Downstream sensor heater signal check

Let the engine warm up and reach operating temperature

Prepare the Examiner diagnostic equipment to download a voltage graph.

Select the VOLTMETER function from the INSTRUMENT menu with the time set at 10 seconds.

Connect the probes between pins 3 and 4 of the sensor connector.

Bring the engine up to 3000 rpm and keep this speed constant for the entire download

Press the START button on the diagnostic equipment to begin downloading a graph.

Check that the signal corresponds to the attached graph

Downstream sensor resistance check

Disconnect the negative battery lead

Disconnect the sensor connector

Measure between terminals 3 and 4 and check that the sensor heater resistance is between 6 and 8 Ohm at 20°C and still less than 70 Ohm at higher temperatures.

Check the continuity/insulation of the wiring between the sensor and the engine control unit

See E5030 PETROL ENGINES ELECTRONIC MANAGEMENT

Move on to Step 3

Replace the downstream Lambda sensor

Op. 1080B95 REAR LAMBDA SENSOR TO CATALYTIC CONVERTER - R.R

Restore wiring

Downstream sensor resistance wiring check

Check the continuity of the wiring between pin 1 of the sensor and pin 11 of the engine control unit

Check the continuity of the wiring between pin 2 of the sensor and pin 57 of the engine control unit

Move on to Step 4

Restore the correct wiring.

Replace the engine control unit

Op. 1056B82 INJECTION/IGNITION SYSTEM E.C.U. (ONE) - R + R

Downstream sensor signal check

Prepare the Examiner diagnostic equipment to download a voltage graph.

Select the VOLTMETER function from the INSTRUMENT menu with the time set at 10 seconds.

Check that there is an oscillogram as illustrated in the attached graph between terminals 1 and 2 of the downstream sensor connector

Check on downstream sensor oxygen signal wiring

Check the continuity of the wiring between the sensor and the engine control unit