Dtc P0477 Or P0478 (Flash Code 46) - Isuzu N 2008 Series Workshop Manual

1A-178 Engine Control System (4JJ1)

DTC P0477 or P0478 (Flash Code 46)

Circuit Description
The ECM controls the exhaust brake, which supplies
vacuum pressure to the exhaust brake valve based on
the vehicle running condition. The exhaust brake
solenoid valve energizes to apply vacuum pressure to
the diaphragm chamber of the exhaust brake valve. If
the ECM detects an improper voltage level on the
exhaust brake solenoid control circuit, DTC P0477 or
P0478 will set.
Condition for Running the DTC
• The battery voltage is between 18 to 32 volts.
• The ignition switch is ON.
• The engine is running.
Condition for Setting the DTC
• The ECM detects a low voltage condition on the
exhaust brake solenoid valve control circuit for
longer than 3 seconds when the solenoid is
commanded OFF. (DTC P0477)
• The ECM detects a high voltage condition on the
exhaust brake solenoid valve control circuit for
longer than 3 seconds when the solenoid is
commanded ON. (DTC P0478)
Circuit/ System Testing DTC P0477
Step
Did you perform the Diagnostic System Check -
1 Engine Controls?
1. Install a scan tool.
2. Perform the Exhaust Brake Control with a
scan tool.
2
3. Command the solenoid valve ON and OFF.
Does the exhaust brake solenoid valve click with
each command?
1. Turn OFF the ignition.
2. Disconnect the exhaust brake solenoid valve
harness connector.
3. Connect a test lamp between the ignition
3
voltage feed circuit (pin 1 of J26) 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 2 of J26) and battery voltage.
2. Perform the Exhaust Brake 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?
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.
• 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 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 P0478
3. If the exhaust brake solenoid valve control circuit
between the ECM and the solenoid valve is normal,
voltage level low DTC P0477 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
No
Go to Diagnostic
System Check -
Engine Controls
Go to Step 3
Go to Step 6
Go to Step 5