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Location of exhaust gas warning lamp
Note:
The exhaust gas warning lamp can be switched on in the flashing or permanently on mode. The fault memory must be interrogated in every case
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◆ Flashing: There is a fault which can cause damage to catalyst if driven in this condition. In this case the vehicle must not be driven using full performance!
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◆ Permanently on: There is a fault which will increase exhaust emission. Interrogate Motronic and/or automatic gearbox control units.
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◆ If the exhaust gas warning lamp does not light up, even though there is an engine running problem, or a customer has complained, after a functional check of the exhaust gas warning lamp the fault memory must be interrogated, because faults which do not switch the exhaust gas warning lamp on immediately can also be stored.
Functional check:
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‒ Switch on ignition:
the exhaust gas warning lamp must light-up.
If the exhaust gas warning lamp does not light-up with ignition switched on:
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‒ Check wiring to exhaust gas warning lamp as follows:
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Cause:
Exhaust gas warning lamp is not activated or does not light-up due to open circuit.
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Remedy:
Switch off ignition.
Connect test box V.A.G 1598/18.
Bridge test box sockets 1 and 3.
Switch on ignition.
Exhaust gas warning lamp must light-up.
If the exhaust gas warning lamp does not light-up:
Switch off ignition.
Check bulb in the exhaust gas warning lamp.
If bulb is OK:
Locate and eliminate short or wiring open circuit from Motronic control unit to exhaust gas warning lamp using current flow diagram.
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If no fault can be detected in the wiring to exhaust gas warning lamp:
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Cause of fault
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[rtrif ]
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Control unit (J220) defective, replace. Erase fault memory and generate readiness code.
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If the exhaust gas warning lamp lights-up with ignition switched on, continue check as follows:
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‒ Start engine and run at idling speed:
The exhaust gas warning lamp must go out after a few seconds.
If the exhaust gas warning lamp does not go out:
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‒ Interrogate fault memory => Page 01-11
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If no fault is stored:
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Cause:
Exhaust gas warning lamp is permanently activated by short to earth.
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Remedy:
Switch off ignition.
Connect test box V.A.G 1598/18.
Check wire resistance between test box socket 3 and vehicle earth: Specification: ∞ω
If the specification is not attained:
Short to earth in the activation wire from Motronic control unit (J220) to exhaust gas warning lamp.
Locate and eliminate this fault using current flow diagram.
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If the specification ∞ωis attained and no short to earth can be found:
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Fault cause
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[rtrif ]
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Motronic control unit (J220) defective, replace. Erase fault memory and generate readiness code.
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