2010 Cadillac Truck SRX FWD V6-3.0L Page 2174
4. If equipped, ignition ON, verify that a test lamp illuminates between each ignition circuit terminal and ground.
瀚慖f 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 LIN device for a short to ground. If the circuits test normal, replace the LIN device.
5. Ignition ON, test for 2-11.5 V between the LIN serial data circuit and ground.
瀚慖f greater than the specified range, test the LIN serial data circuit for a short to voltage. If the circuit tests normal, replace the master
control module.
瀚慖f less than the specified range, test the LIN serial data circuit for a short to ground or an open/high resistance. If the circuit tests normal,
replace the master control module.
6. If all circuits test normal, replace the LIN device.
Repair Instructions
Perform the Diagnostic Repair Verification (See: Verification Tests) after completing the repair.
* GMLAN Wiring Repairs (See: Testing and Inspection/Component Tests and General Diagnostics/General Electrical Diagnostic
Procedures/Wiring Repairs/GMLAN Wiring Repairs)
* Control Module References (See: Testing and Inspection/Programming and Relearning) for control module replacement, setup, and
programming
U1814
DTC U1814
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle (See: Testing and Inspection/Initial Inspection and Diagnostic Overview/Diagnostic System
Check - Vehicle) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (See: Testing and Inspection/Initial Inspection and Diagnostic Overview/Strategy Based Diagnosis) for an
overview of the diagnostic approach.
* Diagnostic Procedure Instructions (See: Testing and Inspection/Initial Inspection and Diagnostic Overview/Diagnostic Procedure
Instructions) provides an overview of each diagnostic category.
DTC Descriptor
DTC U1814 00
- Powertrain Wake Up Communication Circuit
Diagnostic Fault Information
Circuit/System Description
The body control module (BCM) activates the serial data communication enable circuit when the ignition key is in ACC, ON or START. The serial
data communication enable circuit wakes up the engine control module (ECM) for serial data bus communication.
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 serial data communication enable circuit.
Action Taken When the DTC Sets
* The output command is turned off while the malfunction is present.
* The modules use a default value for the missing parameters until the next ignition cycle.
* The module(s) is never signaled, therefore the specific subsystem(s) will not function.
* The vehicle will not start while the circuit is shorted to ground.
