Description
Upstream oxygen sensor
(1) upstream oxygen sensor ON/OFF
"a" 4-way grey connector
Downstream oxygen sensor
(2) downstream oxygen sensor ON/OFF
"b" 4-way black connector
Role
Role of the upstream oxygen sensor
- Determining the oxygen content of the exhaust gases
- Resetting the richness following the drift in the fuel injection system
Role of the downstream oxygen sensor
- Determining the oxygen content of the exhaust gases
- Resetting the richness following the drift in the injection system as well as in the catalytic converter
- Checking that the catalytic converter is working properly
Function
The oxygen contained in the exhaust gas is compared with the oxygen contained in the oxygen sensor taken from the ambient air in order to deduce a richness value
If the difference between the oxygen contained in the exhaust gas and the oxygen contained in the oxygen sensor is significant, the mixture will be "rich", if the difference is slight, the mixture will be "lean"
The oxygen sensor compares the composition of the mixture injected with the stoichiometric dosage (lambda = 1) in order to deduce an output voltage
NoteLambda signal ratio = weight of air admitted/theoretical air weight
Connectors
The connector for the upstream oxygen sensor
| channel number | allocation of channels of connector |
|---|---|
| 1 | signal (+): downstream oxygen sensor ON/OFF |
| 2 | signal (-): downstream oxygen sensor ON/OFF |
| 3 | +12 volts supply: oxygen sensor heating ON/OFF |
| 4 | earth: oxygen sensor heating ON/OFF |
The connector of the downstream oxygen sensor
| channel number | allocation of channels of connector |
|---|---|
| 1 | +12 volts supply: oxygen sensor heating ON/OFF |
| 2 | earth: oxygen sensor heating ON/OFF |
| 3 | signal (+): downstream oxygen sensor ON/OFF |
| 4 | signal (-): downstream oxygen sensor ON/OFF |
Programming/initialisation
Programming is necessary if the part is removed/refitted