Injector Resistor Pack Selection for Sequential Injection on Standalone ECU

Fuel Systemintermediate✓ Community Verified

Problem

When converting to a standalone ECU (e.g., ECU Master) and switching from batch fire to sequential injection, the stock Toyota 3-way injector resistor pack shares resistors between paired injectors. This means each resistor serves two injectors in the stock setup, and when only one injector fires at a time in sequential mode, the resistance is half what it should be, resulting in higher than designed current flowing through each injector.

Potential long-term injector failure from excessive current when running sequential injection with stock resistor packHigher than designed current through low-impedance injectors in sequential modeOnly half the expected voltage drop across the resistor when firing a single injector

Root Cause

The stock Toyota injector resistor pack is a 3-way unit designed for paired (batch fire) operation. Each resistor is shared between two injectors. When switched to sequential injection on a standalone ECU, only one injector fires per resistor at a time, cutting the effective resistance in half and doubling the current through each injector.

Confidence

Moderate confidence — Multiple community members agreed on this solution

View Original Thread →Posted June 2022 on SupraForums.com