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 Toyota Yaris Base, Standard TransFACTORY 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) | Battery | Refer to ON-VEHICLE INSPECTION - Step 1 |
| Starter (for except cold area) | Refer to INSPECTION | |
| Starter (for cold area) | Refer to INSPECTION | |
| Cranking holding function circuit | Refer to Cranking Holding Function Circuit | |
| Starter relay | Refer to ON-VEHICLE INSPECTION - Step 1 | |
| Park/neutral position switch | Refer to INSPECTION | |
| Clutch start switch | Refer to INSPECTION | |
| No initial combustion (Does not start) | ECM power source circuit | Refer to ECM Power Source Circuit |
| Crankshaft position sensor | Refer to PROCEDURE - Step 1 | |
| Camshaft position sensor | Refer to PROCEDURE - Step 1 | |
| Ignition system | Refer to ON-VEHICLE INSPECTION | |
| Fuel pump control circuit | Refer to Fuel Pump Control Circuit | |
| Fuel pump | Refer to INSPECTION | |
| Fuel injector circuit | Refer to Fuel Injector Circuit | |
| Valve timing | Refer to PROCEDURE - Step 4 | |
| VC output circuit | Refer to VC Output Circuit | |
| ECM | Refer to TERMINALS OF ECM | |
| Engine immobiliser system | Refer to HOW TO PROCEED WITH TROUBLESHOOTING | |
| Engine cranks normally but difficult to start | Fuel pump control circuit | Refer to Fuel Pump Control Circuit |
| Fuel pump | Refer to INSPECTION | |
| Fuel injector circuit | Refer to Fuel Injector Circuit | |
| Cranking holding function circuit | Refer to Cranking Holding Function Circuit | |
| Engine coolant temperature sensor | Refer to INSPECTION | |
| Intake system | Refer to ON-VEHICLE INSPECTION | |
| Ignition system | Refer to ON-VEHICLE INSPECTION | |
| Spark plug | Refer to ON-VEHICLE INSPECTION - Step 2 | |
| Electronic throttle control system | Refer to ON-VEHICLE INSPECTION | |
| Compression | Refer to ON-VEHICLE INSPECTION - Step 9 | |
| 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 | Refer to ON-VEHICLE INSPECTION | |
| Ignition system | Refer to ON-VEHICLE INSPECTION | |
| Fuel injector circuit | Refer to Fuel Injector Circuit | |
| ECM power source circuit | Refer to ECM Power Source Circuit | |
| Cranking holding function circuit | Refer to Cranking Holding Function Circuit | |
| Crankshaft position sensor | Refer to PROCEDURE - Step 1 | |
| Camshaft position sensor | Refer to PROCEDURE - Step 1 | |
| Valve timing | Refer to PROCEDURE - Step 4 | |
| High engine idle speed | Electronic throttle control system | Refer to ON-VEHICLE INSPECTION |
| Intake system | Refer to ON-VEHICLE INSPECTION | |
| A/C signal circuit | Refer to TERMINALS OF ECU | |
| ECM power source circuit | Refer to ECM Power Source Circuit | |
| Engine coolant temperature sensor | Refer to INSPECTION | |
| PCV valve and hose | Refer to COMPONENTS | |
| Low engine idle speed (Poor idling) | Electronic throttle control system | Refer to ON-VEHICLE INSPECTION |
| A/C signal circuit | Refer to TERMINALS OF ECU | |
| Fuel pump control circuit | Refer to Fuel Pump Control Circuit | |
| Intake system | Refer to ON-VEHICLE INSPECTION | |
| Fuel pump | Refer to INSPECTION | |
| PCV valve and hose | Refer to COMPONENTS | |
| Rough idling | Compression | Refer to ON-VEHICLE INSPECTION - Step 9 |
| Ignition system | Refer to ON-VEHICLE INSPECTION | |
| Spark plug | Refer to ON-VEHICLE INSPECTION - Step 2 | |
| Fuel injector circuit | Refer to Fuel Injector Circuit | |
| ECM power source circuit | Refer to ECM Power Source Circuit | |
| Fuel pump control circuit | Refer to Fuel Pump Control Circuit | |
| Fuel pump | Refer to INSPECTION | |
| Fuel line | Refer to ON-VEHICLE INSPECTION | |
| Electronic throttle control system | Refer to ON-VEHICLE INSPECTION | |
| Intake system | Refer to ON-VEHICLE INSPECTION | |
| Purge VSV | Refer to INSPECTION | |
| PCV valve and hose | Refer to COMPONENTS | |
| Air fuel ratio sensor | Refer to INSPECTION PROCEDURE | |
| Heated oxygen sensor | Refer to INSPECTION PROCEDURE | |
| Mass air flow meter | Refer to ON-VEHICLE INSPECTION | |
| Knock sensor | Refer to INSPECTION | |
| External part malfunction (Increase in load: A/C system, A/T system, etc.) | - | |
| Idle hunting | Electronic throttle control system | Refer to ON-VEHICLE INSPECTION - Step 1 |
| Intake system | Refer to ON-VEHICLE INSPECTION | |
| PCV valve and hose | Refer to COMPONENTS | |
| Air fuel ratio sensor | Refer to INSPECTION PROCEDURE | |
| Mass air flow meter | Refer to ON-VEHICLE INSPECTION | |
| Hesitation/Poor acceleration | Fuel pump control circuit | Refer to Fuel Pump Control Circuit |
| Fuel pump | Refer to INSPECTION | |
| Fuel line | Refer to ON-VEHICLE INSPECTION | |
| Spark plug | Refer to ON-VEHICLE INSPECTION - Step 2 | |
| Ignition system | Refer to ON-VEHICLE INSPECTION | |
| Fuel injector circuit | Refer to Fuel Injector Circuit | |
| ECM power source circuit | Refer to ECM Power Source Circuit | |
| Mass air flow meter | Refer to ON-VEHICLE INSPECTION | |
| Electronic throttle control system | Refer to ON-VEHICLE INSPECTION | |
| Intake system | Refer to ON-VEHICLE INSPECTION | |
| Valve timing | Refer to PROCEDURE - Step 4 | |
| Compression | Refer to ON-VEHICLE INSPECTION - Step 9 | |
| Brake override system | Refer to Brake Override System | |
| Surging (Poor driveability) | Spark plug | Refer to ON-VEHICLE INSPECTION - Step 2 |
| Fuel pump control circuit | Refer to Fuel Pump Control Circuit | |
| Fuel pump | Refer to INSPECTION | |
| Ignition system | Refer to ON-VEHICLE INSPECTION | |
| Fuel injector circuit | Refer to Fuel Injector Circuit | |
| ECM power source circuit | Refer to ECM Power Source Circuit | |
| Mass air flow meter | Refer to ON-VEHICLE INSPECTION | |
| Variable valve timing system | Refer to INSPECTION | |
| Compression | Refer to ON-VEHICLE INSPECTION - Step 9 | |
| Engine stalls soon after starting | Fuel pump control circuit | Refer to Fuel Pump Control Circuit |
| Fuel pump | Refer to INSPECTION | |
| Spark plug | Refer to ON-VEHICLE INSPECTION - Step 2 | |
| Ignition system | Refer to ON-VEHICLE INSPECTION | |
| Fuel injector circuit | Refer to Fuel Injector Circuit | |
| ECM power source circuit | Refer to ECM Power Source Circuit | |
| Mass air flow meter | Refer to ON-VEHICLE INSPECTION | |
| Variable valve timing system | Refer to INSPECTION | |
| Electronic throttle control system | Refer to ON-VEHICLE INSPECTION | |
| Intake system | Refer to ON-VEHICLE INSPECTION | |
| PCV valve and hose | Refer to COMPONENTS | |
| Compression | Refer to ON-VEHICLE INSPECTION - Step 9 | |
| Engine stalls only during A/C operation | A/C signal circuit | Refer to HOW TO PROCEED WITH TROUBLESHOOTING |
| ECM | Refer to TERMINALS OF ECM | |
| Unable/difficult to refuel | Fuel system (canister, refueling valve, fuel tank, etc.) | Refer to INSPECTION |
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.