Electrical - Measuring Closed-Circuit Current
SI B 61 08 00General Electrical Systems
March 2005
Technical Service
This Service Information bulletins supersedes S.I. B61 08 00 dated January 2005.
[NEW] designates changes to this revision
SUBJECT
Closed-Circuit Current Measurement
MODEL
All
SITUATION
Increased closed-circuit currents may occur permanently or intermittently, and cause the battery to discharge prematurely. The increase in closed circuit current may be caused by a faulty control unit, or by the installation of a non-approved accessory.
In a situation where a vehicle has broken down due to a discharged battery, for diagnostic purposes it is important not to disconnect the battery. This is because a control unit will be reset if the battery is disconnected. Following a reset, the faulty control unit may start functioning correctly again, making accurate diagnosis impossible. To correctly measure closed-circuit current, the 50-amp clip-on probe can be used in conjunction with the DISPlus to properly diagnosis closed circuit current problems over an extended period of time. Refer to Service Information B04 07 01 for information about the 50-amp clip-on probe use with the DISPlus. A new 50-amp clip-on probe (refer to SI B04 16 04) can be used with the GT1 in conjunction with the MIB (Measurement Interface Box). Refer to SI B08 02 04 for information about the MIB.
PROCEDURE
1. Check and test the battery using the BMW Battery Tester. Refer to SI B 04 25 02 for information about the BMW Battery. If necessary, recharge or replace the battery.
2. If the battery is installed in the trunk, open the trunk and turn the lock to the locked position using a screwdriver or similar (simulates the trunk lid being closed). The hood must be closed.&line;If the battery is installed in the engine compartment, open the hood and pull the front lid contact switch fully up and lock in this position (workshop position, simulates the front lid being closed). The trunk must be closed.
3. With the exception of the trunk / hood above, all other doors / lids must be closed.
4. In order to simulate normal closed-circuit conditions:
^ Turn ignition on and activate all electrical consumers, including any accessories. Turn ignition off In some cases a drive cycle may need to be carried out in order to duplicate a closed circuit current problem.
^ Open and close the driver's door (simulates somebody getting out).
^ Lock the car, arming DWA if this is installed.
5. In general, closed-circuit current consistently over 50 mA must be investigated. Depending on the vehicle's equipment, closed-circuit current by vehicle model is approximately as follows:
6. If the nominal milliamp reading is not achieved after the appropriate time, then refer to the attached troubleshooting charts
^ E60/63/64 Closed Circuit Current Troubleshooting E6x.
^ E65/66 Closed Circuit Current Troubleshooting up to 3/04 production.
^ E65/66 Closed Circuit Current Troubleshooting from 3/04 production.
CLOSED-CIRCUIT CURRENT MEASUREMENT WITH THE DISPLUS/GT1:
Note:
This technique with a DISPlus/GT1 is particularly suitable for extended measurements and provides a graphical readout of recorded measurements over time. It is recommended for situations where the use of a multimeter provided insufficient information for problem diagnosis.
Select "Oscilloscope display" on the Oscilloscope settings screen to start recording measurements. Select the Log Scale/Lin Scale button to switch over to the Log Scale. This will provide the best visual trace of the closed circuit measurement. Note: Pressing the "Oscilloscope settings" button will delete any recorded measurements.
Oscilloscope Setting
^ Select "Writer mode"
^ Select "Current 50A" under "Test connection"
^ Select "=" under "Type of measurement"
^ Set "Measuring range" to "10 A" scale
^ Set "Frequency range" based on how long of a trace is required. Refer to the chart below for examples.
Frequency range - The frequency range determines how frequently and for how long a measured value is recorded. The larger the frequency range, the more frequently a measured value is recorded, and the shorter the maximum stored recording duration.
Examples:
Oscilloscope Display
^ Select "Oscilloscope Display"
^ A box will pop up calibrating the 50-Amp clamp. Make sure the clamp is not connected to anything, then select "OK".
^ Once the display screen is present the measurement will be started. Select Log Scale/Lin Scale to switch over to Log Scale. The Log Scale screen will then be displayed in 3 different measurement ranges. This ensures that when the closed circuit current measurement drops through the various ranges, the reading will be graphically displayed on one screen without changing settings.
Displaying and Understanding Measurements (see illustration):
^ Stop recording measurements by pressing the "Hold Screen" button. Note: If the "Hold Screen" button is pressed again, the recorded measurements will immediately be deleted and new measurements started.
^ Recorded data may be called up by pressing the screen button "Memory" and paged through with the aid of the "arrow keys" on the upper corners of the screen. When the maximum recording duration has been used, measured values can be called up for a total of 10 screens.
^ Momentary current fluctuations are normal and should be ignored. "Maximum" display captures these momentary fluctuations and also should be ignored.
^ An increased closed-circuit current will also be intermittently measured for a few seconds due to the use of remote-control keys of other vehicles, or other radio transmitters in the frequency range 315 MHz. In these cases, the General Module wakes up for key identification, then goes back to sleep when its own key is not recognized. This is normal operation.
^ On 2005 MY vehicles equipped with BMW ASSIST, there are additional current fluctuations as high as 500ma and last for approximately 2 minutes. The fluctuations occur every 15 minutes for up to 14 hours afier key off. This is considered normal operation of the TCU and should not be considered a fault. This also applies to 2005 TCU's that are installed into earlier production vehicles as a replacement part.
WARRANTY INFORMATION
Information only
E6x Excessive Closed Circuit Current
Closed Circuit Current Monitoring E60/E63/E64
Closed Circuit Current Monitoring Flow Chart E65 Up to 3_2004
E65 (From 3_2004) Excessive Closed Circuit Current