Keyless Entry Intermittent Malfunction

mxyplxDecember 20, 2009

Keyless Entry Intermittent Malfunction

1995 Crown Vic, 79418.3 Miles, 1 Owner, Pristine

There are external buttons on the drivers door, a lock/unlock button on the drivers arm rest and a remote control.

1. Ocasionally the drivers door lock doesn't respond to input from ANY of the above 3. It might; might not. All the other stuff does (trunk, other doors, autolock function).

2. Additionally on occasion I have messed up punching in the combination on the door external buttons but have kept randomly punching buttons and it unlocks. The following exact scenario has happened several times:

Assume a 5 digit combination within this 5 button array: 1/2--3/4--5/6--7/8--9/0

with the combo being 3-4-9-4-5.

Assume a screw up on the first try but within 1-2 seconds further hit 3-4-9. The driver door unlocks.

We are using the permanent code built into the system - not a personal code.

What is the problem and where is it? In the door or the computer?

Car goes for dealer service next month - if it happens to be functioning properly at the time - well there's not much hope they could find the problem is there?

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As I always try and point out, testing during a failure is the only way to be 100% sure about what is wrong, and then especially to prove that the car is genuinely repaired. That being said, the Ford factory scan tool, such as the IDS that I have will access the PATS system and even allow me to monitor which button is being pushed on the drivers door pad. The seals on the door button pad fail and eventually the contacts start to corrode and you can end up with symptoms that would match your description. Another symptom associated with this button pad corrosion is the interior lights can come on by themselves, which occurs if the BCM senses that one of the buttons has made contact. On my scan tool I would see either a NO for no button pushed or 3/4 as in if the BCM thinks it sees the 3/4 button pressed. A false or incorrect response from the keypad while monitoring the scan data is all I would need to confirm the pad is failing. The odds are better than 90% you will need to replace the key pad on the drivers door.

    Bookmark   December 21, 2009 at 8:31AM
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Altho the car is garaged most of the time the seals could, of course, be deteriorated. After all the heap is 14 years old.

However, the same problem occurs simultaneously with both the inside door lock/unlock button as well as with the remote on the key ring.

To open the trunk, for example, I run thru the combination 3-4-9-4-5 then hit 5 again and the trunk opens every time. If within 5 seconds I hit 7 the remaining doors open every time. Similar scenario with locking the doors. So the key pad must be OK.

For sure each individual lock has a solinoid. So it must be the drivers door lock solinoid that is used up or has a corroded connection. Which makes sense since it gets actuated probly 20+ times to everything else's oncet.

Thank's John. Ya got me there. Sometimes we need a push in the right direction eh?

    Bookmark   December 21, 2009 at 12:11PM
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