Description
(1) proportional oxygen sensor
"a" 6-way black connector
Make: BOSCH
Role
The proportional oxygen sensor measures the oxygen content of the exhaust gases relative to the ambient air
The proportional oxygen sensor determines the oxygen content of the exhaust gas and deduces the exact richness of the mixture
Function
"b" exhaust gas supply channel
(2) electrode
(3) pumping cell
(4) measuring chamber
(5) Nernst cell
(6) reference cavity
(7) heating resistor
The oxygen contained in the oxygen sensor is drawn into the exhaust gases by a pumping current and retained in the measuring chamber (4)
The Nernst cell compares the oxygen in the measuring chamber (4) with the oxygen in the reference cavity (6)
To have an oxygen rate of 1, the oxygen in the measuring chamber (4) must be the same as the oxygen in the reference cavity (6)
The value of the pumping current is linked with the flow of oxygen originating from the exhaust gas, necessary in order to regenerate the oxygen in the measuring chamber (4) and have a lambda of 1
When lambda is higher than 1 in the measuring chamber (4), the pumping current is positive, the excess oxygen contained in the measuring chamber is taken off to be sent to the exhaust gas
When lambda is lower than 1 in the measuring chamber (4), the pumping current is negative, the oxygen which is lacking is taken from the exhaust gas and sent to the measuring chamber
To have an oxygen rate of 1, the Nernst cell must deliver a voltage of 0,45 V
The electrical output signal that is proportional to the oxygen content is obtained by measuring the current necessary for the pumping cell to regulate the oxygen content in the measuring chamber
The oxygen sensor is fitted with a heating element (7), controlled via an opening cyclic ratio (OCR) type signal by the engine management ECU, in order to allow it quickly to reach its operating temperature of 780°C
Electrical features
Reference values
"A" pumping current power (mA)
"B" oxygen rate
"C" rich area
"D" poor area
| oxygen rate (λ Lambda signal) | 0,65 | 0,70 | 0,80 | 0,90 | 1,00 | 1,18 | 1,43 | 1,70 | 2,42 | - |
|---|---|---|---|---|---|---|---|---|---|---|
| current | -2,45 mA | -1,99 mA | -1,13 mA | -0,49 mA | -0,010 mA | 0,33 mA | 0,67 mA | 0,94 mA | 1,38 mA | 2,53 mA |
Connections
| channel number | allocation of channels of connector |
|---|---|
| 1 | Pumping current signal |
| 2 | earth |
| 3 | heating controls (-) |
| 4 | 12V heating supply |
| 5 | not used |
| 6 | Nernst voltage |
Programming/initialisation
Programming is necessary if the component is replaced