This document describes the troubleshooting procedure in the event of quiescent current faults.
First check whether the correct quiescent current value sets in through forced sleeping with a Power Down command.
The time period for a normal sleeping procedure is over 1 hour. To reduce the time for troubleshooting, there is the possibility of letting the vehicle go to sleep immediately through a diagnosis command (Power Down).
To place the vehicle in Power Down mode, it is essential for the following preconditions to be satisfied:
Send the Power Down command with a suitable test module
The Power Down mode is terminated when the bus is woken.
Procedure:
Send the Power Down command with a suitable test module
The vehicle must go to sleep approx. 20 seconds after the Power Down command is sent.
Identifying features:
If the identifying features indicate that the vehicle is sleeping, a quiescent current measurement can be carried out after approx. 30 seconds.
The total quiescent current must be < 30 mA
Important: Do not perform any actuations during the measurement. The Power Down mode is terminated when the bus is woken.
Start-button illumination goes out after approx. 2 minutes (after removal of ignition key).
In the case of the natural sleeping process, a quiescent current of < 30 mA must be reached after approx. 70 minutes.
Identifying feature: (after removing ignition key)
Precondition: Read out fault memory and correct stored faults!
If no bus rest is possible, it is necessary to determine which bus or control module is preventing the bus from going to sleep.
Procedure:
Perform forced sleeping with Power Down command.
Does the bus go to sleep with the Power Down command?
Yes, bus sleeping |
No, bus is awake |
A quiescent current measurement can be carried out |
Disconnect fuse of ZGM (Central Gateway Module) Is bus rest reached after approx. 2 minutes? Yes, troubleshooting b No, troubleshooting a |
Troubleshooting a |
Troubleshooting b |
Disconnect fuse from Control Display Is bus rest reached after approx. 2 minutes? Yes, troubleshooting c No, troubleshooting d |
Connect fuse of ZGM Disconnect SIM (Safety and Information Module) Is bus rest reached after approx. 2 minutes? Yes, troubleshooting i No, troubleshooting j |
Troubleshooting c |
Troubleshooting d |
Connect fuse of Control Display Disconnect Control Display Is bus rest reached after approx. 2 minutes? Yes, troubleshooting e No, troubleshooting f |
Disconnect CAS (Car Access System) control module Is bus rest reached after approx. 2 minutes? Yes, troubleshooting g No, troubleshooting h |
Troubleshooting e |
Troubleshooting f |
Connect Control Display Determine defective MOST control module To do so, disconnect MOST control module (not control display) Connect MOST bus with jumper Switch on ignition (wake bus) Switch off ignition If bus rest is reached after approx. 2 minutes, the corresponding control module must be replaced The same procedure is to be applied to all MOST control modules until the defective control module has been determined. The audio system controller is to be disconnected second last and the Control Display as last control module. |
Disconnect the following control modules individually to determine which control module is defective: Center console switch center Controller Rear center console switch center After disconnecting the defective control module, bus rest is reached after approx. 2 minutes Replace defective control module |
Troubleshooting g |
Troubleshooting h |
Connect CAS control module Disconnect fuses for the following control modules individually to determine which control module is defective: All K-CAN PERIPHERIE control modules If several control modules are protected with the same fuse, the corresponding control module must be disconnected After disconnecting the defective control module, bus rest is reached after approx. 2 minutes. The CAS control module is to be disconnected last as it is the gateway |
Disconnect fuses for the following control modules individually to determine which control module is defective: All K-CAN SYSTEM control modules If several control modules are protected with the same fuse, the corresponding control module must be disconnected After disconnecting the defective control module, bus rest is reached after approx. 2 minutes. |
Troubleshooting i |
Troubleshooting j |
Connect SIM control module Disconnecting an ISIS control module Switch on ignition (wake bus) Switch off ignition If bus rest is reached after approx. 2 minutes, the corresponding control module must be replaced The same procedure is to be applied to all ISIS control modules until the defective control module has been determined. Disconnect the SIM as the last control module because it is the gateway for the BYTEFLIGHT bus. |
Connect SIM control module Disconnect fuses for the following control modules individually to determine which control module is defective: All PT-CAN control modules If several control modules are protected with the same fuse, the corresponding control module must be disconnected After disconnecting the defective control module, bus rest is reached after approx. 2 minutes. |
Note!
If a fuse is disconnected from a control module, the corresponding control module can normally not waken the bus.
However, returning the bus to sleep can be disrupted by an internal control-module fault.
If no bus rest is possible in spite of disconnected fuses, the corresponding control module must be disconnected.
The overview of the buses and corresponding control modules can be reached via the bus functions.
A quiescent current measurement is to be run in the case of bus rest.
Begin by measuring the quiescent current with the current probe directly at the battery.
If the quiescent current is less than 4 A, the measurement adapter can be installed for precise measurement.
In order to pinpoint the cause of the quiescent current, measure at the high-current outputs on the power module. This is a quick way to pinpoint the general location of the cause of the quiescent current.
At the corresponding distributor, disconnecting fuses enables detection of the cause.
Control modules that are not protected via the distributor in the engine compartment or luggage compartment must be determined individually by disconnecting the corresponding fuses or the units themselves.