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

1A-194 Engine Control System (4HK1)

DTC P0477 or P0478 (Flash Code 46)

Circuit Description
The ECM control the exhaust brake, which energizes
the exhaust brake solenoid valve based on the vehicle
running condition. The ECM commands the exhaust
brake solenoid valve to apply vacuum pressure to the
diaphragm chamber to operate 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 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 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. Turn OFF the ignition for 30 seconds.
3. Turn ON the ignition, with the engine OFF.
2
4. Monitor the DTC Information with a scan tool.
Does the DTC fail this ignition?
1. Turn OFF the ignition.
2. Disconnect the exhaust brake control solenoid
valve harness connector.
3. Connect a test lamp between the ignition
3
voltage feed circuit (pin 1 of J-26) and a
known good ground.
4. Turn ON the ignition, with the engine OFF.
Does the test lamp illuminate?
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 control circuit between
the ECM and the solenoid valve is normal, voltage level
low DTC P0477 will set.
Schematic Reference: Engine Controls Schematics
Connector End View Reference: Engine Controls
Connector End Views or ECM Connector End Views
Value(s) Yes
—
Go to Step 2
—
Go to Step 3
—
Go to Step 4
No
Go to Diagnostic
System Check -
Engine Controls
Go to Diagnostic
Aids
Go to Step 6