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Q: Engine Power Reduced TPS

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My 2008 Chevy Express 1500 is indicating Engine Power Reduced and Service TPS (Throttle Position Sensor System) was going into Engine Power Reduced mode. I have a faulty catalytic converter and my oil shows 0 % for being effective. When I’m on the highway and driving on a flat stretch of road I can get my car up to about 50 mph. But when I slow down or stop it has really low power when I take off again. When going up any hill or slight incline it is very, very slow. When it’s idling it runs and sounds like a tractor. It vibrates and the engine rattles the whole front end of the car. If I accelerate a little, it quiets down the vibrating. I was told by someone that one of the sensors in the Catalytic Converter, or in the emission system has to do with the throttle, (throttle position sensor), and because it’s bad, the system doesn't know how much gas to give or how fast the car may be going because of not knowing how much the throttle is open when the engine power is reduced as a safety. Can a faulty Throttle Position Sensor system and a faulty catalytic converter be the cause?

A: Hi! Yes the throttle position sensor could ...

Hi! Yes the throttle position sensor could very well be the cause. I highly doubt that it is the oxygen sensor though. When the throttle position sensor goes bad the engine will put itself into reduced power mode.

I was working on a Chevy Trailblazer the other week with the same display message. We ended up tracking the problem down to a bad throttle body. The throttle body is electronically controlled and the throttle body electrical motor would become stuck sometimes during vehicle operation and cause it to go into reduced power mode.

A technician should test the movement of the throttle body and ensure that the throttle body plate can move back and forth freely. I also suggest testing the throttle body input and output with a multimeter. Feel free to contact a certified mechanic who can perform these checks and properly diagnose your loss of power if you need some assistance. Once this is done, the problem will be evident and the mechanic can perform the necessary repairs.

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