Challenger fob not opening door help

Challenger fob not opening door help

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Mexican cuties

Original Poster:

686 posts

121 months

Sunday 29th November 2015
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Hi guys, car not had run for few weeks so when we went to unlock the doors both of the fobs wouldn't unlock the doors/boot. Manually opened with the key, then the alarm goes off, but car started straight away, killing the alarm thank God poor neighbours. Then both the fobs start working and can lock the doors as normal, battery not flat so any ideas ta

MikeSRT8

47 posts

151 months

Sunday 29th November 2015
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Tired key fob batteries? Maybe lost their code matching and restored code match once in a disarmed car? Have you ever replaced them? Probably overdue on an '09 car. Batteries are readily available and easy to change, did mine earlier this year.

vaughan watkins

512 posts

210 months

Monday 30th November 2015
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I would imagine it was because it was a few weeks without being used and now you've started the car it has re-instated them as they have a rolling code system, I have a funny one with one of my keys, it un locks the car, opens the boot and remote starts it but wont allow you to start the car the normal way so I think the key isn't sending out signal to the car that the fob is in the car (comes up fob not detected) haven't gotten around to trying to sort it just using the other key.

MikeSRT8

47 posts

151 months

Monday 30th November 2015
quotequote all
Found a bit more by way of background and explanation on Marv Davis' excellent Top Challenger Tips & Tricks CD


The Keyless Go system actually utilizes two controller modules and three separate antenna. One is the WIN module and one is the PEM (Personal Entry Module). The Keyless Go system works under the KEELOQ encryption system.

This system uses a "rolling code" encryption and the FOBIK may on a rare occasion become "un-synced" from the PEM module. When this happens the FOBIK will appear "dead" or have a dead battery, when in fact it is just "out of sync" with the PEM module.

To find out if this is the case, you will have to pop off the START BUTTON and insert the FOBIK like a key and when doing so it will use the WIN module to sync the system's rolling code "counter".

Once you have used the FOBIK as a key to start the vehicle, you can then remove it after driving or whatever and see if you can now resume functions with the FOBIK. If it works as normal, then this is what happened it lost sync with the "rolling code encryption counter". If this continues on a frequent basis, have the FOBIK checked by your dealer.

Also use the other spare or second FOBIK (you should have two when purchasing the vehicle) about every six months to keep it in sync as well.

Hope this helps.


Edited by MikeSRT8 on Monday 30th November 21:50

vaughan watkins

512 posts

210 months

Tuesday 1st December 2015
quotequote all
MikeSRT8 said:
Found a bit more by way of background and explanation on Marv Davis' excellent Top Challenger Tips & Tricks CD


The Keyless Go system actually utilizes two controller modules and three separate antenna. One is the WIN module and one is the PEM (Personal Entry Module). The Keyless Go system works under the KEELOQ encryption system.

This system uses a "rolling code" encryption and the FOBIK may on a rare occasion become "un-synced" from the PEM module. When this happens the FOBIK will appear "dead" or have a dead battery, when in fact it is just "out of sync" with the PEM module.

To find out if this is the case, you will have to pop off the START BUTTON and insert the FOBIK like a key and when doing so it will use the WIN module to sync the system's rolling code "counter".



Once you have used the FOBIK as a key to start the vehicle, you can then remove it after driving or whatever and see if you can now resume functions with the FOBIK. If it works as normal, then this is what happened it lost sync with the "rolling code encryption counter". If this continues on a frequent basis, have the FOBIK checked by your dealer.

Also use the other spare or second FOBIK (you should have two when purchasing the vehicle) about every six months to keep it in sync as well.

Hope this helps.


Edited by MikeSRT8 on Monday 30th November 21:50
Good find Mike, I did try my key in the ignition but to no avail, it worked to start the car as a key but not with the push button, and it was my main key that I was using that failed so had to revert to using my spare so at some point could be an issue :-( sounds like a part in the key fob has failed