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.
2012 Lexus RX 450h 3.5L Eng VIN CFACTORY OEM SERVICE PROCEDURE
Problem Symptoms Table
HINT:
- Use the table below to help determine the cause of problem symptoms. If multiple suspected areas are listed, the potential causes of the symptoms are listed in order of probability in the "Suspected Area" column of the table. Check each symptom by checking the suspected areas in the order they are listed. Replace parts as necessary.
- Inspect the fuses and relays related to this system before inspecting the suspected areas below.
SFI SYSTEM
| Symptom | Suspected Area | See |
|---|---|---|
| Engine does not crank (Does not start) | Hybrid control system | Refer to HOW TO PROCEED WITH TROUBLESHOOTING |
| VC output circuit | Refer to VC Output Circuit | |
| No initial combustion (Does not start) | ECM power source circuit | Refer to ECM Power Source Circuit |
| VC output circuit | Refer to VC Output Circuit | |
| Crankshaft position sensor | Refer to INSPECTION | |
| Fuel pump control circuit | Refer to Fuel Pump Control Circuit | |
| Ignition system | Refer to ON-VEHICLE INSPECTION | |
| Fuel injector circuit | Refer to Fuel Injector Circuit | |
| Valve timing | Refer to PROCEDURE - Step 4 | |
| Engine cranks normally but difficult to start | Fuel pump control circuit | Refer to Fuel Pump Control Circuit |
| Fuel pump | Refer to INSPECTION | |
| Engine coolant temperature sensor | Refer to INSPECTION | |
| Ignition system | Refer to ON-VEHICLE INSPECTION | |
| Fuel injector assembly | Refer to INSPECTION | |
| EGR valve assembly | Refer to INSPECTION | |
| Compression | Refer to ON-VEHICLE INSPECTION - Step 10 | |
| Fuel injector circuit | Refer to Fuel Injector Circuit | |
| Intake system | Refer to ON-VEHICLE INSPECTION | |
| Throttle with motor body assembly | Refer to ON-VEHICLE INSPECTION | |
| ECM power source circuit | Refer to ECM Power Source Circuit | |
| Incomplete intermittent combustion occurs (Does not start) | Fuel pump control circuit | Refer to Fuel Pump Control Circuit |
| Fuel pump | Refer to INSPECTION | |
| Fuel line | - | |
| Ignition system | Refer to ON-VEHICLE INSPECTION | |
| Fuel injector assembly | Refer to INSPECTION | |
| EGR valve assembly | Refer to INSPECTION | |
| Crankshaft position sensor | Refer to INSPECTION | |
| Valve timing | Refer to PROCEDURE - Step 4 | |
| High engine speed (Poor idle) | Throttle with motor body assembly | Refer to ON-VEHICLE INSPECTION |
| Throttle with motor body assembly control | - | |
| Intake system | Refer to ON-VEHICLE INSPECTION | |
| Engine coolant temperature sensor | Refer to INSPECTION | |
| PCV hose | Refer to ON-VEHICLE INSPECTION - Step 2 | |
| PCV system | Refer to ON-VEHICLE INSPECTION | |
| ECM power source circuit | Refer to ECM Power Source Circuit | |
| Low engine speed (Poor idle) | Fuel pump control circuit | Refer to Fuel Pump Control Circuit |
| Throttle with motor body assembly | Refer to ON-VEHICLE INSPECTION | |
| Throttle with motor body assembly control | - | |
| Intake system | Refer to ON-VEHICLE INSPECTION | |
| PCV hose | Refer to ON-VEHICLE INSPECTION - Step 2 | |
| PCV system | Refer to ON-VEHICLE INSPECTION | |
| Engine stalls on deceleration | Idle speed (refer to "Low engine speed") | Refer to ON-VEHICLE INSPECTION - Step 9 |
| EGR valve assembly | Refer to INSPECTION | |
| Rough idle | Compression (engine mechanical) | Refer to ON-VEHICLE INSPECTION - Step 10 |
| Air fuel ratio sensor | Refer to INSPECTION | |
| Heated oxygen sensor | Refer to INSPECTION | |
| Mass air flow meter sub-assembly | Refer to ON-VEHICLE INSPECTION | |
| Ignition system | Refer to ON-VEHICLE INSPECTION | |
| Fuel line | - | |
| Valve timing | Refer to PROCEDURE - Step 4 | |
| Fuel pump | Refer to INSPECTION | |
| Intake system | Refer to ON-VEHICLE INSPECTION | |
| PCV hose | Refer to ON-VEHICLE INSPECTION - Step 2 | |
| PCV system | Refer to ON-VEHICLE INSPECTION | |
| EGR valve assembly | Refer to INSPECTION | |
| Hunting (Poor idle) | PCV hose | Refer to ON-VEHICLE INSPECTION - Step 2 |
| PCV system | Refer to ON-VEHICLE INSPECTION | |
| Mass air flow meter sub-assembly | Refer to ON-VEHICLE INSPECTION | |
| Air fuel ratio sensor | Refer to INSPECTION | |
| Hesitation/Poor acceleration (Poor driveability) | Fuel line | - |
| Fuel pump | Refer to INSPECTION | |
| Valve timing | Refer to PROCEDURE - Step 4 | |
| Mass air flow meter sub-assembly | Refer to ON-VEHICLE INSPECTION | |
| Throttle with motor body assembly | Refer to ON-VEHICLE INSPECTION | |
| Knock control sensor | Refer to INSPECTION | |
| Surging (Poor driveability) | Fuel line | - |
| Fuel pump control circuit | Refer to Fuel Pump Control Circuit | |
| Fuel pump | Refer to INSPECTION | |
| Ignition system | Refer to ON-VEHICLE INSPECTION | |
| Fuel injector assembly | Refer to INSPECTION | |
| Engine stalls soon after starting | Mass air flow meter sub-assembly | Refer to ON-VEHICLE INSPECTION |
| Intake system | Refer to ON-VEHICLE INSPECTION | |
| Fuel line | - | |
| EGR valve assembly | Refer to INSPECTION | |
| Unable/difficult to refuel | Fuel system (canister, refueling valve, roll over valve, fuel tank, etc.) | - |
Factory Service Tools
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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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