Dtc P0087 (Flash Code 225) - Isuzu 2008MY N Series Workshop Manual

1A-74 Engine Control System (4HK1)

DTC P0087 (Flash Code 225)

Description
The common rail fuel system is comprised of two fuel
pressure sections: a suction side between the fuel tank
and the fuel supply pump and a high-pressure side
between the fuel supply pump and the fuel injectors.
Fuel is drawn from the fuel tank via a feed pump and
then pumped into the fuel rail by two plungers, all of
which are internal to the fuel supply pump. This high
pressure is regulated by the ECM using the fuel rail
pressure (FRP) regulator dependant upon values from
the FRP sensor attached to the fuel rail. In case of fuel
rail overpressure, a pressure limiter valve threaded into
the fuel rail will open to release overpressure and
return fuel back to the fuel tank. If the ECM detects that
the fuel rail pressure went excessively high, then
sharply decreased, this DTC will set indicating high fuel
pressure, which activated the pressure limiter valve.
Condition for Running the DTC
• DTCs P0192, P0193, P060B and P0651 are not
set.
• The ignition switch is ON.
Condition for Setting the DTC
• The ECM detects that the pressure limiter valve is
activated with overpressure (more than 170 MPa
[24,600 psi]) in the fuel rail.
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 limits fuel injection quantity.
• The ECM inhibits EGR control.
Circuit/ System Testing DTC P0087
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.
Is DTC P0088, P0089, P0091, P0092, P0192,
P0193, P0201 - P0204, P2146 or P2149 set?
Action
Condition for Clearing the DTC
• Refer to DTC Type Definitions for Condition for
Clearing the MIL/ DTC - Type A.
Diagnostic Aids
• An intermittently sticking FRP regulator may have
allowed the fuel pressure to become high enough
to open the pressure limiter valve.
• A skewed FRP sensor value can set this DTC. The
FRP Sensor on the scan tool should read 0.9 to
1.0 volt with the ignition switch ON and engine
OFF after the engine has stopped running for a
minimum of 1 minute.
Notice: If the fuel tank is empty or near empty, air
might be allowed to go into the fuel system. With air in
the fuel system, smooth flow of fuel into the supply
pump is interrupted and this DTC may set. Perform
bleeding of fuel system after refilling.
Test Description
The numbers below refers to the step number on the
Circuit/ System Testing.
7. This step checks for a fuel restriction by determining
if a high vacuum is being pulled on the fuel system
during normal operation.
8. This step checks for an air leak on the suction side of
the fuel system by determining if a vacuum can be
pulled when a fuel line is plugged.
Schematic Reference: Fuel System Routing Diagram
and 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 Applicable
DTC
No
Go to Diagnostic
System Check -
Engine Controls
Go to Step 3