1A-308 Engine Control System (4HK1)
DTC U0073 (Flash Code 84)
Circuit Description
The ECM, the variable nozzle turbocharger (VNT)
control module, the transmission control module
(TCM), the electric hydraulic control unit (EHCU) body
control module (BCM) and the data recording module
(DRM) 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 sets CAN Bus OFF status, this
DTC will set.
Condition for Running the DTC
• The battery voltage is more than 20 volts.
• The ignition switch is ON.
Condition for Setting the DTC
• The ECM sets the CAN Bus OFF status.
Action Taken When the DTC Sets
• The ECM illuminates the MIL on the second
consecutive driving cycle when the diagnostic runs
and fails. Refer to DTC Type Definitions for Action
Taken When the DTC Sets - Type B. (Euro 4
specification)
• The ECM illuminates 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 limits fuel injection quantity.
• The ECM inhibits exhaust brake control.
Condition for Clearing the DTC
• Refer to DTC Type Definitions for Condition for
Clearing the MIL/ DTC - Type B. (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.
Schematic Reference:
Engine Controls Schematics
Connector End View Reference:
Engine Controls
Connector End Views or ECM Connector End Views
Circuit/ System Testing DTC U0073
Step
Action
Value(s)
Yes
No
1
Did you perform the Diagnostic System Check
- Engine Controls?
—
Go to Step 2
Go to Diagnostic
System Check -
Engine Controls
2
1.
Install a scan tool.
2.
Turn OFF the ignition for 30 seconds.
3.
Start the engine.
4.
Monitor the DTC Information with a scan tool.
Does the DTC fail this ignition?
—
Go to Step 3
Go to Diagnostic
Aids
3
1.
Turn OFF the ignition.
2.
Disconnect the variable nozzle turbocharger
(VNT) control module harness connector.
3.
Measure the resistance between the CAN
Low and High circuits (pins 15 and 16 of E-4).
Is the resistance within the specified value
(parallel resistance of the 120
Ω
resistor in the
ECM and the IP cluster should be 60
Ω
)?
50 to 70
Ω
Go to Step 11
Go to Step 4
4
1.
Disconnect the IP clucter harness connector.
2.
Measure the resistance of the IP clucter(pins
13 and 14 of B-105).
Is the resistance within the specified value?
110 to 130
Ω
Go to Step 5
Go to Step 17
LG4HKED-WE-0871.book 308
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