| STEP | CHECK TO BE PERFORMED | REMEDIAL ACTION IF THE CHECK IS NOT OK |
|---|
| 1 | Downstream sensor heater signal check Let the engine warm up and reach operating temperaturePrepare 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 downloadPress the START button on the diagnostic equipment to begin downloading a graph.Check that the signal corresponds to the attached graph | Move on to Step 2 |
| 2 | Downstream sensor resistance check Disconnect the negative battery leadDisconnect the sensor connectorMeasure 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 |
| 3 | Downstream sensor resistance wiring check Check the continuity of the wiring between pin 1 of the sensor and pin 11 of the engine control unitCheck the continuity of the wiring between pin 2 of the sensor and pin 57 of the engine control unitMove on to Step 4 | Restore the correct wiring.Replace the engine control unit Op. 1056B82 INJECTION/IGNITION SYSTEM E.C.U. (ONE) - R + R |
| 4 | Downstream sensor signal checkPrepare 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 | Move on to Step 5 |
| 5 | Check on downstream sensor oxygen signal wiringCheck the continuity of the wiring between the sensor and the engine control unit | Restore the correct wiring. |
