Dtc P0651 (Flash Code 56) - Isuzu N 2008 Series Workshop Manual

1A-208 Engine Control System (4JJ1)

DTC P0651 (Flash Code 56)

Circuit Description
The ECM provides 5 volts reference voltage through
the reference circuit 2 to the following sensors:
• Accelerator pedal position (APP) sensor 2
• Barometric pressure (BARO) sensor
• Intake air temperature (IAT) sensor
The ECM also provides 5 volts reference voltage
through the reference circuit 5 to the following sensors:
• Fuel rail pressure (FRP) sensor
• Camshaft position (CMP) sensor
• EGR position sensor
The 5 volts reference circuits 2 and 5 are independent
of each other outside of the ECM, but are bussed
together inside the ECM. Therefore, a short circuit
condition on one sensor 5 volts reference circuit may
affect the entire 5 volts reference circuit 2 and 5. The
ECM monitors the voltage on the 5 volts reference
circuit 2 and 5. If the ECM detects the voltage is
excessively low or high, this DTC will set.
Condition for Running the DTC
• DTC P060B is not set.
• The battery voltage is between 18 to 32 volts.
• The ignition switch is ON.
Condition for Setting the DTC
Either of following condition is met:
Circuit/ System Testing DTC P0651
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. Start the engine.
2
4. Monitor the DTC Information with a scan tool.
Does the DTC fail this ignition?
1. Turn OFF the ignition.
2. Disconnect the camshaft position (CMP)
sensor harness connector.
3. Connect a DMM between the 5 volts reference
3
circuit (pin 3 of E18) and a known good
ground.
4. Turn ON the ignition, with the engine OFF.
Is the DMM voltage less than the specified value?
Is the DMM voltage more than the specified value
4
at Step 3?
Action
• The ECM detects that the 5 volts reference circuit
2 or 5 voltage is less than 4.5 volts.
• The ECM detects that the 5 volts reference circuit
2 or 5 voltage is more than 5.5 volts.
Action Taken When the DTC Sets
• The ECM illuminates 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 limits fuel injection quantity.
• The ECM inhibits pre injection.
• The ECM inhibits EGR control.
• 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.
Notice: If this DTC is set, the engine cranks but does
not start.
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
5.5 volts
Go to Step 4
4.5 volts
Go to Step 11
No
Go to Diagnostic
System Check -
Engine Controls
Go to Diagnostic
Aids
Go to Step 10
Go to Step 5