Rear preheated oxygen sensor (593), Simtec
| Rear preheated oxygen sensor (593), Simtec |
| Location |
Heated oxygen-sensor, rear (593)
| Principal use |
In order to check the condition of the front catalytic converter a further oxygen sensor is fitted to the exhaust system after the catalytic converter. This is called oxygen sensor 2 or O2S 2.
| Type |
| Connection |
| Pin No. | Signal type | Description |
| 1 | Control | Preheating control. Preheating is grounded by ECM pins 18(A) and 51(A) which govern preheating current. |
| 2 | Signal | Oxygen sensor signal. Connected to ECM pin 40(A). |
| 3 | Power supply, B+ | Preheating's power supply from the main relay. |
| 4 | Ground | Oxygen sensor's signal ground. Connected to ECM pin 24(A). |
In order to quickly generate a signal after start the oxygen sensor must be preheated. Preheating is activated by ECM.
The control module estimates the exhaust gas temperature on the basis of load and engine speed. At high temperatures the preheating is disconnected to avoid damaging the oxygen sensor. If the catalytic converter is damaged, its ability to store oxygen is reduced.
The normal swings in the lambda control will then be noted from the voltage signal of the second oxygen sensor and a DTC will be set.
The signal value of the second sensor is also used to adjust the lambda control to compensate for minor faults in the first sensor.
The best emission values are obtained when the voltage from oxygen sensor 2 is 0.6V. If the voltage is, for example, 0.3 V the engine has a slightly weak mixture.
The lambda control factor will then be locked in the rich condition for a certain number of cycles before the voltage from sensor 1 is allowed to influence the factor again.
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