Diagnostic Trouble Codes or DTCs are generated by the on-board diagnostic system and stored in the ECM memory. They indicate the circuit in which a fault has been detected. DTC information remains stored in the ECM long term memory regardless of whether a continuous (hard) fault or intermittent fault caused the code to set. Toyota products with OBD will continue to store a DTC in the ECM long term memory until the code is cleared by removing power from the ECM BATT terminal. In most cases, the EFI fuse powers this keep alive memory.
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