Last time we covered how the C4 Passive Keyless Entry (PKE) system works, how to program the PKE transmitters, how to test the alarm and how to program the different options for the PKE system.
This time we will cover the PKE component location and diagnostics. In Part 3 we will cover how to remove the PKE module and how to possibly repair the PKE receiver instead of having to replace it.
PKE Component location
The transmitter is the operator’s key fob and the receiver can only be accessed by removing the upper dashpanel.
The coupe’s receiver antennas are located in the driver’s door and in the rear luggage compartment. The convertible’s receiver antennas are located in the driver’s door and in the passenger’s door.
The CCM (Central Control Module) controls the interior lights, security system and starter enable and normally does not give any problems but if you need to access it you will find the CCM for most 1993-’96 Corvettes located behind the radio in center console, under the driver-side knee bolster behind a metal bracket.
The ECM (Engine Control Module) controls the engine, injectors and emissions equipment and is located in the driver’s side of the engine bay, just forward of the firewall.
Checking the Fuses
The first thing to check whenever working with any electrical component connected with a fuse is to test all of the fuses using a test light. To test, first turn the key to the On position then probe the back side of each fuse. There are two places on the back side of each fuse to probe. If the test light does not light on both sides of the fuse that fuse is most likely blown. If the test light does not light on either side of the fuse you will need to look in the owner’s manual to see what that circuit feeds. Certain circuits will require that you activate something to illuminate the test light, such as turning the headlamp switch on to energize that particular fuse.
Some key fuses on the C4 PKE system are:
#40 BATT 5A, provides constant power to the PKE module.
#26 PKE 5A, provides 12 volts when the ignition switch is in Run position.
#42 POWER LOCK, provides voltage to the indicator bulb and power door lock relays in the module.
How to Run a Diagnostic Test on the 1993-’96 Corvette 12- or 16-Pin ALDL System
To enter the onboard diagnostic mode.
For 1993-’94, connect a jumper between pins A and G on the 12-pin Assembly Line Data Link (ALDL) connector.
For 1995-’96, connect a jumper between pins 5 and 8 on the 16-pin Assembly Line Data Link (ALDL) connector.
Turn the key to the Run position, engine off.
If fault codes are not flashing in the Driver Info Center the most common failure is a faulty PKE receiver. This is assuming you have verified that all of the fuses are good.
With pins A and G connected, the PKE light in the Driver Info Center will flash any fault codes.
An example of how to interpret the flashes you may see in the Driver Info Center: one flash, pause, two flashes would indicate code 12. One flash, pause, three flashes would indicate code 13, etc.
The following is the list of Diagnostic Trouble Codes (DTC) and what they mean:
12: Receiver Memory Bad
13: Transmitter Not in Range
14: Non-Valid Transmitter Received
15: Valid Transmitter Received
16: Passenger Door Button Depressed
17: Hatch Button Depressed
Most Common Fault Code Failures
There are several things that can cause a fault code, the following are the most common failures associated a specific fault code, only use this as a guideline.
Fault code 12 more than likely indicates you have a PKE receiver with an internal failure (common failure).
Fault code 13 more than likely indicates you have transmitter with a faulty battery (common), a faulty transmitter (common), or a faulty or unplugged antenna (uncommon).
Fault code 14 more than likely indicates your transmitter is not programmed or it has a defective battery (common).
Fault code 15 more than likely indicates you have a system input that the CCM is looking at that is not in a ready state. An example of this could be the key in the ignition switch has failed (uncommon), etc. You will need to test all of the system inputs to determine which one is at fault. If no input faults can be found you most likely have a PKE receiver with an internal failure.
Fault code 16 more than likely indicates a malfunctioning or misadjusted door switch (common).
Fault code 17 more than likely indicates you have a faulty transmitter (common).
If you have two transmitters, bring your secondary transmitter into range, shake it and see if the fault goes away. If so, your primary transmitter is faulty.
If you do not have a secondary transmitter, turn the ignition key to the locked position and connect a jumper between pins H and A on the 12-pin ALDL connector. Push and hold the hatch release button for 5 seconds. Does fault code 15 change to fault code 17? If not, replace the transmitter. If so, you have an open circuit in the wiring or a faulty PKE receiver.
Key in Ignition Switch Test
If the “key in ignition” switch is not working correctly the PKE system will not operate. This is to prevent you from accidentally locking the keys inside of your vehicle if you have left the key in the ignition.
If the system is functioning correctly and the key is left in the ignition the programmed door or doors will remain unlocked. Verify you have not accidentally left the secondary transmitter in the vehicle.
To verify your key in ignition switch is working. Open the driver’s door with the key inserted in the ignition and listen for the warning chime.
If no chime is heard you have either a defective key in ignition switch in the steering column or there is a wiring problem between the ignition switch and the CCM module or PKE receiver. It’s possible that the CCM module or PKE receiver is defective.
To test for an intermittent open circuit within the steering column, turn the key to the On position and actuate the tilt steering wheel mechanism while moving the steering wheel up and down and listen for the chime. If you hear the chime while actuating the steering column you have an open circuit within the steering column.
You can also test for an intermittent open circuit at the key in ignition switch by wiggling the ignition key and listening for the chime. If you hear the chime while wiggling the key you have a faulty key in ignition switch.