Remote start not working and battery dying

Robert Mobile Technician Delaware Posted   Latest   Edited  
Case Study
Electrical
2017 Ford F-150 XLT 5.0L (F) 10-spd (10R80)
Battery Draw

I posted this in some other tech groups but I wa a asked to share here on DN so here it goes…

I want to share a recent Diag that I had on a 2017 F150 with a customer complaint of remote start not functioning as well as a battery draw. Apparently the customer brought it in saying that the remote start did not work and the battery was dying overnight. The shop called me to check it and before I could get there they had figured out that if they disconnected the battery, touched the leads together, then reconnected it the vehicle could be remote started. Once the vehicle was driven the remote start would not work again. I should mention that this is a factory remote start that was built as an option on this vehicle. I had a feeling that the battery draw and the remote start problems were related so I decided to go down the path of investigating the remote start issue and seeing if that fixed the battery draw issue. I started with a full scan of every module on the vehicle and found no fault codes present anywhere. When I tried to remote start the vehicle it did not respond at all. The remote LED would flash red three times which indicates it did not receive feedback that the vehicle started remotely.

 I decided the next step would be to go through any and all data pids that could have given any clues as to why the vehicle would not start remotely. I could not find anything wrong. The hood was showing closed as well as the doors. The vehicle was showing that it was in park. All door switches showed that they were closed. So I disconnected the battery, performed a hard reset, then reconnected the battery. I started the vehicle with the remote start with no issues. I got inside the vehicle and observed the message on this dash saying to put the key in and turn to the on position to drive the vehicle. I turned the key on, put it in drive, then back into park. I then got out, locked the door waited a minute then attempted the remote start again. No go. Just three flashes of the LED on the remote.

I had a hunch that this supposed battery draw would be gone after the hard battery reset and only showed up after the remote start attempt. I decided to go after that assumption and found it to be true. Very minimal battery draw after a hard reset. I even took it one step further and tested for a draw after starting and shutting it off from the remote. I still had less than a 100 mA draw. So then I started it remotely, opened the door, put the key in and turned it to the on position. Then I shut the truck off with the key, closed the door and locked it with the remote. At this point I had a half amp draw that never went away. I let it sit for some time and it was still there. That’s when I realized that the gear indication display in the cluster was always lit up. The PRND2L was always illuminated white no matter how long the truck sat. The modules were not going to sleep.

So now I know for sure that there is a relationship between the remote start not functioning and the battery draw. But now I have to find out what is related between the two. After the gear display illumination getting my attention I realized that I failed to notice a very important clue. When I put the key in the ignition and started the vehicle the gear display letters were all illuminated white. As soon as I pulled the shifter out of park and into reverse the other letters would light up red. Every other gear did the same thing but as soon as I went back into park the P would be white instead of red. This was a huge red flag and I needed to find out why the Cluster did not know it was in park. I connected IDS and scrolled through the instrument cluster data pids and there was not a single pid for gear position. I went into the one module that I knew would have it (PCM) and every year displayed correctly.

What would cause this thing to start remotely one time after a hard battery reset then not start remotely again. In the process of checking this problem I found that it would not only start once, it would remote start all day long as long if you did not put the key in the ignition. You could start it up, shut it off, start it up,shut it off with no issue. So then I got in the vehicle and tried it. Again I could start it up and shut it off from the remote no problem. I put the key in the ignition without turning it on and used the second key and the remote start function perfectly. Once I started it remotely, put the key in and turned to the on position as the IPC suggested, it would not start remotely again. Keep in mind even up to this point I still had no fault codes in any modules.

In the process of realizing that the problem started as soon as the key was turned on I also stumbled onto a very important clue. When starting it with the remote start and hitting the unlock button to open the door I noticed that my P indicator in the cluster was red showing that it was in park. As soon as I put the key in the ignition and turned to on the P went from red to white and would never turn red again. So now I have a relationship with the gear display and the remote start not working. But why? Researching service information showed that the instrument cluster received gear display information from the powertrain control module over the data bus. As I previously stated everything looked normal when I checked the Pcm data pids. 

I had a hunch that when turning the key on, a module was coming online and causing this issue. It was just a thought but I needed to figure out how to prove it. I decided to grab my Autel 909 which was very useful for this particular job because of the network topology screen. I took the keys out of the ignition and put them in my van. I then scanned the entire network and noted which modules communicated. Then I started the vehicle remotely and again took note of what modules were online. By doing this it made it glaringly obvious that the IPC was likely the module that was causing the issue. When the vehicle is started remotely the instrument cluster does not communicate. It does this by design. If you notice in the one picture the Cluster is completely black except for the message display about turning the key on to drive.

So this allowed me to focus on the instrument cluster and all of its inputs. When looking at a wiring diagram for the Cluster I found a circuit called park detect. It appeared to be a microswitch on the shifter according to the diagram. The diagram showed that the body control module supplied a ground through a field effect transistor to the switch.  The switch is closed when the shifter is in park sending a ground to the instrument cluster. Once you grab the shifter to pull it out of park the ground goes away. When testing I found that the switch worked perfectly as in it supplied the ground as it should and opened the circuit when grabbing the shifter but I wasn’t seeing any voltage coming from the ipc for the switch to pull to ground. 

At this point I knew that I needed to get to the instrument cluster to check the same circuit to see if I had a different result. I found that the ipc was providing 12 volts to the circuit but it wasn’t getting to the switch for some reason.  I started pulling the center console covers and dash apart and inspecting the wiring. I found some wires under the shifter that looked suspect. It wasn’t obvious at first. It wasn’t broken in two. It’s just that the insulation had that white texture suggesting that the wires had been pulled really hard. With very slight pressure the wires broke apart. I fixed the wires and all of the problems went away. 

So looking back on this and knowing what was wrong it makes total sense why it was doing what it was doing. If the instrument cluster is responsible for reporting the state of the park detect circuit then it cannot do that when it’s not online. But the funny thing about it is that it can do that. It just needs to see it in a bad state one time. Performing a hard reset on the battery must make it forget about what it saw. 🤷. Overall this was a fun diagnostic job and a perfect example of how you can have a problem with a circuit but no fault codes because it is technically in a valid state. One thing just came to mind that I wanted to mention. If you started the vehicle with the key and pulled it out of park in to any other gear with the door open, the Cluster would give you a message that it was not in park. Had I not seen this message I may have went after the park detect circuit sooner but I figured it must be seeing park if it’s telling me to put it in park when I had it in any other gear. Anyway, I hope you enjoyed reading this as much as I enjoyed diagnosing it! On to the next problem car…

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Interesting
Thanks
Conrad Owner
Minnesota
Conrad Default
   

Great find, and review.

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Martin Instructor
British Columbia
Martin Default
 

Good job Robert! Personally, I find those types of faults most interesting, because they force you to think and use logic. Then there's the guys who bang out brake jobs and almost mindless routine service work all day long, who cannot for the life of them understand why anyone would enjoy diagnostics!

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Agree
Paul Mobile Technician
United Kingdom
Paul Default
 

Great write up ! That must have been a satisfying find when the wire broke.

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Andrew Technician
Texas
Andrew Default
 

Yes, very good find. I like that type of work.. (most times) :)

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Ray Diagnostician
Ontario
Ray Default
 

Robert, thank you for the excellent post!

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Gary Owner/Technician
Colorado
Gary Default
 

Great write up on a tough problem, Robert! I bet if it went to another shop, it might have had a new instrument cluster installed…

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Geoff Diagnostician
Hawaii
Geoff Default
   

I have read numerous cases, of the micro-switch in the shifter going bad causing battery draws (on iATN). I think the remote start complaint really acted as a red herring, glad you got her sorted, and found it was really just a wire. For others unfamiliar, Ford usually only sells the complete shifter but the Omron switch (iirc) inside it, is available separately from Mouser or the like…

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