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Home >> Mazda >> 2006 >> 6 s, 4D Wagon, Automatic >> Repair and Diagnosis >> External Pages >> Different variant/trim >> Section 10 (Symptom Troubleshooting [Engine Control System L3 With TC)) >> No. 8 Engine Runs Rough/Rolling Idle >> Diagnostic procedure

Diagnostic procedure

WARNING: This page is about a different variant/trim than selected.
DIAGNOSTIC PROCEDURE

STEP INSPECTION RESULTS ACTION
1 Inspect for the following:
  • Fuel quality (proper octane, contamination, winter/summer blend)
  • Intake-air system restriction or leakage
  • Electrical connectors connection
  • Fuel leakage in fuel system
  • Vacuum leakage

Are all items normal?
Yes Go to the next step.
No Service if necessary.
Repeat Step 1.
2 Perform the self-test function using the WDS or equivalent.
Turn the ignition switch to the ON position.
Retrieve any DTCs.
Is a DTC displayed?
Yes DTC is displayed: 
Go to the appropriate DTC test.
(See DTC TABLE ).
No No DTC is displayed: 
Go to the next step.
3 Access the ECT PID.
Verify that the ECT PID is less than 116°C {241°F}  during driving.
Is the ECT PID less than specified?
Yes Go to the next step.
No The cause of this concern could be from the cooling system overheating.
Perform the symptom troubleshooting "NO. 17 COOLING SYSTEM CONCERNS - OVERHEATING."
(See NO. 17 COOLING SYSTEM CONCERNS-OVERHEATING ).
4 Perform the A/C Cut-off Operation Inspection.
(See A/C CUT-OFF CONTROL SYSTEM INSPECTION ).
Does the A/C Cut-off Operation work properly?
Yes Go to the next step.
No Repair or replace the malfunctioning parts according to inspection results.
5 Perform the EGR system operation inspection.
(See EGR CONTROL SYSTEM INSPECTION ).
Does the EGR system operate properly?
Yes Go to the next step.
No Inspect or replace the malfunctioning parts, according to the inspection results.
6 Perform the TP sweep inspection.
(See THROTTLE POSITION (TP) SWEEP INSPECTION ).
Does the electronic throttle control system work properly?
Yes Visually inspect the throttle body (damaged/scratching). If normal, go to the next step.
No Inspect or replace the malfunctioning parts, according the to inspection results.
7 Perform the Purge Control System Operation inspection.
(See PURGE CONTROL SYSTEM INSPECTION ).
Does the purge solenoid valve work properly?
Yes Go to the next step.
No Inspect or replace the malfunctioning parts, according to the inspection results.
8 Perform the Variable Valve Timing Control System Operation Inspection.
(See VARIABLE VALVE TIMING CONTROL SYSTEM OPERATION INSPECTION ).
Does the variable valve timing control system work properly?
Yes Go to the next step.
No Inspect or replace the malfunctioning parts, according to the inspection results.
9 Inspect CMP and CKP sensor for the following;

Is there any malfunction detected?
Yes Repair or replace the malfunctioning part according to the inspection results.
No Go to the next step.
10 Connect the WDS or equivalent to the DLC-2.
Access and monitor following PIDs using the data monitor function.
  • ACSW
  • APP
  • ECT
  • MAF
  • MAP
  • CPP (PCM terminal 1H)
  • PNP (PCM terminal 1W)
  • PSP (PCM terminal 1Z)

Do the PIDs indicate the correct values under trouble condition?
(See USING THE WDS OR EQUIVALENT ).
Yes Go to the next step.
No Inspect and repair or replace suspected parts and the related harnesses.
If the malfunction remains, perform the intermittent concern troubleshooting procedure.
(See INTERMITTENT CONCERN TROUBLESHOOTING ).
11 Inspect for restriction in the exhaust system and three-way catalytic converter (TWC).
Is there any restriction?
Yes Replace the malfunctioning part.
No Go to the next step.
12 Remove and shake the PCV valve.
Does the PCV valve rattle?
Yes Go to the next step.
No Replace the PCV valve.
13 Perform the spark test.
(See SPARK TEST ).
Is a strong blue spark visible at each cylinder?
Yes Go to the next step.
No Inspect or replace the malfunctioning parts, according to the inspection results.
14 Access and monitor the FUEL_PRES PID.
Is the FUEL_PRES PID value within the specification?
(See USING THE WDS OR EQUIVALENT ).
Yes Go to Step 18.
No Go to the next step.
15 Is the vehicle accelerate performance normally? Yes Go to the next step.
No Go to Step 17.
16 Inspect the fuel pressure sensor.
(See FUEL PRESSURE SENSOR INSPECTION ).
Is the fuel pressure sensor normal?
Yes Go to Step 18.
No Replace the delivery pipe.
17 Replace the high pressure fuel pump.
Monitor FUEL_PRES PID.
Is the FUEL_PRES PID value within the specified?
(See USING THE WDS OR EQUIVALENT ).
Yes Troubleshooting is completed.
Go to Step 21.
No Go to the next step.
18 Connect the fuel pressure gauge between the fuel pump and the high pressure fuel pump.
Measure the fuel pressure line of the low pressure side.
(See FUEL LINE PRESSURE INSPECTION ).
Is the fuel pressure within the specification?
Yes Go to the next step.
No Inspect for the following:
  • Fuel line restriction
  • Fuel filter clogging

If normal replace the fuel pump.
19 Inspect fuel injector for each cylinder.
(See FUEL INJECTOR INSPECTION ).
Are the fuel injectors normal?
Yes Go to the next step.
No Replace the suspected fuel injector.
(See FUEL INJECTOR REMOVAL/INSTALLATION ).
20 Measure the compression pressure for each cylinder.
(See COMPRESSION INSPECTION ).
Are compression pressures within the specification?
Yes Replace the injector driver module.
If the problem remains, overhaul the engine.
No Inspect for the following:
  • Damaged valve seat
  • Worn valve stem and valve guide
  • Worn or stuck piston ring
  • Worn piston, piston ring or cylinder
  • Improper valve timing

Service if necessary.
21 Verify test results.
  • If normal, return to the diagnostic index to service any additional symptoms.
  • If a malfunction remains, inspect the related Service Bulletins and/or On-line Repair Information and perform the 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.