Isuzu 2008MY N Series, Руководство по ремонту

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Engine Control System (4HK1) 1A-229
DTC P0685 or P0687 (Flash Code 416)
Circuit Description
The ECM main relay is energized to feed the battery
voltage to the ECM through the relay switch side when
the ECM receives an ignition voltage switch ON signal.
When the ignition switch is OFF, the ECM main relay is
de-energized after a certain length of time passed.
If the ECM detects a low voltage condition on the ECM
main relay voltage feed circuit when the relay is
commanded ON, DTC P0685 will set.
If the ECM detects the ECM has been ON when the
relay is commanded OFF, DTC P0687 will set.
Condition for Running the DTC
• The battery voltage is between 18 to 32 volts.
(DTC P0685)
• The ignition switch is ON. (DTC P0685)
• The ignition switch is OFF. (DTC P0687)
Condition for Setting the DTC
• The ECM detects a low voltage condition on the
ECM main relay voltage feed circuit for 3 seconds
when the relay is commanded ON. (DTC P0685)
• The ECM detects that the ECM has been ON
when the ECM main relay is commanded OFF.
(DTC P0687)
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)
• 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)
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.
Schematic Reference: Engine Controls Schematics
Connector End View Reference: Engine Controls
Connector End Views or ECM Connector End Views
Circuit/ System Testing DTC P0685
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. Turn ON the ignition, with the engine OFF.
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 for 30 seconds.
2. Replace the ECM main relay with the glow
relay or replace with a known good relay.
3. Turn ON the ignition, with the engine OFF.
Does the DTC fail?
—
Go to Step 4 Go to Step 6
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