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C4 Passive Keyless Entry System

Technically Speaking: 1993-’96 Corvette C4 Passive Keyless Entry System, Part 1

James Berry Jan 3, 2017
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Q: I have a 1996 C4 Corvette I purchased recently. The car did not come with a key fob at the time of purchase. I have purchased a GM key fob correct for this year model and when I went to program it, the PKE light would not illuminate and I am unable to program the new key fob. The car has 85k miles and has been well taken care of over the last 20 years. I have researched possible causes as to this malfunction and even had the local Chevrolet dealership take look at the issue. The technician says he has checked everything up to the PKE module and all is working as it should be. He said without replacing the module there is no way to know if this unit is actually the problem.

I have reviewed replacement procedures and decided not to pay dealer rates for this unit to be replaced just to find out if the module is the problem. I will want to do this myself and save the money.

Do you have any other ideas before I commit to a replacement module and the process of removing the dash to make this repair? Please reply as to any advice you may have to offer.

David Finley

A: David, you are not the only reader having this problem. I have received several questions on this recently. We covered this problem a few years ago but with the influx of questions about the C4 Corvette PKE (Passive Keyless Entry) system and the UTD (Universal Theft Deterrent) system problems I think this is worth reviewing again.

Let’s start from the beginning and go through the entire process just so we cover all of the fundamentals. First off, all 1993-’96 Corvettes are PKE factory equipped.

How the System Works

The factory theft deterrent system on most C4 Corvettes provides an audible warning using the vehicle’s horn in the event of an unauthorized entry through either door or the vehicle hatch. If a non-permitted 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 vehicle to crank or any fuel to be delivered to the injectors.

The PKE, although a separate system, is a vital part of the UTD system. The PKE 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 like any other key fob. However, to set the vehicle alarm you will need to manually lock the doors using either the auto lock on the door or use the key when you get out.

In Passive mode, the PKE receiver senses the transmitter located on the user and knows when to automatically lock or unlock the doors. 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.

This is how it works: Once the PKE receiver has gone into sleep mode it is awakened when it senses movement coming toward the vehicle through a motion sensor located inside of the transmitter. It will unlock the doors if the system is in Passive mode.

Simply stated, when you get the transmitter into a close enough proximity of the receiver it activates the system. The transmitter sends out a digital identification code and an operation code that is unique to each transmitter that the PKE receiver recognizes. If the code is recognized the system will turn off the Universal Theft Deterrent system and then unlock the selected doors.

When the transmitter is in a close enough proximity of the receiver there will be constant chatter, or communication, between the PKE receiver and the transmitter. The PKE receiver is always checking to see where the transmitter is and how to respond. Once you walk away from the vehicle and the transmitter is out of range the system will wait five seconds and then lock the doors and arm the Universal Theft Deterrent system, sounding the horn.

PKE Transmitter Battery

If your transmitter is not working, one of the first things to check should be the transmitter battery. Also, a weak battery will reduce the range in which the PKE operates. If you have noticed you need to be closer to your vehicle for the transmitter to function it may be time for a new battery. The procedure for changing the transmitter battery is as follows:

Insert a pocket screwdriver or dime-size coin into the slot on the back of the transmitter and gently pry apart the two halves.

Gently pull the battery out of the transmitter and, if needed, clean the inside of the transmitter with a spray contact cleaner. (This procedure is similar to cleaning the mouse on your home computer.)

When replacing the battery, inspect the transmitter for broken prongs. This is a common failure with Corvette transmitters.

Put the new battery in the transmitter. Use a battery type CR2032 or equivalent. The battery is held in place by two retaining clips and can be difficult to install. The easiest way to install the battery is to hook the battery into the bottom retaining hook first and then press the battery into the top hook.

Reassemble the transmitter.

Test the transmitter.

PKE Transmitter Programming

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

The PKE system is capable of using three different transmitters, with each transmitter having its own distinctive VAC (Vehicle Access Code).

Corvette Transmitter Programming Mode 2/6

The transmitter programming mode is initiated by entering a specific button sequence on the DIC (Drivers Information Center) on your dash. To enter the transmitter programming mode use the following steps: Move the transmitters to be programmed approximately 12-15 feet away from the car. Turn the ignition to the Run position, engine off.

Corvette Odo Button 3/6

Push the Trip ODO button once and release. Push the Trip ODO button again and hold for 5 seconds.

Corvette Fuel Button 4/6

Within five seconds, push and hold the Fuel Info button for 10 seconds until the passive keyless lamp illuminates constantly.

Turn the ignition key to the Lock position with the key remaining in the ignition. The passive keyless system lamp should flash once per second, signaling that the system is ready to program the first transmitter. The number of times the light flashes corresponds to the number of the transmitter you’re programming. One flash per second is for the first transmitter, two per second for the second and three per second for the third.

Bring only the transmitter to be programmed into range at this time.

The Passive Keyless Entry light will come on and stay on, signaling that the code has been stored.

Move the transmitter out of range. The system light will flash again and the system is ready for the next transmitter.

You can exit the programming mode by removing the key from the ignition or by turning the ignition on.

Turning off the programming mode will not cancel the programming of any transmitters that have been previously programmed into the system. Bringing more than one transmitter into range at a time will make it difficult for the system to search for individual codes. The programming mode will automatically shut off after two minutes if no transmitters have been programmed or the key is removed.

Passive Unlock/Lock Enable/Disable Procedure

The passive unlock/lock disable procedure allows you the ability to turn off the passive function of the PKE system. The passive unlock/lock feature can be enabled or disabled with the following procedure:

First, a transmitter must be in range of the PKE receiver.

The key must not be in the ignition.

Corvette Door Lock Switch 5/6

Push the door lock switch for approximately 5 seconds.

The PKE module will then lock the doors and then will unlock the doors to verify the command has been sent.

When the passive feature has been disabled, the “passive keyless entry” lamp will not illuminate when the key is first turned on before the vehicle is started.

If the passive feature has been disabled, simply repeating the procedure above will enable the passive unlock/lock function. To verify the system has been enabled, the “passive keyless entry” lamp will illuminate when the key is first turned on before the vehicle is started.

Program One or Both Doors to Unlock When In the Passive Mode

On your C4 Corvette you can choose if you want the passenger door to unlock passively. The PKE will always unlock the driver’s door when the system is in the passive mode. To enable or disable the passenger door you can perform the following procedure:

First, a transmitter must be in range of the PKE receiver.

The key must be in the ignition. With the ignition in the Off position.

Push the door lock switch for approximately 5 seconds.

The PKE module will then lock the doors and then will unlock the doors to verify the command has been sent.

If the driver’s door only unlock option has been chosen you can always unlock the passenger door using the transmitter.

How to Arm and Test the C4 Alarm System

Let’s go over how to run a simple test on your Corvette’s theft deterrent system.

Lower the driver’s side window before turning off the vehicle.

With the ignition in the Off position, the Security light should flash. The flashing light is your cue to arm the security system.

To arm the theft deterrent system, open the door.

With the door open, lock the door using the power door lock switch or the transmitter.

Corvette Security Light 6/6

The Security light should come on. If you lock the vehicle with the manual door lock or the key your system will not arm.

Now close all of the doors; the Security light should go off and your system should be armed.

To test the alarm, arm the theft deterrent system as described above.

Wait approximately 10 seconds.

Now reach inside the open window, unlock the door using the manual door lock and open the door from the inside door handle. The alarm should sound.

The alarm should sound off for approximately 3 minutes. After 3 minutes the alarm will no longer sound off to save battery power. Even though the alarm may not be sounding off, the vehicle will not start until the system is deactivated.

If the alarm did not sound off make sure your horns are working. It is possible you could have a blown horn fuse or a defective horn.

How to Turn the Alarm Off If It Accidently Goes Off

Unlock the door with your key.

Put the ignition key into the ignition and turn it to the Run position.

You can use the fob to deactivate the alarm.

David, the C4 Corvette PKE system may seem complicated but once you have an understanding of how the system works I think with some time and patience you will be able to get your Corvette repaired. Next month we will cover the PKE diagnostics, component location and how to repair PKE receiver instead of having to replace it.



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