarios:

- A control module on the data communication circuit was disconnected while the communication circuit is awake.

- Power to one or more control modules was interrupted during diagnosis.

- A low battery condition was present, so some control modules stop communicating when battery voltage drops below a certain threshold.

- Battery power was restored to the vehicle and control modules on the communication circuit did not all re-initialize at the same time.

- If a loss-of-communication U-code appears in history for no apparent reason, it is most likely associated with one of the scenarios above. These are all temporary conditions and should never be interpreted as an intermittent fault, causing you to replace a part.

^ A control module may have a U-code stored in history that does not require any repairs. Issues with late or corrupted messages between control modules can be temporary with no apparent symptom or complaint; this does not mean the control module is faulty. Do not replace a control module based only on a history U-code.
^ Do not replace a control module reporting a U-code. The U-code identifies which control module needs to be diagnosed for a communication issue.
^ Communication may be available between the BCM and the scan tool with either the low or high speed GMLAN serial data system inoperative. This condition is due to the BCM using both the low and high speed GMLAN systems.
^ Use Data Link References to determine if the control module uses high or low speed GMLAN serial data communications.
^ Some control modules may not have internal protection for specific control circuits and may open a B+ or ignition fuse. If a fuse is open and the B+ or ignition circuit is not shorted to ground, ensure none of the control circuits are shorted to ground before replacing the control module.
^ Some intermittent communication concerns may be caused by fretting corrosion on the serial data circuit terminals. Inspect all connectors at the control module that set the communication DTC, the control module that the communication DTC was set against, and any inline harness connectors between the two control modules. Do not replace a control module based only on fretting corrosion. Refer to bulletin 09-06-03-004 for assistance with the diagnosis and repair of this condition.
^ Multiple control modules may not communicate due to the serial data circuits being shorted, faulty terminating resistor, corrosion or poor connections in various control module connectors or inline connectors. Refer to bulletin 08-07-30-021 for assistance with the diagnosis and repair of these conditions, if applicable.
^ This diagnostic can be used for any control module that is not communicating, regardless of the type of serial data circuit it is connected to, providing the vehicle is equipped with the control module.

Reference Information

Schematic Reference

^ Data Communication Schematics Electrical Diagrams
^ Control Module References Control Module References

Connector End View Reference

Component Connector End Views Connector Views

Description and Operation

Data Link Communications Description and Operation Description and Operation

Electrical Information Reference

^ Circuit Testing Circuit Testing
^ Connector Repairs Connector Repairs
^ Testing for Intermittent Conditions and Poor Connections Testing for Intermittent Conditions and Poor Connections
^ Wiring Repairs Wiring Repairs

Scan Tool Reference

Control Module References Control Module References for scan tool information

Circuit/System Verification

Verify that DTC U0073, U2100, U0074, U1814, U2099, B1428, B1370, B1380, B1440, or B1441 is not set.

-> If any of the DTCs are set, refer to Diagnostic Trouble Code (DTC) List - Vehicle Diagnostic Trouble Code (DTC) List - Vehicle.

Circuit/System Testing

Note: Use the schematic to identify the following:

^ Control modules the vehicle is equipped with
^ Control module locations on the low and high speed GMLAN serial data circuits
^ The control modules B+, ignition, ground, communication enable and serial data circuit terminals

1. Determine the control module that is not communicating. Refer to Control Module U Code List.
2. Ignition OFF, disconnect the harness connector of the control module that is not communicating.
3. Test for less than 10 ohm between each ground circuit terminal and ground.
-> If greater than the specified range, test the ground circuit for an open/high resistance.
4. If equipped, verify that a test lamp illuminates between each B+ circuit terminal and ground.
-> If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. If the circuit fuse is open, test the control circuits of the control module for a short to ground. If the circuits test normal, replace the control module.
5. If equipped, ignition ON, verify that a test lamp illuminates between each ignition circuit terminal and ground.
-> If the test lamp does not illuminate, test the ignition circuit for a short to ground or an open/high resistance. If the circuit fuse is open, test the control circuits of the control module for a short to ground. If the circuits test normal, replace the control module.

Note: Only the high speed GMLAN modules have a serial data communication enable circuit OR an accessory wakeup serial data circuit, and the BCM is the output for these circuits. Refer to the module schematics to identify which modules have these circuits.

6. If equipped, ignition ON, verify that a test lamp illuminates between the communication enable circuit terminal OR the accessory wakeup circuit terminal and ground.
-> If the test lamp does not illuminate, test the circuit for an open/high resistance. If the circuits test normal, replace the BCM.
7. Ignition OFF, all access doors closed, all vehicle systems OFF, and key out of ignition switch. It may take up to 2 minutes for all vehicle systems to power down. Test for less than 5 ohm between the serial data circuit terminals and the appropriate DLC terminal listed below:
^ Class 2 serial data circuit terminal 2
^ Low speed GMLAN serial data terminal 1
^ High speed GMLAN serial data terminal 6 or 14
-> If greater than the specified range, test the serial data circuit for an open/high resistance between the non communicating control module and a control module setting the DTC or a serial data splice pack.
8. If all circuits test normal, replace the control module that is not communicating.

Repair Instructions

Perform the Diagnostic Repair Verification Diagnostic Repair Verification after completing the diagnostic procedure.

^ GMLAN Wiring Repairs GMLAN Wiring Repairs
^ Control Module References Control Module References for control module replacement, setup, and programming

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