Mazda CX-9 Grand Touring 2007 Manual page 659

2007 ENGINE PERFORMANCE On-Board Diagnostic (MZI-3.5) - CX-9
PROCEDURE [MZI-3.5].)
Are any DTCs present?
DTC P0642 [MZI-3.5]
DTC P0642 (MZI-3.5) DETECTION CONDITION AND POSSIBLE CAUSES
DTC P0642
DETECTION
CONDITION
POSSIBLE CAUSE
2007 Mazda CX-9 Grand Touring
Sensor reference voltage circuit low
Indicates the reference voltage circuit is lower than reference voltage minimum.
Short to ground between fuel tank pressure sensor terminal C and PCM terminal 1
Fuel tank pressure sensor malfunction
Connector or terminal malfunction