J
Jack Klarich
Guest
CAN communication uses a set of wires in a twisted pair.These
two wires are designated as CAN low and CAN high circuits.
Both circuits are connected to the ECM, BCM, instruments,
both hand control modules and the ABS module (if equipped).
The ECM and the right hand control module contain 120 Ohm
terminating resistors. Typical resistance between the two circuits
is approximately 60 Ohms.
• DTC U0001 indicates there is a fault on the CAN bus circuits.
This code can be set by the ECM, BCM, instruments
and ABS module (if equipped). This code is usually
accompanied by other "U" codes, due to it causing a loss
of communication between the modules on the CAN bus.
• DTC U0011 indicates the high and low CAN circuits are
shorted together. This fault will be accompanied by other
"U" codes and may cause the odometer display not to
function.
• DTC B2274 indicates there is a fault with the battery fuse
or the (R/O) wire. This code will only set when there is an
issue with the battery power circuit and no "U" codes are
present.
NOTE
Always start from 2.1 INITIAL DIAGNOSTICS before proceeding
with this test.
Diagnostic Tips
The speedometer does not have an ignition input. Instead, it
receives a message over the CAN bus, indicating the IGN is
ON. Also, the trip odometer reset switch is a CAN communication
to the speedometer.Therefore, CAN bus errors can cause
the odometer self-diagnostics to be completely inoperative or
to only partially function. The speedometer backlighting may
not function along with the hand control switches and the
indicators.The odometer may read "BUS Err" in this condition,
prior to the odometer becoming inoperative.
NOTE
If DIGITAL TECHNICIAN II (Part No. HD-48650) is connected
to the DLC [91] and communicating with the vehicle, then the
odometer self-diagnostics will not function properly. Disconnect
DIGITAL TECHNICIAN II (Part No. HD-48650) before entering
odometer self-diagnostics.
The BCM supplies power to several systems on the vehicle.
When testing for a short to voltage, perform all tests before
disconnecting the BCM to keep from powering down systems
on the vehicle. If the short to voltage goes away when the BCM
is disconnected, test for continuity between the circuit in
question and BCM [242B] terminals F4, J3, L3, L4 and M2 to
verify the tested circuit is not shorted to one of these circuits.
If continuity is present, repair short to circuit instead of replacing
the BCM.
__________
two wires are designated as CAN low and CAN high circuits.
Both circuits are connected to the ECM, BCM, instruments,
both hand control modules and the ABS module (if equipped).
The ECM and the right hand control module contain 120 Ohm
terminating resistors. Typical resistance between the two circuits
is approximately 60 Ohms.
• DTC U0001 indicates there is a fault on the CAN bus circuits.
This code can be set by the ECM, BCM, instruments
and ABS module (if equipped). This code is usually
accompanied by other "U" codes, due to it causing a loss
of communication between the modules on the CAN bus.
• DTC U0011 indicates the high and low CAN circuits are
shorted together. This fault will be accompanied by other
"U" codes and may cause the odometer display not to
function.
• DTC B2274 indicates there is a fault with the battery fuse
or the (R/O) wire. This code will only set when there is an
issue with the battery power circuit and no "U" codes are
present.
NOTE
Always start from 2.1 INITIAL DIAGNOSTICS before proceeding
with this test.
Diagnostic Tips
The speedometer does not have an ignition input. Instead, it
receives a message over the CAN bus, indicating the IGN is
ON. Also, the trip odometer reset switch is a CAN communication
to the speedometer.Therefore, CAN bus errors can cause
the odometer self-diagnostics to be completely inoperative or
to only partially function. The speedometer backlighting may
not function along with the hand control switches and the
indicators.The odometer may read "BUS Err" in this condition,
prior to the odometer becoming inoperative.
NOTE
If DIGITAL TECHNICIAN II (Part No. HD-48650) is connected
to the DLC [91] and communicating with the vehicle, then the
odometer self-diagnostics will not function properly. Disconnect
DIGITAL TECHNICIAN II (Part No. HD-48650) before entering
odometer self-diagnostics.
The BCM supplies power to several systems on the vehicle.
When testing for a short to voltage, perform all tests before
disconnecting the BCM to keep from powering down systems
on the vehicle. If the short to voltage goes away when the BCM
is disconnected, test for continuity between the circuit in
question and BCM [242B] terminals F4, J3, L3, L4 and M2 to
verify the tested circuit is not shorted to one of these circuits.
If continuity is present, repair short to circuit instead of replacing
the BCM.
__________