Mazda CX-9 Grand Touring 2009 Manual page 1354

Information and perform repair or diagnosis.
NO.14 POOR FUEL ECONOMY [MZI-3.7]
NO.14 POOR FUEL ECONOMY (MZI-3.7) DETECTION CONDITIONS AND POSSIBLE CAUSES
14 POOR FUEL ECONOMY
DESCRIPTION Fuel economy is unsatisfactory.
POSSIBLE
CAUSE
2008 Mazda CX-9 Grand Touring
2008 ENGINE Symptom Troubleshooting (MZI-3.7) - Mazda CX-9
If vehicle is repaired, troubleshooting completed.
If vehicle is not repaired or additional diagnostic information is not available,
replace the PCM.
(See PCM REMOVAL/INSTALLATION [MZI-3.7] .)
Contaminated air cleaner element
Engine cooling system malfunction
Improper ATF level
Weak spark
Poor fuel quality
Erratic or no signal from CMP sensor
Improper variable valve timing control system operation
Improper coolant level
Inadequate fuel pressure
Spark plug malfunction
PCV valve malfunction
Brake dragging
Improper valve timing due to jumping out of timing chain
Contaminated MAF sensor
Improper engine compression
Exhaust system clogging
WARNING:
The following troubleshooting flow chart contains fuel system diagnosis and
repair procedures. Read following warnings before servicing fuel system:
Fuel vapor is hazardous. It can easily ignite, causing serious injury
and damage. Always keep sparks and flames away from fuel.
Fuel line spills and leakage are dangerous. Fuel can ignite and cause
serious injuries or death and damage. Fuel can also irritate skin and
eyes. To prevent this, always complete "BEFORE SERVICE
PRECAUTION" and "AFTER SERVICE PRECAUTION" described in this
manual.