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 MANUALSMAZDA1999626 ES, 2.5 D, STANDARDREPAIR AND DIAGNOSISENGINE PERFORMANCETESTING & DIAGNOSISENGINE CONTROLS - SELF-DIAGNOSTICSDIAGNOSTIC TESTSDTC P0107: EGR BOOST SENSORCONDITION
1999 Mazda 626 ES, 2.5 D, Standard
DTC P0107: EGR Boost Sensor: Condition
1999 Mazda 626 ES, 2.5 D, StandardSECTION Condition
This DTC indicates EGR boost pressure sensor circuit input signal is less than the self-test minimum. Possible causes for this fault are:
- Faulty EGR boost sensor.
- Faulty EGR boost solenoid valve.
- Faulty EGR solenoid valve-to-EGR boost sensor hose.
- Faulty PCM.
- Check EGR Boost Sensor VREF Voltage
Ensure freeze frame data is recorded. Turn ignition off. Disconnect EGR boost sensor. Turn ignition on. Measure voltage between SIG RTN terminal and VREF terminal at EGR boost sensor wiring harness connector. If voltage is 4-6 volts, go to next step. If voltage is not 4-6 volts, repair open VREF circuit. - Check EGR Boost Circuit Resistance
Leave EGR boost sensor disconnected. Turn ignition off. Disconnect PCM 104-pin connector. Inspect for damaged pins and repair if necessary. Connect Breakout Box (014-00950), leaving PCM disconnected. Measure resistance between test pin No. 34 (EGR Boost) and EGR boost terminal at EGR boost sensor wiring harness connector. If resistance is less than 5 ohms, go to next step. If resistance is 5 ohms or more, repair open in EGR boost circuit and repeat QUICK TEST . - Check EGR Boost Circuit For Short To Ground
Leave ignition off and EGR boost sensor disconnected. Measure resistance between test pin No. 34 (EGR Boost) and test pins No. 91 (SIG RTN), 51 and No. 103 (PWR GND) at breakout box. If each measurement is 10 k/ohms or more, go to next step. If any measurement is less than 10 k/ohms, repair short in EGR boost circuit and repeat QUICK TEST . - Check EGR Boost Sensor Response
Leave ignition off. Disconnect vacuum hose between EGR boost sensor and EGR boost solenoid. Inspect hose for damage and repair if necessary. Connect vacuum pump to EGR boost sensor vacuum port. Turn ignition on. While measuring voltage between test pins No. 34 (EGR boost) and No. 51 (PWR GND), slowly apply 21 in. Hg. If voltage response is 0.8-1.5 volts, go to next step. If voltage is not as specified, replace EGR boost sensor and repeat QUICK TEST .
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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.