| CAUTION | If Engine Control Module (ECM) replacement is instructed in following test, always ensure ECM electrical connectors and ground circuits are okay. If either are defective, repair and repeat testing to confirm ECM malfunction. On models equipped with engine immobilizer, if ECM is replaced, ECM must be programmed with proper ignition key code for engine immobilizer system. For programming procedures, see COMPUTER RELEARN PROCEDURES article in GENERAL INFORMATION, or appropriate ENGINE IMMOBILIZER SYSTEMS article in ACCESSORIES & EQUIPMENT. |
Note. This DTC may be caused by a loose or improperly installed fuel tank cap. If DTC P0441, P0446, P0450 or P0451 is output after DTC P0440, perform appropriate test for these DTCs first before performing test for DTC P0440.
Circuit Description
Vapor pressure sensor, canister closed valve Vacuum Switching Valve (VSV) and pressure switching valve Vacuum Switching Valve (VSV) are used to detect abnormalities in the EVAP system. DTC is set if a leak is detected in EVAP system or vapor pressure sensor malfunctions. Canister closed valve VSV may also be referred to as CCV VSV. Possible causes are
- Damaged, disconnected or restricted vacuum hose(s) or tubes.
- Fuel tank cap is loose or improperly installed.
- Defective fuel tank cap.
- Damaged fuel inlet pipe or fuel tank.
- Defective charcoal canister.
- Vapor pressure sensor circuit is open or shorted.
- Defective vapor pressure sensor.
- Defective overfill check valve on fuel tank.
- Defective ECM.
Diagnostic Aids
Verify with customer if fuel tank cap has been left off or not completely tightened recently. This may cause DTC to be set. Using Toyota hand-held tester or scan tool, read FREEZE FRAME data. Freeze frame data records engine conditions when malfunction is detected.
Scheme 315
- Check for cracks and deformations in fuel tank, charcoal canister and fuel inlet pipe. Fuel inlet pipe may also be referred to as fuel filler pipe. Charcoal canister is located near fuel tank. (Scheme 315) Check for loose connections and disconnected hoses and tubes around fuel tank and charcoal canister. If no problems exist, go to next step. If any problem exists, repair as necessary.
- Check fuel tank cap to ensure fuel tank cap is a Original Equipment Manufacturer (OEM) fuel tank cap. If fuel tank cap is an OEM fuel tank cap, go to next step. If fuel tank cap is not an OEM fuel tank cap, replace fuel tank cap with an OEM fuel tank cap.
- Ensure fuel tank cap is properly installed and tightened. If fuel cap is properly installed and tightened, go to next step. If fuel cap is not properly installed or tightened, reinstall and tighten as necessary.
- Check fuel tank cap for damage and damaged gasket. If fuel tank cap is not damaged and gasket is okay, go to next step. If fuel tank cap or gasket is damaged, replace fuel tank cap with an OEM fuel tank cap.
- Visually inspect fuel inlet pipe for damage. (Scheme 315) If fuel inlet pipe is not damaged, go to next step. If fuel inlet pipe is damaged, replace fuel inlet pipe.
- Check vapor pressure sensor connection at fuel pump. (Scheme 315) Check vacuum hoses to charcoal canister, EVAP VSV and pressure switching valve VSV for correct installation, loose connections, disconnected hoses and damage. (Scheme 315)for component location. If no problems exist, go to next step. If any problem exists, repair or replace components as necessary.
- Check hoses and tubes between fuel tank, fuel inlet pipe and charcoal canister for correct installation, loose connections, being disconnected and damage. (Scheme 315) If no problems exist, go to next step. If any problem exists, repair or replace components as necessary.
- Check charcoal canister for cracks or damage. If charcoal canister is okay, go to next step. If charcoal canister is cracked or damaged, replace charcoal canister. See CHARCOAL CANISTER under EMISSION SYSTEMS & SUB-SYSTEMS in REMOVAL, OVERHAUL & INSTALLATION - 4-CYLINDER article.
- Remove glove box and passenger's side kick panel (if necessary) for access to ECM with electrical connectors still installed on ECM. see scheme 2 Turn ignition on. Using voltmeter, check voltage between terminals No. 2 (Yellow wire) and No. 18 (Brown wire) at ECM electrical connector E5. see scheme 4 This is the VC and E2 terminals on ECM. Voltage should be 4.5-5.5 volts. If voltage is within specification, go to next step. If voltage is not within specification, replace ECM.
- Turn ignition off. Connect voltmeter between terminals No. 18 (Brown wire) at ECM electrical connector E5 and No. 21 (Blue/Black or White wire) at ECM electrical connector E7. see scheme 4 This is the E2 and PTNK terminals on ECM. There are 2 different wiring harnesses used and wire color varies according to wiring harness used. Remove fuel tank cap. Turn ignition on and note voltage. Voltage should be 3.0-3.6 volts. If voltage is not within specification, go to next step. If voltage is within specification, go to step 12.
- Check for open and short in wiring harness and electrical connectors between vapor pressure sensor and ECM. See WIRING DIAGRAMS article. If wiring harness and electrical connectors are okay, replace vapor pressure sensor. See VAPOR PRESSURE SENSOR under EMISSION SYSTEMS & SUB-SYSTEMS in REMOVAL, OVERHAUL & INSTALLATION - 4-CYLINDER article. If wiring harness or electrical connector is defective, repair as necessary.
- Inspect fuel tank and overfill check valve for cracks and damage. If fuel tank or overfill valve are defective, repair or replace components as necessary. If fuel tank and overfill valve are okay, it is likely that DTC was caused by fuel tank cap not being fully tightened or was improperly installed.