Toyota 25052-20030 Exhaust Manifold Converter Sub-Assembly, No.2

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Remove the sensor.

Disconnect the negative cable from the battery. Spray penetrating oil on the exhaust manifold fasteners and allow it to soak in. Remove the heated oxygen sensors from the front and rear manifolds. Remove the EGR pipe from the rear exhaust manifold and cylinder head. Remove the nuts retaining the exhaust pipes to the front and rear exhaust manifolds. Disconnect the electrical connector from the oxygen sensor at each manifold. Unbolt the exhaust manifolds from the cylinder heads and slip them off the mounting studs. Carefully inspect the manifolds and fasteners for cracks and damage. Use a scraper to remove all traces of old gasket material and carbon deposits from the manifolds and cylinder head mating surfaces. If the gasket was leaking, check the manifolds for warpage on the cylinder head mounting surface by placing a straightedge over the surface and trying to insert a feeler gauge. If the clearance exceeds the limit, have the manifold resurfaced at an automotive machine shop. Position new gaskets over the cylinder head studs. Install the manifolds and thread the mounting nuts into place. Working from the center out, tighten the nuts. Reinstall the remaining parts in the reverse order of removal. Use new gaskets when connecting the exhaust pipes. Run the engine and check for exhaust leaks.

A vacuum gauge can be used to diagnose a restricted converter. If the exhaust system is restricted, the catalytic converter may be plugged or an exhaust pipe or muffler could be restricted.