DTC 4, or 1 and 4

Fig. 24 Code 4 Or Codes 1 & 4: RAM-ROM Failure:

DIAGNOSTIC TROUBLE CODE (DTC) 4 OR 1 AND 4
Each time the ignition is turned on, the TCCM calculates a checksum for the internal program memory and compares it to a checksum stored within the program. This ensures that the software is operating properly. If the TCCM detects a fault with the internal program, a "RAM/ROM Failure" DTC 4 is flagged.