A BMW owner drove his BMW with 110 thousand miles to our garge for repair his console trouble, oil level inactive.Here I share this repair case which caused by DME trouble,hope it can give you some inspiration for you work.
Trouble:Oil level Inactive.
Our technicians use ISTD to diagnosed and found the trouble:
DME-2E7C: Bit serial data interface, signal
BSD is abbr of serial data interface, and the serial data interface is a single-wire data bus with a data transfer rate of 1.2 Kbit/s. The following components are connected to the DME Control Module via a serial data interface:
Generator (depending on the type)
Intelligent battery sensor (depending on the model series)
Electric coolant pump (related to model)
Oil status sensor (related to model)
The following data will exchange between the DME/DDE and related components:
Feature request from DME
Identification data sent to DME
System parameter value sent to DME
System trouble information sent to DME
If the component recognizes a fault, it notifies the DME/DDE the fault via the serial data interface. The DME will record the fault in the fault code memory.
The system does not have a detailed description of the fault code, and a brief introduction to the fault details, as shown in the table.
|Item||1th Fault Record||Last/Current Fault Record|
|Engine Speed||0 r/min||0 r/min|
|Bus KL.87 Voltage||11.48 V||11.58 V|
|Speed||0 km/h||0 km/h|
|Engine Control Status||ENG STOP 0-n||ENG STOP 0-n|
|Mileage||117000 mile||117000 mile|
|SAE Trouble Code||U119D||U119D|
Technician try to clean the trouble code with ISTD (BMW Rheingold ISTA-D 4.12.12 ISTA-P 22.214.171.1240 Free download),but it show current and can not clean.
The BSD communication circuit diagram,show as below:
Technician measured the communication voltage ,you need to disconnect the battery sensor ,electric coolant pump,generator and oil status sensor before,then measure the communication voltage between DME to BSD,it showed as 0.02 V.
The communication waveform of the BSD is measured as a straight line with no signal, as shown in Figure 2. The description is that DME does not have any signal voltage output, DME is mulfunction.
In order to verify whether the inference is correct, the same model is found to measure in the same way. The measurement result shows that the BSD communication voltage is 7.9V, and the level of this voltage is affected by the voltage of the vehicle network.
Measuring the BSD communication waveform is shown in Figure 3. The DME has a signal voltage for the control unit and a signal waveform, indicating that there is no problem with this DME output control. It also proves that the DME of the faulty vehicle does have a fault.
Troubleshooting: Replace and reprogram the DME,the fault code can be clean directly, the vehicle’s oil measurement function work correctly.