Which fuses power the PCM and fuel pump relays on the 4.9L engine?

Three 20A fuses in the Engine Compartment Fuse Box: fuse U (hot in start or run) feeds circuit 16 R/LG through the PCM power diode, and fuses I and O (hot at all times) feed circuit 37 Y to the PCM Power Relay and Fuel Pump Relay.

What wire circuit powers the PCM from the PCM Power Relay?

Circuit 361 (Red), which splits at splice S136 and is 12V with the relay energized; it also feeds the E4OD transmission (page 30-2) and circuit 912 W/R.

What circuit runs from the Fuel Pump Relay to the inertia fuel shutoff switch?

Circuit 238 DG/Y (dark green/yellow), through splice S139 and connector C202, continuing to the Inertia Fuel Shutoff on page 23-7.

How is the PCM grounded in this diagram?

Through circuit 57 BK to grounds G100 and G104 (via splice S102), and circuit 570 BK/W through splice S106 to ground G101. Grounds are detailed on pages 10-1 and 10-3.

What functions does the PCM control according to this diagram?

The PCM receives inputs from various sensors and uses the information to control fuel flow, Exhaust Gas Recirculation (EGR), ignition, transmission controls (with E4OD), and evaporative emissions.

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Ford 4.9L Engine Controls Wiring Diagram 23-1 - PCM & Fuel Pump Relay Power

Engine Controls wiring diagram, 4.9L, page 23-1, PCM power relay and fuel pump relay circuits

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Ford 4.9L engine controls wiring diagram showing PCM power relay, fuel pump relay and engine compartment fuse box with color-coded wires.

AI caption August 2018 · Photo 358 of 386

This document is page 23-1 of a Ford factory-style wiring diagram covering Engine Controls for the 4.9L engine. It shows the power distribution and grounding for the Powertrain Control Module (PCM). Power comes from the Engine Compartment Fuse Box: a 20A fuse (position U, hot in start or run) feeds circuit 16 R/LG through the PCM power diode to circuit 175 BK/Y, while two 20A fuses (positions I and O, hot at all times) feed circuit 37 Y to the PCM Power Relay and Fuel Pump Relay. The PCM Power Relay output on circuit 361 R (splice S136) powers the PCM, the E4OD transmission circuits (page 30-2), and circuit 912 W/R. The Fuel Pump Relay output feeds circuit 926 LB/O to the VIP Data Link Connector (C198) and circuit 238 DG/Y through splice S139 and connector C202 to the Inertia Fuel Shutoff (page 23-7). PCM pins 387, 57, 1, 22, 8, 40, 60, and 20 are shown, with grounds via circuits 57 BK and 570 BK/W to grounds G100, G101, and G104 through splices S102 and S106. Callouts explain that the relays direct voltage to the PCM and fuel pump, and that the PCM controls fuel flow, EGR, ignition, transmission (E4OD), and evaporative emissions.

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Frequently asked questions

Which fuses power the PCM and fuel pump relays on the 4.9L engine?: Three 20A fuses in the Engine Compartment Fuse Box: fuse U (hot in start or run) feeds circuit 16 R/LG through the PCM power diode, and fuses I and O (hot at all times) feed circuit 37 Y to the PCM Power Relay and Fuel Pump Relay.
What wire circuit powers the PCM from the PCM Power Relay?: Circuit 361 (Red), which splits at splice S136 and is 12V with the relay energized; it also feeds the E4OD transmission (page 30-2) and circuit 912 W/R.
What circuit runs from the Fuel Pump Relay to the inertia fuel shutoff switch?: Circuit 238 DG/Y (dark green/yellow), through splice S139 and connector C202, continuing to the Inertia Fuel Shutoff on page 23-7.
How is the PCM grounded in this diagram?: Through circuit 57 BK to grounds G100 and G104 (via splice S102), and circuit 570 BK/W through splice S106 to ground G101. Grounds are detailed on pages 10-1 and 10-3.
What functions does the PCM control according to this diagram?: The PCM receives inputs from various sensors and uses the information to control fuel flow, Exhaust Gas Recirculation (EGR), ignition, transmission controls (with E4OD), and evaporative emissions.