Ford 4.9L Engine Controls Wiring Diagram 23-5 - PCM, ECT, IAT & Knock Sensor

This document is page 23-5 of a Ford factory wiring diagram covering Engine Controls for the 4.9L engine. It shows the sensor input side of the Powertrain Control Module (PCM), including the Knock Sensor (KS) at connector C1009 (circuit 310 Y/R to PCM pin 23), the Engine Coolant Temperature (ECT) sensor at connector C183 (circuit 354 LG/R to PCM pin 7), and the Intake Air Temperature (IAT) sensor at connector C164 (circuit 743 GY to PCM pin 25). Both temperature sensors share sensor signal return/reference circuit 359 GY/R through splice S138 and connector C125. Callout notes explain each sensor's function: the knock sensor detects engine detonation (spark knock), while the ECT and IAT are thermistors whose resistance decreases with temperature, used by the PCM for idle speed, fuel delivery, spark timing and EGR control. Additional PCM inputs shown include the brake pedal signal (circuit 511 LG, 12V with pedal depressed) from the Turn/Stop/Hazard Lamps circuit (page 90-2), and A/C-heater inputs (883 PK/LB and 348 P) from page 54-2. PCM outputs at the bottom connect to the Vehicle Speed Sensor (676 PK/O, 679 GY/BK; pages 64-1, 64-2) and the VIP data link connectors (915 PK/LB, 914 T/O, 209 W/P via C198/C199).