Safety Warning

DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.

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HOMESERVICE MANUALSMAZDA20113 MAZDASPEED, 2.3 3REPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT VARIANT/TRIMSECTION 3 (ENGINE CONTROL SYSTEM [LF, L5])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 variant/trim than selected.

Cooling fan control

PCM terminals

1 R(+)-body ground(-)

Oscilloscope setting

5 V/DIV (Y), 20 ms/DIV (X), DC range

Vehicle condition

Idle after warm up

Fig 1: Cooling Fan Control Signal Waveform
Courtesy of MAZDA MOTORS CORP.

APP sensor No. 2 signal

Accelerator pedal released

Fig 2: APP Sensor (No. 2) Signal Waveform (Released)

Courtesy of MAZDA MOTORS CORP.

Accelerator pedal depressed

PCM terminals

1X(+)-body ground(-)

Oscilloscope setting

2.5 V/DIV (Y), 2 ms/DIV (X), DC range

Vehicle condition

Switch the ignition to ON.

Fig 3: APP Sensor (No. 2) Signal Waveform (Depressed)
Courtesy of MAZDA MOTORS CORP.

Purge control

PCM terminals

1BA(+)-body ground(-)

Oscilloscope setting

10 V/DIV (Y), 20 ms/DIV (X), DC range

Vehicle condition

Idle after warm up

Fig 4: Purge Control Signal Waveform
Courtesy of MAZDA MOTORS CORP.

A/F sensor heater control

PCM terminals

2A(+)-body ground(-)

Oscilloscope setting

5 V/DIV (Y), 200 ms/DIV (X), DC range

Vehicle condition

Idle (immediately after starting the engine)

Fig 5: A/F Sensor Heater Control Signal Waveform
Courtesy of MAZDA MOTORS CORP.

HO2S heater control

PCM terminals

2B(+)-body ground(-)

Oscilloscope setting

5 V/DIV (Y), 1 s/DIV (X), DC range

Vehicle condition

Idle (immediately after starting the engine)

Fig 6: HO2S Heater Control Signal Waveform
Courtesy of MAZDA MOTORS CORP.

OCV control signal

PCM terminals

2E(+)-body ground(-)

Oscilloscope setting

2 V/DIV (Y), 0.8 ms/DIV (X), DC range

Vehicle condition

Idle after warm up

Fig 7: OCV Control Signal Waveform
Courtesy of MAZDA MOTORS CORP.

CMP signal

PCM terminals

2S(+)-body ground(-)

Oscilloscope setting

1 V/DIV (Y), 25 ms/DIV (X), DC range

Vehicle condition

Fig 8: CMP Signal Waveform

Courtesy of MAZDA MOTORS CORP.

Idle after warm up

CKP signal

PCM terminals

2W(+)-body ground(-)

Oscilloscope setting

1 V/DIV (Y), 5 ms/DIV (X), DC range

Vehicle condition

Idle after warm up

Fig 9: CKP Signal Waveform
Courtesy of MAZDA MOTORS CORP.

IGT1, IGT2, IGT3, IGT4 control

PCM terminals

IGT1 (ignition coil No. 1): 2G(+)-body ground(-)
IGT2 (ignition coil No. 2): 2K(+)-body ground(-)
IGT3 (ignition coil No. 3): 2L(+)-body ground(-)
IGT4 (ignition coil No. 4): 2H(+)-body ground(-)

Oscilloscope setting

1 V/DIV (Y), 50 ms/DIV (X), DC range

Vehicle condition

Idle after warm up

Fig 10: IGT1, IGT2, IGT3, IGT4 Control Signal Waveform
Courtesy of MAZDA MOTORS CORP.

Generator field coil control

PCM terminals

2AA(+)-body ground(-)

Oscilloscope setting

0.5 V/DIV (Y), 2 ms/DIV (X), DC range

Vehicle condition

Idle after warm up

Fig 11: Generator Field Coil Control Signal Waveform
Courtesy of MAZDA MOTORS CORP.

Generator output voltage

PCM terminals

2AF(+)-body ground(-)

Oscilloscope setting

2 V/DIV (Y), 2 ms/DIV (X), DC range

Vehicle condition

Idle after warm up

Fig 12: Generator Output Voltage Signal Waveform
Courtesy of MAZDA MOTORS CORP.

Fuel injection (#1, #2, #3, #4) control

PCM terminals

Fuel Injection No. 1: 2BB(+)-body ground(-)
Fuel Injection No. 2: 2BC(+)-body ground(-)
Fuel Injection No. 3: 2BD(+)-body ground(-)
Fuel Injection No. 4: 2AZ(+)-body ground(-)

Oscilloscope setting

10 V/DIV (Y), 25 ms/DIV (X), DC range

Vehicle condition

Idle after warm up

Fig 13: Fuel Injection (1, 2, 3, 4) Control Signal Waveform
Courtesy of MAZDA MOTORS CORP.

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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.