Avital 5108L Remote Start Module Limp Mode - 12V Constant Wire Voltage Drop

Electricalintermediate✓ OP Confirmed

Problem

Avital 5108L remote start and alarm system would not complete the remote start sequence on a JZZ30 (Soarer/Supra). When the remote start button was pressed, IGN 1 would turn on for about 1 second then shut off, repeating indefinitely. The starter never engaged at all.

IGN 1 (clock/head unit) turns on for ~1 second then shuts off when remote start is pressedAvital module box makes relay clicking sounds with each pulseStarter does not engage at allIf car is running and turned off, pressing remote start lights up IGN 1 and IGN 2 (speedo/tach/odo) but does not crank the engineRemote start cycle repeats indefinitely without completing

Root Cause

One of the 12V constant wires supplying the Avital remote start module was dropping from 12V to 8V, causing the module to enter a protective 'limp mode' where it would not complete the start sequence. The 12V constant was connected to an unreliable source rather than the black/red wire from the ignition harness.

Confidence

Moderate confidence — Original poster confirmed this resolved the issue

View Original Thread →Posted April 2025 on SupraForums.com