Exhaust Gas Recirculation (Egr) Diagnosis - Isuzu 1999 RODEO Workshop Manual

EXHAUST GAS RECIRCULATION
(EGR) DIAGNOSIS
An EGR flow check diagnosis of the linear EGR system is
covered by DTC P0401, P0404, and P0405. If EGR
diagnostic trouble code P0401 is encountered, refer to
the DTC charts.
ENGINE Tech 2 DATA DEFINITIONS
AND RANGES
A/C CLUTCH – Tech 2 Displays ON or OFF
Indicates whether the PCM has commanded the A/C
clutch ON. Used in A/C system diagnostics.
A/C REQUEST – Tech 2 Displays YES or NO
Indicates the state of the A/C request input circuit from the
HVAC controls. The PCM uses the A/C request signal to
determine whether A/C compressor operation is being
requested.
AIR/FUEL RATIO – Tech 2 Range 0.0–25.5
Air/fuel ratio indicates the PCM commanded value. In
"Closed Loop", the air/fuel ratio should normally be
displayed around "14.2–14.7." A lower air/fuel ratio
indicates a richer commanded mixture, which may be
seen during power enrichment or TWC protection modes.
A higher air/fuel ratio indicates a leaner commanded
mixture. This can be seen during deceleration fuel mode.
BARO kPa – Tech 2 Range 10–105 kPa/0.00–5.00
Volts
The barometric pressure reading is determined from the
MAP sensor signal monitored during key up and wide
open throttle (WOT) conditions. The barometric pressure
is used to compensate for altitude differences and is
normally displayed around "61–104" depending on
altitude and barometric pressure.
CMP ACT. COUNTER – Cam Position Activity
RODEO X22SE 2.2L ENGINE DRIVEABILITY AND EMISSION
057RX001
DECEL FUEL MODE – Tech 2 Displays ACTIVE or
INACTIVE
"ACTIVE" displayed indicates that the PCM has detected
conditions appropriate to operate in deceleration fuel
mode. The PCM will command the deceleration fuel
mode when it detects a closed throttle position while the
vehicle is traveling over 20 mph. While in the deceleration
fuel mode, the PCM will decrease the amount of fuel
delivered by entering "Open Loop" and decreasing the
injector pulse width.
DESIRED EGR POS. – Tech 2 Range 0%–100%
Represents the EGR pintle position that the PCM is
commanding.
DESIRED IDLE – Tech 2 Range 0–3187 RPM
The idle speed that the PCM is commanding. The PCM
will compensate for various engine loads based on engine
coolant temperature, to keep the engine at the desired
speed.
ECT – (Engine Coolant Temperature) Tech 2 Range
–40°C to 151°C (–40°F to 304°F)
The engine coolant temperature (ECT) is mounted in the
coolant stream and
information to the PCM. The PCM applies 5 volts to the
ECT sensor circuit. The sensor is a thermistor which
changes internal resistance as the temperature changes.
When the sensor is cold (high resistance), the PCM
monitors a high signal voltage and interprets that as a cold
engine. As the sensor warms (decreasing resistance),
the voltage signal will decrease and the PCM will interpret
the lower voltage as a warm engine.
EGR DUTY CYCLE – Tech 2 Range 0%–100%
Represents the EGR valve driver PWM signal from the
PCM. A duty cycle of 0% indicates that no EGR flow is
being commanded; a 100% duty cycle indicates
maximum EGR flow commanded.
EGR FEEDBACK – Tech 2 Range 0.00–5.00 Volts
Indicates the EGR pintle position sensor signal voltage
being monitored by the PCM. A low voltage indicates a
fully extended pintle (closed valve); a voltage near 5 volts
indicates a retracted pintle (open valve).
EGR TEST COUNT – Tech 2 Range 0–255
Indicates the number of EGR flow test samples collected
during the current ignition cycle. Under normal operation,
only one sample is allowed during an ignition cycle. If the
PCM battery feed has been disconnected or a DTC
P0401 has been cleared, 10 EGR flow test samples will
be allowed during the ignition cycle. This is to allow repair
verification during a single ignition cycle.
ENGINE LOAD – Tech 2 Range 0%–100%
Engine load is calculated by the PCM from engine speed
and MAP sensor readings. Engine load should increase
with an increase in RPM or air flow.
ENGINE RUN TIME – Tech 2 Range 00:00:00–
99:99:99 Hrs:Min:Sec
Indicates the time elapsed since the engine was started.
If the engine is stopped, engine run time will be reset to
00:00:00.
ENGINE SPEED – Range 0–9999 RPM
Engine speed is computed by the PCM from the 58X
reference input. It should remain close to desired idle
under various engine loads with engine idling.
6E1–69
sends engine temperature