Mitsubishi 3000GT Service Manual page 148

MULTIPORT FUEL INJECTION - Troubleshooting
DTC No.
PO400 Exhaust Gas Recirculation Flow Malfunction
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Background
When the EGR solenoid switches from OFF to ON while the engine is running, EGR gas
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flows.
The engine control module checks how the EGR gas flow signal changes.
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Range of Check, Set Conditions
The EGR gas flow signal changes little when the EGR solenoid switches from OFF to ON.
DTC No.
PO403 Exhaust Gas Recirculation Solenoid Malfunction
Background
The engine control module checks current flows in the EGR solenoid drive circuit when
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the solenoid is ON and OFF.
Range of Check, Set Conditions
DTC No.
PO421 Warm Up Catalyst Efficiency Below Threshold (Bank 1)
Background
The signal from the heated oxygen sensor which follows the catalytic converter differs
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from that which precedes the catalytic converter. That is because the catalytic converter
purifies exhaust gas. When the catalytic converter has deteriorated, the signal from the
heated oxygen sensor which follows the catalytic converter becomes similar to that which
precedes the catalytic converter.
The engine control module checks the outputs of the heated oxygen sensor signals.
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Range of Check, Set Conditions
The relation between the signals from the heated oxygen sensors preceding (engine side) and
following the catalytic converter meets specified condition.
Title
Title
Title
Probable causes
EGR control vacuum is too low.
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EGR solenoid failed.
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Open or shorted EGR solenoid
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circuit, or loose connector.
Manifold differential pressure
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sensor failed.
Probable causes
EGR solenoid failed.
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Open or shorted EGR solenoid
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circuit, or loose connector.
Probable causes
Engine control module failed.
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Probable causes
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