Mazda Mazda6 - Page 336

F2–184
TROUBLESHOOTING
NO.7 SLOW RETURN TO IDLE
A6E408018881209
Diagnostic Procedure
7 SLOW RETURN TO IDLE
DESCRIPTION
• Engine takes more time than normal to return to idle speed.
• Engine speed continues at fast idle after warm-up.
POSSIBLE
CAUSE
• Thermostat is stuck open
• Fuel injection timing is incorrect
• Erratic signal from CKP sensor
• Erratic signal from CMP sensor
• ECT sensor or related circuit malfunction
• Accelerator position sensor or related circuit malfunction
• Idle switch or related circuit malfunction
• MAF/IAT sensor or related circuit malfunction
• Fuel pressure sensor or related circuit malfunction
• Incorrect adjustment accelerator pedal position sensor and/or idle switch
• Incorrect idle speed
• Excessive fuel pressure
• Supply pump malfunction
• Suction control valve malfunction (built-in supply pump)
• Fuel pressure limiter malfunction (built-in common rail)
• Fuel injector malfunction (incorrect fuel regulate pressure)
• Neutral switch or related circuit malfunction
• IDM or related circuit malfunction
Warning
The following troubleshooting flow chart contains the fuel system diagnosis and repair
procedures. Read the following warnings before performing the fuel system services:
• 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 injury or death
and damage. Fuel can also irritate skin and eyes. To prevent this, always complete “BEFORE
REPAIR PROCEDURE” and “AFTER REPAIR PROCEDURE” described in this manual.
STEP INSPECTION RESULTS ACTION
1 Connect WDS or equivalent to DLC-2.
Turn engine switch to ON.
Retrieve any DTC.
Is DTC displayed?
Yes DTC is displayed:
Go to appropriate DTC test.
Communication error message is displayed:
Inspect for following:
• Open circuit between PCM control relay and PCM
terminal 53 or 79
• Open circuit PCM control relay and PCM terminal
69
• PCM control relay stuck open
• Open or poor GND circuit (PCM terminal 65, 85,
103 or 104)
• Poor connection vehicle body GND
No No DTC is displayed:
Go to next step.
2 Access ECT PID.
Start and warm-up engine to normal operating
temperature.
Is ECT PID reading between 82—112 °C {180—
233 °F}?
Yes Go to next step.
No ECT PID is higher than 112 °C {233 °F}:
Go to symptom troubleshooting “NO.17 COOLING
SYSTEM CONCERNS-OVERHEATING”.
ECT PID is less than 82 °C {180 °F}:
Go to symptom troubleshooting “NO.18 COOLING
SYSTEM CONCERNS-RUNS COLD”.