Service Interaction Protocol
Control DTC Setting
Overview
“The ControlDTCSetting service is used by a client to stop or resume the setting of DTCs in the server.”
Practical Use: Technicians use this service during component replacement (like unplugging a battery or sensor) to prevent the vehicle from storing hundreds of “communication lost” or “circuit open” codes that aren’t real faults.
Message Format
Request
85 01> Sub-fn 0x01 (ON)
Response
C5 01> Success
Request
85 02> Sub-fn 0x02 (OFF)
Response
C5 02> Success
Optional: DTCSettingType
A third byte can be added to target specific groups of DTCs:
- 0x00: All DTCs
- 0x01: Emissions
- 0x02: Safety
DTC Recording Behavior
Internal logic of DTC recording suppression vs. fault detection.
Non-Volatile Persistence: Unlike session states, the DTC disabled state is temporary. ECU power-on always defaults to ENABLED to ensure safety diagnostics are never permanently muted.
Detection != Recording: Even when disabled, the ECU still detects faults. It simply skips the ‘Write to NVRAM’ and ‘Set Status Bit’ steps.
Maintenance Workflow
Workflow: Clean Sensor Replacement
8 stepsNegative Response Codes
Logic_Exceptions