On the '90 through '93 Eldorado/Sevilles 4.9L's the ECM (Electronic Control Module), aka PCM (Power Control Module), is a metal box mounted underneath the interior passenger side kick panel with three electronic harness connectors attached to the bottom of it. Perform the following procedures for removal:

Disconnect negative cable from battery

  • Remove the kick panel, x3 - 7mm hex screws.
  • Pull the carpet back, pull back the hush panel insulation by moving it out of the way of the ECM/PCM.
  • Disconnect all three harness connectors from the ECM/PCM. You may have to pull hard using both hands, or wedge a flat screwdriver into the side of the plastic harness halves and twist. Image 1
  • Visually identify the ECM/PCM retaining screw closest to the passenger door. I did this by coming from the driver side door, laying across the center console, looking up at the bottom of the ECM. Use a small flashlight. Image 2 & 3
  • With a 7mm 1/4" offset socket wrench, locate the retainer screw with your hand and connect socket to remove. (I backed it off 2-3 turns with the wrench then used my hand to back it all the way off). I sat in a kneeling position to the right of the passenger seat facing the front of the car, coming up under the kick panel with my left hand to reach the retaining screw.
  • With screw removed, drop ECM by pulling slightly towards the passenger door and down towards the floor to remove. The ECM is attached to the driver side with a small plastic pin that slides into and out of a hole.

Replace with new service module by inserting existing MEM/CAL PROM into the service modules PROM male pin connector. Shift attachment hardware from bad module to replacement module (x1 plastic retainer secured with two bolts, and x1 plastic pin on lower left side of ECM/PCM module). Image 3

I used petroleum jelly to lubricate exterior plastic harness guides on the female connectors before inserting into new/replacement module.

Insert plastic pin into hole on driver side, attach ECM/PCM retaining screw to hole on the passenger side.

Note: Reattach negative battery cable. Turn key on, enter diagnostics and clear codes (should have an E054, A054, and I054). Turn ignition on, *perform TPS/Idle Learn procedure*, test drive.

PCM harness.jpg

Image 1


Image 2

PCM plastic retainer.jpg

Image 3