OBD2 code diagnosis

Random / multiple cylinder misfire

• •Worn spark plugs or coils
• •Low fuel pressure
• •Intake vacuum leak

Avoid long drives — it can destroy the catalytic converter. Check plugs and coils first.

Catalyst efficiency below threshold

• •Worn catalytic converter
• •Faulty downstream O2 sensor
• •Exhaust leak

Test O2 sensors and the exhaust before replacing the expensive converter.

System too lean — bank 1

• •Vacuum leak
• •Dirty MAF sensor
• •Clogged fuel filter

Clean the MAF sensor and smoke-test the intake for leaks.

Coolant temperature below thermostat regulating temperature

• •Thermostat stuck open
• •Faulty coolant temp sensor

Replace the thermostat — it hurts economy and heater performance.

Small EVAP system leak

• •Loose fuel cap
• •Cracked EVAP hose
• •Purge valve fault

Retighten the fuel cap first, then clear the code.

Input / turbine speed sensor circuit malfunction

• •Failed speed sensor
• •Low transmission fluid
• •Wiring fault

Avoid hard driving and visit a transmission specialist.

Large EVAP system leak

• •Damaged fuel cap
• •Cracked charcoal canister

Smoke-test the cap and hoses.

Camshaft timing over-advanced (bank 1)

• •Low or dirty oil
• •VVT solenoid fault
• •Stretched timing chain

Change the oil to spec and test the VVT solenoid.