Wtf? Is my tow package missing left brake light fuse fitting?

[RangerBill]

F73 and F87 don't exist in my fuse block. Just blank spots. I replaced the harness and installed the seven pin/four pin plug. Previously I just had the factory installed flat four under the bumper. When it was first plugged into a trailer everything worked fine, including the left turn signal! Yay! And now it doesn't. Boo! I'm at the WTF stage of this journey.

If you are using the 4 pin trailer connector, then the left turn/stop light on the trailer is fed by fuse F56 in the battery junction box (BJB). I would check that fuse.

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[airline tech]

Ok
I dug into this and confirmed the wiring diagrams for the Trailer Lighting Circuit is misleading
and all available diagrams are wired as such.
I have a Lariat -With the TRM & 4/7 Way Connector
I along with others were confused by the factory wiring diagram that made it appear the relays were on all trucks, that is not the case

If you ONLY HAVE the 4-Way Trailer Connector - The wiring is as such and the included relays
and your truck came from the factory with (ONLY) this connector

Now

If you have the TRM & 4/7 Way Trailer Connector there is not a full circuit diagram that is correct
So we have to look at 2 separate diagrams and note that the Trailer Stop / Turn Relays are removed and not used - It uses the TRM for that.
However, the Park Lamp Relay - is still used and we gain another relay (Trailer Back-Up Lamp) Relay

So, If your truck came from the factory with a 4/7 Way connector (it includes a TRM)
The TRM takes the place of the (Trailer Stop/Turn) relays that are noted in all wiring diagrams and misleading that the (4-Way) of the 4/7 Way connector routes to the BJB & Includes those relays in the circuit (They are NOT-INSTALLED) and the TRM provides that relay function.
The Park Lamp - Relay and the Back-Up Relay are the only relays in the BJB when you have the 4/7 Way Tow Connector and associated TRM.
The 4-Way side of the connector is spliced into the 7-way wiring, the wiring diagrams do not depict that.

I have to split it up into 2 diagrams.
But this should make it clear now and this is how the 4/7 Way is wired

Note: I edited this from the original post

So, for the OP if the Left Trailer Turn is not working and the others are. It's not the fuse.
It's the TRM or Wiring

 

[RangerBill]

Ok
I dug into this and confirmed the wiring diagrams for the Trailer Lighting Circuit is misleading
and all available diagrams are wired as such.
I have a Lariat -With the TRM & 4/7 Way Connector
I along with others were confused by the factory wiring diagram that made it appear the relays were on all trucks, that is not the case

If you ONLY HAVE the 4-Way Trailer Connector - The wiring is as such and the included relays

Now

If you have the TRM & 4/7 Way Trailer Connector there is not a full circuit diagram that is correct
So we have to look at 2 separate diagrams and note that the Trailer Stop / Turn Relays are removed and not used - It uses the TRM for that.
However, the Park Lamp Relay - is still used and we gain another relay (Trailer Back-Up Lamp) Relay

I have to split it up into 2 diagrams.
But this should make it clear now and this is how the 4/7 Way is wired

View attachment 227914

So, for the OP if the Left Trailer Turn is not working and the others are. It's not the fuse.
It's the TRM or Wiring

@Chkls states:
" F73 and F87 don't exist in my fuse block. Just blank spots. I replaced the harness and installed the seven pin/four pin plug. Previously I just had the factory installed flat four under the bumper. When it was first plugged into a trailer everything worked fine, including the left turn signal! Yay! And now it doesn't. Boo! I'm at the WTF stage of this journey. "

He says that he doesn't have F73 or F87 fuses in his BJB so it would appear that he doesn't have the TRM ?

 

[airline tech]

@Chkls states:
" F73 and F87 don't exist in my fuse block. Just blank spots. I replaced the harness and installed the seven pin/four pin plug. Previously I just had the factory installed flat four under the bumper. When it was first plugged into a trailer everything worked fine, including the left turn signal! Yay! And now it doesn't. Boo! I'm at the WTF stage of this journey. "

He says that he doesn't have F73 or F87 fuses in his BJB so it would appear that he doesn't have the TRM ?

That would be the case

 

[ControlNode]

@Chkls states:
" F73 and F87 don't exist in my fuse block. Just blank spots. I replaced the harness and installed the seven pin/four pin plug. Previously I just had the factory installed flat four under the bumper. When it was first plugged into a trailer everything worked fine, including the left turn signal! Yay! And now it doesn't. Boo! I'm at the WTF stage of this journey. "

He says that he doesn't have F73 or F87 fuses in his BJB so it would appear that he doesn't have the TRM ?

@Chkls is not the OP, @charwest is. Since Charwest mentioned that the truck has both flat for and round 7 it as been pointed out several times that the TRM equipped trucks to not use F56 & F63. For Chkls the issue is different, was a flat 4 only truck and then got a 7-pin added, no mention if TRM was added as well. Without knowing more about how the 4->7 upgrade was done, I would say take it back to who did the install to troubleshoot it, if Chkls did it themself.... who's your most electrically knowledgeable friend that wants to spend time with you for some food and troubleshooting.

 

[Chkls]

F56&F63, F73&F87 don't exist. The TRM is there. When pugged into the computer it shows the TRM working. I'm down to a wire fault somewhere between the connector on the frame rail under the drivers seat and the right kick panel where the TRM is located. Looking forward to pulling the dash to track it down.

 

[Big Blue]

F56&F63, F73&F87 don't exist. The TRM is there. When pugged into the computer it shows the TRM working. I'm down to a wire fault somewhere between the connector on the frame rail under the drivers seat and the right kick panel where the TRM is located. Looking forward to pulling the dash to track it down.

OK, this just got confusing! You are saying F56 & F63 don't exist on your truck, that would indicate a factory tow package with a TRM. You also say that F73 & F87 do not exist on your truck. That would indicate a non-tow package truck. Yet you have the TRM. What is powering it? You should have one or the other pair of fuses. Without any of them your trailer brake/turn lights should never have worked.

You have also said you added the 4-7 plug in place of the OEM 4 pin plug. Also an indicator of a non-tow package truck. Did you also add the receiver hitch?

 

[airline tech]

F56&F63, F73&F87 don't exist. The TRM is there. When pugged into the computer it shows the TRM working. I'm down to a wire fault somewhere between the connector on the frame rail under the drivers seat and the right kick panel where the TRM is located. Looking forward to pulling the dash to track it down.

Ok, can you look at both of these pics and note on the 1st pic - if the relays (R39 & R38) are installed.
If they are installed, then - Fuses 56 & 63 - Should also be installed.
Fuse 56 = Trailer Tow LH Stop / Turn Relay
Fuse 63 = Trailer Tow RH Stop / Turn Relay


Then Note:
Relay (R40)
This should only be installed (if the TRM) is also installed
Trailer Tow (Back-Up Lamp) Relay

And
Note Relay (R6) Trailer Tow Park Lamp Relay
This should be installed on either (Option)
and
Fuse 34 -Trailer Tow Park Lamp Relay

For Reference my 2022 Lariat - Does NOT have Relays (R39 & R38)
and only has the (R6 & R40) Relays with Fuse #34 Installed for the Top View

This is a pic of the BOTTOM side of the BJB, you MUST REMOVE the BJB and pull the cover off of the box to access these fuses.

Fuses 56 & 63 - Feeding Relays R39 & R38

Fuses 73 & 87 - Feeding the TRM

Fuse 71 - Feeding Park Lamp Relay

This pic shows (Fuses 56 & 63) Empty and (Fuses 73 & 87) Installed
It also shows (Fuse 71) Installed

Note: If the scan tool shows (TRM)
Can you actually (COMMUNICATE) to it?
as some SCAN tools will use a (preset) list of modules that MAY or MAY NOT be installed and with the TRM as a (Available) module it auto populates the TRM in the list, but that does not indicate if it is installed.

If using Forscan - when you load the truck - it scans for all connected modules on the network


Ref this pic (Borrowed)

TRM - Installed

In the Right Passenger Kick Panel - you will see the TRM (Circled) If Installed

Ref: Note
Top Connector - C2498B
Pin #1 - Ground - (Black/Blue)
Pin # 2 - MS Can Bus (-) (Violet/Orange)
Pin #3 - MS Can Bus (+) (Grey/Orange)

Middle Connector - C2498A
Pin # 1 - Fuse 73 (Red)
Pin # 2 - Fuse 87 (White/Red)

Bottom Connector -C2498C
Pin #1 - Trailer Tow - Stop / Turn (Left) (Yellow)
Pin #3 - Trailer Charging (Orange)
Pin #8 - Trailer Tow - Stop / Turn (Right) (Green)
Pin # 12 - Trailer Park Lamps (Brown)

 

[airline tech]

With using Ebay as a reference to the BJB (Engine Bay Fuse Box) and noting that all US version rangers at least pictured with the cover (OFF) all show the R38 & R39 relays removed, however the (ROW) Rangers have them.

A second confirmation is using the Ford Parts Diagrams, the part number of the BJB only changes for Rear-Wheel-Drive Trucks and With or Without Parking Sensors, all 4WD show the same Part Number.

So, with that guidance and reflecting back on a previous thread and trailer wiring.

I am fairly certain (ALL) US Version Rangers have the TRM Installed, and the (configuration) difference point is at the C405 Connector (This changes the wiring harness part numbers) from C405 (aft) to the trailer connectors either (4-Way) or (4/7 Combo) the Rear Parking Sensors also come into play with those part numbers.

So, either configuration 4-Way (Only) or the (4/7 Way - Combo) the LH & RH Stop / Turn lamps are routed through the TRM.
The TRM (4/7 Way) Option will add the (Reverse Lamp) Relay into the circuit as well as Trailer Charging.

Both configurations use the (Park Lamp Relay)

This is how I see it being actually wired and unless I am wrong as someone with a (US Version) Ranger and without the TRM and having the Relays (R-38 & R39) Installed would have to chime in, as the documentation I see so far - That is not an option for the US Version Ranger.

For added Information.

from a previous thread - this is the Harness part numbers for C405 Rearward to the Trailer Connector. (Options)

If the TRM is installed, then these are the harness part number options to add the 4/7 Way trailer harness to the truck.

 

[Chkls]

My mystery is solved. The wiring harness that contains the yellow wire from the TRM (left trailer turn signal) exits the cab and runs along the left frame rail. Under the driver's seat there is a larger connector. Maybe 25 pins? The pin connected to the yellow wire was pushed out. Previous owner had apparently pulled this connector apart (lock tab was broken off) and pushed the pin out when they put it back together. Pin is back in place and the lights all work. Great thanks to my local custom body shop owner, who finally tracked it down.

 

[airline tech]

Cool - C422 (Pin#15) in the diagram above
Is a 34 Pin Connector

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