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Conducting a diagnostic test to identify any damaged or severed electrical cables.


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Seeking advice from anybody who can provide guidance.
I have identified a malfunction in my vehicle (C43 S205 2019) that I feel is mostly due to one or more broken wires in the wiring harness leading to the front bumper. I have had to rejoin severed wires on this wiring harness using solder sticks. I would want to test for continuity starting at the front bumper loom connection plug, which is attached to the front bumper, and extending all the way to the repaired area. Currently, my only method of doing this task would involve severing the wires closer to the vehicle above the damaged area, and then examining the continuity by testing the connecting socket at the front bumper. I would want to avoid this situation if feasible, since it would lead to more repairs of wire junctions that have previously been fixed.
May I inquire about the possible placement of the termination point for this loom, namely the front parking sensors and pedestrian protection sensors, inside the fuse box? Alternatively, is there any alternative method that I may use to do this test without causing any damage? What is wire pinning?

Thank you very much

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Excellent decision, I have placed an order and it is expected to arrive tomorrow. Meanwhile, I have recently conducted an experiment involving piercing a sewing needle through the solder stick, and it was successful. The first wire is functioning properly, since it maintains continuity from the sensor socket over its whole length.
If it is determined that a broken wire is not the cause, what other factors may result in a fault code indicating a 'short to positive or open circuit'? This error notice pertains to one of the two sensors responsible for detecting and ensuring the safety of pedestrians. The current trouble code is B273715. The only remaining possibility I can consider is that the sensor itself is faulty, which would be unexpected because it is a newly manufactured original equipment manufacturer (OEM) component.

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I have seen instances where there are faulty wires located on the side of the plug that is connected to the bumper, in close proximity to the larger plug. The insulation is filled with green material. I have previously conducted repairs on them, nevertheless, acquiring a new bumper loom is the optimal solution.

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The repair is not on the bumper loom; otherwise, I would have simply replaced the whole unit. It is located on the spur of the main loom, which connects to the mentioned plug. Today, I spoke with an autonomous Mercedes garage about the cost of replacement, which was quoted at £1100 with a lead time of 3 months. Consequently, we have decided against pursuing that option.

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After the rain stopped, I checked for continuity on the second wire and found no signal. Therefore, I cut and replaced the original fix. I tested it again and confirmed that everything was functioning properly when plugged in. Reassembled all the components, performed a thorough scan of the automobile, and encountered the same issue once again. I assume that there may have been wires that were destroyed at a higher point in the weave. Upon the arrival of my piercing probes tomorrow, I will have the opportunity to do a thorough examination of the loom at a far higher level than the extent of the accident damage. With any luck, this investigation will uncover any potential issues. I will provide you with regular updates.

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Indeed, it is a feline restoration endeavour. If you have an available hour, you may read my developing journal by clicking here, which includes some photographs.

Regarding water intrusion, the sensor is a recently manufactured original equipment manufacturer (OEM) component from Mercedes-Benz. The bumper has undergone a complete reconstruction and has been stored at my home for the last 2 months, awaiting the return of the vehicle from the paint job.
I have affixed the wires in close proximity to the bulkhead and am still seeing a consistent flow of electrical current at the sensor connector.
Therefore, I speculated that it may be the actual plug that was changed. While I may have achieved continuity, the resistance is not within the specified range owing to the repair joint. After obtaining the old, authentic sensor, I verified that it did not trigger the error when used on the left side. Subsequently, I directly connected it to the wiring harness socket, although the malfunction persists. In addition, I have exchanged the sensors from the left side to the right side, nevertheless I continue to get the same issue.

Therefore, the issue does not stem from the sensor, plug, or a damaged cable. What other possibilities exist?
It seems improbable that the code cannot be cleared by my scanner, since I am able to reproduce the code and clear it simply connecting and disconnecting the left hand one.
Currently, I am facing a significant obstacle and unable to make progress. I have a final expectation that this code is being impacted in some way by the other code associated with the petrol cylinder code B280613. The replacement component for this code was expected to come yesterday, but it has not been received yet. Consequently, I am sceptical about my ability to proceed with the task until next week, since I will be occupied with work from Monday to Friday. Although it may seem like wishful thinking, it is worth considering this possibility before spending money on an alternative.

My last hypothesis is that it is connected to resistance. My experiment with hard wiring likely resulted in an increase in resistance due to the use of excessively thin wires. Should I do it once again today with a wire that has a greater diameter?

While I am able to replace the front bumper loom, I fail to understand how this will resolve the issue if there is currently a consistent flow of electrical current to the sensor socket.

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While I lack knowledge about this specific sensor, I can provide some general advice for troubleshooting.

Testing for continuity is feasible when you have confirmed the presence of a signal at point A, but not at point B. However, I believe that you are not now in that particular job.
Navigating without prior knowledge of the path, both starting and ending sites, or the appearance of the signal is more challenging. Have you considered examining a wiring diagram?

Although it may be challenging, it is nonetheless feasible to accomplish the task by using the other sensor as a reference.Therefore, I will attempt to determine the signal present on each of the pins (either 2 or 3) on the functional side. Then return to the negative aspect and see whether you are lacking one or more. I mention signals, but without knowledge of their nature, they may potentially be power signals, ground signals, PWM signals, analogue signals (although I am uncertain), or other types of signals. The quantity of pins would aid in determining the potential signal type used.

If you own just a multimeter, this task may provide challenges, but it remains feasible. An oscilloscope would be the most suitable option, however I would not recommend pursuing this road if you lack confidence in electronics, as mentioned in your previous discussion. Even when using a metre set to the DC volts range, if the signal is a pulse width modulation (PWM), you will get a result that aids in identifying the circuit. Certain metres may possess a duty cycle and frequency configuration.
It is advisable to do this experiment both with the sensors unplugged and with them attached.

The fault description, indicating a short to positive or open circuit, essentially means that the module is detecting a signal of 5 volts or higher on that particular pin. The uncertainty on whether a short or open circuit will occur is due to the internal pull-up of the pin to a supply voltage, which is likely to be 5V. During an open circuit scenario, all signal pins will be either pushed up or pulled down to guarantee that they are in a predetermined state.
If the pin is set to a voltage of 5 volts, every wire connected to it will also have a voltage of 5 volts. Therefore, this is something you can verify.

Another factor to take into account is the distinct possibility that the connection between this signal pin and the sensor is fully intact. In order for the sensor to function properly, it requires at least one additional connection, namely a ground connection and maybe a power connection as well. Is this the root cause of the fault?

Best wishes.

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