On-Off Ratio Test

On-Off Ratio Test

The on-off ratio tests the operation of the 02S (Lambda) control system and additionally, recognizes certain malfunctions present during the test.
Malfunctions are distinguished between those that occur with the Ignition ON and those that occur with the Engine at closed throttle position (CTP) (idle).
The on-off ratio can be checked with the on-off ratio tester or with the engine analyzer. For this purpose, the purge line to the engine must be disconnected at the purge control valve and closed with a plug. Check on-off ratio at closed throttle speed and at 2500 rpm. A readout of 50% or an oscillating needle indicates that all input signals and the 02S control system are OK. Readouts of 10% to 90% or 95% refer to a particular malfunction source. In addition, after testing the on-off ratio, an impulse readout must be performed using the impulse counter scan tool.