Brand new key fob not working?

[applesauce98]

I bought a 2013 C-Max Hybrid SEL back in February and recently my key fob stopped working, so I went and replaced the battery with a brand new one and none of the buttons were working still. I unlocked using the key and ended up setting off the alarm but was able to start the car, turning off the alarm. I took it to a ford dealer to figure out the problem and they couldn’t find anything wrong with the car. When I got the fob back, it STILL wasn’t working so they programmed a new fob for me and determined the old one wasn’t transmitting a signal. It still sometimes works so I use the old one as a spare. Flash forward to about a week now and the new fob isn’t working. I left my doors unlocked, so I can get in but none of the buttons on the fob will work and if I put the fob in the special steering column slot it won’t start. The lights on the dash and the touchscreen come on when I open the door, but it doesn’t even give me the “no key detected” message. It also didn’t set off the alarm when I opened the door this time. Did I get another fob that doesn’t work or is there an actual problem with my car?

[applesauce98]

I have the intelligent access key type 1 (three buttons) in case if that matters

[homestead]

Check the 12V battery in the car and see if it is dead/low.

[raadsel]

Additionally, there is a physical key inside the key fob -- you can use that to unlock the driver's door if the key fob quits working.

[plus 3 golfer]

Here's how the Remote Keyless Entry System is suppose to work. 

 

1) When you touch the door handle, the Remote Function Actuator module sends a low frequency signal with a range of about 3 feet via three antenna.  When an FOB is within this range and detects the signal OR alternatively, when you push the FOB to unlock the door, the FOB transmits a high frequency message to the RF Receiver.  The RF Receiver via the RFA sends the message to the Body Control Module on the Medium Speed-CAN.  The BCM validates that the FOB data is correct and sends a command to the Door Module to unlock the door. - DOES NOT WORK 

 

2) When the start/stop button is pressed, a voltage signal is sent to the RFA module. When the RFA module detects the signal from the start/stop switch, it begins the key initialization sequence by activating the 3 interior PATS antennas. Each PATS antenna transmits a low frequency signal with an approximate range of 1 m (3 ft). The passive key activates if it is within range of 1 of the 3 PATS antennas.  The BCM validate the data and if OK initiates the startup sequence. - DOES NOT WORK 

 

3) A no start condition may exist if the FOB battery is low, an antenna has failed, or the RFR has failed.  This is when one places the FOB in the backup transceiver slot on the right side of the steering wheel and pushes the start/stop button to start. - DOES NOT WORK 

 

4)  When you push the start/stop button, no message is being displayed that a key is not detected.  This to me is puzzling.  It implies a key was detected, but the startup process stopped.  What if you don't push the brake pedal? any different.  What happens, if you leave FOB away from car and attempt to start? any messages? 

 

So, first make sure your 12 V battery voltage is fine.   If voltage is fine, then the only common component with the the first three items above on your car is the FOB.    It could be possible that there is a double contingency events - failure of the backup transceiver in addition to another component like the RFR / RFA / antenna but I would think that there would be DTCs stored for these component failures.  If the BCM is expecting something to happen that doesn't, there is virtually always a DTC that dealer should have found.

[applesauce98]

I recently had my oil changed and my battery tested back green, so I don’t think it’s that but I do have a spare 12v battery so we can see if changing that works. I’m going to have the new key fob taken back to the dealership to get it tested to see if it’s transmitting a signal or not

[applesauce98]

Just went to start the car and it immediately shut off on me. I opened the door, and it started right back up but as soon as I closed it, it shut off again. I did this about three times before it actually stayed on which makes me think a bigger problem is the case. A warning message popped up each time telling me to get to safety now before shutting off. Definitely taking it back to have it looked at now

[plus 3 golfer]

Yes, so the BCM likely has always been detecting the key. During the startup process and continually thereafter, the are many monitors that run to check the status of the Hybrid power system, for example are the high voltage battery contractors closed. If a monitor check fails when trying to restart, the software will not allow the car to start normally if at all. There is likely an intermittent issue where most times the startup checks pass but later a monitor finds an problem with the Hybrid system, issues the stop safely now message, and allows driving but in a limited mode. Most times upon restart the car starts and runs fine for example, the HVB contractors closed correctly and passed the startup check upon restart. Hopefully, the stop safely now and DTCs will reoccur at dealer.

[applesauce98]

Having that 12V battery replaced today. I’ve got a spare one in my trunk and I think the one in my car currently might be the original one anyway so it doesn’t hurt to replace it. I’ve had a suspicion it was that battery all along but constant testing of it always came back in the green. At least if we replace it, it’ll rule out a problem if it continues acting up but I’m glad to know it’s a common issue and I didn’t just buy a lemon. I love this car, it runs great when it’s not having issues and I could see myself keeping it a few more years after I pay it off, but if it continues to have these issues I may just trade it in. Will let you guys know if the battery change works though!

[plus 3 golfer]

Having that 12V battery replaced today. I’ve got a spare one in my trunk and I think the one in my car currently might be the original one anyway so it doesn’t hurt to replace it. I’ve had a suspicion it was that battery all along but constant testing of it always came back in the green. At least if we replace it, it’ll rule out a problem if it continues acting up but I’m glad to know it’s a common issue and I didn’t just buy a lemon. I love this car, it runs great when it’s not having issues and I could see myself keeping it a few more years after I pay it off, but if it continues to have these issues I may just trade it in. Will let you guys know if the battery change works though!

When you replace the 12V battery, you need to reset the Battery Monitoring System (Age). If the 12 V battery was replaced at one time and the age was not reset when replaced (even dealers fail to reset it) , then the charging algorithm will continue to use the estimated capacity losses of the old battery via “coulomb counting” in determining how to charge the new battery. This can result in a very low state of charge in the single digits because the PCM will reduce the set point charging voltage of the DC-DC converter believing the battery is reaching the max Ah capacity left in the battery. You can reset the age with the FORScan app for smartphones using the appropriate OBDII adapter ($15 or so).

 

http://fordcmaxhybridforum.com/topic/7721-forscan-lite-service-and-test-functions-available/

https://forscan.org/

[C-MaxA2]

Thanks Plus 3 Golfer - from this forum it's clear to me all the warning signs of a dying battery.  We've all heard about keys, etc. not working and it was the battery!  Just had mine replaced, the original (and asked the dealer to make sure the battery - and oil change system  - were reset).  It's the wonderful expertise and experience from folks like you and Paul that make this forum so valuable!   Thanks again. 

[jestevens]

My 12V -always- tested good by whatever procedure Ford is using as well, but locked out and having to use the manual key three times wasn't fun in February.  Factory battery 5 years old, I told the advisor to change 12V anyway.  She was concerned I would be upset if that didn't solve the issue but issue was solved after about 24 hours with new battery installed in car.  Low voltage causes all sorts of weird issues with these cars.

[applesauce98]

It’s been about a month since the battery was replaced and everything was going fine at first but I’ve been having problems with the fob again. Sometimes I can start it just fine in the morning and get all the way to work and as soon as I turn off my vehicle, I go to lock it and none of the buttons work. If I go to start it it takes me about 5-6 tries of the “no key detected” failure message popping up before it actually does start. The last couple of days I’ve been able to get my car locked, but then when I try to go home after work I can’t get it unlocked and I have to use the key and then another 5-6 tries of trying to start it to get it going. What’s weird is that once it does start, the check engine light comes on and the car does not move until I press the start/stop button again, in which case the check engine light turns off again and I’m good to go. If I’m in park and I open the drivers side door, my car says thanks for driving a hybrid and shuts off until I close the door again, and then it’s miraculously back on. I have heard of no one having these same issues and every time I take it somewhere nobody has these same issues that I do. I’m about at the point of just paying this car down and then trading it in for a different car because I can’t seem to figure out what’s wrong with this one

[Bill-N]

I have just one thought.  The "new" fob might in fact be pretty old.  Try replacing the fob battery with one from someplace that sells a lot of batteries.

 

Hope this helps.

[plus 3 golfer]

It could be that the 12V battery is not being charged because of a bad 150 A 12 V fuse assembly which is attached to the + terminal of the 12 V battery. The battery once externally charged will check OK. There have been several members that have had the assemblies develop high resistance and cause the no start issue. The issue is hard to detect by the dealer because the 12 V battery checks OK and there are no DTCs. See the red circled assembly in the attachment.

 

Apparently, the fuse assembly develops high resistance and prevents proper charging of the 12 V battery by limiting the charging voltage to the battery. So, even though the DC/DC converter is putting out say 14.5 V, the 12 V battery may see a lot less voltage since the resistance of the fuse assembly is in series with the battery resistance. Once the PCM sends the set point voltage to the DC/DC converter, the car runs fine as the converter holds the voltage to the set point. But, when the car is shut off, it won't take long for the 12 V battery to drain down from normal "car off" load to the point where restarting can be problematic depending on how low the voltage is. So, the module voltage may or may not be sufficient to allow modules to detect key and if key detected, other modules voltages may not be sufficient to allow startup of the car.

 

IIRC, one way to check the fuse assembly without disconnecting it is by feel or IR gun. If there is higher resistance, it should heat up.

 

 

Edited August 22, 2019 by Plus 3 Golfer

[stratosurfer]

All, I know this thread is old, but I’m having a similar problem on my 2013 SEL. My FOB works only on the ‘Emergency’ receiver. I will start with that 150 amp fuse on the 12v battery. How was the problem here finally resolved?