ECM Power And Ground Circuits Wiring Diagram (1990-1991 4.9L, 5.0L, 5.8L Ford F-Series Pickup)

  • By: Abraham Torres-Arredondo
  • Created: 09 July 2025
  • Updated: 10 July 2025
  • Articl Id: 734
ECM Power And Ground Circuits Wiring Diagram. EEC Power Relay Circuit Diagram. (1990, 1991 4.9L, 5.0L, 5.8L F150, F250, And F350 Pickups)

APPLIES TO: This simplified ECM power and Ground circuits wiring diagram applies to the following vehicles:

F150:

  • 4.9L L6 Ford F150 Pickup: 1990, 1991.
  • 5.0L V8 Ford F150 Pickup: 1990, 1991.
  • 5.8L V8 Ford F150 Pickup: 1990, 1991.

F250:

  • 4.9L L6 Ford F250 Pickup: 1990, 1991.
  • 5.0L V8 Ford F250 Pickup: 1990, 1991.
  • 5.8L V8 Ford F250 Pickup: 1990, 1991.

F350:

  • 4.9L L6 Ford F350 Pickup: 1990, 1991.
  • 5.8L V8 Ford F350 Pickup: 1990, 1991.

This wiring diagram includes the following circuits:

  • EEC Power Relay.
  • EEC Module Grounds.

EEC POWER RELAY TESTS: Learn how to check if your Ford's EEC Power Relay is feeding power to the PCM like it should.

WHERE TO BUY THE EEC POWER RELAY: These are two EEC Power Relays, from known automotive brands I've used many times and still recommend today —reliable parts from brands that haven't let me down.

Purchasing through these links helps support the work I do here —and keeps this content free for everyone. I truly appreciate it!

EEC Power Relay Circuit Wiring Diagrams

More Ford F-Series Pickup Tutorials

You can find a complete list of Ford F-Series pickup wiring diagrams and tutorials in this index:

Here's a sample of the tutorials you'll find in the index:

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