Bit Serial Data Interface Bmw Usa

• Bit Serial Data Interface Bmw Usa Price

I don’t know about you, but there are times when I cringe at the amount of technology loaded into one vehicle and the potential for things to fail. The good news is, the more they load in the more opportunities pour out when they go wrong. Here is one such vehicle that has been suffering from repeated breakdowns as a result of what proved to be overvoltage.To break with case study tradition I can reveal the cause of our customer’s complaint proved to be an intermittent alternator failure which I am sure, comes as no surprise and so you may choose to read no further. With all the testing to this point we have found evidence to warrant an internal investigation of the alternator but we cannot categorically rule out the PCM or IBS from the equation (items 6 and 7 of our action plan).One suggestion was to contact the local BMW dealership to ask if they have the facility within their diagnostic equipment to either decode the BSD line or to drive the alternator using an ‘active test’ function (scan tool to command high and low charge output by simulating BSD line command message). To my surprise they do not have such a function within the dealer scan tool, so placing us all in the same boat at this stage of the diagnosis!There are tools on the market that can simulate such charge control commands as BSD, LIN and PWM signals etc. When it comes to alternator evaluation but these are expensive and generally purchased by reconditioning agents given the value of such a tool in a refurbishing application.After hours of study I came across a little gem of information that proved incredibly simple yet invaluable to confirming our alternator was in fact the root cause of our overvoltage.

Bit Serial Data Interface Bmw Usa Price

What would happen if the BSD line failed between the PCM and the Alternator? Would the battery discharge and vehicle break down? No!Should the BSD line become open circuit between the PCM and alternator, the alternator assumes 'machine sensed' control and will monitor the charge output internally as with a traditional machine sensed device.Armed with this information, the BSD line was removed from the alternator and the battery voltage monitored via the OBD socket using the PicoScope. Here we could log battery voltage fluctuations over extended time periods.At last, undeniable evidence the overvoltage was a result of alternator internal regulation failure and not as a result of BSD control (over 17 V captured with no input from the BSD line). Time now to remove and inspect the alternator with confidence given its challenging location!Close inspection of the alternator confirmed no signs of overheating or scorching, but the rotor slip rings revealed a deep wear pattern with 'grooving'.