Skip the auto shop - Our mechanics make house calls

Q: Engine Power Reduced TPS

asked by on

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.

Was this answer helpful?

Need advice from certified mechanic? Get help now!

Over 1000 mechanics are ready to answer your question.
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Fair and transparent pricing

Get a quote

What others are asking

Q: Ticking and rattling after parts were replaced

It sounds to me like the valve timing is now incorrect. The pin that you are referring to might be an alignment pin of some kind. If the valve timing is not correct, this can cause the valves to tick...

Q: Transmission. Car turning off when changing gears.

Hi there, thanks for writing in. This is a common issue on a lot of Nissan vehicles. Most of the time it is due to a faulty throttle body. The throttle motor fails at times and cannot keep the throttle...

Q: No reverse in transmission 1997 Chevrolet Express Van 1500

Hello - I believe you have a failure in the reverse input clutch in the transmission. This could be caused by several components in this clutch, all of which will require removal and disassembly of the transmission to repair. To...

Related articles

P0240 OBD-II Trouble Code: Turbocharger Boost Sensor B Circuit Range/Performance
P0240 code definition Turbocharger Boost Sensor B Circuit Range/Performance What the P0240 code means P0240 is an OBD-II generic code triggered when the Engine Control Module (ECM) detects the intake boost...
How Much Does a Mechanic Make in Vermont?
Automotive technician jobs in Vermont have an average mechanic salary of $37k, with some mechanics earning a salary of $53k.
P2103 OBD-II Trouble Code: Throttle Actuator Control Motor Circuit High
P2103 means there is a fault with the throttle actuator control motor circuit, likely due to a defective electrical component or part.