P0450
WIRING DIAGRAM
CIRCUIT DESCRIPTION
An evaporative emission control system is used to prevent emission of fuel vapor. The vapor generated in the fuel tank while driving or the engine at a stop passes through a tank pressure control valve and enters the EVAP canister where the charcoal absorbs and stores the fuel vapor. EVAP canister is purged or cleaned in the same way as EVAP control system for vehicle not equipped with tank pressure control solenoid vacuum valve. Tank pressure control valve operates as follows: As tank pressure control solenoid vacuum valve closes under either of the following conditions, vapor passage of tank pressure control valve also closes.
- Engine stops or
- Engine is running, vehicle stops and fuel level is higher than specified.
Therefore, when the pressure of the vapor generated in the fuel tank increases higher than specified pressure, it pushes open the tank pressure control valve and enters EVAP canister. However, under the conditions that the engine is running and the fuel level is lower than the specified level (or vehicle is running and fuel level is higher than the specified level), tank pressure control solenoid vacuum valve is turned ON by ECM and vacuum is applied to the diaphragm of tank pressure control valve. Thus, the vapor passage of tank pressure control valve opens to allow continuity between the fuel tank and EVAP canister. The EVAP canister air valve and the fuel tank pressure sensor are installed so that ECM diagnoses leakage of the fuel vapor from the evaporative emission control system. The EVAP canister air valve is usually open but it is closed by ECM when checking such leakage.
DETECTING CONDITION AND POSSIBLE CAUSE
NOTE: When other DTC(s) is indicated together, it is possible that "Lg" or "Lg/B" circuit is open.
DTC CONFIRMATION PROCEDURE
WARNING:
- When performing a road test, select a place where there is no traffic or possibility or a traffic accident and be very careful during testing to avoid occurrence of an accident.
- Road test should be carried out with 2 persons, a driver and a tester, on a level road.
1. Turn ignition switch OFF.
2. Clear DTC with ignition switch ON.
3. Check that indication of fuel level meter in combination meter is within 1/4 - 3/4.
4. Drive vehicle above 10 mph 15km/h for 1 min.
5. Check pending DTC in "ON BOARD TEST" or "PENDING DTC" mode and DTC in "DTC" mode.
INSPECTION
FUEL TANK PRESSURE SENSOR CHECK
- Remove fuel tank pressure sensor from fuel tank
- Check sensor air vent hole and pressure passage for clog. Clean if clogged.
- Arrange 3 new 1.5V batteries in series (check that total voltage is 4.5 - 5.0V) and connect its positive terminal to "VIN" terminal of sensor and negative terminal to "Ground" terminal. Then check voltage between "Vout" and "Ground". Also, check if voltage reduces when vacuum is applied up to 6.6kPa (5OmmHg) by using vacuum pump and if it increases when positive pressure applied up to 6.6kPa (5OmmHg) by using hand pump. If measured voltage doesn't show such characteristic as shown in left figure, replace.
TANK PRESSURE CONTROL VALVE INSPECTION
1. Remove tank pressure control valve.
2. Air should pass through valve smoothly from fuel tank side (TANK mark side of tank pressure control valve) to EVAP canister side when blown hard.
3. From CAN mark side, even when blown softly, air should come out of TANK mark side.
4. If air doesn't pass through valve in step 2 or hard blow is required in step 3, replace tank pressure control valve
WARNING: DO NOT SUCK air through tank pressure control valve. Fuel vapor inside the valve is harmful.
5. Apply vacuum to vacuum port. In this state, blow TANK mark port. Air should come out of CAN mark port. If check result is not as described, replace tank pressure control valve.
WARNING: DO NOT SUCK air through tank pressure control valve. Fuel vapor inside the valve is harmful.
6. Install tank pressure control valve.