New guy with really odd engine issue!
Logistics Pro
Joined: Jan 2001
Posts: 3,740
Likes: 37
From: Central NYS
Next to that wire I see (nice pics, BTW) I see the WH/LB wire that gets current from the diode and GOES to socket 86 of the PCM relay.
That's where we are dropping voltage, either along that wire, or within the diode and/or its sockets.
Thread Starter
|
Junior User
Joined: Feb 2018
Posts: 70
Likes: 0
Don't worry about diode 502, that has to do with the A/C clutch.
So you have battery voltage at the SOCKET for the PSM relay diode (501).
That means the circuit from fuse 30 to the PCM diode is good.
But when you go to pin 86's socket you only have 0.95 V,
so we are dropping a lot of volts between these two points.
Take the diode out of the circuit and the PCM relay out of the circuit.
Therefore there should be no power between these two points.
Set your DMM to ohms, put one probe in the diodes output socket,
and the other probe in the PCM relay pin 86 socket.
If you have over a few ohms, that is the resistance between the diode socket and the PCM relay socket 86.
The wire that runs from the diode output socket to the PCM relay pin 86 socket is a white with light blue striped wire under the BJB.
Take a look under the BJB and see what has happened to that wire.
If the resistance reading is near 0 ohms, the whit/light blue wire is good,
so the problem must be in the diode.
Do you remember when you last turned the key to "ON", did your CEL lamp light up during the bulb check?
So you have battery voltage at the SOCKET for the PSM relay diode (501).
That means the circuit from fuse 30 to the PCM diode is good.
But when you go to pin 86's socket you only have 0.95 V,
so we are dropping a lot of volts between these two points.
Take the diode out of the circuit and the PCM relay out of the circuit.
Therefore there should be no power between these two points.
Set your DMM to ohms, put one probe in the diodes output socket,
and the other probe in the PCM relay pin 86 socket.
If you have over a few ohms, that is the resistance between the diode socket and the PCM relay socket 86.
The wire that runs from the diode output socket to the PCM relay pin 86 socket is a white with light blue striped wire under the BJB.
Take a look under the BJB and see what has happened to that wire.
If the resistance reading is near 0 ohms, the whit/light blue wire is good,
so the problem must be in the diode.
Do you remember when you last turned the key to "ON", did your CEL lamp light up during the bulb check?
1. CJB is central junction box under the dash
2. BJB is the battery junction box under the hood.
When I turn the key to the on position I do get the CEL or in my case the (Service Engine Soon) light.
It's pouring outside so I'll have to wait for a break. Figures, I have an electrical issue and all we get is rain!
Thread Starter
|
Junior User
Joined: Feb 2018
Posts: 70
Likes: 0
Okay, but the way I think of it is the way the current flows, so to my thinking that RD/LG wire comes FROM fuse #30 and goes into the diode.
Next to that wire I see (nice pics, BTW) I see the WH/LB wire that gets current from the diode and GOES to socket 86 of the PCM relay.
That's where we are dropping voltage, either along that wire, or within the diode and/or its sockets.
Next to that wire I see (nice pics, BTW) I see the WH/LB wire that gets current from the diode and GOES to socket 86 of the PCM relay.
That's where we are dropping voltage, either along that wire, or within the diode and/or its sockets.
Once the weather clears, I will check the wires again. As you can see by the pics there are no glaring/obvious issues with the wiring as far as visible damage or corrosion... If there is an issue with a wire, it will be a wire that is damaged within it's sheathing.
Thanks again to everyone for all the assistance. If not for your help, I would have set the truck on fire and pushed it down a hill by now!
Thread Starter
|
Junior User
Joined: Feb 2018
Posts: 70
Likes: 0
"The wire that runs from the diode output socket to the PCM relay pin 86 socket is a white with light blue striped wire under the BJB.
Take a look under the BJB and see what has happened to that wire."
Actually, I think there is an error here or I'm not understanding. If you look at the last pic in post #76. I am pointing to the diode spot #501. The wires that come from there are red with yellow stripe and yellow with a grey stripe. The yellow with grey stripe actually ends up going to the Fuel Pump Relay.
I don't know how to edit or add circles and arrows to my pics (it would make things 100% times easier)- but if you look at the same pic, near the top of the box as shown in the pic, you see the bottom of the relay spots- the first one to the left corresponds with Relay #302 The one to the right of it is the PCM Relay #301. As you can see, the first wire you see coming from is the green with the yellow stripe. There is no white with light blue
Am I looking at the wrong things???
Take a look under the BJB and see what has happened to that wire."
Actually, I think there is an error here or I'm not understanding. If you look at the last pic in post #76. I am pointing to the diode spot #501. The wires that come from there are red with yellow stripe and yellow with a grey stripe. The yellow with grey stripe actually ends up going to the Fuel Pump Relay.
I don't know how to edit or add circles and arrows to my pics (it would make things 100% times easier)- but if you look at the same pic, near the top of the box as shown in the pic, you see the bottom of the relay spots- the first one to the left corresponds with Relay #302 The one to the right of it is the PCM Relay #301. As you can see, the first wire you see coming from is the green with the yellow stripe. There is no white with light blue
Am I looking at the wrong things???
Posting Guru
Joined: Dec 2014
Posts: 1,792
Likes: 3
The input wire to the diode should be the red/light green wire, output from diode should be a white/blue wire going to the coil (86) on PCM relay. Keep in mind that these are old wires so it may have faded a bit, it looks kind of yellowed on your picture. Look at the diagrams posted previously.
Thread Starter
|
Junior User
Joined: Feb 2018
Posts: 70
Likes: 0
ok. I think that's where the disconnect is. The wire is actually white with blue, I didn't think it would fade that much.
That wire from the diode goes to the #304 (which I was referring to as the fuel pump relay.) Apparently it is the PCM. I'm an idiot.
It's #301 that is not getting power. So, I guess I need to find what is supposed to send that relay power...
I've been a little overwhelmed with this and a few other issues... Not sure how I messed that up. Sorry.
Back to the drawing board.
That wire from the diode goes to the #304 (which I was referring to as the fuel pump relay.) Apparently it is the PCM. I'm an idiot.
It's #301 that is not getting power. So, I guess I need to find what is supposed to send that relay power...
I've been a little overwhelmed with this and a few other issues... Not sure how I messed that up. Sorry.
Back to the drawing board.
Thread Starter
|
Junior User
Joined: Feb 2018
Posts: 70
Likes: 0
FTE Stories
Ford Trucks for Ford Truck Enthusiasts
2027 Ford Super Duty Buyer's Guide (Every Model, Engine, & Package)
Brett Foote
Top 10 Ford Truck Tragedies
Joe Kucinski
AEV FXL Super Duty - the Super Duty Raptor Ford Doesn't Make
Brett Foote
Lobo Vs Lobo: Proof the F-150 Lobo Should Be Even Lower!
Michael S. Palmer
Ford's 2001 Explorer Sportsman Concept Looks For a New Home
Verdad Gallardo
10 Best Ford Truck Engines We Miss the Most!
Joe Kucinski
2026 Shelby F-150 Off-Road: Better Than a Raptor R?
Brett Foote
2027 Super Duty Carhartt Package First Look: 12 Things You NEED to Know!
Michael S. Palmer
10 Most Surprising 2026 Ford Truck Features!
Joe Kucinski
Posting Guru
Joined: Dec 2014
Posts: 1,792
Likes: 3
Ok, good. Now, when you put a relay into the socket, does it click? At this moment, if the PCM still doesn't wake up (flashing anti theft, not possible to connect OBD scantool), verify that the relay is good, swap it with another, like the fuel pump relay or something. If it still doesn't wake up, you need to check the wire going out from the relay, pin 87 and then check fuses 23 and 18 in the fuse box under the hood, verify that battery voltage is going out from those when key is ON.
Posting Guru
Joined: Dec 2014
Posts: 1,792
Likes: 3
If it's clicking on and off rapidly, it sounds like it's not getting a stable voltage on the coil side. This might point to a bad connection on wither battery voltage pin 86 or the ground pin 85. This might be a damaged wire from when the work was done on the car. As a "quick and dirty" test, you could try to jump the ground wire directly to ground and see if the clicking stops. If it's still clicking, try to wiggle the diode and the wires around it. That wire would run in a loom to the internal fuse box under the dash, so check for damages to the wiring loom.
Thread Starter
|
Junior User
Joined: Feb 2018
Posts: 70
Likes: 0
Almost a success! Almost. I ran a light ground wire to the fender.
The relay stopped clicking and the engine fired. The my wife moved the box and nothing.
The small green with orange stripe is the ground.
I did see the dash briefly cooperate and stop giving me "-----" in the odometer but then it was back to it and the theft light was still flashing. We're trying to trace the ground now. Would it be unwise to simply run a new ground from the fender or firewall?
The relay stopped clicking and the engine fired. The my wife moved the box and nothing.
The small green with orange stripe is the ground.
I did see the dash briefly cooperate and stop giving me "-----" in the odometer but then it was back to it and the theft light was still flashing. We're trying to trace the ground now. Would it be unwise to simply run a new ground from the fender or firewall?
Posting Guru
Joined: Dec 2014
Posts: 1,792
Likes: 3
Well, a "quick and dirty" fix is to run a new wire to the nearest chassis bolt. What I would do is to find out where the nearest actual ground connection is and connect it there. The best is of course to run the ground to the same spot the original wire is connected to ground, or find where the original wire is damaged and repair the original wire.
But this is great news! Nothing is better than finding out where the problem is. Will be interesting to hear if it will be running solid once you get a proper ground connection to the relay.
But this is great news! Nothing is better than finding out where the problem is.
Will be interesting to hear if it will be running solid once you get a proper ground connection to the relay.
Thread Starter
|
Junior User
Joined: Feb 2018
Posts: 70
Likes: 0
Well, I'm not out of the woods yet.
We fiddled with the jumper ground and got a better connection: no clicking but still had ----- and flashing theft light
The we pulled the jumper off just to see and checked again: no clicking, but still had ----- and flashing theft light and then all of a sudden started clicking
We put the jumper back on and the relay stopped clicking but still had ----- and flashing theft light
I'm not hearing the fuel pump prime
We fiddled with the jumper ground and got a better connection: no clicking but still had ----- and flashing theft light
The we pulled the jumper off just to see and checked again: no clicking, but still had ----- and flashing theft light and then all of a sudden started clicking
We put the jumper back on and the relay stopped clicking but still had ----- and flashing theft light
I'm not hearing the fuel pump prime