Diagnostic Trouble Code (Dtc) P0406 Exhaust Gas Recirculation (Egr) Sensor Circuit High - Isuzu 1999 RODEO Workshop Manual

6E1–244 RODEO X22SE 2.2L ENGINE DRIVEABILITY AND EMISSION
DIAGNOSTIC TROUBLE CODE (DTC) P0406 EXHAUST GAS RECIRCULATION
Circuit Description
An Exhaust Gas Recirculation (EGR) system is used to
lower Oxides of Nitrogen (NOx) emission levels caused
by high combustion temperatures. It accomplishes this by
feeding small amounts of exhaust gases back into the
combustion chamber. When the air/fuel mixture is diluted
with the exhaust gases, combustion temperatures are
reduced.
A linear EGR valve is used on this system. The linear
EGR valve is designed to accurately supply exhaust
gases to the engine without the use of intake manifold
vacuum. The valve controls exhaust flow going into the
intake manifold form the exhaust manifold through an
orifice with a PCM controlled pintle. The PCM controls the
pintle position using inputs from the Throttle Position (TP)
and Manifold Absolute Pressure (MAP) sensors. The
PCM then commands the EGR valve to operate when
necessary by controlling an ignition signal through the
PCM. This can be monitored on a Tech 2 as the Desired
EGR Position.
The PCM monitors the results of its command through a
feedback signal. By sending a 5 volt reference and a
ground to the EGR valve, a voltage signal representing
the EGR valve pintle position is sent to the PCM. This
feedback signal can also be monitored on a Tech 2 and is
the actual position of the EGR pintle. The Actual EGR
Position should always be near the commanded or
Desired EGR Position.
(EGR) SENSOR CIRCUIT HIGH
If the PCM detects a continuous short to ground in the
signal circuit or the sensor, then DTC P0406 will set.
Diagnostic Trouble Code P0406 is a type A code.
Conditions for Setting the DTC
f IAT is greater than 5°C (41°F).
f The PCM sees less than 0.10 voltage from the EGR
valve sensor.
f A malfunction is present for 10 seconds.
Action Taken When the DTC Sets
f The Malfunction Indicator Lamp (MIL) will illuminate.
f The PCM will record operating conditions at the time
the diagnostic fails.
f A history Diagnostic Trouble Code is stored.
f The EGR Valve is disabled.
Conditions for Clearing the MIL/DTC
f The MIL will turn OFF after three consecutive ignition
cycles in which the diagnostic runs without a fault.
f A history Diagnostic Trouble Code will clear after 40
consecutive warm–up cycles without a fault.
f Diagnostic Trouble Code(s) can be cleared by using
the Tech 2.
Diagnostic Aids
Due to the moisture associated with exhaust systems, the
EGR valve may freeze and stick in colder weather at
D06RX055