U2176

DTC U0073 or U2100

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle Diagnostic System Check - 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 Descriptors

DTC U0073 00
- Control Module Communication Bus Off Malfunction

DTC U2100 00
- CAN Bus Communication Malfunction

Circuit/System Description

The serial data circuits are used to communicate information between the devices. The serial data circuits also connect directly to the data link connector (DLC).

Conditions for Running the DTCs

* Supply voltage to the devices is in the normal operating range.

* The vehicle power mode requires serial data communications.

Conditions for Setting the DTC

The device 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 device suspends all message transmission.

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

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

* In the engine control module and transmission control module, DTC U0073 will cause the malfunction indicator lamp (MIL) to illuminate.

* If equipped with eAssist, DTC U0073 in the hybrid powertrain control module is a type B DTC and will cause the malfunction indicator lamp to illuminate and result in the engine operating in conventional engine mode and will maintain 14 V module operation.

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

Conditions for Clearing the DTC

* The engine control module or transmission control module turns OFF the MIL after 4 consecutive ignition cycles that the diagnostic runs and does not fail.

* If equipped with eAssist, the hybrid powertrain control module turns off the MIL after the diagnostic runs and does not fail during subsequent ignition cycles. Normal operation will resume 5 seconds after subsequent ignition cycle.

* A current DTC clears when the malfunction is no longer present.

* A history DTC clears when the device ignition cycle counter reaches the reset threshold of 50, without a repeat of the malfunction.

Circuit/System Verification

1. Refer to Data Link References Initial Inspection and Diagnostic Overview to determine which serial data communication system is used for a specific device.

2. This DTC may not be retrieved with a current status. Diagnosis is accomplished using the symptom. Refer to Symptoms - Data Communications Symptoms - Data Communications.