2002 BMW X5 3.0i E53 electrical malfunction preventing engine cranking

[IrvesBMW]

Greetings everyone, I want your assistance about the persistent issue of my X5 failing to start. I will begin with my acquisition and detail my attempts and observations so far.

The former owner reported intermittent starting issues; it functioned properly one day, starting in the morning and ceasing in the evening, yet failed to start the following morning. When the key was turned, there was no response—no clicking sound, although the lights remained illuminated, with some flickering as if attempting to start. Occasionally, a jump start would succeed, but often it would not. Subsequently, the ignition switch was replaced, and a new key was programmed, yet these measures proved ineffective.


Since acquiring it, we have had no success. Despite installing a new battery, there was no improvement; nonetheless, we saw that the battery consistently discharged to 11.5 volts, suggesting a potential power loss. I have not yet been able to verify, since I have been eager to attempt to start the automobile; despite a newly charged battery, it failed to start.

One evening, in my absence, my father attempted to start it with a companion. They were examining the ignition switch wires, confirming the presence of 12 volts, and probed one of the lines, which he identified as purple. The vehicle unexpectedly began and operated without any issues, leading us to exclude the possibility of a faulty starter or mechanical difficulties. We suspected a defective ignition switch connector, since the ignition switch had been changed, and I had no more information because I was not there.

The next morning, the vehicle failed to start again. My father attempted to start it, and then connected a jump pack, which enabled it to start. We then took the car on an extended trip without any issues. Although we did not verify the functionality of the alternator, it presumably operated well, since we drove for around one hour.

The following morning, I attempted to start the vehicle, but it failed to respond. I connected a jump pack to the engine bay terminals, yet there was no change; the battery registered 11.5V, and the jump pack did not enhance the voltage during the starting attempt. Unsure of my jumping technique, I suspected the front terminals might be faulty. Consequently, I disassembled the rear to connect the jump pack directly to the battery, but the voltage remained unchanged, and the car still would not start. Subsequently, I charged the battery until it reached a healthy 12.7V, but the vehicle still failed to start. I inspected and manipulated the ignition wires extensively, but to no avail.

I am uncertain if the issue is a nightly power drain causing the vehicle to fail to start due to a depleted battery, or whether there is a malfunction in the ignition wiring, or maybe both. The car seems to operate erratically, and I find electrical systems perplexing, leaving me unable to assess the problem.

Any assistance would be welcomed; please feel free to guide me through a comprehensive diagnosis from the beginning, providing explicit instructions in case I have overlooked any details.

Best regards

[DreamWeaver]

Inspect the grounding straps connecting the chassis to the engine.
Consider connecting a jump wire from the body earth jump point to the engine

[IrvesBMW]

Are you proposing to connect a cable from the earth terminal on the passenger side inner wing in the engine compartment to any point on the engine, such as a lift hook, and then attempting to start or jump the vehicle as usual?

[dave783]

Indeed, he is verifying if the engine is properly grounded by the earth straps.

[DreamWeaver]

Affirmative.

[IrvesBMW]

I completed that task, connecting the earth mount on the body to a lift hook on the engine, nevertheless the engine would not start.

[IrvesBMW]

[TDudette]

Does the starter produce a sound?
Does the starting relay emit a clicking sound?


When you turn the key, do you measure 12 volts at the starter's exciter terminal?

[DreamWeaver]

Ensure that the wires at the +jump point are securely fastened.

[DreamWeaver]

😁