Warm up the engine. The oil temperature should be around 80°C.
Disconnect the lambda probe heating plug and connect a voltmeter. The voltage with the ignition on must be min. 11.5 V. Then reconnect the plug.
Check temperature sensor.
Attention: Only connect test devices with the ignition switched off.
Engines 90, 113, 115 hp:
Connect the ammeter to the electro-hydraulic regulator using the VAG 1315 A/1 test lead. Set the measurement limit to 200 mA.
Connect the CO measuring device to the measuring pipe in the engine compartment. The measuring tube is welded to the downpipe of the muffler and usually plugged with a blue plug.
Caution: Push the instrument hose tightly onto the measuring socket. Make sure there is no leakage.
Start the engine and let it idle for at least 2 minutes.
Engines 90, 113 hp
Clamp the crankcase ventilation hose with a suitable clamp or pliers. The CO content will increase for a while, but then fall again. If so, then the lambda control is working.
If the CO content does not drop or the control current does not increase, the lambda probe should be checked as follows.
Open the plug connection of the lambda probe cable and close it for 20 sec. to ground (green wire) to the control device.
If the CO content and control current change now, replace the lambda probe.
Otherwise, check the electrical wires to the control device, I also check the control device (performed in the workshop), otherwise replace.
Engines 115, 136 hp
Take readings of the control current and record.
Remove the oil level dipstick.
The control current should increase, which means that the lambda control is working.
Open the plug connection of the lambda probe cable and short to ground for 20 seconds. (green wire) to the control device.
If now the control current changes, replace the lambda probe.
Otherwise, check the electrical wires to the control device and the control device itself (performed in the workshop), replace if necessary.
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