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 MANUALSMITSUBISHI2005LANCER L4-2.4L SOHCREPAIR AND DIAGNOSISPOWERTRAIN MANAGEMENTEMISSION CONTROL SYSTEMSEXHAUST GAS RECIRCULATIONEGR VALVETESTING AND INSPECTIONOSCILLOSCOPE CHECK
2005 Mitsubishi Lancer L4-2.4L SOHC
Oscilloscope Check
2005 Mitsubishi Lancer L4-2.4L SOHCSECTION Oscilloscope Check
EGR VALVE (STEPPER MOTOR)
Required Special Tool:
- MB991658: Test Harness
Measurement Method
1. Disconnect the EGR valve connector and connect the test harness special tool (MB991658) between the separated connector. (All terminals should be connected.)
2. Connect the oscilloscope probe to the EGR valve connector terminal No. 1, terminal No. 3, terminal No. 4, No. terminal 6 respectively.
Alternate method (Test harness not available)
1. Connect the oscilloscope probe to ECM or PCM terminals No. 3, No. 12, No. 19 and No. 26.
Standard Wave Pattern
Wave Pattern Observation Points
1. Check that the standard wave pattern appears when the EGR valve is operating.
Point A: Presence or absence of induced electromotive force from the motor turning. (Refer to abnormal wave pattern.)
Point B: Height of coil back electromotive force
Examples of Abnormal Wave Patterns
Example 1
Cause of problem
- Malfunction of motor. (Motor is not operating.)
Wave pattern characteristics
- Induced electromotive force from the motor turning does not appear.
Example 2
Cause of problem
- Open circuit in the line between the EGR valve and the ECM or PCM .
Wave pattern characteristics
- Current is not supplied to the motor coil on the open circuit side. (Voltage does not drop to 0 volt.) Furthermore, the induced electromotive force wave pattern at the normal side is slightly different from the normal wave pattern.
Required Special Tool:
- MB991658: Test Harness
Measurement Method
1. Disconnect the EGR valve connector and connect the test harness special tool (MB991658) between the separated connector. (All terminals should be connected.)
2. Connect the oscilloscope probe to the EGR valve connector terminal No. 1, terminal No. 3, terminal No. 4, No. terminal 6 respectively.
Alternate method (Test harness not available)
1. Connect the oscilloscope probe to ECM
Standard Wave Pattern
Wave Pattern Observation Points
1. Check that the standard wave pattern appears when the EGR valve is operating.
Point A: Presence or absence of induced electromotive force from the motor turning. (Refer to abnormal wave pattern.)
Point B: Height of coil back electromotive force
Examples of Abnormal Wave Patterns
Example 1
Cause of problem
- Malfunction of motor. (Motor is not operating.)
Wave pattern characteristics
- Induced electromotive force from the motor turning does not appear.
Example 2
Cause of problem
- Open circuit in the line between the EGR valve and the ECM
Wave pattern characteristics
- Current is not supplied to the motor coil on the open circuit side. (Voltage does not drop to 0 volt.) Furthermore, the induced electromotive force wave pattern at the normal side is slightly different from the normal wave pattern.
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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.