Over the last two installments we covered how the C4 Passive Keyless Entry (PKE) system works, how to program the transmitters, how to test the alarm, how to program the different options for the PKE system and the component locations and diagnostics.
In this last installment we will cover the PKE module removal procedure, the Central Control Module (CCM) removal procedure, the PKE inputs and how to possibly repair the PKE receiver instead of having to replace it.
C4 Passive Keyless Entry (PKE) System Module Removal
The PKE receiver can only be accessed by and after removing the upper dashpanel. There are a few hard-to-find fasteners you will need to locate to remove the upper dashpanel.
First, remove the negative battery cable.
Some of the hard-to-find fasteners are located under the dash air vent outlets. You will need to remove all three air vent outlets. This will expose two small Torx head screws inside of each vent outlet.
There are more hidden fasteners located under the fuse panel. Detach the fuse box cover then locate and remove the three hex head screws that retain the side panel.
Behind the side panel there is a hex head screw for the lower knee pad and dashpad.
Behind the passenger-side vents there are three hex nuts that hold the lower dashpad in place. Remove these retainers and pop the lower dashpad off. You will not need to completely remove the lower dashpad but this will allow you to access the upper dashpad tabs.
Behind the center vent are two hex head screws, one on the left (holding the upper dashpad) and one on the right (holding the center trim). Remove these hex head screws and pop out the center trim about 4 inches.
Behind the driver’s vent is one hex head screw holding the dashpad.
Next, pop off the defroster vent trim in the center of the dash; take care not to damage the light sensor, which is attached. After removing the defroster vent this will expose two Torx screws under the defroster vent that are attached to the dashpad. You will need to remove these screws.
Once all the screws are removed, carefully lift up on the dashpad and pull back to release the rear dash pins from the dashpad reinforcement frame. The entire upper dash should come out. If you find that the upper dash is not coming loose effortlessly, go back and make sure all of the hidden fasteners have been removed. The dashpad may have some random spots of adhesive holding the edges in place. If you find you have a glued dashpad it will take a little more time and patience to remove but should not give you too much trouble.
Next, remove the instrument cluster.
Once the instrument cluster has been removed look under the center air-conditioning vent tube directly behind the air-conditioning control head in the center of the dash and you will see two boxes. The top box is the tone generator module (vehicle’s chime), which is held in place with Velcro. You will need to remove the tone generator to access the PKE receiver.
The PKE receiver is located directly under the tone generator. The PKE receiver is held in place with either Velcro or spring clips on the sides. Now comes the tricky part. The PKE module will only come out the passenger-side direction, but it won’t come out easily. You will need to tug and tweak until you can manipulate the unit out.
Central Control Module (CCM) Removal
The Central Control Module (CCM) normally does not give any problems, but if you need to access it you will find the CCM for most 1993-’96 Corvettes located under the driver-side knee bolster behind a metal bracket.
Remove the fuel pump relay for access to the CCM and then tilt it upward to access the wiring harness connector and remove the CCM.
PKE Module Inputs
The PKE inputs are the things needed in order for the PKE module to work correctly. The following is my cheat sheet for the PKE module inputs and will work for most—but not all—C4 Corvette applications. You can check the wiring diagram for your model for any changes.
A1 is a Black wire that is the ground.
A4 is a Light Green wire that will cycle from 12 volts to 0 when you put the key in the ignition.
A5 is a Pink wire that is key on 12 volts, key off 0 volts.
A6 is a Gray/Black wire that is the left door ajar, 12 volts with the door closed and 0 volts with the door open.
A7 is a Black/White wire that is the right door ajar, 12 volts with the door closed and 0 volts with the door open.
A8 is an Orange wire that should be 12 volts at all times.
PKE Module Repair
Intermittent problems with electronic modules or circuit boards are often the result of a broken cold-solder joint. Cold-solder joints are quite common in remote keyless entry fobs and PKE receivers as well as a multitude of other modules on Corvettes.
The term “cold-solder joint” refers to a solder connection that wasn’t heated enough during manufacturing, was cooled too quickly or had its component pins moved before the solder had a chance to solidify. With time, cold-solder joints can become problematic due to vibration, repeated thermal cycling or constant exposure to high temperatures.
When diagnosing a bad solder joint, try tapping on the suspect component. If this causes it to work temporarily, you have a pretty good indication that you’ve found the problem. For example, when trying to determine why the PKE receiver would not automatically lock or unlock the doors when the transmitter was in range, we found that tapping the top of the PKE receiver briefly rectified the glitch. This led us to deduce that the PKE receiver was the culprit.
You can repair cold-solder joints without knowing anything about circuitry. Use a light and a magnifying glass to examine components for hairline cracks in the solder around the pins. Fixing them will require a low-wattage, pencil-style soldering iron and some rosin-core solder, which can be found at any retail electronics (e.g., Radio Shack) or auto-parts store.
Apply a small amount of solder to the heated iron, then use the tip of the iron to heat the joint and apply the solder at the same time. The solder should flow evenly on the joint, repairing the connection. This process should only take a second or two. Any longer and the heat from the iron could damage the circuit board or the component itself. Repeat as needed, soldering any and all questionable connections.
Repairing cold-solder joints may fix your Corvette’s PKE intermittent electrical problem(s). Don’t be afraid to try this simple repair. Remember, the components in question are already broken and would normally be discarded.
As most of you C4 Corvette owners already know, most items for the C4 Corvette have been discontinued and this holds true for the PKE receiver. So if you cannot repair yours it leaves you the option of a salvage yard component or sending your unit out to be rebuilt. If you chose to send your unit out for a rebuild be sure to give the rebuilder a detailed list of the symptoms so that they can verify the repair before returning the unit to you.
Well, what started out as a simple question turned into some not-so-simple answers. But by understanding how the PKE system works it will allow you to have a path to take when diagnosing your problem. I hope this article can be used as a diagnostic aid for my C4 Corvette friends.