Download Dual Electronic Automatic Temperature Control (DATC) Module Diagnostic Trouble Codes — DTCs If using the scan tool or front panel diagnostics to check for DATC DTCs: 1. Check continuous DTCs. 2. Run DATC self-test. Refer to Front Panel DATC Self-Test (On-demand Diagnostic Trouble Codes — DTCs). General Information: If the DTC is continuous only and does not appear in the self-test, this indicates an intermittent fault condition, such as a poor wiring connection or a loose terminal. If the DATC does not appear after running the self-test it may also indicate that the DTC may no longer exist. If the DTC is continuous and appears in the self-test, this indicates a hard fault. A hard fault suggests a permanent wiring failure, disconnected connector or component failure. Front Panel DATC Module Self-Test (On-Demand Diagnostic Trouble Codes — DTCs) On-demand DTCs are those that are reported by an ECU when a failure is detected while executing a diagnostic test. For the DATC module this means that all faults (hard) that occur while the module is conducting a self-test shall be reported as an on-demand DTC.