Random horn and interior lights...
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Joined: Jan 2005
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From: Maple Valley, 25 miles from Seattle WA.
Random horn and interior lights...
I'm stumped on this one. My '98 has developed an issue where the horn sounds and interior lights (mirror) illuminate randomly when the car is off. After much trouble shooting and head scratching, I determined that if I remove the battery from the key FOB, the horn and lights do not come on randomly. It appears that the car's internal electronics is communicating with the FOB and interpreting the data as a signal to toot the horn and turn the lights on even though I did not push the Lock or Unlock buttons. It acts the same way with both FOBs so it's not a defective FOB, it is internal to the car. I've changed batteries, re-synched the FOBs, disconnected the car battery and discharged all internal capacitors by shorting the battery plus to ground (after being disconnected), examined FOB solder joints under a microscope and don't see any cracks or cold joints.
I've been using the key manually to open and lock the door/hatch but after several weeks, it has become a nuisance. Any suggestions or similar experience?
I've been using the key manually to open and lock the door/hatch but after several weeks, it has become a nuisance. Any suggestions or similar experience?
Thread Starter
Advanced
Joined: Jan 2005
Posts: 82
Likes: 18
From: Maple Valley, 25 miles from Seattle WA.
Problem solved! No DTC's found but took a second look at BOTH key FOBs.
Whoa Nellie, not so fast... this time, I did notice cracked solder joints on both FOBs, I resoldered those joints, removed the PCB boards and cleaned with alcohol where the buttons touch the board, reassembled and re-sync'd. The car no longer toots nor do the lights illuminate. So, I was premature to assume the TPMS receiver was sending bad data to the PCM which tooted the horn and commanded the lights to illuminate. The key FOBs were apparently sending signals to the TPMS receiver which interpreted the signals to toot and turn lights on.
Cracked solder joints are generally caused by heating and contraction but there no measurable heat being generated in a key FOB to stress solder joints but the depression of the buttons does flex the circuit board. It seems that over time, the board was stressed enough to crack solder joints.
it's not a defective FOB
Cracked solder joints are generally caused by heating and contraction but there no measurable heat being generated in a key FOB to stress solder joints but the depression of the buttons does flex the circuit board. It seems that over time, the board was stressed enough to crack solder joints.
Last edited by Vulcan73; Dec 17, 2019 at 05:14 PM.
