P0401 Egr Flow Insufficient - Isuzu 2000 Trooper Workshop Manual

6E–310
TROOPER 6VE1 3.5L ENGINE DRIVEABILITY AND EMISSIONS
Diagnostic Trouble Code (DTC) P0401 EGR Flow Insufficient
Circuit Description
The powertrain control module (PCM) tests the exhaust
gas recirculation (EGR) system during deceleration by
momentarily commanding the EGR valve to open while
monitoring the manifold absolute pressure (MAP) sensor
signal. When the EGR valve is opened, the PCM
monitors the change in MAP input signal. The PCM
compares the MAP change to a RPM vs. BARO table.
When the PCM interprets the change in MAP to be out of
limits, the PCM will set DTC P0401. The number of test
samples required to accomplish this may vary according
to the severity of the detected flow error.
Normally, the PCM will only allow one EGR flow test
sample to be taken during an ignition cycle. To aid in
verifying a repair, the PCM allows twelve test samples
during the first ignition cycle following a Tech 2 "Clear Info"
or a battery disconnect.
samples should be sufficient for the PCM to determine
adequate EGR flow and pass the EGR test.
Conditions for Setting the DTC
D No TP sensor, vehicle speed sensor (VSS), MAP
sensor, EGR Pintle Position sensor, ECT sensor,
misfire, or automatic transmission DTCs set.
D Engine coolant temperature is greater than 60°C
(140°F).
D Ignition voltage between 11.5 and 16 volts.
D Vehicle speed is greater than 24 km/h (15 mph).
D A/C clutch status is unchanged.
Between nine and twelve
D TCC status is unchanged.
Start Test
D TP angle is less than 1%.
D EGR duty cycle is less than 1%.
D MAP is steady, changing less than 2 kPa.
D Engine speed is between 1100 RPM and 2000 RPM.
D MAP between 10 kPa and 40 kPa.
The test will be aborted if the vehicle speed changes by
more than 16 km/h (10 mph), engine speed changes by
more than 100 RPM or the EGR is opened less than 95%
of commanded position.
D The PCM will only run the EGR test during a closed
throttle condition.
D The PCM will only run the EGR test at vehicle speeds
above 24 km/h (15 mph).
D Several deceleration cycles will be necessary to run a
sufficient number of EGR flow tests.
Diagnostic Aids
Check for the following conditions:
D Poor connection or damaged harness – Inspect the
wiring harness for damage. If the harness appears to
be OK, observe the Actual EGR Position display on the
Tech 2 while moving connectors and wiring harnesses
related to the EGR valve. A change in the display will
indicate the location of the fault.
D Ensure EGR valve is correctly mounted.
On-Vehicle Service .
D06RY00178
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