Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Diagnostic Trouble Code (DTC) Memory
When the engine control module (ECM) detects a fault, a diagnostic trouble code with qualifier and status is stored in the control unit's diagnostic trouble code memory. Fault code storage has four status levels: TEMPORARY, NOT YET STORED, STORED and ERASED . When the engine control module (ECM) detects a fault, the diagnostic trouble code is stored with the status TEMPORARY . If the fault persists the next time diagnostics is performed, diagnostic trouble code status switches to NOT YET STORED . At that time, the diagnostic trouble code will appear during normal DTC readout in VIDA (Volvo scan tool). If the fault is still active during the next operating cycle, the diagnostic trouble code receives the status STORED . If the diagnostic trouble code causes the malfunction indicator lamp (MIL) to illuminate, that process starts now. For more information, see: LIGHTING THE MALFUNCTION INDICATOR LAMP (MIL)
If an existing fault disappears and does not return, the engine control module (ECM) stores the code (after a number of fault-free operating cycles depending on the fault code and previous status) with the status ERASED . In this status, the diagnostic trouble code remains until the engine control module (ECM) is cleared of diagnostic trouble codes or the power to it is cut off.
HINT: A diagnostic trouble code with the status ERASED can be read in VIDA using extended DTC readout. This is often useful when explaining a customer-reported symptom that occurred some time ago.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.