Test Point 9 - Oxygen Sensor
TEST POINT 9 - Oxygen sensor (V) (Sensor signal) - Fault code 1_24Possible Causes, Elimination, Remarks
Checking the sensor signal
- Using the System Tester 9288, the oxygen sensor signal may be read directly under the Actual values menu item. Diagnosis can only be carried out if an engine temperature of 70 deg. C has been reached for more than 1 minute.
If not:
Disconnect oxygen sensor plug. Connect digital voltmeter with test connector (sensor voltage signal) and ground at the sensor end.
- Start engine and allow to warm up so that the oxygen sensor reaches its operating temperature. When the mixture is enriched, e.g. acceleration, a change in the voltage signal must be displayed.
Test connection:
1 = Sensor voltage
2 = Sensor heating
3 = Sensor heating
Voltmeter display: approx. 150 mV - 900 mV (acc. to mixture composition)
If the regulator sets in with a certain delay, the oxygen sensor heater must be checked. To do so, connect voltmeter at control unit end with sensor plug disconnected and engine running. System voltage must be present.
NOTE: If the control unit detects an oxygen sensor voltage signal of more than 1.4 V or less than 0.1 V, the control unit switches to operation without oxygen sensor. (Short to ground or open circuit)
If regulation does not work and the sensor voltage is O.K., check the coding of the control unit before replacing it.