Checking and replacing the lambda probe (BMW 5 Series E34)

Every 80,000 km, the lambda probe must be checked for proper operation with the measuring device in the installed position; experience has shown that the lambda probe must be replaced after 100,000 km. A full check can be carried out at a BMW service station via the diagnostic connector. However, the lambda probe's functionality can already be confirmed by checking the CO content, which also includes checking the lambda control.

Checking the lambda probe heating

Since the lambda probe only works properly when hot, it is additionally heated when the engine warms up. Thanks to this, the lambda control starts to function normally within 1-2 minutes after starting the engine. If, in addition to checking the CO content, the lambda probe heating is checked, it can be assumed that the lambda control is functioning.



Check the reliability of the lambda probe fastening in the front exhaust pipe.

Screw the detachable connection of the lambda probe onto the bulkhead (Figure 2210).



Checking the lambda probe heating: Connect the ohmmeter to sockets 3 and 4 (from the side of the lambda probe connector) and measure the resistance. Specified value: maximum 5 Ohm, otherwise replace the lambda probe.

Replacement

To replace the lambda probe, you need to purchase a special BMW paste for threads. In addition, pay attention to the fact that the lambda probe does not touch the body of the probe from the front.