Mazda MX-6 1998, Workshop Manual

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TROUBLESHOOTING [ENGINE CONTROL FS]
DTC P1450 Evaporative emission control system unable to bleed up fuel tank vacuum
DESCRIPTION
•
DTC P1450 indicates that self-test has detected Evaporative Emission Control System is
unable to bleed up fuel tank vacuum
[Possible Cause]
• Contaminated filter on the purge solenoid valve
•
Damaged FTP sensor
• Damaged the purge solenoid valve
• Constant voltage circuit open between fuel tank
pressure (FTP) sensor and PCM
STEP INSPECTION ACTION
1
CHECK PURGE SOLENOID VALVE
• Key off.
• Remove vacuum line from the input
vacuum port to intake manifold on control
vacuum solenoid part of purge solenoid
valve.
•
Apply 33 kPa (0.33 kgf/cm2, 210 inHg} of
vacuum with a hand-held vacuum pump to
the open port on solenoid part of the purge
solenoid valve.
•
Does vacuum to the solenoid on purge
solenoid valve release rapidly?
Yes REMOVE vacuum pump.
RECONNECT all components.
Go to next step.
No SERVICE purge solenoid valve.
If unable to repair filter, REPLACE damaged purge
solenoid valve.
REMOVE vacuum pump.
RECONNECT all components.
RESET PCM to completely clear DTCs.
cr After Repair Procedure
COMPLETE OBD II Drive Mode.
RERUN OBD Test.
2
CHECK PURGE SOLENOID VALVE
RESISTANCE
•
Key off.
•
Purge solenoid valve disconnected.
• Measure resistance between purge
solenoid valve and power circuit on purge
solenoid valve.
•
Is resistance between 30 and
36
ohms?
Yes Go to next step.
No
REPLACE damaged purge solenoid valve.
RESET PCM to completely clear DTCs.
ezr After Repair Procedure
COMPLETE OBD II Drive Mode.
RERUN OBD Test.
3
CHECK PURGE SOLENOID VALVE CIRCUIT
FOR SHORT TO GROUND CIRCUIT
• Key off.
• Purge solenoid valve disconnected.
• Breakout box installed.
• PCM disconnected.
• Disconnect NGS tester from DLC.
•
Measure resistance between Test Pin 67
and Test Pins 24 and 103 at breakout box.
• Is each resistance greater than 10,000
ohms?
Yes Go to next step.
No SERVICE harness short between purge solenoid valve
and ground circuit.
REMOVE breakout box.
RECONNECT all components.
RESET PCM to completely clear DTCs.
cr After Repair Procedure
COMPLETE OBD II Drive Mode.
RERUN OBD Test.
4 VISUAL CHECK OF CONSTANT VOLTAGE
CONNECTIONS AT FUEL TANK PRESSURE
SENSOR AND PCM
•
Key off.
• Observe constant voltage circuit at both
FTP sensor and PCM connectors.
• Does constant voltage circuit appear to
be connected at both FTP sensor and
PCM?
Yes Go to next step.
No SERVICE as necessary.
RESET PCM to completely clear DTCs.
cr After Repair Procedure
COMPLETE OBD II Drive Mode.
RERUN OBD Test.
5 CHECK RESISTANCE OF CONSTANT
VOLTAGE CIRCUIT AT FTP SENSOR
• Key off.
• Disconnect FTP sensor.
• Disconnect PCM. Inspect for damaged or
pushed out pins, corrosion and loose wires.
Service as necessary.
• install breakout box. Leave PCM
disconnected.
• Measure resistance between Test Pin 90 at
breakout box and constant voltage circuit
at FTP sensor connector.
• Is resistance less than 5.0 ohms?
Yes Constant voltage is open in FTP sensor.
REPLACE damaged FTP sensor.
REMOVE breakout box.
RECONNECT all components.
RESET PCM to completely clear DTCs.
cr
After Repair Procedure
COMPLETE OBD II Drive Mode.
RERUN OBD Test.
No SERVICE open in constant voltage harness to FTP
sensor.
REMOVE breakout box.
RECONNECT all components.
RESET PCM to completely clear DTCs.
cr
After Repair Procedure
COMPLETE OBD II Drive Mode.
RERUN OBD Test.
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