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P0133 Aging of Oxygen Sensor Ahead of Three Way Catalytic Converter (TWC) (cylinders 1-3)

P0139 Aging of Oxygen Sensor After Three Way Catalytic Converter (TWC) (cylinders 1-3)

P0153 Aging of Oxygen Sensor Ahead of Three Way Catalytic Converter (TWC) (cylinders 4-6)

P0159 Aging of Oxygen Sensor After Three Way Catalytic Converter (TWC) (cylinders 4 -6)

This would say the all 4 O2 sensors are taking too long to sense changes.

P0236 Turbocharger Boost Sensor Circuit “A” - Range / Performance Waste Gate Frequency Valve faulty


- Interruption in wiring

- Waste gate frequency valve (coil) interruption

below lower limit

- short to ground

above upper limit

- short to B+

Repair the harness or replace the valve.

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Hard to say - 45,000 miles seems a little early for all 4 O2 sensors. A modified DME program could cause issues too.

You should likely plot the O2 sensor voltage curves and compare it against a well running 993TT.

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Loren, do the 993 TT have the valve guide problem or just the NA cars? I don't think I've heard of any

if so some oil on the sensors might be causing this also

It is my understanding that the 1996's 993 TT had premature valve guide wear issues. Not so much on the 1997 993 TT.

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