With the On/Off Ratio Tester
On-off ratio test (CFI)Diagnostic Socket Location:
Fault memory
Faults which occur with the engine running are recorded into memory only if they have occurred after 4 sequential engine starts. This prevents a fault from being recorded if it occurred only once. If, for example, a fault occurred only 3 times, then the fault counter will be cleared again after a certain number of engine starts.
Only faults which prevent starting of the engine or severely influence engine operation are immediately stored in memory. The fault memory is not erased if the battery is disconnected.
Recalling fault memory with On-off ratio tester
Stored fault's can be recalled with the On-off ratio tester at the diagnostic test connection (Xli)
On-off ratio test: ignition ON
Test conditions:
- Engine coolant temperature approx. 80 °C
- A/C OFF
- Selector lever in park "P" position
1. Connect On-off ratio tester according to connection diagram
2. Engine: OFF
3. Ignition: ON
4. Refer to Trouble Code Descriptions Diagnostic Trouble Code Descriptions and Trouble Code Diagnostic Charts. Testing and Inspection
Testing Lambda control system with On-off ratio tester.
The operation of the Lambda control system can be checked with the On-off ratio test. The On-off ratio test can also be used to identify momentary faults not stored in fault memory. Faults are distinguished between those that occur with the ignition on and those that occur with the engine at idle. The On-off ratio can be checked with the On-off ratio tester or with the diagnostic test unit. A readout of 50% or an oscillating needle indicates that all input signals and the Lambda control unit are ok. Readouts of 10% to 90% refer to a particular fault source (see Fault Tables). In addition, after testing the On-off ratio, an DTC readout must be performed using the impulse counter scan tool.
On-off ratio test: Engine at idle
Test conditions:
- Engine coolant temperature approx. 80 °C
- A/C OFF
- Selector lever in park "P" position
1. Connect On-off ratio tester according to connection diagram
2. Ignition: ON
3. Engine: At idle
4. Refer to Trouble Code Descriptions Diagnostic Trouble Code Descriptions and Trouble Code Diagnostic Charts. Testing and Inspection