C4 Keyless Entry and Alarm Repair, Part 1 - Technically Speaking

James Berry Sep 1, 2011 0 Comment(s)
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Q: The Passive Keyless Entry (PKE) system and alarm on my '96 C4 don't seem to be working properly. I was talking to some other Corvette owners at a car show recently, and they thought my PKE unit itself might be defective, since my key fob works fine. I would like to repair the system myself, since my local dealer wants more than $100 just to look at the car. Can you tell me where the PKE unit is located? Also, do you know if replacing it is a pretty straightforward job?

Vemp 1109 00 C4 Corvette Passive Keyless Entry And Alarm Repair 2/7

- DeWayne
Via the Internet

A: All '93-'96 Corvettes were factory-equipped with Passive Keyless Entry. Let's start with a general overview on how the car's Universal Theft Deterrent System (UTD) works. This system provides an audible warning using the vehicle's horns in the event of an unauthorized entry through either door or the hatch. If such an entry is detected, the PASS-Key (Personalized Automotive Security System) and FEDS (Fuel Enable Data Stream) system will disable the vehicle by not allowing the engine to crank and preventing fuel from being delivered to the injectors.

Although a separate system, PKE is a vital part of the car's theft-deterrent strategy. The system has two modes: passive and manual. The passive mode allows the doors to lock and unlock as you walk toward or away from the vehicle. The manual mode allows you to unlock the doors as you would with any other key fob. However, to set the alarm in the manual mode, you'll need to manually lock the doors using either the auto lock on the door or the key.

In the passive mode, the PKE receiver senses the transmitter located in the fob and automatically locks or unlocks the doors at a preset distance from the car. (Even in this mode, the user also has the capability to manually operate the door or hatch lock by pushing the corresponding button on the transmitter.) The transmitter sends out unique digital identification and operation codes that are only recognized by its corresponding receiver.

When the transmitter is in close enough proximity to the receiver, the two will be in constant communication to determine where the transmitter is and how to respond. Once the transmitter is out of range, the system waits five seconds, locks the doors, arms the UTD system, and beeps the horn.

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Replacing the PKE Transmitter Battery
If your transmitter isn't working, the first thing to check is the transmitter battery. Let's go over the process of replacing it.

1. Insert a pocket screwdriver or dime-size coin into the slot on the back of the transmitter and gently pry apart the two halves.
2. Gently pull the battery out of the transmitter and then clean the inside of the transmitter with a spray contact cleaner. This procedure is similar to cleaning the mouse on your home computer.
3. When replacing the battery, inspect the transmitter for broken prongs. This is a common failure with Corvette transmitters.
4. Put the new battery in the transmitter; use a CR2032-type or equivalent. The battery is held in place by two retaining clips and can be difficult to install. The easiest method is to hook it into the bottom retaining hook first and then press it into the top hook.
5. Reassemble the transmitter.
6. Test the transmitter.

A weak battery will cause the range at which the PKE operates to be reduced. If you have noticed that you need to be closer to your vehicle for the transmitter to function, it's possible that the battery is getting weak.

Replacing the battery in your transmitter will not require the transmitter to be reprogrammed to the PKE receiver. However, a new transmitter or any additional transmitters will need to be programmed.

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