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	Verify the following: Vacuum connection Restriction in the intake air system (such as the air cleaner element, fresh air duct) No air leakage from the intake air system No restriction of the intake air system Proper sealing of the intake manifold and components attached to the intake manifold, such as the EGR valve Fuel quality (such as proper octane, contamination, winter/summer blend) Are all the 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 the engine overheating?	Yes	Go to the symptom troubleshooting "No. 17 Cooling system concerns - Overheating". (See NO. 17 COOLING SYSTEM CONCERNS-OVERHEATING [L5] .)
3	Is the engine overheating?	No	Go to the next step.
4	Connect the M-MDS to the DLC-2 Access the APP1, APP2, RPM, MAF, TP REL, IAT and VSS PIDs. Drive the vehicle while monitoring PIDs. Are the PIDs within specifications? (See PCM INSPECTION [L5] .)	Yes	Go to the next step.
4		No	APP1, APP2 PIDs: Inspect if the output signal APP sensor changes smoothly. RPM PID: Inspect the CKP sensor and the related wiring harness for vibration or intermittent open/short circuit or both. MAF PID: Inspect for an intermittent open circuit of MAF sensor and the related wiring harness. TP_REL PID: Inspect if the output signal TP sensor changes smoothly. IAT PID: Inspect for air suction in the intake air system. If normal, inspect for an intermittent short circuit in the IAT sensor and related wiring harnesses. VSS PID: Inspect for an intermittent open circuit in the VSS and related wiring harness.
5	Visually inspect the CKP sensor and teeth of the crankshaft pulley. (See CRANKSHAFT POSITION (CKP) SENSOR INSPECTION [L5] .) Are the CKP sensor and the teeth of the crankshaft pulley normal?	Yes	Go to the next step.
5		No	Replace the malfunctioning part.
6	Inspect the spark plug condition. (See SPARK PLUG INSPECTION [L5] .) Are the spark plugs wet, covered with carbon or grayish white?	Yes	Spark plug is wet or covered with carbon: Inspect the fuel injector for fuel leakage. Inspect spark plug and high-tension lead. Spark plug is grayish white: Inspect the fuel injector for clogging.
6		No	Install the spark plugs on original cylinders. Go to the next step.
7	Remove and shake the PCV valve Does the PCV valve rattle?	Yes	Go to the next step.
7	Remove and shake the PCV valve Does the PCV valve rattle?	No	Replace the PCV valve. (See POSITIVE CRANKCASE VENTILATION (PCV) VALVE REMOVAL/INSTALLATION [L5] .)
8	Perform electronic throttle control system operation inspection. (See ENGINE CONTROL SYSTEM OPERATION INSPECTION [L5] ) Does the electronic throttle control system function properly?	Yes	Go to the next step.
8		No	Repair or replace the malfunctioning part according to the electronic throttle control system operation inspection results
9	Visually inspect for deformed exhaust system parts. Are there any deformed exhaust system parts?	Yes	Replace the suspected part.
9		No	Go to the next step.
10	Inspect the fuel line pressure. (See FUEL LINE PRESSURE INSPECTION [L5] .) Is the fuel line pressure correct?	Yes	Go to the next step
10		No	Zero or low: Inspect the fuel pump relay and 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] .)
11	Inspect the variable tumble control operation (See ENGINE CONTROL SYSTEM OPERATION INSPECTION [L5] ) Does the variable tumble control function properly?	Yes	Go to the next step
11		No	Repair or replace the malfunctioning part.
12	Inspect the variable intake air control operation. (See ENGINE CONTROL SYSTEM OPERATION INSPECTION [L5] ) Does the VIS function properly?	Yes	Go to the next step.
12		No	Repair or replace the malfunctioning part.
13	NOTE: The following test is for an engine stalling with the A/C on concern If other symptoms exist, go to the next step Connect the pressure gauge to the A/C low and high side pressure linesTurn the A/C on and measure the low side and high side pressuresAre the pressures within specifications?(See REFRIGERANT PRESSURE CHECK .)	Yes	Go to the next step
13		No	If the A/C is always on, go to the symptom troubleshooting "No. 24 A/C is always on or A/C compressor runs continuously". (See NO. 24 A/C IS ALWAYS ON OR A/C COMPRESSOR RUNS CONTINUOUSLY [L5] .) For other symptoms, inspect the following Refrigerant charging amount Condenser fan operation
14	Inspect the A/C cut-off operation. (See ENGINE CONTROL SYSTEM OPERATION INSPECTION [L5] .) Does the A/C cut-off function properly?	Yes	Go to the next step.
14		No	Inspect the A/C cut-off system components
15	Disconnect the vacuum hose between the purge solenoid valve and the intake manifold from the purge solenoid valve side. Plug the open end of the vacuum hose. Drive the vehicle Does the engine condition improve?	Yes	Inspect if the purge solenoid valve is stuck open mechanically. Inspect the evaporative emission control system
15		No	Go to the next step
16	Visually inspect the CMP sensor and teeth of the camshaft. (See CAMSHAFT POSITION (CMP) SENSOR INSPECTION [L5] .) Are the CMP sensor and teeth of the camshaft normal?	Yes	Go to the next step
16		No	Replace the malfunctioning part
17	Inspect EGR system (See ENGINE CONTROL SYSTEM OPERATION INSPECTION [L5] .) Is the EGR system normal?	Yes	Go to the next step.
17		No	Replace the malfunctioning part according to the EGR control system operation inspection results.
18	Inspect the variable valve timing control system operation. (See ENGINE CONTROL SYSTEM OPERATION INSPECTION [L5] .) Does the variable valve timing control system function properly?	Yes	Go to the next step.
18		No	Repair or replace the malfunctioning part according to the variable valve timing control system inspection results.
19	Is the engine compression correct? (See COMPRESSION INSPECTION [L5] .)	Yes	Inspect the following: Valve timing Internal transaxle components (ATX) Clutch (MTX) Brake system for dragging
19		No	Inspect for cause.
20	Verify test results. If normal, return to the diagnostic index to service any additional symptoms. (See SYMPTOM DIAGNOSTIC INDEX [L5] .) If the 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.