Hey everyone! I've had my 05 b4000 5mt for a while now and this summer the engine finally blew (timing chain failure @320k kms) and a couple of weeks ago i replaced the engine with a same model year 4.0 sohc from an auto, i swapped wiring harnesses to keep the original in the truck. everything went smoothly, no check engine light, truck starts and runs fine, sounds super smooth.My only issue is the oil pressure warning light is on in my dash. I've replaced the oil pressure sensor with a known working one from the previous engine, no change, and concerned it may actually be an oil pressure issue i installed a mechanical oil pressure gauge. oil pressure on cold start sits @55PSI at idle and maintains about the same pressure until it warms up. once warm idle pressure is about 20psi and up to around 50psi under load, from what I've read this is a pretty healthy oil pressure.

I've tried cleaning connector contacts and spraying with contact cleaner but nothing has made any change. does anyone have any suggestions on what i can check out to try to fix this issue? i guess its possible i damaged the wiring harness at some point but i don't remember any moments where it could have happened so id say its unlikely also everything else works 100% so seems improbable.

At the time i was troubleshooting the oil pressure light my fuse was blown for my OBD2 port, but i assume this wouldn't have any effect. Obd2 shows no codes even with the light on.

If there's nothing obvious I'm missing I'm probably just going to pull the bulb out of the dash and rely on my mechanical gauge instead of the light in the dash. If there's a simple solution ill add a t fitting and use both.

Thanks for your time and any input, much appreciated!!
Alex

 

Welcome to the forum

2005 uses a Digital Dash/cluster but Oil Pressure gauge is still analog
There is an ON/OFF SWITCH on the engine, so not a "sensor", has been that way since 1989 on most Fords, lol
This switch is the GROUND for the dash oil pressure gauge, or light, one wire connection
If oil pressure is above 5psi switch turns ON, grounds wire to engine
When oil pressure is under 5psi then switch is OFF, no ground to engine

So to test if wire and gauge are OK, unplug the 1 wire on the switch and GROUND it to battery negative with a jumper wire
Turn on the key, engine OFF
Gauge should go up to the "normal range", if so all is well with wire and gauge, or if there is No Gauge then Oil Light should go OFF
If gauge doesn't go up, or light doesn't go OFF then there is a problem with wire or gauge/light
In a 2005 it should be a dark green/white stripe wire, it runs to the firewall connector, the big one under brake booster/master

Because this is a 1 wire switch the switch needs a good ground to the engine metal, which is done via its THREADS, so always leave some BARE THREADS at the bottom when you screw these in, do not over tape them or they can't work

 

This is awesome info, ill give this a shot and report back.

Thank you Ron

 

SOLVED... wow i cant believe how easy of a fix that was... Thanks RonD, grounding the plug turned the light off therefore was just a bad ground between the switch and the engine. Took a drill and a wire wheel to the switch threads for 30 seconds, swapped the gauge i had plumbed in for the original switch, plugged it in, started the engine, and voila! No oil pressure warning light. Now i can say the engine swap is a 100% success.

Thanks again Ron!