Oscilloscope Patterns and Waveforms
Oscilloscope Measurement on System Locks
A system lock with preliminary damage cannot be distinguished from an intact system lock. At the moment, a system lock with preliminary damage remains fully functional, with there is a high probability that it will fail. No intact system lock may be replaced. A system lock with preliminary damage must be replaced. The preliminary damage to a system lock can only be determined by measuring the power characteristic curve using an oscilloscope.
Preconditions
The fuse for the central locking system F57 (up to 09/07) or F73 (as of 09/07) must be replaced. The 15 A fuse is to be replaced by a 20 A fuse. Use a 20 A fuse, even if a 15 A fuse is still indicated on the circuit diagram or on the fuse board.
IMPORTANT
- A system lock may only be replaced if its failure or preliminary damage has been determined beyond doubt by means of an oscilloscope measurement.
- It is possible that simply replacing the 15 A fuse with a 20 A fuse is effective.
1. Test sequence for preliminary damage to a system lock
Steps 1 to 10 must be carried out for each system lock that has not obviously failed after replacement of the fuse and a number of operations. Obvious failure can be seen by the fact that the locking button no longer moves.
1. At the relevant door connector (X257, X256, X274 or X273), fit adapter 612360 between the body wiring harness and door wiring harness.
2. Set the measurement system using DIS/GT1 for oscilloscope measurement:
- Measuring connection to current 50 A
- Measuring range ±5 A
- Frequency range 0.2 Hz
- Recorder mode
Comparison image for the settings for the oscilloscope measurement.
The measurement must be carried out using the DIS/GT1 as long as there is no measurement system available for the ISID.
The specifications for setting the oscilloscope and the comparison images only apply to the diagnosis unit DIS/GT1. The measurement system on the ISID will have to be set differently. The visual display of the measurement system on the ISID differs from the display on the DIS/GT1.
3. Calibrate the 50 A current measuring clip and confirm the calibration. During the calibration, the current measuring clip must not clasp around any strands of wire. The calibration must be carried out for each individual system lock.
4. Connect the current measuring clip around the 2 wire strands of pin 18 on the adapter. The MVR cable (signal name) between the JBE control module and system lock is measured at pin 18 of the adapter.
Comparison image for connection of the current measuring clip.
IMPORTANT: The current measuring clip must clasp around both wire strands at pin 18 of the adapter.
5. Close the rotary catch at the relevant system lock by hand.
If the driver's door is to stand open during the test of one of the rear system locks or of the system lock on the passenger's door, the rotary catch in the driver's door must also be closed for the measurement.
IMPORTANT: After the measurement, open the rotary catch again by hand, as otherwise the system lock will be damaged if the door is closed with a closed rotary catch.
6. Start or switch on the measurement.
7. Use the remote control to unlock and lock the central locking system
8. Compare the measuring result with the comparison images and determine whether the measured system lock is OK. Help for evaluation of the measurement results.
9. The measurement must be carried out 5 times (unlock and lock the central locking system with the remote control 5 times). If one of 5 measurements clearly indicates that there is preliminary damage to the lock, it must be replaced.
10. After the measurement, remove the adapter, reconnect the door connector and open the rotary catch by hand if it is still closed. To be able to open the rotary catch by hand, the last operation of the central locking system with the remote control must be unlocking.
11. Repeat steps 1 to 10 for the remaining system locks and adhere to the specified order.
2. Assessment of the measurement results
The measured values displayed on the DIS/GT1 for the minimum and maximum must not be used for assessment of the power characteristic curve (display at bottom right). The value for the measured current consumption of the central-locking drive must be read from the characteristic curve.
For assessment of the characteristic curve, the measured current consumption of the central-locking drive must be examined in combined operation. The current consumption in combined operation must not exceed 3.3 A.
A current spike above 3.3 A on starting the central-locking drive is permitted and is the normal operating status.
The central-locking drive is activated for 500 ms. A tolerance in the activation time of ±50 ms is permitted and is the normal operating status.
The following illustrations show power characteristic curves from which intact and defective central-locking drives can be read.
The following illustrations each show the power characteristic curve of an unlocking and a locking operation.
Depending on how the current measuring clip was connected around the two wire strands, the measuring result can be turned around 180 degrees. Either connect the current measuring clip the other way around or assess the characteristic curve offset by 180 degrees.
The following illustrations only refer to a measurement using the DIS/GT1.
2.1 Power characteristic curve of an intact system lock
Illustration: Measuring result of an intact system lock
2.2 Power characteristic curve on system locks with preliminary damage
Illustration: Measuring result of a system lock with preliminary damage
Illustration: Measuring result of a system lock with preliminary damage
Illustration: Measuring result of a system lock that has failed completely
3. Comparison images, setting the measurement
Illustration: Adapter on door connector with connected current measuring clip
Illustration: Settings for oscilloscope measurement
