22 · Diagnostics

Co emissions low, nox emissions high

Make: Alfa Romeo
Model: GT Factory Service Manual
Year: 2003–2010
Section: Emissions › Co emissions low, nox emissions high

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Fault diagnosisCo emissions low, nox emissions high

CO EMISSIONS LOW, NOX EMISSIONS HIGH

1.8 T.SPARK

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

1	CHECKING WITH DIAGNOSTIC EQUIPMENT	All OK	Problems met	Operation
		Results of the tests
	Connect diagnostic equipment (Examiner or other instruments) to the diagnostic socket. Check that there are no faults in the engine management control unit	Continue to Step 2	''Fuel system'' error appears	See table See table Z50 MIXTURE STRENGTH ERROR
			''Misfiring'' error appears	See table See table Z53 MISFIRE ERROR
			''Catalytic converter'' error detected	See table See table Z55 CATALYZER ERROR
			''Upstream lambda sensor'' error detected	See table See table Z56 UPSTREAM LAMBDA SENSOR SIGNAL ERROR
			''Downstream lambda sensor'' error detected	See table See table Z58 DOWNSTREAM LAMBDA SENSOR SIGNAL ERROR
			Another error dected in the control unit	Continue following the instructions for the diagnostic equipment
			Lack of dialogue with the control unit	Restore the connection between the engine management control unit and the diagnostic connector See See E5030 PETROL ENGINE ELECTRONIC MANAGEMENT
2	ACTIVE DIAGNOSIS WITH DIAGNOSTIC EQUIPMENT	All OK	Problems met	Operation
	Using the diagnostic equipment (Examiner or other instruments) carry out the active diagnosis of the injectors	Continue to Step 3	Connections faulty	Restore the connection of the injectors and the solenoid with the control unit See See E5030 PETROL ENGINE ELECTRONIC MANAGEMENT
		Continue to Step 3	Faulty injector	Replace injector Op. 1056B70
3	UPSTREAM LAMBDA SENSOR CHECK	All OK	Problems met	Operation
	Check that the upstream Lambda sensor is working properly See Test See Test 1080BA CHECK ON UPSTREAM LAMBDA SENSOR OPERATION''	Continue to Step 4	Lambda sensor defective	Replace the Lambda sensor Op. Op. 1080B94 FRONT LAMBDA PROBE WITH CATALITIC CONVERTER R R
4	DOWNSTREAM LAMBDA SENSOR CHECK	All OK	Problems met	Operation
	Check that the downstream Lambda sensor is working properly See Test See Test 1080BD CHECK ON DOWNSTREAM LAMBDA SENSOR OPERATION''	Continue to Step 5	Lambda sensor defective	Replace the Lambda sensor Op. Op. 1080B95 REAR LAMBDA PROBE WITH CATALITIC CONVERTER R R
5	CHECKING AIR CIRCUIT	All OK	Problems met	Operation
	Check the condition of the air supply circuit	Continue to Step 6	Circuit component damaged	Replace the component involved
6	CHECKING BLOW-BY CIRCUIT	All OK	Problems met	Operation
	Check the condition of the blow-by gas intake circuit, in particular, check that there are no obstructions in the separator or the pipes	Continue to Step 7	Circuit faulty	Restore the operation of the system
		Continue to Step 7	Fault in the separator	Replace the separator
7	CHECKING FUEL PRESSURE	All OK	Problems met	Operation
	Check the fuel supply pressure Op. Op. 0510C10 FUEL SYSTEM - CHECK DELIVERY PRESSURE	Continue to Step 8	Pressure not correct	Replace the fuel pump
8	CHECKING CORRECT OPERATION	All OK	Problems met	Operation
	Check that the fault is no longer present		Fault persists	Search for the fault starting from another symptom''

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

1	CHECKING WITH DIAGNOSTIC EQUIPMENT	All OK	Problems met	Operation
		Results of the tests
	Connect diagnostic equipment (Examiner or other instruments) to the diagnostic socket. Check that there are no faults in the engine management control unit	Continue to Step 2	''Fuel system'' error appears	See table See table Z50 MIXTURE STRENGTH ERROR
			''Misfiring'' error appears	See table See table Z53 MISFIRE ERROR
			''Catalytic converter'' error detected	See table See table Z55 CATALYZER ERROR
			''Upstream lambda sensor'' error detected	See table See table Z56 UPSTREAM LAMBDA SENSOR SIGNAL ERROR
			''Downstream lambda sensor'' error detected	See table See table Z58 DOWNSTREAM LAMBDA SENSOR SIGNAL ERROR
			Another error detected in the control unit	Continue following the instructions for the diagnostic equipment
			Lack of dialogue with the control unit	Restore the connection between the engine management control unit and the diagnostic connector See See E5030 PETROL ENGINE ELECTRONIC MANAGEMENT
2	ACTIVE DIAGNOSIS WITH DIAGNOSTIC EQUIPMENT	All OK	Problems met	Operation
	Using the diagnostic equipment (Examiner or other instruments) carry out the active diagnosis of the injectors	Continue to Step 3	Connections faulty	Restore the connection of the injectors and the solenoid with the control unit See See E5030 PETROL ENGINE ELECTRONIC MANAGEMENT
		Continue to Step 3	Faulty injector	Replace injector Op. 1056B70
3	UPSTREAM LAMBDA SENSOR CHECK	All OK	Problems met	Operation
	Check that the upstream Lambda sensor is working properly See Test See Test 1080BA CHECK ON UPSTREAM LAMBDA SENSOR OPERATION''	Continue to Step 4	Left Lambda sensor faulty	Replace the left Lambda sensor Op. Op. 1080B93 RIGHT UPPER LAMBDA SENSOR R R
		Continue to Step 4	Right Lambda sensor faulty	Replace the right Lambda sensor Op. Op. 1080B92 LEFT UPPER LAMBDA SENSOR R R
4	DOWNSTREAM LAMBDA SENSOR CHECK	All OK	Problems met	Operation
	Check that the downstream Lambda sensor is working properly See Test See Test 1080BD CHECK ON DOWNSTREAM LAMBDA SENSOR OPERATION''	Continue to Step 5	Lambda sensor defective	Replace the Lambda sensor Op. 1080B90
5	CHECKING AIR CIRCUIT	All OK	Problems met	Operation
	Check the condition of the air supply circuit	Continue to Step 6	Circuit component damaged	Replace the component involved
6	CHECKING BLOW-BY CIRCUIT	All OK	Problems met	Operation
	Check the condition of the blow-by gas intake circuit, in particular, check that there are no obstructions in the separator or the pipes	Continue to Step 7	Circuit faulty	Restore the operation of the system
		Continue to Step 7	Fault in the separator	Replace the separator
7	CHECKING FUEL PRESSURE	All OK	Problems met	Operation
	Check the fuel supply pressure Op. Op. 0510C10 FUEL SYSTEM - CHECK DELIVERY PRESSURE	Continue to Step 8	Pressure not correct	Replace the fuel pump
8	CHECKING CORRECT OPERATION	All OK	Problems met	Operation
	Check that the fault is no longer present		Fault persists	Search for the fault starting from another symptom''

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Parts & tools for this job For 2003 Alfa Romeo GT

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