Trunk release fault - Need testing tips

Bob Owner/Technician East Longmeadow, Massachusetts Posted   Latest   Edited  
Question
Electrical
Security
2015 Ford Taurus Limited 3.5L (8 Flex) 6-spd (6F)—1FAHP2F85FG101290
The Trunk Opens When Touching The Door Handles

2015 Taurus -- Intelligent Key System -- 1fahp2f85fg101290 

I'm looking for some direction or confirmation on this problem. The car was originally towed in as a no crank no start. It's a push button start with the Intelligent key system. No response from the start button. 

Long story short, I found this wiring damage. It's the harness in the left foot well. I had to repair thirteen damaged or broken wires. After the harness repair the vehicle starts and runs normally. 

However, I'm now left with a strange fault that I'm having trouble isolating. 

There are several issues with the trunk lock. When you grab the door handle, the trunk pops open, every time. I found that it happens with the driver and passenger side handles. These have the proximity sensors in them.

The trunk will NOT open with the key fobs or the interior trunk release switch. I should say that the trunk doesn't open with the (2x) button but it will pop open if you tap the regular door unlock button. 

This is the intelligent key system. Here is a block diagram of the system and description and operation

I have tested and verified the trunk switch input at the RFA module. When the switch is pressed I hear clicking in the RFA module but the trunk doesn't open. As far as I can see it's the job of the RFA module to power the trunk latch. I know the system is capable of working because the trunk pops open when touching the door handles. 

If I activate the door locks with the scanner from the RFA module, only the door locks activate. If I activate the door locks through the DDM, the trunk pops open.

I have tried re-flashing the RFA module with no change. I have re-programmed the key fobs with no change. 

I'm having a hard time wrapping my head around this system operation but it seems to me at this point that the RFA module (which is in charge of operating the locks) must be the culprit. 

I would love to hear some other ideas or some other test I could do to be 100% certain. Oh, I almost forgot, it doesn't set any fault codes either.

UPDATE: 4/22/2019

This morning I pulled the drivers door panel off and disconnected the DDM, the latch and other switches. The problem is still present. This does have the key pad on the window frame. If I input the security code the trunk pops open, even with the DDM and other switches disconnected. This is making me lean more towards the RFA module as the culprit.

I reconnected everything and did an all module scan. As you can see there are 23 modules found and no codes stored. I would think if anything was cross wired somewhere I would have some codes. As I mentioned before, it doesn't happen if you use the manual lock switches, it seems to be isolated to the wireless proximity system. 

I have tested both trunk switches at pins 4-5 of the RFA module. I have B+ not pressed and ground when pressed but the trunk does not function from either switch. So the manual switches and the trunk button on the fob don't open the trunk. The trunk only opens when touching a door handle, inputting the code on the keypad or pressing the regular door unlock button on the fob.

I may just have to just bite the bullet and plug in a "Known good" RFA module but I can't get one for a few days. I would gladly accept a silver bullet for this one.

FIX UPDATE 6/11/2019

This problem is finally resolved. It took awhile to get the customer to leave the car again but when he did, he mentioned that he had noticed another symptom. 

The trunk opens when the right directional is engaged.

I'm surprised I did not see that previously but I quickly realized that was a BIG clue. Here is what happens when the directional is engaged

Before I did anything I consulted the wiring schematics again. I checked the control wires for the right blinker bulb and the trunk latch motor. Wouldn't you know it, one was Grn/Brn and the other was Grn/Org. 

In the original thread Caleb Mohler suggested something was wired incorrectly. I was confident in my original repair as I had found it easy to identify all the matching wires. Turns out Caleb was right. I cross wired the turn signal and trunk wires. It turns out the tracers on those two wires were easy to confuse. Must have been the last two wires I repaired and after 13 some odd wires, I was probably going cross-eyed.

In hindsight it all makes so much sense. My original confidence with the wiring repair led me to waste a lot of time trying to wrap my head around all the inner workings of the intelligent keyless entry system. 

It's been said before but it's worth saying again, basics, basics, basics. Also, look for all the clues you can find to help zero in on the fault. If I had tried the directionals I would have solved this a lot sooner.

After correcting the wire mismatch, all system functions were back to normal and all the trunk switches and fobs worked correctly. 

0
Eri Technician
Larchmont, New York
Eri
 

Have you observed data pids in the rfa module for a input such as 1 of the trunk release switch’s being grounded when you grab the door handle?

0 Ð Bounty Awarded
Bob Owner/Technician
East Longmeadow, Massachusetts
Bob
 

Yes I have. I don't see any response on the scanner when pushing the trunk button on the dash or the fob. However, when I push those buttons I do hear clicking from the RFA module so there is something happening. As I mentioned before, I tested the trunk switch wire at the RFA module and it does toggle from B+ to ground when I push the button. It looks like the module is not recognizing it, but

0 Ð Bounty Awarded
Zachary Mobile Technician
Austin, Texas
Zachary
 

Have you spoken with the customer to see if that particular issue was occurring prior to the no start? I see that the BCM appears to be in the same general area as the wiring damage you found. Any chance of additional damage not yet discovered? Clues as to what the cause of said damage is? Couldn't tell for sure if that was rodent induced or not. What about accidental crossing of circuits during

0 Ð Bounty Awarded
Bob Owner/Technician
East Longmeadow, Massachusetts
Bob
 

Zach, I appreciate all the questions. This is what I need to jog my brain cells and figure this out. The wiring damage looked mechanical like possibly a drill run through the harness. I'm wondering if something in the RFA module could have got zapped when the wires were shorted together. The customer has no idea what could have happened although he said he had let his brother use the car for a

0 Ð Bounty Awarded
Caleb Technician
Mishawaka, Indiana
Caleb
 

Personally I think something got wired incorrectly, there's still some wiring damage or there's a fault with the trunk IA antenna.

0 Ð Bounty Awarded
Bob Owner/Technician
East Longmeadow, Massachusetts
Bob
 

I'm definitely going to take another look at the wiring repair. How do you think the trunk IA antenna could cause the problem?

0 Ð Bounty Awarded
Caleb Technician
Mishawaka, Indiana
Caleb
 

I've seen malfunctioning rear antennas on 2015 an newer Chrysler 200 cause this when the remote was near the car . Instead of setting a code the module simply interpreted the fault as a request to open the trunk. But don't read to far into this . It's simply an quick idea.

0 Ð Bounty Awarded
Anthony Technical Support Specialist
Kirkwood, Pennsylvania
Anthony
 

Hi Bob: I don't know what tool you're using. Aside from what has already been mentioned, a couple of thoughts come to mind. Have you performed an All CMDTC Self Test or Network Test? Any issues with the MS-CAN? The RTM and DDM appear to be on MS-CAN. If there are no network issues, the only item which appears to be in common is the Gateway Module. HTH, Guido

0 Ð Bounty Awarded
Bob Owner/Technician
East Longmeadow, Massachusetts
Bob
 

Hi Guido, I have done an all system scan with a Verus Pro and an Autel. I have no codes. If I remember correctly it showed 19 modules, does that sound right?

0 Ð Bounty Awarded
Anthony Technical Support Specialist
Kirkwood, Pennsylvania
Anthony
 

Hi Bob: I only have access to a 2014 Network schematic. There could be 28 modules, over 4 networks, on that model. For MS-CAN, there is: the Gateway, FCIM, PDM, DDM, GPSM, RTM, SOD-L, SOD-R, DSM, SCME & HSWM. You'll have to determine which ones don't apply. The way that I see it, the system is receiving a request from the DDM. Whether, or not, it is appropriate is beside the point. It sees

+2 Ð Bounty Awarded
Geoff Diagnostician
Lahaina, Hawaii
Geoff
 

I would think that attacking the simplest "does NOT work" issue, (which you have addressed when you tested for the button not popping the trunk) would lead to the answer. And it may be a red herring, but the diagram shows 2 (?!?) Luggage Compartment Lid Release Switch right next to each other, that both feed a ground signal to the RFA. Where or what is that second switch?

+1 Ð Bounty Awarded
Bob Owner/Technician
East Longmeadow, Massachusetts
Bob
   

That's a great question. That diagram has bothered me a bit as I have not found a rear switch. There is a rear inside pull handle but I don't think that's it. I identified the switch wires in C405 but I'll be damned if I can find the switch. I think your right about the simplest route being the piece that does not function. The RFA module powers the trunk latch motor. The dash switch is

0 Ð Bounty Awarded
Geoff Diagnostician
Lahaina, Hawaii
Geoff
 

I wonder if it is one sub-model vehicle vs another and Ford left the designation off of the diagram. Was there a Taurus Wagon that year? Probably not the problem, but good that we at least both saw it there.

0 Ð Bounty Awarded
Zachary Mobile Technician
Austin, Texas
Zachary
 

Is one switch perhaps the release button inside the vehicle and the other the button at the trunk itself? That was my assumption when I saw that but perhaps I'm reading too much into it.

0 Ð Bounty Awarded
Glen Owner/Technician
Arthur, Illinois
Glen
   

Can you monitor the Ext switch pid in the RFA module? Did you try the other key? Follow PPT S or P in the WSM section 501-14B Does this vehicle have remote start? According to my info it does. The ext release switch should be in the above the license plate, part #1L2Z14018AC. The WSM says the rear bumper cover has to be removed in order to replace.

0 Ð Bounty Awarded
Bob Owner/Technician
East Longmeadow, Massachusetts
Bob
 

I did finally find the rear switch above the plate. (i must have been brain dead earlier) I monitored it on the scanner and the PID does not change when the button is pushed, however, I can hear clicking from the RFA module when I push the switch. I also tested pin4 at RFA connector C2153B. I see Battery voltage and when the switch is pushed, the voltage goes to zero, just like it should, but

+1 Ð Bounty Awarded