Wiring Issue/Brake Lights On after replacing PCM - 5.0

[ShoeSlinger]

I had to replace my PCM on my 5.0 conversion after water got to it. Wiring harness and PCM from EFI Guy. Motor runs fine but my check engine light is now on along with my brake lights. Brake lights stay on after disconnecting brake light switch. I have to remove the alternator fuse from the Power Distribution Box to get the brake lights to turn off. I am really lost. Any ideas on where to start? Appreciate any help.

 

[Steve83]

Contact EFIGuy about a wiring diagram. Since it's not stock, we can't guess how it's wired, or why those might be related.

But water alone doesn't hurt an EEC. Was it saltwater, or did it stay wet for a long time? Were there any symptoms? Do you still have it? I'd try putting it back in.

 

[EPB72]

Knowing the year could help but looking at a 97 explorer there is a brake on off input to the PCM on pin 92 other years as well ,, If yours has this set up or not IDK but thinking it would be spliced in after the brake light switch ,, so a wire goes back to brake lights through turn signal switch and guessing before TS it’s spliced and goes to PCM ,, so guessing as well would have to isolating parts of the circuit and possibly but very uncommon if the PCM is defect and sending out voltage on circuit ,

 

[EFI Guy]

Some of the later Explorer computers put out a trace amount of voltage on the brake input wire, this is normal. Regular bulbs draw enough current that you would never see them light up from the trace amount of power present. However, it will cause some very low power LEDs to illuminate.

The best solution is to buy a set of the resistor devices used to eliminate "hyperflash". (Google it)
You can probably just add in resistors but I'm unsure of the value required and resistors create heat so I don't want to tell you to do anything potentially dangerous. It's probably best to use a commercial product designed for this purpose.

Having said that...The trace voltage should only be present when the key is on. The alternator fuse is not related to this circuit in any way. So unless it is one of the EFI fuses being pulled that shuts it down, there may be another issue at play here,

 

[ShoeSlinger]

Some of the later Explorer computers put out a trace amount of voltage on the brake input wire, this is normal. Regular bulbs draw enough current that you would never see them light up from the trace amount of power present. However, it will cause some very low power LEDs to illuminate.

The best solution is to buy a set of the resistor devices used to eliminate "hyperflash". (Google it)
You can probably just add in resistors but I'm unsure of the value required and resistors create heat so I don't want to tell you to do anything potentially dangerous. It's probably best to use a commercial product designed for this purpose.

Having said that...The trace voltage should only be present when the key is on. The alternator fuse is not related to this circuit in any way. So unless it is one of the EFI fuses being pulled that shuts it down, there may be another issue at play here,

Unfortunately the brake light stays on even with the key turned off. Painless harness and in great shape. I am lost on this one since when I pull the alternator fuse, the brake light (among other things) goes off. Not looking forward to tracing everything back, but that might be the only way. I even have the brake switch at the pedal disconnected.

 

[EFI Guy]

Try unplugging the PCM completely and see if it is still there.

 

[DirtDonk]

Which alternator fuse? The small exciter fuse in the fuse panel? Or the large mega/midi style in the charge wire to the battery?