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Home >> Mazda >> 2021 >> 3 Base >> Repair and Diagnosis >> Engine Performance >> System >> Symptom Troubleshooting - Engine (VINS 7, L, M) >> Fast Idle/Runs On >> Notes
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Fast Idle/Runs On: Notes

FAST IDLE/RUNS ON (VINs 7, L, M), US) DESCRIPTION AND POSSIBLE CAUSE

Troubleshooting item Fast idle/runs on
Description
  • Engine speed continues at fast idle after warm-up.
  • Engine runs after ignition is switched off.
Possible cause
  • Cooling system malfunction
  • PCM DTC is stored
  • Accelerator pedal stuck depressed
  • Erratic signal to PCM
  • APP sensor or related circuit malfunction
  • Clutch stroke sensor or related circuit malfunction (MTX)
  • Communication error between TCM and PCM (ATX)
  • ECT sensor No. 1 or related circuit malfunction
  • ECT sensor No. 2 or related circuit malfunction
  • A/F sensor or related circuit malfunction
  • HO2S or related circuit malfunction
  • Improper load signal input
  • Improper A/C request signal
  • Improper operation of drive-by-wire control system
  • Throttle body malfunction
  • Fuel injector malfunction
  • Spill valve control solenoid valve malfunction (built-into high pressure fuel pump)
  • Air leakage from intake-air system
  • Injector driver (built-into PCM) 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.
  • Highly pressurized fuel may spray out if the fuel line is cut. Due to the following dangers occurring with a fuel spray, always complete the "Fuel Line Safety Procedure" to prevent the fuel from spraying. (See BEFORE SERVICE PRECAUTION [(VIN M)] .) (See BEFORE SERVICE PRECAUTION [(VIN 7 & VIN L)] .)
  • Fuel may cause irritation if it comes in contact with skin and eyes.
  • If fuel ignites and causes a fire, it may lead to serious injury or death, and damage to property and facilities.
CAUTION:
  • Disconnecting/connecting the quick release connector without cleaning it may possibly cause damage to the fuel pipe and quick release connector. Always clean the quick release connector joint area before disconnecting/connecting, and make sure that it is free of foreign material.
System wiring diagram
  • Not applicable
Connector diagram
  • Not applicable
CAUTION:
  • Verify the malfunction symptom according to not only the PID value but also the symptom troubleshooting.