This page provides information about the 1990 thru 1996 Corvette "Central Control Module", or CCM for short. A similar device, called "Body Control Module" or BCM, became a part of the Corvette vernacular starting in the 1997 model year. Knowing these various product references is helpful if you're searching for a replacement CCM, since both names and both abbreviations are used interchangeably.
When the C4 Corvette received its new interior in the model year 1990, a number of electronic modules were consolidated into a centralized device. The hardware of the CCM is the same over its 7-year production run but the firmware varies with each model year. The most notable firmware difference took place in the 1992 Corvette when a revised cluster and an upgraded Vehicle Anti Theft System were implemented. As a result, the 1990 and 1991 LCD and VATS are not compatible with CCM firmware designed for the 1992 through 1996 Corvette years. In spite of these annual variations in the CCM firmware, the Base, Convertible and ZR1 models utilize the same firmware for any given model year. There is no such thing a ZR1 specific Central Control Module, unlike the Engine Control Module (ECM).
It is noteworthy that the EEPROM of each CCM is encoded with Vehicle Specific Data, including its Vehicle Identification Number, Engine type, Transmission type, Options, Season Odometer (mileage), Oil Life Status and VATS Pass-Key Code. For this reason, if you intend to replace the CCM in your Corvette with a used one from eBay or an automotive parts recycler it can become a daunting task. Not only will the used replacement CCM provide an improper mileage in the instrument cluster but your ignition key will probably not match the VATS Pass-Key Code already stored in the used CCM, which means your Corvette will not readily start.
Specialized tools and knowledge are required to clear and rewrite the Vehicle Specific Data stored in a Corvette CCM. A "TECH 1", "TECH 1 SERIES A" or "TECH 1A" GM Service Tool cannot update a CCM EEPROM after its first 100 miles of use. For most do-it-yourselfers, refurbished CCMs are the preferred replacement approach since, the reseller can customize the replacement CCM to match your Corvette, prior to shipping it to you. ZR1ECM.com provides this service.
1990 - 1996 CORVETTE Central Control Module
Firmware IDs by Model YearFor the "Do-It-Yourselfer", the first step in replacing the "Central Control Module" (aka CCM or BCM) in a 1990 thru 1996 Corvette is obtaining one with the proper firmware for your model year.
The 1990 thru 1996 Corvette CCM manages a number of critical in-car functions ranging from operation of the instrument cluster, to vehicle security, to interior chimes and lighting. It also serves as a serial communications and diagnostics hub for various electronic modules within the vehicle. Each model year is assigned an alphabetized firmware ID, to account for the year-to-year variations in CCM features and capabilities. These firmware IDs include:
ATTJ - 1990 Corvette: Base, Convertible and ZR1;
AWXT - 1991 Corvette: Base, Convertible and ZR1;
AXAK - 1992 Corvette: Base, Convertible and ZR1;
BFUP - 1993 Corvette: Base, Convertible and ZR1;
BHZS - 1994 Corvette: Base, Convertible, 40th Anniversary Edition and ZR1;
BNFY/BRBR* - 1995 Corvette: Base, Convertible, Indianapolis 500 Pace Car and ZR-1;
BSKR - 1996 Corvette: Base, Convertible, Collector's Edition and Grand Sport.
In spite of the year to year variations in the CCM firmware, there is substantial interoperability with the 1990 and 1991 versions since these two model years employ the same Cluster LCD and built-in diagnostic features. The main difference in the embedded software is that the 1991 provides for a Delayed Accessory Bus (DAB) relay, whereas the 1990 does not. The 1990 and 1991 firmware iterations are not compatible with any other model years.
Since the 1992 thru 1996 Clusters incorporate the same LCD, the CCM firmware covering these five model years will provide LCD interoperability; However, there are functional differences with the built-in diagnostic features embedded in the code of these versions. It is recommended that the year-specific CCM firmware be utilized for the 1992, 1993 and 1996 model years, whereas, the 1994 and 1995 firmware iterations provide substantial interoperability.
*NOTE: The 1995 BNFY and BRBR firmware versions are exactly the same. BRBR CCMs contain a minor hardware modification. A rare VATS - Starter Relay issue was discovered in some CCMs loaded with BNFY, which is discussed in TSB# 53-64-02. If using a BNFY CCM, the Starter Relay might not fully activate in cold temperatures, making it necessary to turn the Ignition Key to "ON", then "OFF" then "ON" again to fully engage the relay.
Tag: C4, Corvette, ZR1, LT5, ECM, DIS, LT1, LT4, CCM, BCM, VATS, Pass-Key
