Central Control Module Chevrolet Corvette C4

DESCRIPTION & OPERATION

The Central Control Module (CCM) performs the following functions

1. Ambient light signal processing
2. Chime control
3. Courtesy light control
4. Delayed Accessory Bus (DAB) control (power windows and audio system)
5. Dimming control(instrument cluster, gauges, radio, HVAC)
6. Driver Information Center (DIC) switches
7. Fuel level detection/processing
8. Instrument panel LCD digit display
9. Personal Automotive Security System (PASS)-Key(R)
10. Rear defog control
11. Odometer processing
12. Oil level monitoring
13. Status warnings
14. System component malfunction detection
15. System diagnostics processor/controller
16. Trip computer processing
17. UART serial communications master
18. Universal Theft Deterrent (UTD) control
19. Vehicle speed detection/processing

Signals that activate the CCM are known as "wake-up" signals. CCM is asleep when it is not controlling or monitoring any wake-up functions. CCM will wake-up when any of the following occur

1. Key is inserted in door lock switch.
2. Door ajar switch is activated.
3. Power door lock/unlock switch is activated.
4. Hatch ajar switch is activated.
5. Key is inserted into ignition switch.
6. Ignition is turned ON.
7. Parking lights are turned ON.

When CCM is awake and wake-up signals are removed, CCM will return to sleep after 5-15 seconds. An exception to this is if the CCM sees engine RPM while awake, CCM will stay awake for about 30 seconds after ignition is turned off and all wake-ups are removed, including removing ignition key. CCM will stay awake for 30 minutes if key is in ignition but ignition switch is not in START or RUN position.

If CCM receives a door ajar wake-up signal and wake-up remains active after 15 minutes, CCM will turn off courtesy light (if illuminated) to prevent battery drain. If CCM receives a hatch ajar wake-up signal and hatch remains open, but all other wake-ups are removed, CCM will go to sleep after 10 minutes. However, cargo lights will remain illuminated until hatch is closed.

CCM battery terminals operating current should not exceed one amp while CCM is awake. An approximate normal value is 200 milliamps. If delayed accessory bus is active, amperage may be higher. Delayed accessory bus allows operation of power windows and radio until a door is opened or 15 minutes has elapsed. When CCM is asleep, current should not exceed 15 milliamps. CCM IGN 1 and IGN 3 terminals operating current should not exceed 100 milliamps. Most CCM functions will properly operate with a system voltage of 9-16 volts.

OIL LEVEL MONITORING

CCM monitors engine oil level with a normally-closed grounding switch. The following are the low oil warning light parameters

1. Oil temperature during previous ignition cycle must have been at least 195°F (90.6°C).
2. Oil temperature must have dropped at least 105°F (40.6°C) since engine was last running.
3. Oil level sensor must be open when ignition switch is turned ON.

To verify that the oil level is low, it is necessary to wait 10 minutes for VIN 8 (L98) engine and 2 hours for VIN J engine before checking dipstick. Oil must have sufficient time to drain into oil pan, especially VIN J engine.

COMPONENT LOCATIONS

COMPONENT LOCATIONS

Note. Engine code is eighth character of VIN.

Scheme 1

Scheme 2

Scheme 3

Scheme 4

Scheme 5

Scheme 6

Scheme 7

RESETTING "CHANGE OIL" INDICATOR

1. Turn ignition ON with engine off. Ensure ALDL connector terminal G is not grounded.
2. Press ENG/MET button and release, then within 5 seconds press ENG/MET button again. (Scheme 10)
3. Within 5 seconds of pressing ENG/MET button for second time, press and hold RANGE button. While button is being held, change oil indicator should begin to flash.
4. Hold RANGE button until indicator stops flashing and goes out. This should take about 10 seconds. Indicator is now reset.
5. Turn ignition OFF and repeat procedure if indicator fails to reset.

CCM PROGRAMMING/EEPROM DOWNLOAD

If the Central Control Module (CCM) is replaced, the service CCM must be programmed for the PASS-Keys(R) which came with the vehicle. See CCM PASS-KEY PROGRAMMING PROCEDURE in GAUGES & INSTRUMENT PANEL article.

PRELIMINARY INSPECTION

1. Ensure LCD, A/C and CCM fuses are not open. Ensure G106 is clean and tight. see scheme 8
2. Check for a broken or partially broken wire inside insulation, which could cause system malfunction but prove good in a continuity/voltage check with system disconnected. These circuits may be intermittent or resistive when loaded and should be checked by monitoring the voltage drop with the system under load. Ensure any aftermarket electronic equipment is properly installed. If fault is found, repair as necessary.
3. Check for DTCs. See «SELF-DIAGNOSTIC SYSTEM»(/chevrolet/corvette/c4-1984-1998/remont/communication-devices/#central-control-module__self-diagnostic-system).

SYMPTOM TROUBLE SHOOTING

If CCM appears completely inoperative, see TEST A: CENTRAL CONTROL MODULE APPEARS COMPLETELY INOPERATIVE . If CCM will not enter diagnostic mode, see TEST B: CENTRAL CONTROL MODULE WILL NOT ENTER DIAGNOSTIC MODE .

SELF-DIAGNOSTIC SYSTEM

Central Control Module (CCM) is equipped with a self-diagnostic system which detects system failures or abnormalities. When a malfunction occurs, CCM will store a numerical code. Codes are recorded as history/intermittent or as current.

Current Failures

Current codes indicate CCM has detected a fault which is currently present. Current codes can be identified by the letter "C" preceding the code.

History/Intermittent Failures

History/intermittent codes indicate CCM previously detected a fault which later disappeared. History/intermittent codes can be identified by the letter "H" preceding the code. If a history/intermittent code is set, fault may be intermittent or the system for which the code is set may not be currently operating.

All ECM codes will be displayed as history by CCM whether they are current or not. Even though conditions may exist for setting these codes, codes cannot set as current because code-testing procedures vary from code-setting criteria. If code is displayed as history and malfunction cannot be determined, clear codes and operate system for previously set code. If code resets, condition is present and code can be considered current.

History/intermittent codes will clear from CCM memory if fault does not repeat for 100 ignition cycles. Intermittent failures may be caused by problems with electrical circuit. If a visual inspection does not locate problem, vehicle may be driven with a DVOM attached to suspect circuit. Abnormal voltage or resistance readings when problem occurs may indicate problem is within that circuit.

ENTERING & EXITING DIAGNOSTICS

Speedometer, odometer and trip monitor are used to display Central Control Module (CCM) information while in diagnostic mode. Speedometer displays CCM and ECM Diagnostic Trouble Codes (DTCs). Odometer displays CCM data. Trip monitor displays system being tested and test being performed. (Scheme 8)and (Scheme 9). Driver Information Center (DIC) buttons are used to transmit instructions to CCM while in diagnostic mode. (Scheme 10)

If a code-setting malfunction is present, "SYS" (SYSTEM ERROR) will flash on instrument cluster trip monitor. SYS will flash 3 times every 15 seconds when a current code is set. If a PASS-Key(R) malfunction code (DTCs 51-54) is set, SECURITY indicator will flash.

Scheme 8

Scheme 9

Scheme 10

Note. Ensure A/C fuse is not blown. If fuse is blown, CCM will not receive IGN 3 power and will not enter diagnostic mode. DTC 16 will be set if A/C fuse is open.

Automatic Diagnostic Mode

1. To enter automatic diagnostic mode, ground terminal G of Assembly Line Diagnostic Link (ALDL) connector. (Scheme 18) Turn ignition switch to ON position. CCM will display codes and module associated with code in an automatic code display sequence. CCM is module No. 1 and ECM is module No. 4. (Scheme 8)
2. During automatic display sequence each code is displayed for 3 seconds followed by a one second pause before displaying next code. A 3 second pause separates code display for each module. After each module code display, "--" will display on speedometer indicating end of display. If a communication problem exists between CCM and ECM, speedometer will display "Err".The particular module being interrogated is indicated on the trip monitor and the codes are displayed on the speedometer. The speedometer also indicates is fault code is current (C) or history (H), respectively. All ECM codes are displayed by CCM as history codes, whether they are current or history.
3. After all codes are displayed for all modules, trip monitor will display "1.0" and speedometer will be blank. CCM has now entered manual diagnostic mode, waiting for input from the technician.At any time during the automatic code display sequence, the manual mode may be entered by pressing any button on the DIC.

Manual Diagnostic Mode

1. To enter manual diagnostic mode, press any button on DIC during automatic diagnostic mode display. Manual diagnostic mode will also be entered automatically after automatic diagnostic mode is complete.
2. Upon entry into mode, speedometer will be blank and trip monitor will display "1.0" indicating module No. 1 (CCM) is awaiting further instruction.
3. Press buttons on DIC to perform desired function. If the beginning of a list of codes is arrived at by pressing either the ENG MET (next value) button or the INST/AVER (previous value) button on DIC, speedometer will display "--". Speedometer will also display "--" if no codes are present for module being checked. (Scheme 9)and (Scheme 10).

Using Driver Information Center (DIC)

To display CCM DTCs, select display codes mode by pressing TRIP/ODO (next test) button on DIC until "1.1" displays on trip monitor. Press ENG/MET (next value) button to display first code. Continue pressing ENG/MET button to display additional CCM DTCs until "--" is displayed on speedometer. If CCM DTC C12 is displayed, no CCM DTCs are stored. Press INST/AVER (previous value) button to go backward in list. Speedometer will display "--" when top of code list is reached. (Scheme 10)

Using Scan Tool

To display CCM DTCs, connect scan tool to Assembly Line Diagnostic Link (ALDL) connector and follow menu prompts. Current (last test failed) DTCs will be displayed on scan tool when test mode for current DTCs is entered. History DTCs will be displayed on scan tool when test mode for history DTCs is entered. Refer to scan tool operator's manual for further information on scan tool usage.

CCM DTC DEFINITION

CCM DTC DEFINITION

CLEARING DTCS

1. To clear codes, ground terminal G of Assembly Line Diagnostic Link (ALDL) connector. (Scheme 18)
2. Turn ignition switch to ON position, with engine off.
3. Press TRIP/ODO button on DIC until "1.7" displays on trip monitor.
4. Press ENG/MET (next value) button and hold until "--" is displayed on speedometer. CCM DTCs should now be cleared.
5. Turn ignition OFF and back ON to check if DTCs reset. Remove ground from ALDL connector.

CCM INPUT STATUS & DATA VALUES

In addition to displaying CCM DTCs, CCM is capable of displaying the status of its inputs and data values. CCM is also capable of cycling outputs on and off. CCM functions are accessible through the Driver Information Center (DIC). CCM functions may be referenced in CCM diagnostic testing and may assist in the diagnosis of non-code setting problems without extensive diagnosis or disassembly of vehicle. Functions will be displayed on trip monitors as follows

1. 1.0 Waiting For Instructions (CCM)
2. 1.1 Display CCM DTCs
3. 1.2 Display CCM Data
4. 1.3 Display CCM Inputs Status
5. 1.4 Cycle CCM Outputs
6. 1.7 Clear CCM DTCs

Displaying CCM Data

1. CCM can display data used to determine control decisions. Data may be useful in determining if a system is properly operating and/or sending correct data to CCM.
2. To enter display CCM data function, press TRIP/ODO (next test) button on DIC until "1.2" displays on trip monitor.
3. Press ENG/MET (next value) button until identifying number for data value is displayed in the first 2 digits of odometer. See «CCM DATA IDENTIFICATION NUMBER»(/chevrolet/corvette/c4-1984-1998/remont/communication-devices/#central-control-module) . Press INST/AVER (previous value) button to go backward in the list.
4. Data value is displayed in the last 3 digits of odometer. Data values are different for each system data. See «CCM DATA IDENTIFICATION NUMBER»(/chevrolet/corvette/c4-1984-1998/remont/communication-devices/#central-control-module) .

CCM DATA IDENTIFICATION NUMBER

Scheme 11

Displaying CCM Input Status

Display of CCM input status is used to determine if CCM is monitoring proper system operation.For example, courtesy light operation requires seeing a door open, indicated by the door ajar switch. If the courtesy lamps are not operating properly, a starting point may be selecting this diagnostic function and watching if the CCM recognizes the door opening and closing.

1. To enter display CCM input status function, press TRIP/ODO (next test) button on DIC until "1.3" displays on trip monitor. Press ENG/MET (next value) button until identifying number for input status is displayed in the first 2 digits of odometer. See «CCM INPUT IDENTIFICATION NUMBER»(/chevrolet/corvette/c4-1984-1998/remont/communication-devices/#central-control-module) table. Press INST/AVER (previous value) button to go backward in the list.
2. Input status is displayed in the last 3 digits of odometer. Input status will display as "1" (on) or "0" (off). Display will constantly move to the left one digit at a time. First 2 digits in odometer indicate last 2 states of selected input. Third digit indicates current state of input. For example, "101" when in door ajar status indicates door was open(on), closed (off), then opened again (on).
3. If input status does not change during testing, a "1" indicates a possible short or faulty switch, and a "0" indicates a possible open or faulty switch. Exceptions to this are input status 01, 02, 06 and 14, which should not change and cannot be changed during diagnostics.

CCM INPUT IDENTIFICATION NUMBER

Cycling CCM Outputs

1. Cycling CCM outputs on and off is used to determine if circuits and components are properly operating.
2. To enter cycling CCM outputs function, press TRIP/ODO (next test) button on DIC until "1.4" displays on trip monitor. Press ENG/MET (next value) button until identifying number for component to be cycled is displayed in the first 2 digits of odometer. See «CCM OUTPUT IDENTIFICATION NUMBER»(/chevrolet/corvette/c4-1984-1998/remont/communication-devices/#central-control-module) . Press INST/AVER (previous value) button to go backward in the list.
3. Output status cycling is displayed in the last digit of odometer. Output status will display as "1" (on) or "0" (off). Output will cycle between on and off every 3 seconds.

CCM OUTPUT IDENTIFICATION NUMBER

DIAGNOSING & REPAIRING CCM DTCS

Before performing any diagnostic tests, ensure CCM is properly communicating. Also check CCM fuses, CCM power and ground connections, and CCM power and ground circuits for possible faults.

Note. For diagnostic procedures, see TESTING & DIAGNOSIS in GAUGES & INSTRUMENT PANELarticle.

For diagnostic procedures, refer to flowchart. (Scheme 12)

Scheme 12

For diagnostic procedures, refer to flowchart. See .

Scheme 13

Note. Before replacing CCM due to PASS-Key(R) failure, ensure PASS-Key(R) resistor contacts are clean and free of contaminants and any obstruction.

Removal Precations

If CCM is being replacedas opposed to being removed and installed (as for access to other components), please read the following information.

If the Central Control Module (CCM) is replaced, the service CCM must be programmed for the PASS-Keys(R) which came with the vehicle. See CCM PASS-KEY PROGRAMMING PROCEDURE in GAUGES & INSTRUMENT PANEL article.

When replacing the CCM, it will also be necessary to program the EEPROM chip in the new CCM. The EEPROM stores information such as option content, odometer mileage and other operating parameters. Programming is performed using a GM TECH II Scan tool, or equivalent aftermarket scan tool.

Do NOT drive the vehicle more than 100 miles after CCM replacment before performing the EEPROM download procedure. Doing so will make it impossible to download odometer information. In addition, the interior (dome) light timer is set for only 10 seconds of operation until

1. Odometer mileage is downloaded
2. Vehicle is driven 16 miles or more
3. TECH II is used to communicate with any vehicle system

Before replacing CCM due to PASS-Key(R) Codes 51-65, be sure PASS-Key(R) key resistor contacts are clean and free of any grease, oil, etc. These substances interfere with PASS-Key(R) key detection circuit, possibly causing CCM to set faulty code. Using a clean key, clear all trouble codes, and check if code resets after using clean key.

Scheme 14

Scheme 15

1. BEFORE removing CCM, please read «Removal Precations»(/chevrolet/corvette/c4-1984-1998/remont/communication-devices/#central-control-module__removal-precations).
2. Remove negative battery cable, driver's side lower trim panel and knee bolster. (Scheme 14) Remove center console left side trim panel. (Scheme 15) Remove driver's knee bolster right inner bracket (behind front of left side trim panel). (Scheme 14)
3. Remove CCM from left side of instrument panel center support system to access CCM harness connectors. Unplug connectors from CCM and from DIC light panel. To install, reverse removal procedure. If necessary, program PASS-Key(R) ignition keys into CCM.

Scheme 16

Scheme 17

Scheme 18

Scheme 19

Scheme 20

Scheme 21

Scheme 22

Scheme 23

Scheme 24

See also:
• AIR BAG RESTRAINT SYSTEM
• CCM PASS-KEY PROGRAMMING PROCEDURE
• INSTRUMENT PANEL - ELECTRONIC
• TESTING & DIAGNOSIS
• SELF-DIAGNOSTIC SYSTEM
• TEST A: CENTRAL CONTROL MODULE APPEARS COMPLETELY INOPERATIVE
• Removal Precations