Diagnostic Trouble Codes (DTC)
In Arabicرموز الأعطال التشخيصية (DTC)
Standard codes that a vehicle's control units store when they detect a fault, telling the technician which system has failed and how.
What are diagnostic trouble codes (DTC) in fleet management?
When a control unit in the vehicle detects a reading outside its limits, it stores a diagnostic trouble code and often lights the check-engine lamp. On cars and light vehicles, an OBD-II code has five characters: a letter for the system (P powertrain, B body, C chassis, U network) followed by four digits, such as P0217 for engine overheating. Heavy trucks using the J1939 standard report a fault as an SPN, which identifies the value affected, and an FMI, which identifies the type of failure.
A code shows where to look, not always which part to replace: the same code can come from a failed sensor or a loose connector. Read remotely, it reaches the fleet office while the vehicle is still working, instead of waiting for a workshop scan.
How it works
- 1Control unit detects a fault
- 2Code stored, warning lamp lit
- 3Code read by scanner or tracker
Why do diagnostic trouble codes (DTC) matter in fleet management?
Many faults give a code days or weeks before they stop the vehicle, but a lamp on the dashboard only helps if the driver reports it. Seeing codes centrally lets the workshop separate urgent faults, such as overheating or low oil pressure, from those that can wait for the next service, and schedule the repair before the vehicle needs a tow. Codes that return after a repair also expose poor workmanship or a wrong diagnosis.
What you gain
- Faults seen while the vehicle works
- Urgent repairs sorted from minor
- Fewer roadside tows
How does Safee help you keep track of diagnostic trouble codes?
Safee puts fault information alongside the fleet's other alarms: OBD alarms arrive through the V-IVMS video service on the Gold licence, and Thermo-King reefer units report their Fridge Alarm Type and Fridge Alarm Code in the Thermo-King Explorer. Where the tracker reads the CAN bus, engine temperature is available too, an early sign of the faults that end in overheating codes. Notifications send these alarms straight to the workshop, so the repair is booked while the vehicle is still on the road.
A field example
A facilities-maintenance company in Ajman runs 85 vans fitted with mobile digital video recorders (MDVR) on the V-IVMS Gold licence. Drivers rarely reported dashboard warnings, and the company logged 12 roadside tows in four months. It routed OBD alarms to the workshop supervisor, with a rule that any van reporting the same fault twice in a week is booked in within 48 hours. In the next four months 23 vans were booked early, mostly for failing sensors and ignition coils, and tows fell to four.
Frequently asked questions
Does clearing a code fix the fault?
No. Clearing only switches off the warning; if the cause remains, the code comes back, often within a few drive cycles. Clear codes only after the repair.
What is the difference between an active and a stored code?
An active code describes a fault present now; a stored code records one that occurred earlier and has since cleared. Stored codes that keep returning deserve a check even when no active code shows.
Want to put this to work in your fleet?
Talk to a Safee fleet expert about your vehicles and how you operate, and we will suggest what fits.
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