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GMTechBernard, Shop Foreman - GM World Class Tech
Category: Chevy
Satisfied Customers: 2158
Experience:  GM
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Cause of REDUCED ENGINE POWER message 2005 Suburban

Customer Question

Cause of REDUCED ENGINE POWER message 2005 Suburban
Submitted: 7 years ago.
Category: Chevy
Expert:  GMTechBernard replied 7 years ago.

Hello! "Reduced Engine Power" is not caused by engine overheating, I will look into what the owners manual states, but your Reduced Power mode is a failure of the electronic throttle system. Your throttle system is made up of four components: 1) electric throttle body, complete with throttole motor and sensors, 2) accelerator pedal w/ position sensors, 3) throttle module 4)all of the wiring that connects them.


Without knowing what code is stored, its hard to isolate exactly where the problem may lie, but I can tell you from experience, that 75% of throttle system failures require either a new throttle body or connector to fix, often times both. On a few, I have had to run new wires from the throttle body to the module, but before you spend any money on parts, it would be best to get the codes checked out. many places offer "free code scans" in hopes of selling you parts or service.

Please let me know how I can be of further assistance!

Customer: replied 7 years ago.

You were right -- the AutoZone guy read Codes of P0120 and P2135, both of which have to do with Throttle Position Sensor or the wiring harness/connector.


They have one in stock for $ 30. Is this a part a competent shade tree mechanic can replace or does it require a shop computer to "calibrate?"


And do these codes rule out the throttle pedal assembly?



Expert:  GMTechBernard replied 7 years ago.
These codes do rule out the pedal assembly, since these are throttle codes. However, what they have for $30 is not what you need. They are trying to sell you just the throttle position sensor, which is not servicable on this model (they are selling you the wrong part). The part you need (throttle body) is usually around $200. The throttle body isn't too hard to replace and does not need calibrated, however, if any of the wires are damaged at the connector (replacement of connected reccomended if thats the case), then its a little more difficult of a job, because if not done properly, can cause more codes, if not the same codes to return.
Customer: replied 7 years ago.

If I buy the throttle body assy at around $ 200, will it include a new TPS?


Also, 1 of the codes referred to the difference betwen TPS1 and TPS2. Are there 2 sensors to replace?



Expert:  GMTechBernard replied 7 years ago.

Your truck has two throttle sensors and both are internal to the throttle assembly, which is a sealed unit, which is why you cannot replace just the sensor.