EVAP system: Notes

DTC No.	Monitoring items	Reference pages
P0441	Purge flow	DTC P0441 Purge flow
P0451	Difference in pressure between canister pressure sensor (integrated into canister pump module) and air pressure sensor	DTC P0451 EL CONTROL MODULE evaporative emission control system pressure sensor performance; DTC P0452 EL CONTROL MODULE evaporative emission control system pressure sensor (continuity LOW); DTC P0453 EL CONTROL MODULE evaporative emission control system pressure sensor (continuity HIGH)
P0452	Canister pressure sensor (integrated into canister pump module) voltage LOW
P0453	Canister pressure sensor (integrated into canister pump module) voltage HIGH
P0455	Large leak from EVAP	DTC P0455 Evaporative emission control system leak detected (gross leak); DTC P0456 Evaporative Emission Control System Leak Detected (very small leak); DTC P1451 Fuel tank pressure sensor range/performance; DTC P2404 Evaporative emission system leak detection pump sense circuit range/performance
P0456	Small leak from EVAP
P0458	Purge VSV voltage LOW	DTC P0458 Evaporative Emission System Purge Control Valve Circuit Low; DTC P0459 Evaporative Emission System Purge Control Valve Circuit High
P0459	Purge VSV voltage HIGH
P1449	Clogged air filter (integrated into canister pump module)	DTC P1449 Vent control filter clogging
P1451	Clogged pipe	DTC P0455 Evaporative emission control system leak detected (gross leak); DTC P0456 Evaporative Emission Control System Leak Detected (very small leak); DTC P1451 Fuel tank pressure sensor range/performance; DTC P2404 Evaporative emission system leak detection pump sense circuit range/performance
P2404	Flow rate rises at reference orifice (integrated into canister pump module). Flow rate reduces at reference orifice (integrated into canister pump module).
P2401	Leak detection pump stuck OFF (integrated into canister pump module)	DTC P2401 Evaporative Emission Leak Detection Pump Stuck OFF; DTC P2402 Evaporative Emission Leak Detection Pump Stuck ON; DTC P2419 Evaporate Emission System Switching Valve Control Circuit Low; DTC P2420 Evaporate Emission System Switching Valve Control Circuit High
P2402	Leak detection pump stuck ON (integrated into canister pump module)
P2419	Closing of vent valve stuck (integrated into canister pump module) or not
P2420	Opening of vent valve stuck (integrated into canister pump module) or not
P2610	Soak timer (integrated into ECM)	Inspection steps

When the DTCs related to the EVAP system have been stored, the malfunctioning section can be located using the table below.

Malfunctioning Areas/DTCs	P0441	P0451	P0452	P0453	P0455	P0456	P0458	P0459
Purge valve stuck open	•				•
Purge valve stuck closed	•
Purge valve low output							•
Purge valve high output								•
Canister pressure sensor signal fixed		•
Canister pressure sensor low output			•
Canister pressure sensor high output				•
Gross leak	•				•
Small leak						•

Malfunctioning Areas/DTCs	P1449	P1451	P2401	P2402	P2404	P2419	P2420
Reference orifice low-flow					•
Reference orifice high-flow					•
Leak detection pump stuck OFF			•
Leak detection pump stuck ON				•	•
Vent valve stuck closed					•	•
Vent valve stuck open					•		•
Canister filter clogged		•
Pipe clogged	•

Circuit description

With the engine running, under the specified condition (closed loop, etc.), the ECM opens the purge VSV and purges the fuel vapor accumulated in the canister to the intake manifold. The ECM changes the duty cycle ratio of the purge VSV and controls the purge flow rate.

The purge flow rate is determined by the intake manifold pressure. Pressure in the canister via vent valve ensures the retention of the purge flow when the negative (vacuum) pressure is applied to the canister.

In order to confirm the appropriate operation of the EVAP system, the following 2 monitors work.

1. Purge flow monitor

   The purge flow monitor consists of two monitors. First monitoring is performed every time, and the second monitoring is performed as necessary.

   • First monitoring

     With the engine running, when the purge VSV is ON (open), the ECM monitors the purge flow by measuring the fluctuation in EVAP pressure. If the pressure variation exceeds the threshold value, the ECM initiates second monitoring.

   • Second monitoring

     The vent valve turns to ON (Closed) and EVAP pressure monitoring is carried out. If the pressure fluctuation exceeds the threshold, the ECM judges that the purge VSV is in the stuck close status and illuminates the MIL, and stores DTC P0441 (2 trip detection logic).

Atmospheric pressure measurement:

In order to securely perform a reliable malfunction detection, the ECM measures the fluctuation in barometric pressure (before and after the purge flow monitor).

Parts	Operation
Canister	Contains activated charcoal to absorb the EVAP (evaporative emission) generated in the fuel tank.
Cutoff valve	Located in the fuel tank. This valve is designed to prevent the accidental fuel spill when the vehicle overturns.
Purge VSV (vacuum switching valve)	Opens and closes the line between canister and intake manifold. The ECM controls the EVAP purge flow by the purge VSV. The ECM opens the purge VSV to release the evaporative emission absorbed by the canister into the intake manifold. Amount of evaporative emission released into the intake manifold controlled by the purge VSV duty cycle (energized time) (Open: ON, Close: OFF)
Fuel tank vent valve	Located in the fuel tank. Purges the fuel vapor generated during refueling into the canister. Also detects the highest fuel level in the fuel tank.
Soak timer	Integrated into the ECM. In order to ensure the accuracy of the EVAP monitor, 5-hours (+/-15 min.) measurement is performed after ignition switch has been turned to OFF. This will lower the fuel temperature and stabilize the EVAP pressure. After approximately 5 hours have passed, the ECM will start up. (Fig. 3)
Canister pump module	Consists of the following components (a, b, c, d). The canister pump module cannot be disassembled.
(a) Vent valve	Ventilates and closes the EVAP system. When the ECM turns on the valve, the EVAP system is closed. When the ECM turns off the valve, the EVAP system is ventilated. Closes the purge VSV, turns the vent valve to ON (close), and operates the leak detection pump. In order to inspect for EVAP leakage, build up negative pressure (vacuum) into the EVAP system. (Fig. 1)
(b) Canister pressure sensor	Indicates pressures such as voltage. The ECM applies the adjusted 5 V to the pressure sensor and monitors the EVAP system pressure using the feedback from the sensor. (Fig. 2)
(c) Leak detection pump	Builds up the negative pressure (vacuum) in the EVAP system for leak detection.
(d) Reference orifice	Equipped with an opening of 0.02-in. dia. In order to monitor the standard pressure, closes the purge VSV, turns the vent valve to OFF, and operates the leak detection pump. Eventually, the negative pressure (vacuum) is built up through the orifice. Standard pressure indicates the small leakage from the EVAP.