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Diagnostic procedure

WARNING: This page is about a different car, the 2005 Mazda 6. However, it is still accessible from the selected car via links, so may be relevant.
NO. 12 LACK/LOSS OF POWER - ACCELERATION/CRUISE DIAGNOSTIC PROCEDURE

STEP INSPECTION RESULTS ACTION
1 Verify the following:
  • Vacuum connection
  • Air cleaner element
  • No air leakage from intake-air system
  • No restriction of intake-air system
  • Proper sealing of intake manifold and components attached to intake manifold; such as EGR valve
  • Fuel quality (e.g. proper octane, contamination, winter/summer blend)

Are all items normal?		 Yes Go to the next step.
No Service if necessary.
Repeat Step 1.
2 Connect WDS or equivalent to DLC-2.
Turn ignition switch to ON position (Engine off).
Retrieve any DTCs.
Are there any DTCs displayed?		 Yes DTC is displayed: 
Go to appropriate DTC test.
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 ".
No Go to the next step.
4 Connect WDS or equivalent to DLC-2.
Access APP1, APP2, RPM, MAF, TP_REL and VSS PIDs.
Drive vehicle while monitoring PIDs.
Are PIDs within specifications?
(See PCM INSPECTION .)		 Yes Go to the next step.
No APP1, APP2 PIDs: 
Inspect if output signal accelerator position sensor changes smoothly.
RPM PID: 
Inspect CKP sensor and related wiring harness for vibration or intermittent open/short circuit or both.
MAF PID: 
Inspect for intermittent open circuit of MAF sensor and related wiring harness.
TP_REL PID: 
Inspect if output signal TP sensor changes smoothly.
VSS PID: 
Inspect for intermittent open circuit of VSS and related wiring harness.
5 Visually inspect CKP sensor and teeth of crankshaft pulley.
Are CKP sensor and teeth of crankshaft pulley normal?		 Yes Go to the next step.
No Replace malfunctioning parts.
6 Inspect spark plug condition.
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.
Inspect spark plug and high-tension lead.(1)
Inspect spark plug and ignition coil related harness.(2)
Spark plug is grayish white: 
Inspect for clogged fuel injector.
No Install spark plugs on original cylinders.
Go to the next step.
7 Remove and shake PCV valve.
Does PCV valve rattle		 Yes Go to the next step.
No Replace PCV valve.
8 Perform electronic throttle control system operation inspection.
(See ELECTRONIC THROTTLE CONTROL SYSTEM INSPECTION .)
Does electronic throttle control system work properly		 Yes Go to the next step.
No Repair or replace malfunctioning part according to electronic throttle control system operation inspection results.
9 Inspect for restriction in exhaust system.
Is there any restriction?		 Yes Inspect exhaust system.
No Go to the next step.
10 Install fuel pressure gauge between fuel pipe and fuel distributor.
Short check connector terminal F/P to body GND using a jumper wire.
Turn ignition switch to ON position.
Is fuel line pressure correct with ignition switch to ON position?
(See FUEL LINE PRESSURE INSPECTION .)		 Yes Go to the next step.
No Zero or low: 
Inspect fuel pump relay and fuel pump circuit.
Inspect for clogged fuel line.
If okay, replace fuel pump unit.
High: 
Replace fuel pump unit.
11 Inspect Variable tumble system operation.
(See VARIABLE TUMBLE SYSTEM OPERATION INSPECTION .)
Does Variable tumble system work properly?		 Yes Go to the next step.
No Repair or replace malfunctioning parts.
12 Inspect Variable intake air system operation.
(See VARIABLE INTAKE AIR SYSTEM OPERATION INSPECTION .)
Does Variable intake air system work properly		 Yes Go to the next step.
No Repair or replace malfunctioning parts.
13
NOTE:
  • The following test is for engine stalling with A/C on concern. If other symptoms exist, go to the next step.
Connect pressure gauge to A/C low and high side pressure lines.Turn A/C on and measure low side and high side pressures.Are pressures within specifications?(See REFRIGERANT PRESSURE CHECK .)		 Yes Go to the next step.
No If A/C is always on, go to symptom troubleshooting "NO. 24 A/C IS ALWAYS ON OR A/C COMPRESSOR RUNS CONTINUOUSLY ".
For other symptoms, inspect the following:
  • Refrigerant charging amount
  • Condenser fan operation
14 Inspect for A/C cut-off operation.
(See A/C Cut-off Control System Inspection .)
Does A/C cut-off work properly?		 Yes Go to the next step.
No Inspect A/C cut-off system components.
15 Disconnect vacuum hose between purge solenoid valve and intake manifold from purge solenoid valve side.
Plug opening end of vacuum hose.
Drive vehicle.
Does engine condition improve		 Yes Inspect if purge solenoid valve is stuck open mechanically.
Inspect EVAP control system.
No Go to the next step.
16 Visually inspect CMP sensor and projections of camshaft pulley.
Are CMP sensor and projections of camshaft pulley normal?		 Yes Go to the next step.
No Replace malfunctioning parts.
17 Inspect EGR system.
(See EGR Control System Inspection .)
Is EGR system normal?		 Yes Go to the next step.
No Replace malfunctioning parts according to EGR control system operation inspection results.
18 Inspect variable valve timing control system operation.
(See VARIABLE VALVE TIMING CONTROL SYSTEM OPERATION INSPECTION .)
Does variable valve timing control system work properly?		 Yes Go to the next step.
No Repair or replace malfunctioning parts according to variable valve timing control system inspection results.
19 Is engine compression correct Yes Inspect the following:
  • Valve timing
  • Internal transaxle components (ATX)
  • Clutch (MTX)
  • Brake system for dragging
No Inspect for cause.
20 Verify test results.
  • If okay, return to diagnostic index to service any additional symptoms.
  • If malfunction remains, inspect related Service Bulletins and/or On-line Repair Information and perform repair or diagnosis.
    • If vehicle is repaired, troubleshooting completed.
    • If vehicle is not repaired or additional diagnostic information is not available, reprogram PCM if later calibration is available. Retest.
(1) California emission regulation applicable ATX model
(2) Except for California emission regulation applicable ATX model
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