MatthewHitchcock
11-06-2025, 01:47 PM
Hey everyone, need some help with an electrical issue please.
Quick summary:
After shorting the alternator positive terminal to ground on my 2007 Yaris, the car now cranks as soon as the battery is connected (key out). Cranking stops when the relay is removed.
What happened:
Noticed ABS and emergency brake warning lights on, recommended to check and tighten alternator belt if needed.
While tightening the alternator belt, I accidentally touched the alternator’s positive terminal to ground.
Big spark — fusible link blew.
I replaced the fusible link.
Symptom:
After reconnecting the battery, the engine cranks immediately, even with the key out of the ignition.
Additonal replacement parts: starter relay, and starter motor.
Testing done:
With the starter relay removed, the cranking stops
Battery charged to 12.6 V
Relay socket voltages (key out relay removed):
Top pin: 0 V
Middle pin: 12.75 V
Bottom left: 0 V
Bottom right: 11.74 V
Visual findings:
The small alternator connector (4-wire plug: green, blue, white, pink) going into a black junction box shows damage to pins, I recall seeing this when I replaced the alternator last year.
I am a bit of a loss as to what steps to do next, I live in Northern Canada and reasonably far from town so a tow truck is expensive so hoping to learn and fix this myself if possible,
Quick summary:
After shorting the alternator positive terminal to ground on my 2007 Yaris, the car now cranks as soon as the battery is connected (key out). Cranking stops when the relay is removed.
What happened:
Noticed ABS and emergency brake warning lights on, recommended to check and tighten alternator belt if needed.
While tightening the alternator belt, I accidentally touched the alternator’s positive terminal to ground.
Big spark — fusible link blew.
I replaced the fusible link.
Symptom:
After reconnecting the battery, the engine cranks immediately, even with the key out of the ignition.
Additonal replacement parts: starter relay, and starter motor.
Testing done:
With the starter relay removed, the cranking stops
Battery charged to 12.6 V
Relay socket voltages (key out relay removed):
Top pin: 0 V
Middle pin: 12.75 V
Bottom left: 0 V
Bottom right: 11.74 V
Visual findings:
The small alternator connector (4-wire plug: green, blue, white, pink) going into a black junction box shows damage to pins, I recall seeing this when I replaced the alternator last year.
I am a bit of a loss as to what steps to do next, I live in Northern Canada and reasonably far from town so a tow truck is expensive so hoping to learn and fix this myself if possible,