Lambda Sensor (Not Simtec)
| Measurement: | Plot of signal voltage for the Lambda sensor. |
|---|---|
| Check Objective: | Checking Operation. |
Preparation
Engine oil temperature > 80 �C. Switch off the engine and ignition.
Connections
| INPUT A | COM/TRIGGER |
|---|---|
| Connect the red measurement lead with the blue filter adapter to the plug connector for the Lambda sensor. | |
| MULTEC | |
| Pin 1, except 6 VD 1 engine to pin 2. Connect the ground lead to ground. | |
| MOTRONIC | |
| Pin C, except Motronic 1.5.5 to pin 4. Connect ground lead to ground, except Motronic 1.5.5 to pin 3. |
Procedure
Start the engine and allow it to idle. If either little or no voltage variation can be detected, the engine speed must be slightly increased.
Reference Curve
Ageing of the Lambda sensor can affect signal frequency for particular measurements. The frequency is thus reduced as the sensor becomes older.
Fault Scheme 1
Symptoms:
Control frequency too low when engine is idling and under partial load.
Guideline: At least 5 rising and falling slopes must be visible (for a horizontal scaling factor of 2s/DIV).
| Possible Causes | Countermeasures |
|---|---|
| Faulty Lambda sensor | Check O 2 circuit as specified in the checking procedure. If necessary replace the Lambda sensor. |
Fault Scheme 2
Symptoms:
Lambda sensor voltage consistently too low. Maximum value: < 450 mV
| Possible Causes | Countermeasures |
|---|---|
| Mixture too lean | Check and repair the electronic engine system as specified in the checking procedure. |
Fault Scheme 3
Symptoms:
Lambda sensor voltage consistently too high. Maximum value: > 450 mV
| Possible Causes | Countermeasures |
|---|---|
| Mixture too rich | Check and repair electronic engine system as specified in the checking procedure. |