Gray Ghost Silverado

iTrader: (1)

Uh....... :/

01WS6/tamu

iTrader: (36)

Are you in texas anywhere. I know sounds crazy does the radio and HVAC control panel function correctly. I'm digging for you trying to come up with ideas. ME thinks BCM I have a 08 standard bcm I can flash and send to you for diag purposes to rule it out and give a better direction to go. Do you have any friends or um er trucks in the shop you could borrow a bcm from.

01WS6/tamu

iTrader: (36)

Scan Tool Does Not Communicate with High Speed GMLAN Device

Diagnostic Instructions

Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. See: Testing and Inspection\Initial Inspection and Diagnostic Overview
Review Strategy Based Diagnosis for an overview of the diagnostic approach.
Diagnostic Procedure Instructions provides an overview of each diagnostic category.

Diagnostic Fault Information




Circuit/System Description

Modules connected to the high speed GMLAN serial data circuits monitor for serial data communications during normal vehicle operation. Operating information and commands are exchanged among the modules when the ignition switch is in any position other than OFF. The high speed GMLAN serial data circuits must be operational for the vehicle to start due to body control module (BCM) and engine control module (ECM)/powertrain control module (PCM) communications. The theft deterrent module and ECM/PCM exchange information using the BCM as the gateway module allowing communication between the high and low speed serial data busses. The low speed GMLAN serial data circuit must also be operational for vehicle starting.

Diagnostic Aids

Use the Data Link References to identify the high speed GMLAN serial data modules.
This test is used for a total high speed GMLAN communication failure. If only one module is not communicating and sets no DTC, ensure that the vehicle is equipped with the module, then use DTC U0100-U0299 for diagnostics.
An open in the DLC ground circuit terminal 5 will allow the scan tool to operate to set up the vehicle on the tool and then not communicate with the vehicle. When the scan tool is to the point of communicating with the vehicle, a message on the scan tool will indicate "no CANdi module detected" and will not communicate.
The engine will not start when there is a total malfunction of the high speed GMLAN serial data bus. The following conditions may cause a total loss of high speed GMLAN data communication:
A short between high speed GMLAN (+) and high speed GMLAN (-) circuits
Any of the high speed GMLAN serial data circuits shorted to ground or voltage
A module internal malfunction that causes a short to voltage or ground on the high speed GMLAN circuits

Circuit/System Testing

Test for less than 1 ohm between the DLC ground circuit terminal 5 and ground.

If greater than 1 ohm, test the ground circuit for open/high resistance.

Ignition OFF, disconnect the harness connector of the BCM.
Ignition ON, test for B+ between each voltage input circuit of the BCM and ground.

If less than specified, test each voltage output circuit of the BCM for a short to ground, and each voltage input circuit of the BCM for a short to ground or and open/high resistance. If the circuits test normal, replace the faulty module.

Test for less than 1 ohm between each ground circuit of the BCM and ground.

If greater than the specified range, repair the ground circuit for an open/high resistance.

Attempt to communicate with the electronic brake control module (EBCM). Communication should not be available.

If communication is established, test or replace the resistor.

Ignition OFF, disconnect the harness connector of the suspension control module.
Attempt to communicate with the EBCM. Communication should not be available.

If communication is established, test the serial data circuits for a short between them, short to ground or a short to voltage between the suspension control module and the terminator resistor. If the circuits test normal, replace the suspension control module.

Ignition OFF, disconnect the harness connector of the distance sensing cruise control module.
Attempt to communicate with the EBCM. Communication should not be available.

If communication is established, replace the cruise control module.

Ignition OFF, disconnect the harness connector of the vehicle communication interface module (VCIM).
Attempt to communicate with the EBCM. Communication should not be available.

If communication is established, test the serial data circuits for a short between them, short to ground or a short to voltage between the between the VCIM and the suspension control module. If the circuits test normal, replace the VCIM.

Ignition OFF, disconnect harness connector C3 of the BCM.
Test for infinite resistance between the serial data circuits of BCM harness connector C3 terminal 8 and ground and between BCM harness connector C3 terminal 9 and ground.

If less than the specified range, test the circuit for a short to ground.

Ignition OFF, disconnect the harness connector of the ECM. Connect harness connector C3 of the BCM.
Attempt to communicate with the EBCM. Communication should not be available.

If communication is established, replace the ECM.

Ignition OFF, disconnect the harness connector of the transmission control module (TCM).
Attempt to communicate with the EBCM. Communication should not be available.

If communication is established, test the serial data circuits for a short between them, short to ground or a short to voltage between the TCM and the ECM. If the circuits test normal, replace the TCM.

Ignition OFF, connect the harness connector of the suspension control module. Disconnect the harness connector of the EBCM.
Attempt to communicate with the suspension control module. Communication should not be available.

If communication is established, test the serial data circuits for a short between them, short to ground or a short to voltage between the EBCM and the TCM. If the circuits test normal, replace the EBCM.

Ignition OFF, disconnect harness connector C3 of the BCM.
Test for less than 1 volt between the high speed GMLAN serial data circuits of the DLC and ground.

If greater than the specified range, test the serial data circuit for a short to voltage.

Test for infinite resistance between the high speed GMLAN serial data circuit of the DLC and ground.

If less than the specified range, test the serial data circuit for a short to ground.

Test for infinite resistance between the high speed GMLAN serial data (+) and (-) circuits of the DLC.

If less than the specified range, test the serial data circuits for a short between them.

If the circuits test normal, replace the BCM.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the repair. See: A L L Diagnostic Trouble Codes ( DTC )\Testing and Inspection\Verification Tests

GMLAN Wiring Repairs


From gm shop manual.

01WS6/tamu

iTrader: (36)

The U)1814 is the key to all of your troubles all the other u codes are just modules that are saying hey I can't talk and I need to talk.

Follow this trouble tree below. Everything I see points to a fragged BCM

DTC U1814

Diagnostic Instructions

Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. See: Testing and Inspection\Initial Inspection and Diagnostic Overview
Review Strategy Based Diagnosis for an overview of the diagnostic approach.
Diagnostic Procedure Instructions provides an overview of each diagnostic category.

DTC Descriptor

DTC U1814 00

Powertrain High Speed Communication Enable Circuit

Diagnostic Fault Information




Circuit/System Description

The accessory wake up serial data circuit is a voltage wake up signal from the body control module (BCM) to the engine control module (ECM) and the transmission control module (TCM). The signal is activated in 2 ways; any time the ignition switch is in the ACC or RUN position, or anytime the BCM determines that communication is needed from the powertrain. When the ignition switch is in the ACC or RUN position, the accessory voltage circuit input to the BCM is internally connected to the accessory wake up serial data circuit output, and voltage is supplied to the modules. The BCM also supplies voltage to the accessory wake up serial data circuit when it determines that communication is necessary with the powertrain and the ignition is not in the ACC or RUN position such as during remote start.

Conditions for Running the DTC

The system voltage is between 9-16 volts.
The vehicle power mode master requires serial data communication to occur.

Conditions for Setting the DTC

The BCM senses a short to ground on the accessory wake up serial data circuit.

Action Taken When the DTC Sets

The modules use a default value for the missing parameters until the next ignition cycle.
The modules is never signaled, therefore the specific subsystems will not function.
The vehicle may not start.

Conditions for Clearing the DTC

A current DTC clears when the malfunction is no longer present.
A history DTC clears when the module ignition cycle counter reaches the reset threshold of 50, without a repeat of the malfunction.

Diagnostic Aids

Short to ground may open the fuse feeding the ignition switch.
Short to ground may also set multiple no communication codes for GMLAN high speed modules.

Circuit/System Testing

Ignition OFF, disconnect the X1 harness connector at the ECM and the TCM one at a time. After each disconnect, test for current DTCs. DTC U1814 should remain current.

If the DTC becomes history, replace the module disconnected when the DTC became history.

Ignition OFF, disconnect the X4 harness connector at the BCM.
Test for infinite resistance between the voltage circuit terminal 19 and ground.

If less than the specified value, test the voltage circuit for a short to ground.

If all circuits tests normal, replace the BCM.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure. See: Verification Tests

Gray Ghost Silverado

iTrader: (1)

Thanks to your help I found the issue!!!

The main ground pin inside the TCM somehow had lost contact within its case. I found this by accident because I grounded the TCM case to my CAI and everything started working perfectly. I simply cut the ground wire, bolted it to the outside of the case and everything is working beautifully!

Also PM sent!

And Jake, you were on the right track. Thanks bro.

NKPPhil

CONGRATULATIONS! That's fantastic, and just before the holiday weekend too. Time to celebrate!

(ps - I'm constantly amazed at the outstanding helpful atmosphere and great info on this forum!)

(pps - I'm also amazed at the complexity of these trucks, and how some little tiny-*** thing can uck it fup.)

Gray Ghost Silverado

iTrader: (1)

Lol nope. Lost a fuel pump last night during tuning. It actually sucked the sock up through the inside of the pickup and melted it down

Oh well, at least it RAN. Now just to find a fuel pump.

And indeed the people here are great. LS1Tech guys are sometimes iffy, so this is the way to go

And I know..... It's awful the electrical crap on these trucks.

NKPPhil

OK, I'm back to the "kick me" sign question ....

01WS6/tamu

iTrader: (36)

Man I'm glad you got it all sorted out. glad one of my suggestions helped. If it makes you feel any better the new UBEC will save you a ton of future headaches at least for what it's worth.