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Say, Paul ... Did You Say You Were Hearing Voices?Posted 6/8/1998By Paul Mensink
I got a call on a 1993 Town Car with a 4.6L Overhead Cam engine. The initial symptom was a high idle condition with a surge at steady in-town speed driving conditions. The technician, Mark, called after determining that the PCM was not controlling the IAC and that disconnecting it did not change the idle speed. I suggested replacing the IAC because it was sticking, causing high idle speed. The next day Mark called to tell me that the high idle condition was gone but now the car had an intermittent misfire condition. I explained that the 4.6L engine design with long plug wire boots makes it difficult to pinpoint a bad plug wire and generally the voltage loss is due to arcing of the plug wire to ground, down in the spark plug cavity of the cylinder head. Several days later Mark called to tell me that replacing the plug wires took care of the intermittent misfire and the engine was running fine. But now a REALLY strange problem had developed. When the customer drove the car, he could hear a voice - intermittently - coming from the rear of the vehicle saying, "Identify yourself. What is your destination?" Sometimes it happened every day and sometimes the customer wouldn't hear the voice for two weeks. I was thinking he should tell the vehicle owner to get a psychiatric evaluation, but instead, I asked Mark if he had been able to duplicate the condition. He said, "Yeah, and it's the strangest thing I've ever heard. It scared the heck out of me." When Mark and the customer had taken the car for a drive, the radio had been on. All at once, the radio shut off automatically and the voice came through the radio speakers. The message ("Identify yourself. What is your destination?") was repeated three or four times, then the speakers made a clicking noise, and then the radio resumed normal operation. At this point, I thought about suggesting Mark join the customer for that psychiatric evaluation! Mark had examined the trunk and found a 25-pin modul he couldn't identify, but when he disconnected it, the speakers stopped clicking. Mark said at first the module looked like a dealer add-on, but since he couldn't find any part numbers and it fit so nicely into its mounting spot, maybe it was factory equipment. Mark was sure the module was tied to the ignition system since one of the wires showed a change in power when the ignition switch was turned on. He was hoping I could help him identify this unit and tell him how to deactivate it. Thinking he was possibly working with an anti-theft device, I opened the Ford Electrical and Vacuum Troubleshooting Manual and scanned the diagram of the anti-theft system. Nowhere could I see any ties to the rear speakers, nor could I find the 25-pin connector he had described. I checked the manual for radio system, speakers and related component connectors, but found nothing. I told Mark that he was probably dealing with a module that someone had installed with "who-knows-what" in mind and that I might not be of much assistance to him. But then as I flipped pages just past the radio section, I saw his 25-pin connector - it was a Mobile Telephone Transceiver! After telling Mark, he said the car didn't have a phone. I described the wiring layout and told him that the phone system is capable of hands-free operation by means of the left rear speaker and a microphone behind the visor on the driver's side. Mark found the microphone. As it turned out, the customer was the second owner. The original owner had taken the handset with him when he sold the car. So Mark and his customer really were hearing that funny little voice and the Town Car was doing all the talking!
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Copyright (c) 1996-2008. Automotive Service Association. All rights reserved.
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