Diagnosis & Repair
WARNING: This page is about a different car, the 2002 Lexus RX 300. However, it is still accessible from the selected car via links, so may be relevant.
- Check with vehicle driver if fuel tank cap was found loose at any time. If fuel tank cap was loose, it probably was cause of DTC P0440 or P0442 being set. If fuel tank cap was not loose, check for cracks, deformations or loose connections in following:
- Fuel tank.
- Charcoal canister.
- Fuel tank filler pipe.
- Hose and tubes around fuel tank and charcoal canister.
Repair as necessary. If components are okay, go to next step.
- Check if fuel tank cap is an original manufacturer's cap. If fuel tank cap is an original manufacturer's cap, go to next step. If fuel tank cap is not an original manufacturer cap, replace cap with a manufacturer's cap.
- Check if fuel tank cap is installed properly. Reinstall fuel cap as necessary. If fuel cap is installed properly, go to next step.
- Check for damaged fuel tank cap and gasket. Replace fuel cap as necessary. If fuel tank cap and gasket are okay, go to next step.
- Remove fuel tank cap. Visually inspect fuel tank filler neck for damage. Replace filler neck as necessary. If filler neck is okay, go to next step.
- Check vacuum hoses between vapor pressure sensor and fuel tank, and between pressure switching valve VSV and charcoal canister. Check hoses for correct installation, looseness and damage. Repair as necessary. If vacuum hoses are okay, go to next step.
- Check hose and tube between fuel tank and charcoal canister for correct installation and damage. Repair as necessary. If hose and tube are okay, go to next step.
- Visually inspect charcoal canister for cracks or damage. Replace canister as necessary. If canister is okay, go to next step.
- Access ECM harness connectors behind glove box. Turn ignition on. Backprobing ECM harness connector, measure voltage between terminals No. 2 (Yellow/Black wire) and No. 18 (Brown wire) at ECM E8 connector. See Figure. If voltage is 4.5-5.5 volts, go to next step. If voltage is not 4.5-5.5 volts, replace ECM and retest system.NOTE: DO NOT apply more than 19.7 in. Hg (66.7 kPa) to vapor pressure sensor.
- Locate vapor pressure sensor on top of fuel tank. See Fig 1. Leaving harness connector attached, remove vapor pressure sensor from top of fuel tank. See Fig 2. Backprobing ECM harness connectors, connect voltmeter between terminal No. 17 (Blue/Orange wire) at ECM E5 connector and terminal No. 18 (Brown wire) at ECM E8 connector. See Figure. Connect a vacuum pump to vapor port on sensor. Voltage should be 2.9-3.7 volts without vacuum applied, and .5 volts or less with 1.18 in. Hg (4.0 kPa) applied. If voltage is as specified, go to step 12. If voltage is not as specified, go to next step.
- Check for an open or short in wiring harness between vapor pressure sensor and ECM. See WIRING DIAGRAMS article. Repair as necessary. If wiring is okay, replace vapor pressure sensor.
- Check fuel tank and fuel tank overfill check valves for cracks and damage. Overfill check valve is located on top of fuel tank. See Fig 1. Replace fuel tank or overfill check valve as necessary. If fuel tank and overfill check valve are okay, probable cause of DTC P0440 or P0442 to set was an incorrectly installed fuel tank cap.NOTE: Overfill check valve may also be referred to as fill check valve. Cut-off valve may also be referred to as fuel cut-off valve.