Test Point 9 - Oxygen Sensor, Open Circuit
TEST POINT 9 - Oxygen sensor Open circuit - Fault code 1_25Possible Causes, Elimination, Remarks
a) Checking sensor signal (V)
- Disconnect the oxygen sensor plug close to the central electrics. Connect voltmeter at the sensor end to the single plug pin and ground.
Test connection
1 = Sensor voltage
2, 3 = Sensor heating
- Start the engine and warm it up so that the oxygen sensor can reach its regular operating temperature. When the mixture is richened (for example when the accelerator pedal is pressed down), the voltage signal displayed must go up.
Display on voltmeter: 0.1 - 1 V
b) Checking the control unit
- Raise engine to operating temperature. Connect the exhaust tester to the exhaust test tube. Disconnect the oxygen sensor and connect the plug sleeve to ground on the control-unit side. Watch the exhaust tester: The CO content must go up.
NOTE: Continue this test only until a change is noted in the CO content at the CO tester.
If the control unit does not process the ground signal, Service and Repair, Ignition Control Module