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.
Leak Diagnostic Unit
The function of the leak diagnostic unit is to perform leak diagnostics on the fuel tank system.
The leak diagnostic unit consists of a plastic housing with:
- Electrical air pump.
- A valve/solenoid which governs the air flow in the unit between the reference leak and tank system.
- a heater element (PTC resistor) which warms up the pump.
The electrical pump, valve and heater element in the unit are supplied with voltage (12V) by the system relay. Ground in the Engine Control Module (ECM).
When leakage diagnostics is not active, the valve is kept open to ambient air so that EVAP-control can be performed.
At leakage diagnosis, the pump in the leakage diagnostic unit will start, and the valve in the leakage diagnostic unit will be controlled by Engine Control Module (ECM) by grounding the various circuits internally in Engine Control Module (ECM).
Engine Control Module (ECM) checks sealing in the fuel tank system by pressurizing the system and at the same time monitor a number of relevant parameters. See also Leak diagnostics.
The Engine Control Module (ECM) can diagnose the leak diagnostic unit with its component parts.
The leak diagnostic unit is at the upper front edge of the fuel tank.
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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.
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