width ISUZU AXIOM 2002 Service Owner's Guide
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Page 1171 of 2100
6E±204
6VE1 3.5L ENGINE DRIVEABILITY AND EMISSIONS
Diagnostic Trouble Code (DTC)
P0154 HO2S Circuit Insufficient Activity Bank 2 Sensor 1
060R200054
Circuit Description
The powertrain control module (PCM) supplies a bias
voltage of about 450 mV between the heated oxygen
sensor (HO2S) high and low circuits. When measured
with a 10 megaohm digital voltmeter, this may display as
low as 320 mV. The oxygen sensor varies the voltage
within a range of about 1000 mV when the exhaust is rich,
down through about 10 mV when exhaust is lean. The
PCM constantly monitors the HO2S signal during ªclosed
loopº operation and compensates for a rich or lean
condition by decreasing or increasing injector pulse width
as necessary. If the Bank 2 HO2S 1 voltage remains at or
near the 450 mV bias for an extended period of time, DTC
P0154 will be set, indicating an open sensor signal or
sensor low circuit.
Heated oxygen sensors are used to minimize the amount
of time required for ªclosed loopº fuel control operation
and to allow accurate catalyst monitoring. The oxygen
sensor heater greatly decreases the amount of time
required for fuel control sensors Bank 1 HO2S 1 and Bank
2 HO2S 1 to become active. Oxygen sensor heaters are
required by post-catalyst monitor sensors to maintain a
sufficiently high temperature for accurate exhaust oxygen
content readings further from the engine.
Conditions for Setting the DTC
No related DTCs.
Engine coolant temperature is above 60C (140F).The engine has been running for over 5 seconds.
Oxygen sensor heater is functioning properly.
Bank 2 HO2S 1 signal voltage remains between
400 mV and 500 mV for a total of 77 seconds over a
90-second period of time.
Action Taken When the DTC Sets
The PCM will ON the MIL after second trip with
detected fault.
The PCM will store conditions which were present
when the DTC was set as Freeze Frame and in the
Failure Records data.
ªOpen loopº fuel control will be in effect.
Conditions for Clearing the MIL/DTC
The PCM will turn the MIL ªOFFº on the third
consecutive trip cycle during which the diagnostic has
been run and the fault condition is no longer present.
A history DTC P0154 will clear after 40 consecutive
warm-up cycles have occurred without a fault.
DTC P0154 can be cleared by using the Tech 2 ªClear
Infoº function or by disconnecting the PCM battery
feed.
Diagnostic Aids
Check for the following conditions:
Poor connection or damaged harness ± Inspect the
harness connectors for backed-out terminals,
Page 1239 of 2100
6E±272
6VE1 3.5L ENGINE DRIVEABILITY AND EMISSIONS
Diagnostic Trouble Code (DTC) P0325
ION Sensing Module/ION Sensing Knock Intensity Circuit Fault
060R200055
Circuit Description
The Power Control Module (PCM) checks the validity of
the signals used in the ION Sensing module at the
following engine operating conditions.
The test is performed to evacuate the Knock Intensity
(KI) signal pulse width if it is within a predetermined
range. If the KI signal pulse width is out of the
predetermined range, the fail counter will be
incremented. If the failure counter exceeds the
calibration, then test is complete and a failure will be
reported. If the sample counter threshold is reached
before the failure threshold, then the test is complete
and a pass will be reported. This test will detect an
open/short in the KI line circuit, ION module faults and
analog input faults in the PCM.
Conditions for setting the DTC
Ignition voltage is between 10volt and 16 volts.
No Crank DTCs set.
No EST DTCs set.
No Misfire DTCs set.
Action Taken When the DTC Sets
The PCM will ON the MIL after second trip with
detected the fault.
The PCM calculates an air flow value based on idle air
control valve position, throttle position, RPM and
barometric pressure.The PCM will store condition which were present when
the DTC was set as Freeze Frame and in the Failure
Records data.
Conditions for Clearing the MIL/DTC
The PCM will turn the MIL ªOFFº on the third
consecutive trip cycle during which the diagnostic has
been run and the fault condition is no longer present.
A history DTC P0325 will clear after 40 consecutive trip
cycles during which the warm up cycles have occurred
without a fault.
DTC P0325 can be cleared using the Tech2 ªClear
Infoº function or by disconnecting the PCM battery
feed.
Diagnostic Aids
An intermittent may be caused by the following:
Poor connections.
Misrouted harness.
Rubbed through wire insulation.
Broken wire inside the insulation.
Check for the following conditions:
Poor connection at PCM- Inspect harness connectors
for backed out terminals, improper mating, broken
locks, improperly formed or damaged terminals, and
poor terminal to wire connection.
Damaged harness-Inspect the wiring harness for
damage.
Page 1426 of 2100
6E±459
6VE1 3.5L ENGINE DRIVEABILITY AND EMISSIONS
Diagnostic Trouble Code (DTC) P1310 ION Sensing Module Diagnosis
060R200068
Circuit Description
The Power Control Module (PCM) checks the validity of
the signals used in the ION Sensing module at the
following engine operating conditions.
The Deceleration Fuel Cut Off (DFCO) test is
performed to evaluate the Combustion Quality (CQ)
signal pulse width
If it is below a predetermined value, the value it is
expected to be during DFCO conditions. If the CQ
signal pulse width is above the predetermined
threshold, the fail counter will be incremented. If the
failure counter exceeds the calibration, then the test is
complete and a failure will be reported.
The Power Enrichment (PE) test is performed to
evaluate the Combustion Quality (CQ) signal pulse
width
If it is below a predetermined value, the value is
expected to be during PE conditions.
If the CQ signal pulse width is above the
predetermined threshold, the fail counter will be
incremented. If the failure counter exceeds the
calibration, then the test is complete and a failure will
be reported.
The Combustion Quality (CQ) test is performed to
check if inappropriate (CQ) signal status were
detected. If missing CQ pulses or multiple CQ pulses
or CQ pulse width calculation errors were detected, the
fail counter will be incremented. If the failure counter
exceeds the calibration, then the test is complete and
a failure will be reported.
Conditions for setting the DTC
Ignition voltage is between 10volt and 16 volts.
MAP sensor signal is between 26kPa and 100 kPa.
Fuel level is more than 19%.
Engine speed is between 650rpm and 6500rpm.
No Crank DTCs set.
No System voltage DTCs set.
Action Taken When the DTC Sets
The PCM will illuminate the malfunction indicator lamp
(MIL) the first time the fault is detected.
The PCM calculates an air flow value based on idle air
control valve position, throttle position, RPM and
barometric pressure.
The PCM will store conditions which were present
when the DTC was set as Freeze Frame and in the
Failure Records data.
Conditions for Clearing the MIL/DTC
The PCM will turn the MIL ªOFFº on the third
consecutive trip cycle during which the diagnostic has
been run and the fault condition is no longer present.
A history DTC P1310 will clear after 40 consecutive trip
cycle during which the warm up cycles have occurred
without a fault.
DTC P1310 can be cleared using the Tech 2 ªClear
Infoº function or by disconnecting the PCM battery
feed.
Page 1429 of 2100
6E±462
6VE1 3.5L ENGINE DRIVEABILITY AND EMISSIONS
Diagnostic Trouble Code (DTC)
P1311 ION Sensing Module SEC Line 1 Circuit Fault
060R200068
Circuit Description
The Power Control Module (PCM) will compare the
secondary current reading to predetermined maximum
and minimum thresholds.
If the secondary current signal pulse width is out of
the predetermined range, the fail counter will be
incremented. If the failure counter exceeds the
calibration, then the PCM is complete and a failure
will be reported. If the sample counter threshold is
reached before the failure threshold, then the PCM is
complete and pass will be reported.
This PCM will detect an open/short circuit in the
secondary current sense input circuit, misfire on the
entire bank for the secondary current sense input
circuit, coil failure, and same internal Ignition Current
Sense System (ICSS) module faults.
Conditions for setting the DTC
Ignition voltage is between 10volt and 16 volts.
MAP sensor signal is between 26kPa and 100 kPa.
Fuel level is more than 19%.
Engine speed is between 650rpm and 6500rpm.
ION Sensing Module circuit is open or shorted signals
on the SEC 1 line.
Action Taken When the DTC Sets
The PCM will illuminate the malfunction indicator lamp
(MIL) the first time the fault is detected.
The PCM calculates an air flow value based on idle air
control valve position, throttle position, RPM and
barometric pressure.
The PCM will store conditions which were present
when the DTC was set as Freeze Frame and in the
Failure Records data.
Conditions for Clearing the MIL/DTC
The PCM will turn the MIL ªOFFº on the third
consecutive trip cycle during which the diagnostic has
been run and the fault condition is no longer present.
A history DTC P1311 will clear after 40 consecutive trip
cycles during which the warm up cycles have occurred
without a fault.
DTC P1311 can be cleared using the Tech 2 ªClear
Infoº function or by disconnecting the PCM battery
feed.
Diagnostic Aids
An intermittent may be caused by the following:
Poor connections.
Misrouted harness.
Rubbed through wire insulation.
Broken wire inside the insulation.
Check for the following conditions:
Page 1432 of 2100
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6VE1 3.5L ENGINE DRIVEABILITY AND EMISSIONS
Diagnostic Trouble Code (DTC)
P1312 ION Sensing Module SEC Line 2 Circuit Fault
060R200068
Circuit Description
The Power Control Module (PCM) will compare the
secondary current reading to predetermined maximum
and minimum thresholds.
If the secondary current signal pulse width is out of
the predetermined range, the fail counter will be
incremented. If the fail counter exceeds the
calibration, then the PCM is complete and a failure
will be reported. If the sample counter threshold is
reached before the failure threshold, then the PCM is
complete and pass will be reported.
This PCM will detect an open/short circuit in the
secondary current sense input circuit, misfire on the
entire bank for the secondary current sense input
circuit, coil failure, and same internal Ignition Current
Sense System (ICSS) module faults.
Conditions for setting the DTC
Ignition voltage is between 10volt and 16 volts.
MAP sensor signal is between 26kPa and 100 kPa.
Fuel level is more than 19%.
Engine speed is between 650rpm and 6500rpm.
ION Sensing Module circuit is open or shorted signals
on the SEC 2 line.
Action Taken When the DTC Sets
The PCM will illuminate the malfunction indicator lamp
(MIL) the first time the fault is detected.
The PCM calculates an air flow value based on idle air
control valve position, throttle position, RPM and
barometric pressure.
The PCM will store conditions which were present
when the DTC was set as Freeze Frame and in the
Failure Records data.
Conditions for Clearing the MIL/DTC
The PCM will turn the MIL ªOFFº on the third
consecutive trip cycle during which the diagnostic has
been run and the fault condition is no longer present.
A history DTC P1312 will clear after 40 consecutive trip
cycles during which the warm up cycles have occurred
without a fault.
DTC P1312 can be cleared using the Tech 2 ªClear
Infoº function or by disconnecting the PCM battery
feed.
Diagnostic Aids
An intermittent may be caused by the following:
Poor connections.
Misrouted harness.
Rubbed through wire insulation.
Broken wire inside the insulation.
Check for the following conditions:
Page 1435 of 2100
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6VE1 3.5L ENGINE DRIVEABILITY AND EMISSIONS
Diagnostic Trouble Code (DTC)
P1326 ION Sensing Module Combustion Quality Input Circuit Fault
060R200068
Circuit Description
The Power Control Module (PCM) checks the validity of
the signals used in the ION Sensing module at the
following engine operating conditions.
The test is performed to evacuate the Combustion
Quality (CQ) signal pulse width if it is within a
predetermined range. If the CQ signal pulse width is
out of the predetermined range, the fail counter will be
incremented. If the failure counter exceeds the
calibration, then test is complete and a failure will be
reported. If the sample counter threshold is reached
before the failure threshold, then the test is complete
and a pass will be reported. This test will detect an
open/short in the CQ line circuit, ION Sensing module
faults and analog input faults in the PCM.
Conditions for setting the DTC
Ignition voltage is between 10volt and 16 volts.
No Crank DTCs set.
No cylinder ID DTCs set.
Action Taken When the DTC Sets
The PCM will illuminate the malfunction indicator lamp
(MIL) the first time the fault is detected.
The PCM calculates an air flow value based on idle air
control valve position, throttle position, RPM and
barometric pressure.
The PCM will store conditions which were present
when the DTC was set as Freeze Frame and in the
Failure Records data.
Conditions for Clearing the MIL/DTC
The PCM will turn the MIL ªOFFº on the third
consecutive trip cycle during which the diagnostic has
been run and the fault condition is no longer present.
A history DTC P1326 will clear after 40 consecutive trip
cycles during which the warm up cycles have occurred
without a fault.
DTC P1326 can be cleared using the Tech 2 ªClear
Infoº function or by disconnecting the PCM battery
feed.
Diagnostic Aids
An intermittent may be caused by the following:
Poor connections.
Misrouted harness.
Rubbed through wire insulation.
Broken wire inside the insulation.
Check for the following conditions:
Poor connection at PCM-Inspect harness connectors
for backed out terminals, improper mating, broken
locks, improperly formed or damaged terminals, and
poor terminal to wire connection.
Damaged harness-Inspect the wiring harness for
damage. If the harness appears to be OK, observe the
moving connectors and wiring harnesses related to the
sensor.
A change in the display will indicate the location of
the fault. If DTC P1326 cannot be duplicated, the
information included in the Failure Records data can
Page 1444 of 2100
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6VE1 3.5L ENGINE DRIVEABILITY AND EMISSIONS
Diagnostic Trouble Code (DTC)
P1441 EVAP System Flow During Non-Purge
060RY00398
Circuit Description
Canister purge is controlled by a solenoid valve that
allows manifold vacuum to purge the canister. The
powertrain control module (PCM) supplies a ground to
energize the solenoid valve (purge ªONº). The EVAP
purge solenoid control is pulse-width modulated (PWM)
or turned ªONº and ªOFFº several times a second. The
duty cycle (pulse width) is determined by engine
operating conditions including load, throttle position,
coolant temperature and ambient temperature. The duty
cycle is calculated by the PCM and the output is
commanded when the appropriate conditions have been
met.
Conditions for Setting the DTC
No active ECT sensor, IAT sensor, MAP sensor, or TP
sensor DTCs set.
BARO reading is above 85 kPa.
Engine coolant temperature is below 70C (158F).
Start-up intake air temperature (IAT) and start-up
engine coolant temperature (ECT) are both above 5C
(41F).
The difference between start-up ECT and start-up IAT
is less than 25C (45F).
TP sensor indicates a throttle position above 12%.
Battery voltage is between 11.5 volts and 16 volts.
Engine speed is between 800 and 6,000 RPM.
Canister purge duty cycle is below 3%.Fuel level is between 15% and 85%.
All conditions are present for at least 3 seconds.
Action Taken When the DTC Sets
The PCM will illuminate the malfunction indicator lamp
(MIL) after the second consecutive trip in which the
fault is detected.
The PCM will store conditions which were present
when the DTC was set as Freeze Frame and in the
Failure Records data.
Conditions for Clearing the MIL/DTC
The PCM will turn the MIL ªOFFº on the third
consecutive trip cycle during which the diagnostic has
been run and the fault condition is no longer present.
A history DTC P1441 will clear after 40 consecutive
warm±up cycles have occurred without a fault.
DTC P1441 can be cleared by using the Tech 2 ªClear
Infoº function or by disconnecting the PCM battery
feed.
Diagnostic Aids
Check for the following conditions:
Poor connection at PCM ± Inspect harness connectors
for backed-out terminals, improper mating, broken
locks, improperly formed or damaged terminals, and
poor terminal-to-wire connection.
Damaged harness ± Inspect the wring harness for
damage. A change in the display will indicate the
location of the fault.
Page 1539 of 2100
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6VE1 3.5L ENGINE DRIVEABILITY AND EMISSIONS
General Description (PCM and
Sensors)
58X Reference PCM Input
The powertrain control module (PCM) uses this signal
from the crankshaft position (CKP) sensor to calculate
engine RPM and crankshaft position at all engine speeds.
The PCM also uses the pulses on this circuit to initiate
injector pulses. If the PCM receives no pulses on this
circuit, DTC P0337 will set. The engine will not start and
run without using the 58X reference signal.
A/C Request Signal
This signal tells the PCM when the A/C mode is selected
at the A/C control head. The PCM uses this to adjust the
idle speed before turning ªONº the A/C clutch. The A/C
compressor will be inoperative if this signal is not
available to the PCM.
Refer to
A/C Clutch Circuit Diagnosis section for A/C
wiring diagrams and diagnosis for the A/C electrical
system.
Crankshaft Position (CKP) Sensor
The crankshaft position (CKP) sensor provides a signal
used by the powertrain control module (PCM) to calculate
the ignition sequence. The CKP sensor initiates the 58X
reference pulses which the PCM uses to calculate RPM
and crankshaft position.
Refer to
Electronic Ignition System section for additional
information.
0013
Engine Coolant Temperature (ECT) Sensor
The engine coolant temperature (ECT) sensor is a
thermistor (a resistor which changes value based on
temperature) mounted in the engine coolant stream. Low
coolant temperature produces a high resistance of
100,000 ohms at ±40C (±40F). High temperature
causes a low resistance of 70 ohms at 130C (266F).
The PCM supplies a 5-volt signal to the ECT sensor
through resistors in the PCM and measures the voltage.
The signal voltage will be high when the engine is cold and
low when the engine is hot. By measuring the voltage, thePCM calculates the engine coolant temperature. Engine
coolant temperature affects most of the systems that the
PCM controls.
The Tech 2 displays engine coolant temperature in
degrees. After engine start-up, the temperature should
rise steadily to about 85C (185F). It then stabilizes
when the thermostat opens. If the engine has not been
run for several hours (overnight), the engine coolant
temperature and intake air temperature displays should
be close to each other. A hard fault in the engine coolant
sensor circuit will set DTC P0177 or DTC P0118. An
intermittent fault will set a DTC P1114 or P1115.
0016
Electrically Erasable Programmable Read
Only Memory (EEPROM)
The electrically erasable programmable read only
memory (EEPROM) is a permanent memory chip that is
physically soldered within the PCM. The EEPROM
contains the program and the calibration information that
the PCM needs to control powertrain operation.
Unlike the PROM used in past applications, the EEPROM
is not replaceable. If the PCM is replaced, the new PCM
will need to be programmed. Equipment containing the
correct program and calibration for the vehicle is required
to program the PCM.
Fuel Control Heated Oxygen Sensors
The fuel control heated oxygen sensors (Bank 1 HO2S 1
and Bank 2 HO2S 1) are mounted in the exhaust stream
where they can monitor the oxygen content of the exhaust
gas. The oxygen present in the exhaust gas reacts with
the sensor to produce a voltage output. This voltage
should constantly fluctuate from approximately 100 mV to
900 mV. The heated oxygen sensor voltage can be
monitored with a Tech 2. By monitoring the voltage output
of the oxygen sensor, the PCM calculates the pulse width
command for the injectors to produce the proper
combustion chamber mixture.
Low HO2S voltage is a lean mixture which will result in
a rich command to compensate.
High HO2S voltage is a rich mixture which will result in
a lean command to compensate.
Page 1550 of 2100
6E±583
6VE1 3.5L ENGINE DRIVEABILITY AND EMISSIONS
between the seats. In extreme cases, exhaust blow-by
and damage beyond simple gap wear may occur.
Cracked or broken insulators may be the result of
improper installation, damage during spark plug
re-gapping, or heat shock to the insulator material. Upper
insulators can be broken when a poorly fitting tool is used
during installation or removal, when the spark plug is hit
from the outside, or is dropped on a hard surface. Cracks
in the upper insulator may be inside the shell and not
visible. Also, the breakage may not cause problems until
oil or moisture penetrates the crack later.
TS23994
A/C Clutch Diagnosis
A/C Clutch Circuit Operation
A 12-volt signal is supplied to the A/C request input of the
PCM when the A/C is selected through the A/C control
switch.
The A/C compressor clutch relay is controlled through the
PCM. This allows the PCM to modify the idle air control
position prior to the A/C clutch engagement for better idle
quality. If the engine operating conditions are within their
specified calibrated acceptable ranges, the PCM will
enable the A/C compressor relay. This is done by
providing a ground path for the A/C relay coil within the
PCM. When the A/C compressor relay is enabled,
battery voltage is supplied to the compressor clutch coil.
The PCM will enable the A/C compressor clutch
whenever the engine is running and the A/C has been
requested. The PCM will not enable the A/C compressor
clutch if any of the following conditions are met:
The throttle is greater than 90%.
The engine speed is greater than 6315 RPM.
The ECT is greater than 119C (246F).
The IAT is less than 5C (41F).
The throttle is more than 80% open.
A/C Clutch Circuit Purpose
The A/C compressor operation is controlled by the
powertrain control module (PCM) for the following
reasons:
It improvises idle quality during compressor clutch
engagement.
It improvises wide open throttle (WOT) performance.
It provides A/C compressor protection from operation
with incorrect refrigerant pressures.
The A/C electrical system consists of the following
components:
The A/C control head.
The A/C refrigerant pressure switches.
The A/C compressor clutch.
The A/C compressor clutch relay.
The PCM.
A/C Request Signal
This signal tells the PCM when the A/C mode is selected
at the A/C control head. The PCM uses this to adjust the
idle speed before turning on the A/C clutch. The A/C
compressor will be inoperative if this signal is not
available to the PCM.
Refer to
A/C Clutch Circuit Diagnosis section for A/C
wiring diagrams and diagnosis for A/C electrical system.
General Description (Evaporative
(EVAP) Emission System)
EVAP Emission Control System Purpose
The basic evaporative emission (EVAP) control system
used on all vehicles is the charcoal canister storage
method. Gasoline vapors from the fuel tank flow into the
canister through the inlet labeled ªTANK.º These vapors
are absorbed into the activated carbon (charcoal) storage
device (canister) in order to hold the vapors when the
vehicle is not operating. The canister is purged by PCM
control when the engine coolant temperature is over 60C
(140F), the IAT reading is over 10C (50F), and the
engine has been running. Air is drawn into the canister
through the air inlet grid. The air mixes with the vapor and
the mixture is drawn into the intake manifold.
EVAP Emission Control System Operation
The EVAP canister purge is controlled by a solenoid valve
that allows the manifold vacuum to purge the canister.
The powertrain control module (PCM) supplies a ground
to energize the solenoid valve (purge on). The EVAP
purge solenoid control is pulse-width modulated (PWM)
(turned on and off several times a second). The duty
cycle (pulse width) is determined by engine operating
conditions including load, throttle positron, coolant
temperature and ambient temperature. The duty cycle is
calculated by the PCM. The output is commanded when
the appropriate conditions have been met. These
conditions are:
The engine is fully warmed up.
The engine has been running for a specified time.
The IAT reading is above 10C (50F).
Page 1554 of 2100
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6VE1 3.5L ENGINE DRIVEABILITY AND EMISSIONS
055RW004
Non-Electrical Components
Purge/Vacuum Hoses. Made of rubber compounds,
these hoses route the gasoline fumes from their
sources to the canister and from the canister to the
intake air flow.
EVAP Canister. Mounted on a bracket ahead of the
fuel tank, the canister stores fuel vapors until the PCM
determines that engine conditions are right for them
to be removed and burned.
Fuel Tank. The tank has a built-in air space designed
for the collection of gasoline fumes.
060R200081
Vacuum Source. The vacuum source is split between
two ports, one on either side of the throttle body.
Fuel Cap. The fuel cap is designed to be an integral
part of the EVAP system.System Fault Detection
The EVAP leak detection strategy is based on applying
vacuum to the EVAP system and monitoring vacuum
decay. The PCM monitors vacuum level via the fuel tank
pressure sensor. At an appropriate time, the EVAP purge
solenoid and the EVAP vent solenoid are turned ªON,º
allowing the engine vacuum to draw a small vacuum on
the entire evaporative emission system.
After the desired vacuum level has been achieved, the
EVAP purge solenoid is turned ªOFF,º sealing the system.
A leak is detected by monitoring for a decrease in vacuum
level over a given time period, all other variables
remaining constant. A small leak in the system will cause
DTC P0442 to be set.
If the desired vacuum level cannot be achieved in the test
described above, a large leak or a faulty EVAP purge
solenoid is indicated.
Leaks can be caused by the following conditions:
Disconnected or faulty fuel tank pressure sensor
Missing or faulty fuel cap
Disconnected, damaged, pinched, or blocked EVAP
purge line
Disconnected or damaged EVAP vent hose
Disconnected, damaged, pinched, or blocked fuel
tank vapor line
Disconnected or faulty EVAP purge solenoid
Disconnected or faulty EVAP vent solenoid
Open ignition feed circuit to the EVAP vent or purge
solenoid
Damaged EVAP canister
Leaking fuel sender assembly O-ring
Leaking fuel tank or fuel filler neck
A restricted or blocked EVAP vent path is detected by
drawing vacuum into the EVAP system, turning ªOFFº the
EVAP vent solenoid and the EVAP purge solenoid (EVAP
vent solenoid ªOPEN,º EVAP purge Pulse Width
Modulate (PWM) ª0%º) and monitoring the fuel tank
vacuum sensor input. With the EVAP vent solenoid open,
any vacuum in the system should decrease quickly
unless the vent path is blocked. A blockage like this will
set DTC P0446 and can be caused by the following
conditions:
Faulty EVAP vent solenoid (stuck closed)
Plugged, kinked or pinched vent hose
Shorted EVAP vent solenoid driver circuit
Plugged EVAP canister
The PCM supplies a ground to energize the purge
solenoid (purge ªONº). The EVAP purge control is PWM,
or turned ªONº and ªOFF,º several times a second. The
duty cycle (pulse width) is determined by engine
operating conditions including load, throttle position,
coolant temperature and ambient temperature. The duty
cycle is calculated by the PCM and the output is
commanded when the appropriate conditions have been
met.