DTC U0002
Diagnostic Instructions
DTC Descriptor
DTC U0002: High Speed CAN Bus |
Circuit/System Description
Control 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 control modules. The control modules have prerecorded
information about what messages are needed to be exchanged on the
serial data circuits, for each virtual network. The messages are
supervised and also, some periodic messages are used by the
receiver module as an availability indication of the transmitter
module. The supervision time-out period is 250 ms. Each message
contains the identification number of the transmitter module.
Conditions for Running the DTC
• |
Voltage supplied to the
modules is in the normal operating voltage range. |
• |
The vehicle power mode
requires serial data communication to occur. |
• |
The DTC U0001 does not have a
current status. |
Conditions for Setting the DTC
A supervised periodic message that includes the transmitter
module availability has not been received.
Action Taken When the DTC Sets
The control module uses a default value for the missing
parameter.
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, without
a repeat of the malfunction. |
Reference Information
Schematic Reference
Data Communication Schematics
Connector End View Reference
Component Connector End Views
Description and Operation
Data Link Communications Description and Operation
Electrical Information Reference
Scan Tool Reference
Control Module References for scan tool information
Circuit/System Verification
With a scan tool, attempt to communicate with all control
modules.
Circuit/System Testing
1. |
With a scan tool, verify DTC
U0100-U02FF or U2105-U2199 is not set as current. |
2. |
Ignition OFF, disconnect the
applicable control module harness connector. |
3. |
Ignition OFF, test for less
than 5 Ω between the applicable control module ground circuit
and ground. |
⇒ |
If greater than the specified range, test the
circuit for an open/high resistance. |
4. |
Ignition ON, verify a test
lamp illuminates between the following circuits of the applicable
control module and ground: |
|
• |
The battery positive voltage
input circuits |
|
• |
The battery positive voltage
output circuits |
|
• |
The ignition voltage input
circuits |
|
• |
The ignition voltage output
circuits |
|
• |
The switched battery positive
voltage supply circuits |
⇒ |
If the test lamp does not illuminate, test the
circuit for an open/high resistance. If the circuit fuse is open,
test the circuit for a short to ground. If the circuit tests
normal, replace the applicable control module. |
5. |
Ignition OFF, test for less
than 5 Ω between the non-communicating control module GMLAN
serial data circuits and the control module reporting DTC
U0002. |
⇒ |
If greater than the specified range, test the
circuit for an open/high resistance. |
6. |
If all circuits test normal,
replace the applicable control module. |
Repair Instructions
Perform the
Diagnostic Repair Verification after completing the diagnostic
procedure.
|