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.
2004 Mazda 3 L4-2.0LFACTORY OEM SERVICE PROCEDURE
Oscilloscope Patterns and Waveforms
INSPECTION USING AN OSCILLOSCOPE (REFERENCE)

Shift Solenoid A signal
PCM Terminals
- 1B (+) - Negative battery terminal (-)
Oscilloscope setting
- 5 V/DIV (Y), 5 ms/DIV (X), DC range
Vehicle condition
- 4GR

Shift solenoid B signal
PCM terminals
- 1C (+) - Negative battery terminal (-)
Oscilloscope setting
- 5 V/DIV (Y), 5 ms/DIV (X), DC range
Vehicle condition
- 1GR

Shift solenoid C signal
PCM terminals
- 1 D (+) - Negative battery terminal (-)
Oscilloscope setting
- 5 V/DIV (Y), 5 ms/DIV (X), DC range
Vehicle condition
- 1GR or 2GR

Pressure control solenoid (+) signal
PCM terminals
- 1G (+) - Negative battery terminal (-)
Oscilloscope setting
- 5 V/DIV (Y), 1 ms/DIV (X), DC range
Vehicle condition
- All of the following conditions are met.
- Ignition switch is turned to the ON position. (engine off)
- P or N position
- CTP

Pressure control solenoid (-) signal
PCM terminals
- 1 H (+) - Negative battery terminal (-)
Oscilloscope setting
- 200 mV/DIV (Y), 1 ms/DIV (X), DC range
Vehicle condition
- All of the following conditions are met.
- Ignition switch is turned to the ON position. (engine off)
- P or N position
- CTP

Vehicle speed signal (ATX)
PCM terminals
- 1J (+) - Negative battery terminal (-)
Oscilloscope setting
- 1 V/DIV (Y), 2.5 ms/DIV (X), DC range
Vehicle condition
- Vehicle speed is 32 km/h {20 mph}

Vehicle speed signal (MTX)
PCM terminals
- 1J(+) - 1N(-)
Oscilloscope setting
- 1 V/DIV (Y), 10 ms/DIV (X), DC range
Vehicle condition
- Vehicle speed is 10 km/h {6.2 mph}

Input/turbine speed sensor (+) signal
PCM terminals
- 1 M (+) - Negative battery terminal (-)
Oscilloscope setting
- 500 mV/DIV (Y), 1 ms/DIV (X), DC range
Vehicle condition
- Idle after warm-up

Input/turbine speed sensor (-) signal
PCM terminals
- 1Q (+) - Negative battery terminal (-)
Oscilloscope setting
- 500 mV/DIV (Y), 1 ms/DIV (X), DC range
Vehicle condition
- Idle after warm-up

Cooling fan control signals
PCM terminals
- 1W(+) - 1AA(-)
Oscilloscope setting
- 5 V/DIV (Y), 1 ms/DIV (X), DC range
Vehicle condition
- Idle after warm up (engine speed approx. 700 rpm, A/C ON)

APP signal
Accelerator pedal is released

Accelerator pedal is depressed
PCM terminals
- 1AL(+) - 2AA(-)
Oscilloscope setting
- 2.5 V/DIV (Y), 2 ms/DIV (X), DC range
Vehicle condition
- Ignition switch is turned to the ON position. (engine off)

HO2S (front) heater control signal (California emission regulation applicable model)
PCM terminals
- 2G(+) - 2AA(-)
Oscilloscope setting
- 5 V/DIV (Y), 50 ms/DIV (X), DC range
Vehicle condition
- Idle after warm up (engine speed approx. 650 rpm, no load)

HO2S (front) heater control signal (except for California emission regulation applicable model)
PCM terminals
- 2G(+) - 2AA(-)
Oscilloscope setting
- 5 V/DIV (Y), 125 ms/DIV (X), DC range
Vehicle condition
- Idle after warm up (engine speed approx. 650 rpm, no load)

CMP sensor signal
(+)
PCM terminals
- 2U(+) - 2AA(-)
Oscilloscope setting
- 1 V/DIV (Y), 25 ms/DIV (X), DC range
Vehicle condition
- Idle after warm up (engine speed approx. 650 rpm, no load)
(-)

PCM terminals
- 2V(+) - 2AA(-)
Oscilloscope setting
- 1 V/DIV (Y), 25 ms/DIV (X), DC range
Vehicle condition
- Idle after warm up (engine speed approx. 650 rpm, no load)

CKP sensor signal
(+)
PCM terminals
- 2Y(+) - 2AA(-)
Oscilloscope setting
- 2 V/DIV (Y), 10 ms/DIV (X), DC range
Vehicle condition
- Idle after warm up (engine speed approx. 650 rpm, no load)
(-)

PCM terminals
- 2Z(+) - 2AA(-)
Oscilloscope setting
- 2 V/DIV (Y), 10 ms/DIV (X), DC range
Vehicle condition
- Idle after warm up (engine speed approx. 650 rpm, no load)

OCV signal
PCM terminals
- 2AF(+) - 2AA(-)
Oscilloscope setting
- 2.5 V/DIV (Y), 1 ms/DIV (X), DC range
Vehicle condition
- Idle after warm up (engine speed approx. 650 rpm, no load)

HO2S (front) signal (except for California emission regulation applicable model)
PCM terminals
- 2AG(+) - 2AA(-)
Oscilloscope setting
- 0.2 V/DIV (Y), 500 ms/DIV (X), DC range
Vehicle condition
- Idle after warm up (engine speed approx. 650 rpm, no load)

Generator output voltage signal
PCM terminals
- 2AM (+) - 2AA (-)
Oscilloscope setting
- 2 V/DIV (Y), 2.5 ms/DIV (X), DC range
Vehicle condition
- Idle after warm up (engine speed approx. 650 rpm, no load)

Purge control signal
PCM terminals
- 2AN (+) - Negative battery terminal (-)
Oscilloscope setting
- 2 V/DIV (Y), 0.1 s/DIV (X), DC range
Vehicle condition
- Idle after warm-up

Generator field coil control signal
PCM terminals
- 2AQ(+) - 2AA(-)
Oscilloscope setting
- 0.5 V/DIV (Y), 1 ms/DIV (X), DC range
Vehicle condition
- Idle after warm up (engine speed approx. 650 rpm, no load)

Fuel injection control
PCM terminals (California emission regulation applicable model)
- Fuel injection No.1: 2AW(+) - 1 AZ(-)
- Fuel injection No.2: 2AS(+) - 1 AZ(-)
- Fuel injection No.3: 2AX(+) - 1 AZ(-)
- Fuel injection No.4: 2AT(+) - 1 AZ(-)
PCM terminals (except for California emission regulation applicable model)
- Fuel injection No.1: 2BB(+) - 1 AZ(-)
- Fuel injection No.2: 2BC(+) - 1AZ(-)
- Fuel injection No.3: 2BD(+) - 1AZ(-)
- Fuel injection No.4: 2AZ(+) - 1AZ(-)
Oscilloscope setting
- 10 V/DIV (Y), 25 ms/DIV (X), DC range
Vehicle condition
- Idle after warm up (engine speed approx. 650 rpm, no load)

IGT1, IGT2, IG3, IG4 control signals
PCM terminals (California emission regulation applicable model)
- IGT1 (No.1):2BE(+) - 1BC(-)
- IGT2(No.2):2BF(+) - 1BB(-)
- IGT3(No.3):2BG(+) - 1BB(-)
- IGT4(No.4):2BH(+) - 1BC(-)
PCM terminals (except for California emission regulation applicable model)
- IGT1 (No.1):2BE(+) - 1BG(-)
- IGT2(No.2):2BF(+) - 1BC(-)
- IGT3(No.3):2BG(+) - 1BC(-)
- IGT4(No.4):2BH(+) - 1BG(-)
Oscilloscope setting
- 10 V/DIV (Y), 25 ms/DIV (X), DC range
Vehicle condition
- Idle after warm up (engine speed approx. 650 rpm, no load)
Shift Solenoid A signal
PCM Terminals
- 1B (+) - Negative battery terminal (-)
Oscilloscope setting
- 5 V/DIV (Y), 5 ms/DIV (X), DC range
Vehicle condition
- 4GR
Shift solenoid B signal
PCM terminals
- 1C (+) - Negative battery terminal (-)
Oscilloscope setting
- 5 V/DIV (Y), 5 ms/DIV (X), DC range
Vehicle condition
- 1GR
Shift solenoid C signal
PCM terminals
- 1 D (+) - Negative battery terminal (-)
Oscilloscope setting
- 5 V/DIV (Y), 5 ms/DIV (X), DC range
Vehicle condition
- 1GR or 2GR
Pressure control solenoid (+) signal
PCM terminals
- 1G (+) - Negative battery terminal (-)
Oscilloscope setting
- 5 V/DIV (Y), 1 ms/DIV (X), DC range
Vehicle condition
- All of the following conditions are met.
- Ignition switch is turned to the ON position. (engine off)
- P or N position
- CTP
Pressure control solenoid (-) signal
PCM terminals
- 1 H (+) - Negative battery terminal (-)
Oscilloscope setting
- 200 mV/DIV (Y), 1 ms/DIV (X), DC range
Vehicle condition
- All of the following conditions are met.
- Ignition switch is turned to the ON position. (engine off)
- P or N position
- CTP
Vehicle speed signal (ATX)
PCM terminals
- 1J (+) - Negative battery terminal (-)
Oscilloscope setting
- 1 V/DIV (Y), 2.5 ms/DIV (X), DC range
Vehicle condition
- Vehicle speed is 32 km/h {20 mph}
Vehicle speed signal (MTX)
PCM terminals
- 1J(+) - 1N(-)
Oscilloscope setting
- 1 V/DIV (Y), 10 ms/DIV (X), DC range
Vehicle condition
- Vehicle speed is 10 km/h {6.2 mph}
Input/turbine speed sensor (+) signal
PCM terminals
- 1 M (+) - Negative battery terminal (-)
Oscilloscope setting
- 500 mV/DIV (Y), 1 ms/DIV (X), DC range
Vehicle condition
- Idle after warm-up
Input/turbine speed sensor (-) signal
PCM terminals
- 1Q (+) - Negative battery terminal (-)
Oscilloscope setting
- 500 mV/DIV (Y), 1 ms/DIV (X), DC range
Vehicle condition
- Idle after warm-up
Cooling fan control signals
PCM terminals
- 1W(+) - 1AA(-)
Oscilloscope setting
- 5 V/DIV (Y), 1 ms/DIV (X), DC range
Vehicle condition
- Idle after warm up (engine speed approx. 700 rpm, A/C ON)
APP signal
Accelerator pedal is released
Accelerator pedal is depressed
PCM terminals
- 1AL(+) - 2AA(-)
Oscilloscope setting
- 2.5 V/DIV (Y), 2 ms/DIV (X), DC range
Vehicle condition
- Ignition switch is turned to the ON position. (engine off)
HO2S (front) heater control signal (California emission regulation applicable model)
PCM terminals
- 2G(+) - 2AA(-)
Oscilloscope setting
- 5 V/DIV (Y), 50 ms/DIV (X), DC range
Vehicle condition
- Idle after warm up (engine speed approx. 650 rpm, no load)
HO2S (front) heater control signal (except for California emission regulation applicable model)
PCM terminals
- 2G(+) - 2AA(-)
Oscilloscope setting
- 5 V/DIV (Y), 125 ms/DIV (X), DC range
Vehicle condition
- Idle after warm up (engine speed approx. 650 rpm, no load)
CMP sensor signal
(+)
PCM terminals
- 2U(+) - 2AA(-)
Oscilloscope setting
- 1 V/DIV (Y), 25 ms/DIV (X), DC range
Vehicle condition
- Idle after warm up (engine speed approx. 650 rpm, no load)
(-)
PCM terminals
- 2V(+) - 2AA(-)
Oscilloscope setting
- 1 V/DIV (Y), 25 ms/DIV (X), DC range
Vehicle condition
- Idle after warm up (engine speed approx. 650 rpm, no load)
CKP sensor signal
(+)
PCM terminals
- 2Y(+) - 2AA(-)
Oscilloscope setting
- 2 V/DIV (Y), 10 ms/DIV (X), DC range
Vehicle condition
- Idle after warm up (engine speed approx. 650 rpm, no load)
(-)
PCM terminals
- 2Z(+) - 2AA(-)
Oscilloscope setting
- 2 V/DIV (Y), 10 ms/DIV (X), DC range
Vehicle condition
- Idle after warm up (engine speed approx. 650 rpm, no load)
OCV signal
PCM terminals
- 2AF(+) - 2AA(-)
Oscilloscope setting
- 2.5 V/DIV (Y), 1 ms/DIV (X), DC range
Vehicle condition
- Idle after warm up (engine speed approx. 650 rpm, no load)
HO2S (front) signal (except for California emission regulation applicable model)
PCM terminals
- 2AG(+) - 2AA(-)
Oscilloscope setting
- 0.2 V/DIV (Y), 500 ms/DIV (X), DC range
Vehicle condition
- Idle after warm up (engine speed approx. 650 rpm, no load)
Generator output voltage signal
PCM terminals
- 2AM (+) - 2AA (-)
Oscilloscope setting
- 2 V/DIV (Y), 2.5 ms/DIV (X), DC range
Vehicle condition
- Idle after warm up (engine speed approx. 650 rpm, no load)
Purge control signal
PCM terminals
- 2AN (+) - Negative battery terminal (-)
Oscilloscope setting
- 2 V/DIV (Y), 0.1 s/DIV (X), DC range
Vehicle condition
- Idle after warm-up
Generator field coil control signal
PCM terminals
- 2AQ(+) - 2AA(-)
Oscilloscope setting
- 0.5 V/DIV (Y), 1 ms/DIV (X), DC range
Vehicle condition
- Idle after warm up (engine speed approx. 650 rpm, no load)
Fuel injection control
PCM terminals (California emission regulation applicable model)
- Fuel injection No.1: 2AW(+) - 1 AZ(-)
- Fuel injection No.2: 2AS(+) - 1 AZ(-)
- Fuel injection No.3: 2AX(+) - 1 AZ(-)
- Fuel injection No.4: 2AT(+) - 1 AZ(-)
PCM terminals (except for California emission regulation applicable model)
- Fuel injection No.1: 2BB(+) - 1 AZ(-)
- Fuel injection No.2: 2BC(+) - 1AZ(-)
- Fuel injection No.3: 2BD(+) - 1AZ(-)
- Fuel injection No.4: 2AZ(+) - 1AZ(-)
Oscilloscope setting
- 10 V/DIV (Y), 25 ms/DIV (X), DC range
Vehicle condition
- Idle after warm up (engine speed approx. 650 rpm, no load)
IGT1, IGT2, IG3, IG4 control signals
PCM terminals (California emission regulation applicable model)
- IGT1 (No.1):2BE(+) - 1BC(-)
- IGT2(No.2):2BF(+) - 1BB(-)
- IGT3(No.3):2BG(+) - 1BB(-)
- IGT4(No.4):2BH(+) - 1BC(-)
PCM terminals (except for California emission regulation applicable model)
- IGT1 (No.1):2BE(+) - 1BG(-)
- IGT2(No.2):2BF(+) - 1BC(-)
- IGT3(No.3):2BG(+) - 1BC(-)
- IGT4(No.4):2BH(+) - 1BG(-)
Oscilloscope setting
- 10 V/DIV (Y), 25 ms/DIV (X), DC range
Vehicle condition
- Idle after warm up (engine speed approx. 650 rpm, no load)
Factory Service Tools
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- β’ You smell fuel, burning insulation, or see smoke.
- β’ Brakes feel soft, pull hard to one side, or make grinding noises.
- β’ The engine overheats, stalls repeatedly, or misfires under load.
- β’ You are missing required tools, torque specs, or safe lifting equipment.
- β’ You are not confident in the next step or safety outcome.
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