Humidity Method
WARNING: This page is about a different car, the 1994 Toyota 4Runner. However, it is still accessible from the selected car via links, so may be relevant.
CAUTION:
DO NOT apply water directly to any electrical component.
If humidity or moisture is suspected of causing intermittent failure, lightly spray water on the front of warm radiator to increase humidity in the engine compartment. Check for malfunction by monitoring suspected circuit or component with a DVOM.
If vehicle has interior water leakage, the water may have damaged the Electronic Control Module (ECM) or corroded the electrical connections. Carefully inspect ECM terminals and electrical connections for corrosion.