|Vehicle details:||BMW E46 318i|
|Symptom:||No OBD communication,
|Author:||Andy Cape | Cape Auto Diagnostics, Cape Town|
The vehicle had been driven through a flooded area, and water had entered the block via the air intake. The car cut out with the engine flooded with water. The cold water entered the hot cylinder block, and caused it to crack due to thermal shock. The engine had been replaced, but could not be started. The vehicle was towed to our garage, but we soon discovered that no diagnostic scan could be performed due to no communication to the modules.
After a thorough investigation of the relevant fuses, checking supply voltages, ground (earth) signals, immobilizer signals, and the primary ignition voltage, we discovered that:
We checked the wiring of the crank shaft sensor and could not find any faults. The sensor itself had been replaced by the client already. We did notice that without the sensor connected — there was no sufficient power supply to the sensor from the ECU. This led us to believe the ECU must be faulty.
We opened the ECU and found the proof. The power connector was destroyed by extreme overload (see Figure 4). We were confused as to why the fuses did not trip to protect the ECU.
May 26 2012
Why is Stuart Duff searching and reading all this if he already knows how everything works??
April 27 2012
NICE ONE ANDY TAKE HEART THERE WILL ALWAYS BE SCEPTIC OR THOSE THAT THINK THEY KNOW MORE AND I HAVE BEEN IN THE MOTOR TRADE FOR OVER 25 YEARS AND SEE THESE TYPES MANY TIMES BEFORE
December 10 2011
Thanks Andy for your answer. I didnÃ‚Â´t know that the signal is constant 12V, when the key is wrong or something else. I have to make more reference signals to learn much more about the diagnostic with Oscilloscope. I even have a question: When I connect my Pico with 2 Channels to two different places (at example channel 1 to battery + with ground on battery - and channel 2 without the ground to battery - only with the red lead to battery +) I get a Signal on Channel 2 12V although I donÃ‚Â´t have there a ground for the channel. Is there a problem with my pico? Thanks for every answer.
December 07 2011
I would like to answer the question from Martin (on top). For my understanding is any signal good from EWS to ECU when it looks like the one I captured. When there is no valid signal from key than the EWS OUT signal to the ECU IN is constant 12V. I made me some reference files with transponder and without transponder in key. From transiver module to EWS and from EWS to ECU. Useful if you suspect wiring or module faults.
December 02 2011
Thanks for taking the time with this one It makes me wonder why some people are still willing to buy flood damaged cars good job
December 02 2011
Nice and thorough, good job
December 01 2011
I`ve seen a crank signal like that with a non BMW part that another shop installed.Caused all kinds of issues.
November 30 2011
It is posible the water got in to the computer?
November 30 2011
Excellent job tracking this down. I would suspect that the fuses would allow more than enough current for this to happen. Most are fused to at least a 10 to 15 amp fuse. That’s plenty for circuit welding. The ECM wouldn’t have to be flooded, just one of the solenoids it controlled. Good job!
November 27 2011
Hello, how did you know that the signal from the immobiliser was right? Had you got a comparatively vehicle where the engine was good working and so you record from this the immo signal and compare it with the problem car? I hope you can answer my question thank you sorry for my english i am german