If excessive exhaust system back-pressure is suspected, remove the TWC from the vehicle. Using a flashlight, make a visual check for plugging, melting or cracking of the catalyst. Replace the TWC if any of the visible area is damaged or plugged. D15Y4, D15Y6, D17A1, D17Z2 engines: D15Y3 (KV model), D15Y2, D15Y4, D16W8, D17Z1, D17A2, D17Z3, D17A5 (KV model), D17Z4 engines:

Connect a tachometer. Start the engine. Hold the engine at 3,000 rpm (min-1) with no load (in Park or neutral) until the radiator fan comes on, then let it idle. Check the idle speed (see page 11-285 ). Warm up and calibrate the CO meter according to the meter manufacturer's instructions. Check idle CO with the headlights, heater blower, rear window defogger, cooling fan, and air conditioner off. Specified CO%: For cars with TWC model (Except KV model): 0.1 % maximum For cars without TWC model: 1.0 + 1.0 % If unable to obtain this reading: Without TWC model, adjust by turning the adjusting screw (A) of the IMA. With TWC model, see DTC troubleshooting index. If unable to obtain a CO reading of specified % by this procedure, check the tune-up condition.