A4 Mk1
Checking lambda control
Checking lambda probe and lambda control after catalytic converter (on vehicles which conform to emission standard EU III)
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Special tools and workshop equipment required
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Note: The lambda control after catalytic converter serves as a correction control. → It corrects slight mixture changes (e.g. enrichment) through the lambda probe before catalytic converter, by maintaining the lambda control for a certain period (dwell time) at the upper / lower point.If the time is in the positive range (e.g. 50 ms), the mixture is made richer. If it is in the negative range (e.g. -50 ms), the mixture is made leaner. Fitting location of connectors . Test conditions
Test sequence
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→ When adjacent display appears: |
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Note: During basic setting, the solenoid valve for the activated charcoal filter (valve -N80) is closed and the air conditioner compressor is switched off. |
→ When adjacent display appears: |
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→ Indicated on display: |
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Note: This process can take a few minutes.
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→ When adjacent display appears: |
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→ When adjacent display appears: |
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Note: The "lambda probe status" indicates the condition of the lambda control and the lambda probes.
Notes:
Significance of 3-digit readout of display group 30
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→ When adjacent display appears: |
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Test conditions
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→ Indicated on display: |
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If specification "B1-P2 OK" is attained:
Test conditions
If specification "B2-P2 OK" is attained:
Note: It is possible that "B2-P2 OK or NOK" will be displayed before "Test ON" appears, since the diagnosis is performed simultaneously with the lambda probe for bank 1. This also applies to further tests. Checking lambda control after catalytic converter
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→ When adjacent display appears: |
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→ Indicated on display: |
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Note on display zone 3: The lambda control after catalytic converter serves as a correction control.It corrects slight rich / lean mixture changes in the lambda probe before catalytic converter, by maintaining the lambda control before catalytic converter at the upper / lower point for a certain period of time (dwell time). If the time is in the positive range (e.g. 50 ms), the mixture is made richer. If it is in the negative range (e.g. -50 ms), the mixture is made leaner.
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→ Indicated on display: (1...4 = display zones) |
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Note on display zone 3: The lambda control after catalytic converter serves as a correction control.It corrects slight rich / lean mixture changes in the lambda probe before catalytic converter, by maintaining the lambda control before catalytic converter at the upper / lower point for a certain period of time (dwell time). If the time is in the positive range (e.g. 50 ms), the mixture is made richer. If it is in the negative range (e.g. -50 ms), the mixture is made leaner. Evaluation of display groups 037 and 038
(cont.) If specification in display groups 37 and 38, display zones 3 or 4 is not attained:
If none of the given causes apply:
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