Troubleshooting a Mitsubishi: Single Click on Start with Good Battery and Starter

Experiencing a single click noise when attempting to start your Mitsubishi can be perplexing, especially when you've confirmed that both the battery and starter are in good condition. This issue, prevalent in many Mitsubishi models with a 3.0L engine and automatic transmission, often leaves no error codes to guide the diagnosis. Yet, this symptom is indicative of a few potential culprits that can be investigated systematically.

First, check the battery connections. A loose or corroded terminal can prevent the necessary power from reaching the starter. Clean and tighten the battery terminals to ensure good contact.

Next, inspect the starter relay and fuses. A faulty relay or a blown fuse can interrupt the signal from the ignition to the starter. Locate the starter relay in the fuse box and try swapping it with another relay with the same rating. If the problem persists, check all related fuses.

Another possibility is a faulty ignition switch. Over time, the electrical contacts inside the switch can wear out, leading to intermittent starting issues. This requires a more in-depth electrical diagnostic or replacement of the switch.

The starting circuit wiring should also be scrutinized for any signs of wear or damage. Frayed or corroded wires can cause resistance in the circuit, preventing the starter from receiving full power.

Finally, although the starter may test as 'good', it's possible for a starter to exhibit intermittent failure due to an internal issue, like a bad solenoid or worn brushes. A bench test at an auto parts store may not reveal these sporadic problems. It's sometimes necessary to test the starter under load or consider its replacement.

In conclusion, while a good battery and starter are essential, they're only part of the starting system. The aforementioned areas should be inspected thoroughly to isolate the problem. If the issue persists, consider seeking professional assistance from a certified mechanic who can provide a more exact diagnosis.