Diagnostic procedure

WARNING: This page is about a different car, the 2009 Mazda 6. However, it is still accessible from the selected car via links, so may be relevant.

STEP	INSPECTION	RESULTS	ACTION
1	Inspect for the following: Vacuum leakage Proper fuel quality (such as proper octane, contamination, winter/summer blend) Loose bands on intake air system Cracks on intake air system parts Intake air system restriction (such as air cleaner element, fresh air duct.) Are all items normal?	Yes	Go to the next step.
1		No	Service if necessary. Repeat Step 1.
2	Connect the M-MDS to the DLC-2 Switch the ignition to ON (Engine off) Retrieve any DTCs. Are there any DTCs displayed?	Yes	DTC is displayed: Go to the appropriate DTC inspection. (See DTC TABLE [L5] .)
2		No	No DTC is displayed: Go to the next step.
3	Is engine overheating?	Yes	Go to symptom troubleshooting "No. 17 Cooling system concerns - Overheating" (See NO. 17 COOLING SYSTEM CONCERNS-OVERHEATING [L5] .)
3	Is engine overheating?	No	Go to the next step
4	Inspect the ignition coil related wiring harness condition (intermittent open or short circuit) for all cylinders (See IGNITION COIL INSPECTION [L5] .) Are the wiring harness conditions normal?	Yes	Go to the next step
4		No	Repair the wiring harnesses.
5	Inspect the spark plug conditions. (See SPARK PLUG INSPECTION [L5] .) Is spark plug wet, covered with carbon or grayish white?	Yes	Spark plug is wet or covered with carbon: Inspect for fuel leakage from fuel injector. Spark plug is grayish white: Inspect the fuel injector for clogging
5		No	Install the spark plugs on original cylinders Go to the next step.
6	Visually inspect the CKP sensor and teeth of crankshaft pulley. Are the CKP sensor and teeth of crankshaft pulley normal?	Yes	Go to the next step
6		No	Replace the malfunctioning part.
7	Attempt to start the engine at part throttle. Does the engine run smoothly at part throttle?	Yes	Inspect the electronic throttle control system operation. (See ENGINE CONTROL SYSTEM OPERATION INSPECTION [L5] .)
7		No	Go to the next step.
8	Inspect the fuel line pressure (See FUEL LINE PRESSURE INSPECTION [L5] .) Is the fuel line pressure correct?	Yes	Go to the next step.
8		No	Zero or low: Inspect the fuel pump relay and the fuel pump circuit. Inspect the fuel line for clogging If there is no malfunction, replace the fuel pump unit (See FUEL PUMP UNIT REMOVAL/INSTALLATION [L5] .) High: Replace the fuel pump unit. (See FUEL PUMP UNIT REMOVAL/INSTALLATION [L5] .)
9	Is the fuel line pressure held after ignition is off? (See FUEL LINE PRESSURE INSPECTION [L5] .)	Yes	Go to the next step.
9		No	Inspect the fuel injector. (See FUEL INJECTOR INSPECTION [L5] .) If the fuel injector is normal, replace the fuel pump unit. (See FUEL PUMP UNIT REMOVAL/INSTALLATION [L5] .)
10	Disconnect the vacuum hose from purge solenoid valve and plug opening end of vacuum hose Start engine Is the starting condition improved?	Yes	Inspect if the purge solenoid valve is stuck open.
10		No	Go to the next step.
11	Inspect the MAF sensor for following: Contamination MAF sensor terminal B voltage (ground circuit) Is there any contamination?	Yes	Repair or replace the malfunctioning part
11		No	Go to the next step
12	Visually inspect the exhaust system part Is there any deformed exhaust system part?	Yes	Replace the suspected part.
12		No	Go to the next step.
13	Inspect the engine condition while tapping the EGR valve housing Does the engine condition improve?	Yes	Replace the EGR valve. (See EGR VALVE REMOVAL/INSTALLATION [L5] .)
13		No	Go to the next step.
14	Inspect the starting system. (See STARTER INSPECTION [L5] .) Is the starting system normal?	Yes	Inspect for loose connectors or poor terminal contact. If there is no malfunction, remove the EGR valve and visually inspect for a mechanically stuck EGR valve.
14		No	Repair or replace components as required.
15	Verify test results. If normal, return to the diagnostic index to service any additional symptoms. (See SYMPTOM DIAGNOSTIC INDEX [L5] .) If a malfunction remains, inspect the related Service Bulletins and/or On-line Repair Information and perform repair or diagnosis. If the vehicle is repaired, troubleshooting is completed. If the vehicle is not repaired or additional diagnostic information is not available, reprogram the PCM if a later calibration is available. Retest.