18 · Diagnostics

W02 Low co, high nox emission

Make: Alfa Romeo
Model: 147 Factory Service Manual
Year: 2000–2002
Section: Emissions › W02 Low co, high nox emission

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Fault diagnosisW02 Low co, high nox emission

W02 Low co, high nox emission

The CO percentage measured is very low, with a corresponding NOx percentage higher than the recommended figure.

Step	Test procedure	Result	Action
1	CHECK WITH DIAGNOSTIC EQUIPMENT Connect diagnostic equipment (Examiner or other instruments) to the diagnostic socket. Check that there are no faults in the engine management control unit	OK	Move onto step 2
		'Fuel system' error appears	See table Z50 MIXTURE STRENGTH ERROR End of diagnosis
		'Misfiring' error appears	See table Z53 MISFIRE ERROR End of diagnosis
		'Catalytic converter' error appears	See table Z55 CATALYZER ERROR End of diagnosis
		'Upstream lambda probe' error appears	See table Z56 UPSTREAM LAMBDA SENSOR SIGNAL ERROR End of diagnosis
		'Downstream lambda probe' error appears	See table Z58 DOWNSTREAM LAMBDA SENSOR SIGNAL ERROR End of diagnosis
		Another error detected in the control unit	Continue following the instructions for the diagnostic equipment End of diagnosis
		Lack of dialogue with the control unit	Restore the connection between the engine management control unit and the diagnostic connector Wiring diagram E5030 PETROL ENGINES ELECTRONIC CONTROL End of diagnosis
2	ACTIVE DIAGNOSIS WITH DIAGNOSTIC EQUIPMENT Using the diagnostic equipment (Examiner or other instruments) carry out the active diagnosis of the injectors.	OK	Move onto step 3
		Connections faulty	Restore the connection of the injectors and the solenoid with the control unit Wiring diagram E5030 PETROL ENGINES ELECTRONIC CONTROL End of diagnosis
		Faulty injector	Replace injector Op. 1056B70 End of diagnosis
3	CHECKING LAMBDA SENSOR Check that the Lambda sensor is working properly	OK	Move onto step 4
3		Lambda sensor defective	Replace the Lambda sensor Op. 1080B60 End of diagnosis
4	CHECKING AIR CIRCUIT Check the condition of the air supply circuit	OK	Move onto step 5
4		Circuit component damaged	Replace the component involved End of diagnosis
5	CHECKING BLOW-BY CIRCUIT Check the condition of the blow-by gas intake circuit, in particular, check that there are no obstructions in the separator or the pipes	OK	Move onto step 6
		Circuit faulty	Restore the operation of the system End of diagnosis
		Fault in the separator	Replace the separator End of diagnosis
6	CHECKING FUEL PRESSURE Check the fuel supply pressure Op. 0510C10	OK	Move onto step 7
6		Pressure not correct	Replace the fuel pump Op. 1040A70 End of diagnosis
7	CHECKING CORRECT OPERATION Check that the fault is no longer present	OK	Incorrect selection of diagnostic procedure
7		Fault persists	Incorrect selection of diagnostic procedure

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Parts & tools for this job For 2000 Alfa Romeo 147

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