Dtc P0079 Or P0080 (Flash Code 38) - Isuzu N 2008 Series Workshop Manual

1A-64 Engine Control System (4JJ1)

DTC P0079 or P0080 (Flash Code 38)

Circuit Description
The ECM controls the exhaust throttle solenoid valve
based on the diesel particulate defuser (DPD) system
regeneration status. The exhaust throttle solenoid
energizes to apply vacuum pressure to the diaphragm
chamber of the exhaust throttle valve that is installed
rear of the DPD housing. If the ECM detects an
improper voltage level on the exhaust throttle solenoid
control circuit, DTC P0079 or P0080 will set.
Condition for Running the DTC
• The battery voltage is between 18 to 32 volts.
• The ignition switch is ON.
Condition for Setting the DTC
• The ECM detects a low voltage condition on the
exhaust throttle solenoid control circuit for longer
than 3 seconds when the solenoid is commanded
OFF. (DTC P0079)
• The ECM detects a high voltage condition on the
exhaust throttle solenoid control circuit for longer
than 3 seconds when the solenoid is commanded
ON. (DTC P0080)
Circuit/ System Testing DTC P0079
Step
Did you perform the Diagnostic System Check -
1 Engine Controls?
1. Install a scan tool.
2. Perform the Exhaust Throttle Control with a
scan tool.
2
3. Command the solenoid valve ON and OFF.
Does the solenoid valve click with each command?
1. Turn OFF the ignition.
2. Disconnect the exhaust throttle solenoid valve
harness connector.
3. Connect the test lamp between the ignition
3
voltage feed circuit (pin 2 of J59) and a known
good ground.
4. Turn ON the ignition, with the engine OFF.
Does the test lamp illuminate?
1. Connect a test lamp between the control
circuit (pin 1 of J59) and battery voltage.
2. Perform the Exhaust Throttle Control with a
scan tool.
4
3. Command the solenoid valve ON and OFF.
Does the test lamp turn ON and OFF with each
command?
Does the test lamp remain illuminated with each
5
command?
Action
Action Taken When the DTC Sets
• 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.
Condition for Clearing the DTC
• Refer to DTC Type Definitions for Condition for
Clearing the MIL/ DTC - Type A.
Diagnostic Aids
• If an intermittent condition is suspected, refer to
Intermittent Conditions in this section.
Test Description
The number below refers to the step number on the
Circuit/ System Testing.
DTC P0080
3. If the exhaust throttle solenoid control circuit
between the ECM and the relay is normal, voltage level
low DTC P0079 will set.
Connector End View Reference: Engine Controls
Connector End Views or ECM Connector End Views
Value(s) Yes
—
Go to Step 2
—
Go to Diagnostic
Aids
—
Go to Step 4
—
Go to Step 9
—
Go to Step 8
No
Go to Diagnostic
System Check -
Engine Controls
Go to Step 3
Go to Step 6
Go to Step 5
Go to Step 7