2010 Cadillac Truck Escalade RWD V8-6.0L Hybrid Page 3003

2010 Cadillac Truck Escalade RWD V8-6.0L Hybrid Page 3003

* Supply voltage at the control modules are in the normal operating range.

* The vehicle power mode requires serial data communications.

Conditions for Setting the DTC

The control module setting the DTC has attempted to establish communications on the serial data circuits more than 3 times in 5 seconds.

Action Taken When the DTCs Sets

* The module suspends all message transmission.

* The module uses default values for all parameters received on the serial data circuits.

* In the TCM, DTC U0073 will cause the transmission to go into default gears.

* In the ECM and TCM, DTC U0073 will cause the malfunction indicator lamp (MIL) to illuminate.

* The module inhibits the setting of all other communication DTCs.

Conditions for Clearing the DTC

* The ECM/TCM modules turn 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.

Circuit/System Verification

1. Refer to Data Link References (See: Powertrain Management/Computers and Control Systems/Information Bus/Testing and

Inspection/Initial Inspection and Diagnostic Overview) to determine which serial data system is used for a specific control module.

2. This DTC cannot be retrieved with a current status. Diagnosis is accomplished using the symptom Scan Tool Does Not Communicate with

High Speed GMLAN Device (See: Powertrain Management/Computers and Control Systems/Information Bus/Testing and

Inspection/Symptom Related Diagnostic Procedures/Scan Tool Does Not Communicate with High Speed GMLAN Device) or Scan Tool

Does Not Communicate with Low Speed GMLAN Device (See: Powertrain Management/Computers and Control Systems/Information

Bus/Testing and Inspection/Symptom Related Diagnostic Procedures/Scan Tool Does Not Communicate with Low Speed GMLAN Device).

U0074

DTC U0074

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 U0074 00

- Control Module Communication Bus B Off

Diagnostic Fault Information

Circuit/System Description

The PTLAN serial data circuits are serial data buses used to communicate information between the control modules. The PTLAN serial data

circuits also connect directly to the data link connector (DLC) for programming purposes. If this serial data system is inoperative the modules will

still communicate with the scan tool due to other serial data systems but not with each other. Communication with the scan tool for the modules on

the PTLAN bus is through the serial data gateway module (SDGM) on the HSGMLAN serial data system.

Conditions for Running the DTCs

* Supply voltage to the modules are in the normal operating range.

* The ignition switch in any position other than START.