* Computer (ECM): This is the brain of the system, located typically under the hood, often near the firewall. It calculates the timing based on various sensor inputs.
* Sensors: Various sensors (crankshaft position sensor, throttle position sensor, etc.) provide data to the ECM. These are distributed throughout the engine compartment.
* Ignition Control Module (ICM): This module receives signals from the ECM and controls the ignition timing. It's usually near the distributor (if equipped) or integrated into the distributor itself (in some applications).
* Distributor (if applicable): Older 5.7L engines used distributors. The distributor would contain the ICM and mechanically distribute the spark. Newer systems are distributorless.
Therefore, there's no single "EST circuit location." You need to diagnose issues within the entire system, checking the ECM, sensors, ICM, and wiring harness connections. A wiring diagram for your specific year and model K3500 is crucial for tracing the circuit.
