Dtc U0101 (Flash Code 85) - Isuzu N 2008 Series Workshop Manual

1A-296 Engine Control System (4JJ1)

DTC U0101 (Flash Code 85)

Circuit Description
The ECM and the transmission control module (TCM)
communicate control and diagnostic information via a
controller area network (CAN) communication bus. The
ECM monitors CAN operational status by expecting a
constant flow of messages from each module. If the
ECM fails to receive an expected message from the
TCM, this DTC will set.
Condition for Running the DTC
• DTC U0073 is not set.
• The battery voltage is more than 20 volts.
• The ignition switch is ON.
Condition for Setting the DTC
• The ECM detects that the CAN Bus messages
from the TCM are not being received.
Action Taken When the DTC Sets
• The ECM illuminates the SVS lamp when the
diagnostic runs and fails. Refer to DTC Type
Definitions for Action Taken When the DTC Sets -
Type C. (Euro 4 specification)
Circuit/ System Testing DTC U0101
Step
Did you perform the Diagnostic System Check -
1 Engine Controls?
1. Install a scan tool.
2. Turn OFF the ignition for 30 seconds.
3. Start the engine.
2
4. Monitor the DTC Information with a scan tool.
Is DTC U0073 or U0110 also set?
Attempt to communicate with the transmission
control module (TCM) via the transmission data
table.
3
Does the scan tool communicate with the TCM?
1. Turn OFF the ignition.
2. Disconnect the TCM B112 harness connector.
3. Turn ON the ignition, with the engine OFF.
4. Connect a DMM between the CAN Low circuit
(pin 13 of B112) and a known good ground.
4
5. Connect a DMM between the CAN High circuit
(pin 12 of B112) and a known good ground.
Are both voltage readings within the specified
value?
Action
• The ECM illuminates the MIL when the diagnostic
runs and fails. Refer to DTC Type Definitions for
Action Taken When the DTC Sets - Type A.
(Except Euro 4 specification)
• The ECM blinks the exhaust brake indicator lamp
when the diagnostic runs and fails.
• The ECM inhibits exhaust brake control.
Condition for Clearing the DTC
• Refer to DTC Type Definitions for Condition for
Clearing the SVS Lamp/ DTC - Type C. (Euro 4
specification)
• Refer to DTC Type Definitions for Condition for
Clearing the MIL/ DTC - Type A. (Except Euro 4
specification)
Diagnostic Aids
• If an intermittent condition is suspected, refer to
Intermittent Conditions in this section.
Connector End View Reference: Engine Controls
Connector End Views or ECM Connector End Views
Value(s)
—
Go to Step 2
—
Go to Applicable
—
Go to Step 4
1.5 to 3.5 volts
Go to Step 6
Yes No
Go to Diagnostic
System Check -
Engine Controls
DTC Go to Step 3
Go to Diagnostic
System Check -
Transmission
Controls in Section
5A Transmission
Control System
Go to Step 5