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Under the Hood: Toyota key fobs aren't working in the cold

Brad Bergholdt, Tribune News Service on

Published in Automotive News

Q. Hi Brad, we had problems with both of our wireless remotes for our 2006 Toyota Avalon. They stopped working altogether. We recently purchased two wireless remotes and were able to program them to work. The problem, we found out, is that they don't work in the dark. The previous ones at first stopped working in the dark, then when it was cold and finally stopped working altogether. We did try replacing the batteries in both fobs, but this worked only in the daylight for about two days and then stopped working. We recently purchased the two remotes and just got them programmed. We don't know if it's something in the remotes or something wrong with our car? The new remotes are acting the same, where they work when it's warm, but not after the sun goes down. What are your thoughts?

Paul M.

A. The first step in diagnosing a keyless entry symptom is renewing the transmitter batteries. You've already accomplished this by purchasing new transmitters. Additionally, the odds of all four transmitters -- original and replacements -- misbehaving in exactly the same way is off the charts. I think the fault is triggered by temperature rather than available light. How about parking the car in the warm sun for a few hours and chill the remotes in the fridge for 30 minutes? Then, park the car outside at night and warm the remotes with a washcloth straight from the drier? Another check would be to see if the trunk-open or panic functions work, using the fobs, and if the door locks function, using the Avalon's door buttons when the car is cold. My hunch is it is the car's door lock receiver that doesn't like the cold, or there is an intermittent connection fault in its related circuits.

If the fault shows up reliably when the car is cold, a scan tool test for diagnostic trouble code B1242 should be performed (this is a body code that requires a pro-grade scan tool). This code may come up if the door lock receiver is faulty, lacks power/ground, or can't communicate with the multiplex network body ECU (the box that ultimately sends the door unlock/lock commands to the door lock actuators). Performing tests of the receiver's pertinent terminals should be done before considering replacement of the part.

Q. I have a 2012 Chrysler 200. The left headlight fogs up and often stays like this for a few days at a time. What's causing this? Can it be fixed?

Dick R.


A. According to Chrysler service bulletin 08-091-14, dated October 2014, some fogging can occur after a warm headlight is shut off under cool/wet conditions because the housings are vented to the atmosphere. If it begins clearing up after being dried externally after 20 minutes of operation in an indoor environment, this quantity of condensation is considered normal. Large drops visible inside (1mm or larger) or failure to clear indicates a seal leak in the composite headlight housing and isn't likely to dry out. Replacement is officially recommended. Removing the headlight housing and applying sealer externally to the housing seams might do the trick as a DIY repair, but the front bumper fascia needs to be removed to access the lamp housing retainers. This is annoying but not particularly difficult to do.


Brad Bergholdt is an automotive technology instructor at Evergreen Valley College in San Jose, Calif. Readers may send him email at; he cannot make personal replies.

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