| Performing adaption of throttle valve module |
| The adaption process enables the engine control unit to learn the different positions of the throttle valve with the ignition switched on and the engine not running. These positions are stored in the control unit. The feedback signal indicating the position of the throttle valve comes from the two angle senders for throttle valve drive. |
| Adaption must always be performed if the throttle valve module -J338- or the engine control unit has been removed/installed or renewed, or if the voltage supply for the engine control unit has been interrupted. |
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| Automatically, if the ignition is switched on for at least 10 seconds without the starter being operated or the accelerator pedal pressed and the engine control unit detects “adaption required”. (In this case, however, there is no definite indication of whether the adaption process was successful or not.) The need for adaption is recognised if the stored angle sender voltage values do not coincide with the currently measured voltage values within a certain tolerance range. |
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| By starting basic setting (function 04), display group 060, with ignition on. |
Note | The engine will not start while the automatic adaption process is being performed. |
| Special tools and workshop equipment required |
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| Vehicle diagnosis and service information system -VAS 5052- |
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| Engine stopped, ignition switched on |
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| Accelerator pedal not depressed. |
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| Coolant temperature 10 ... 95 °C |
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| Intake air temperature 10 ... 90 °C |
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| Voltage supply to engine control unit more than 12.7 V; checking → Chapter. |
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| Connect up the vehicle diagnostic and service information system -VAS 5052- and select the engine electronics control unit. When doing this, the ignition must be switched on. |
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| Select the function “Start basic setting”. |
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| Select “Display group number 060”. |
| After you press the Q key, the throttle valve positioner is first disconnected from the power supply. |
| In this condition the throttle valve is pulled into an emergency running position by a mechanical spring which is located in the throttle valve module. The values supplied by the two angle senders in this emergency running position are stored by the engine control unit. |
| The throttle valve is then opened by a predetermined amount. As soon as it reaches this position the power supply to the throttle valve positioner is again disconnected. The spring should then close the throttle valve mechanically to the previously learnt default position within a specified period of time (spring test). |
| The throttle valve is then closed by the throttle valve positioner; the values supplied by the angle senders in the throttle valve module are stored in the engine control unit. |
| De-energization of the throttle valve positioner by the engine control unit whilst driving becomes apparent in the form of a faster, uneven idling speed. The throttle response of the engine is very slow. |
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| Check the throttle valve module specifications in display zones 3 and 4. |
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