Removal/refitting

The lambda probe is composed of a capsule of ceramic material which acts as a support for two platinum electrodes, one in contact with the exhaust gas and the other in contact with the atmosphere. To avoid corrosion by the exhaust gasses the platinum on the electrode is covered by a layer of porous ceramic and by a metallic capsule which protects it from collision with solid particles present in the gasses.

One electrode is connected to earth while the other is connected electrically to the control unit.

At high temperatures (above 300°C) this ceramic layer becomes porous and allows the oxygen ions contained in the exhaust gasses. To be deposited on the platinum electrode.

Oxygen ions present in the atmosphere are deposited on the electrode which is in contact with the atmosphere and create a difference in potential of around a hundred Mv, a voltage which indicates whether the mixture is lean or rich.

In order for the lambda probe to quickly reach the correct operating temperature of 300°C a heating resistance, supplied when the engine is cold, is located on the inside of the probe.

1. Contact
2. Ceramic support
3. Ceramics of the probe
4. Protective tube
5. Electrode (+)
6. Electrode (-)
7. Shell
8. Protective sheath
9. Cup spring
10. Electrical connection

CAUTION The internal platinum electrodes are subject to chemical attack by lead. FOR THIS REASON PETROL CONTAINING LEAD MUST NOT BE USED AS THIS WOULD CAUSE RAPID AND IRREVERSIBLE DAMAGE TO THE PROBE. NEVER USE PETROL CONTAINING LEAD EVEN IN AN EMERGENCY OR FOR SHORT PERIODS.

REMOVAL/REFITTING

1. Place the vehicle on a lift.
2. Disconnect the negative cable from the battery.