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.
Structure and inner electrical connection
Voltage is applied at the at the pump cell. This means that oxygen ions are pumped into the measurement cell until a voltage of 450 mV settles between the electrode of the measurement cell. The resulting pump current is the measured variable for the fuel-air ratio. This enables the oxygen sensor emissions control to set any desired air/fuel ratio in the combustion chamber.
| Index | Explanation |
|---|---|
| 1 | Oxygen sensor heating |
| 2 | Reference cell (Nernst cell) |
| 3 | Measurement cell (Nernst and pump cell) |
| Pin | Explanation |
|---|---|
| PWM | Pulse-width modulated activation of the oxygen sensor heating |
| Kl. 15N | Battery voltage, Terminal 15 |
| U1 | Pump voltage at the reference cell |
| R | Trimming resistor |
| Kl. 31 | Virtual earth |
| U2 | Nernst voltage |
NO RELATED
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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.