I've been chasing an electrical drain (kills battery in 2 days) without success, but today may have provided a clue. I opened the car to a rapid clicking noise from the passenger dash area. I got to the RH side and started pulling fuses. The clicking stopped when I pulled fuse #39. which decodes as "Central Control Module 2" with no further details as to what it handles (Svc Man en route). Could this be some sort of relay gone bad after 23 years or ? Is the opening step to drop the panel on the underside of the psgr dash? Guesses are welcome.

 

I found this info on another web site. Hope it helps. SYS indicator info This document contains 2 references about the SYS indicator. Corvette 1993 Owner's Manual page 120 ------------------------------------- SYSTEM PROBLEMS The Central Control Module (CCM) controls several electronic systems on your Corvette. SYS will flash three times every 15 seconds on the display near the fuel gage if there is a problem with one of the CCM-controlled systems. Have your vehicle checked by a Chevrolet dealer if SYS keeps appearing. If the SECURITY light flashes at the same time SYS flashes on the instrument panel, a problem has been detected in your theft deterrent system. If this occurs, have your vehicle serviced. ........................................ ...................................... 1993 Corvette Service Manual book 1 page 8D-4 --------------------------------------------- NOTE: SYS isn't listed in the index of Service Manual books 1 and 2. DIAGNOSIS The Central Control Module (CCM) uses the speedometer, odometer, and the trip monitor located on the instrument cluster to display information while in the diagnostic mode. The speedometer is used to display Diagnostic Trouble Codes (DTCs) (CCM, ABS/ARS and ECM), the odometer displays data, and the trip monitor indicates the system being tested and the test which is being performed. The buttons on the Driver Information Center (DIC) are used to send instructions to the CCM when in the diagnostic mode. Unlike other vehicle electronic systems, such as ECM, SIR, etc., there is no specific "CCM" lamp to indicate a malfunction. A DTC-setting malfunction in any of the CCM-monitored systems is indicated by "SYS" (SYSTEM ERROR) flashing in the instrument cluster trip monitor. If a malfunction does not recur within 100 ignition cycles the CCM will automatically clear the DTC. The "SYS" indicator will flash 3 times every 15 seconds while a current-DTC malfunction is present. An exception to the "SYS" malfunction indicator is that PASS-Key malfunctions (DTCs 51-53) will be indicated by the "SECURITY" lamp being illuminated without the "SYS" indicator flashing. If there is a Fuel Enable Data Stream (FEDs) malfunction (DTC 54), the "SECURITY" indicator and "SYS" indicator will flash together, to illustrate that the problem condition affects vehicle security. DIAGNOSTIC MODE To enter the diagnostic mode, ground (connect it to pin "A") pin "G" of the Data Link Connector (DLC) located under the right side of the dash, and turn the ignition switch to the "ON" position. A = Ground B = ECM Diagnostic C = Ride Control Diagnostic F = T.C.C (VIN P) G = CCM Diagnostic J = E&C Bus Data K = SIR Diagnostic L = SIR Serial Data M = Serial Data ------------- DLC connector --> |F| | |C|B|A| |G| |J|K|L|M| ------------- - Important: If the A/C fuse is blown, the CCM will not receive IGN 3 power and will not enter diagnostic mode. This condition should also be indicated by a DCT 16 being set. After turning the ignition "ON", the CCM will display any DTCs and the module for which they apply is an automatic DTC sequence. The CCM is module 1, the ECM is module 4, the ABS/ASR EBTCM is module 9. During the automatic display sequence, each DTC is displayed for three seconds, followed by a one second pause before the next DTC is displayed. There is a three second pause between the DTC display sequence for each module. The end of the DTC list for each module is indicated by "---" being displayed in the speedometer. If there is a communications problem between the ECM or EBTCM and the CCM, the speedometer will display "Err" when the CCM is trying to communicate with the ECM or EBTCM. - Important: The CCM will display "Err" when attempting to display ECM DTCs for the LT5 engine. CCM display and cleaning of ECM DTCs is available only for the LT1. Use the Tech 1 for ECM DTCs on LT5. The particular module being interrogated is indicated on the trip monitor, and the DTCs are displayed on the speedometer. The speedometer also indicates if the DCT is a current DTC (malfunction present now) or history DTC (malfunction has occurred, but is not present now) with a "C" or an "H", respectively. All ECM and EBTCM DTCs will be displayed by the CCM as history DTCs, weather they are current or history. ** reference When all DTCs have been displayed for all modules, the trip monitor will display 1.0 and the speedometer will be blank; this indicates the CCM is in the manual mode, waiting for input from the technician. At any time during the automatic DTC display sequence, the manual mode may be entered by pressing any button on the DIC. MANUAL MODE The manual mode can be entered as described previously, or will automatically be entered after the automatic DTC display sequence is complete. When manual mode is entered, the speedometer will be blank, and the trip monitor will display "1.0", indicating that module "1" (the CCM) is ready for further instructions. The buttons on the DIC are used to control other systems and options as illustrated in Figure 4 (the Driver Information Center). The indicator "--" will be displayed on the speedometer if the end or beginning of a list of malfunction DTC’s is reached (using the "Next Value" or "Previous Value" button). The "--" will also display if no DTC's are present for the module being checked. ........................

 

I would look on youtube to try the paper clip trick

 

The contacts could be stuck closed so yes. This would be the time to check for a current draw since you have the fuse pulled, then check it with the fuse back in.

 

Maybe I wasn't clear - there are NO messages on the screen. The drain occurs when the car is shut down; the clicking relay seems to be a clue of where the problem is.

 

I would puul the pad then put the fuse back and swap the clicking relay.

 

The CCM is like a body control module. It controls interior lights, doors est. and most things that don’t involve the Powertrain or brakes.

Make sure your hood lights and center console light are really off.

The clicking just might be a symptom rather than a route cause. If you hear the clicking, first find out if the battery is charged and has a voltage of 12 volts on it using a external DVM.

I would also like to know what the battery current is with all systems and lights off. FSM says anything under 50ma is OK. The norm is under 25 and I myself run about 20ma.

You have to know if there is really a drain rather than a bad battery. Does the speedometer ever display the SYS error?

Knowing where the clicking is exactly and with the use of a FSM might give a clue as to what system might be activating the relay if need be to go this distance. Try to figure out what is not working or working without being evoked.