No Crank Condition - Factory Security System Disabling Starter

Electricalbeginner✓ OP Confirmed

Problem

1990 Supra would not crank at all after being driven to work and parked. No clicking from starter, dash lights bright, battery load tested fine. Jumping the car did not help. Crossing starter terminals directly caused it to crank, confirming the starter motor itself worked.

Complete no-crank condition (no clicking, no attempt to turn over)Dash lights bright and battery tests goodJumping from another vehicle does not helpStarter cranks fine when terminals are crossed directlyIGN fuse under kick panel was blown (replaced but did not fix issue)Ground wire on starter had fallen off (reattached but did not fix issue)Clutch start switch tested good with continuity

Root Cause

The factory security system had been tripped and was disabling the starter circuit. The security module sits between the power source and the starter relay, cutting voltage when armed. An aftermarket keyless entry system caused the issue — locking with the door button and unlocking with the remote (instead of the physical key) triggered the factory alarm, which then disabled the starter. The security LED on the dash may not always illuminate when the system is activated, making it difficult to diagnose.

Confidence

High confidence — Original poster confirmed this resolved the issue

View Original Thread →Posted April 2022 on SupraForums.com