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HOMESERVICE MANUALSMAZDA20113 MAZDASPEED, 2.3 3REPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 629 (ENGINE CONTROL SYSTEM)PCM INSPECTIONINSPECTION USING AN OSCILLOSCOPE (REFERENCE)
2011 Mazda 3 Mazdaspeed, 2.3 3

Inspection Using An Oscilloscope (Reference)

2011 Mazda 3 Mazdaspeed, 2.3 3SECTION Inspection Using An Oscilloscope (Reference)
WARNING: This page is about a different car, the 2011 Mazda RX-8. However, it is still accessible from the selected car via links, so may be relevant.
NOTE:
  • The duty ratio for the wave pattern can vary with the control conditions. Therefore determine comprehensively where the malfunction occurs among the input systems, output systems, and the PCM.

Throttle control (+) 

Fig 1: View Of Throttle Control (+) Wave Pattern
G05981104Courtesy of MAZDA MOTORS CORP.
  • Terminal connected: 2A (+)-Negative battery terminal
  • Oscilloscope setting: 5 V/DIV (Y): 0.4 ms/DIV (X), DC range
  • Measurement condition: IG SW ON

Throttle control (-) 

Fig 2: View Of Throttle Control (-) Wave Pattern
G05981105Courtesy of MAZDA MOTORS CORP.
  • Terminal connected: 2B (+)-Negative battery terminal
  • Oscilloscope setting: 5 V/DIV (Y): 1 ms/DIV (X), DC range
  • Measurement condition: As soon as the accelerator pedal is fully released from the fully depressed position while the ignition switch is at ON (engine off.)

Purge control 

Fig 3: View Of Purge Control Wave Pattern
G05981106Courtesy of MAZDA MOTORS CORP.
  • Terminal connected: 2C (+)-Negative battery terminal
  • Oscilloscope setting: 5 V/DIV (Y): 20 ms/DIV (X), DC range
  • Measurement condition: Idling after warm-up (no load)
NOTE:
  • Purge control might not be activated depending on the engine conditions.

APV motor control (+) 

Fig 4: View Of APV Motor Control (-) Wave Pattern
G05981107Courtesy of MAZDA MOTORS CORP.
  • Terminal connected: 2D (+)-Negative battery terminal
  • Oscilloscope setting: 5 V/DIV (Y): 20 ms/DIV (X), DC range
  • Measurement condition: High engine speed after warm-up

OCV control 

Fig 5: View Of OCV Control Wave Pattern
G05981108Courtesy of MAZDA MOTORS CORP.
  • Terminal connected: 2E (+)-Negative battery terminal
  • Oscilloscope setting: 5 V/DIV (Y): 2 ms/DIV (X), DC range
  • Measurement condition: Idling after warm-up (no load)

APV motor control (-) 

Fig 6: View Of APV Motor Control (-) Wave Pattern
G05981107Courtesy of MAZDA MOTORS CORP.
  • Terminal connected: 2F (+)-Negative battery terminal
  • Oscilloscope setting: 5 V/DIV (Y): 20 ms/DIV (X), DC range
  • Measurement condition: High engine speed after warm-up

Eccentric shaft position sensor 

Fig 7: Eccentric Shaft Position Sensor Wave Pattern
G05981110Courtesy of MAZDA MOTORS CORP.
  • Terminal connected: 2AG (+)-Negative battery terminal
  • Oscilloscope setting: 2 V/DIV (Y): 5 ms/DIV (X), DC range
  • Measurement condition: Idling after warm-up (no load)

Field coil control (Generator) 

Fig 8: View Of Field Coil Control (Generator) Wave Pattern
G05981111Courtesy of MAZDA MOTORS CORP.
  • Terminal connected: 2AI (+)-Negative battery terminal
  • Oscilloscope setting: 0.5 V/DIV (Y): 1 ms/DIV (X), DC range
  • Measurement condition: Idling after warm-up (no load)

Generator output voltage 

Fig 9: View Of Generator Output Voltage Wave Pattern
G05981112Courtesy of MAZDA MOTORS CORP.
  • Terminal connected: 2AJ (+)-Negative battery terminal
  • Oscilloscope setting: 2 V/DIV (Y): 2 ms/DIV (X), DC range
  • Measurement condition: Idling after warm-up (no load)

Ignition coil (L/F, L/R, T/F, T/R) 

Fig 10: Ignition Coil (L/F, L/R, T/F, T/R) Wave Pattern
G05981113Courtesy of MAZDA MOTORS CORP.
  • Terminal connected:

    • L/F: 2AX (+) -Negative battery terminal

    L/R: 2AT (+) -Negative battery terminal

    T/F: 2BA (+) -Negative battery terminal

    T/R: 2AW (+) -Negative battery terminal

  • Oscilloscope setting: 2 V/DIV (Y): 10 ms/DIV (X), DC range
  • Measurement condition: Idling after warm-up (no load)

Fuel injector (FS, RS) control 

Fig 11: Fuel Injector (FS, RS) Control Wave Pattern
G05981114Courtesy of MAZDA MOTORS CORP.
  • Terminal connected:

    • FS: 2BC (+)-Negative battery terminal

    RS: 2AZ (+)-Negative battery terminal

  • Oscilloscope setting: 5 V/DIV (Y): 5 ms/DIV (X), DC range
  • Measurement condition: Racing after warm-up (no load)

Fuel injector (FP, RP) control 

Fig 12: View Of Fuel Injector (FP, RP) Control Wave Pattern
G05981115Courtesy of MAZDA MOTORS CORP.
  • Terminal connected:

    • FP: 2BB (+)-Negative battery terminal

    RP: 2BD (+)-Negative battery terminal

  • Oscilloscope setting: 5 V/DIV (Y): 10 ms/DIV (X), DC range
  • Measurement condition: Idling after warm-up (no load)
  • Terminal connected:

    • FP: 2BB (+)-Negative battery terminal

    RP: 2BD (+)-Negative battery terminal

  • Oscilloscope setting: 5 V/DIV (Y): 10 ms/DIV (X), DC range
  • Measurement condition: Cranking while the engine is cold. (ECT: Approx. 20 °C {68 °F})
Fig 13: View Of Fuel Injector (FP, RP) Control Wave Pattern
G05981116Courtesy of MAZDA MOTORS CORP.

HO2S heater control 

Fig 14: View Of HO2S Heater Control Wave Pattern
G05981117Courtesy of MAZDA MOTORS CORP.
  • Terminal connected: 2BE (+)-Negative battery terminal
  • Oscilloscope setting: 5 V/DIV (Y): 100 ms/DIV (X), DC range
  • Measurement condition: Idling after warm-up (no load)

A/F sensor heater control 

Fig 15: A/F Sensor Heater Control Wave Pattern
G05981118Courtesy of MAZDA MOTORS CORP.
  • Terminal connected: 2BG (+)-Negative battery terminal
  • Oscilloscope setting: 5 V/DIV (Y): 50 ms/DIV (X), DC range
  • Measurement condition: Idling after warm-up (no load)
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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.