Alphard Starting Issues

The 'Terminal 15 ignition positive interrupted' error suggests a break in the power supply to the ignition system. On a 2013 Alphard, this could stem from several sources. Have you checked the relay switch related to the ignition circuit? A defective relay can cause intermittent or complete loss of power. Also, inspect the wiring harness leading to the ignition switch for any signs of damage or corrosion. A significant voltage drop in that circuit will also prevent the engine from starting. It's also possible that the ignition switch itself may be faulty, but less probable than a wiring or relay issue. Given the age of the vehicle, consider potential corrosion within plug connections. Can you tell me if you've observed any related issues prior to this, like difficulty starting or flickering lights?

Thanks for the detailed response. I haven't checked the relay switch specifically, but I'll look into that. Where exactly is the ignition relay located on the Alphard? Also, how would I go about testing for a voltage drop in the wiring harness? I don't have a ton of experience with electrical diagnostics.

Unfortunately, without inspecting the vehicle directly, providing exact relay location information is challenging as Toyota can vary component placement slightly based on production specifics. Refer to the vehicle's repair manual, if available, or consult online Toyota-specific forums with detailed diagrams. As for testing voltage drop, you'd need a multimeter. Connect the multimeter leads to both ends of the wiring segment you're testing while the circuit is under load attempting to start the vehicle. A reading above a couple tenths of a volt indicates excessive resistance and a potential problem. Given your experience level and the potential complexities of electrical faults, it might be prudent to consult a qualified workshop to avoid further complications, though.

Appreciate the insights! I took it to a local shop, and it turned out to be a corroded connector on the wiring harness, just like you suspected. They cleaned it up and replaced a small section of wire. Total cost was about 95€. Thanks again for pointing me in the right direction!