2010 Cadillac CTS Sedan AWD V6-3.0L Page 2047

2010 Cadillac CTS Sedan AWD V6-3.0L Page 2047

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 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 DTCs for GMLAN high speed modules.

Reference Information

Schematic Reference

* Body Control System Schematics (See: Body and Frame/Body Control Systems/Diagrams/Electrical Diagrams)

* Data Communication Schematics (See: Powertrain Management/Computers and Control Systems/Information Bus/Diagrams/Electrical

Diagrams)

Connector End View Reference

Component Connector End Views (See: Diagrams/Connector Views)

Description and Operation