Q: When the AC is turned on my Check engine light comes on , code reading throttle position sensor, not enough voltage.

asked by on

Only when I run the AC the check engine light pops up along with the triangle with exclamation point , code reading throttle position sensor/ not enough voltage and the cars RPMs fluctuate and car runs really weird. I reset the computer by hooking it up to a code reader. As long as the AC is not running, car runs fine. What could this possibly be, I changed the sensor and bought a new higher voltage battery being that I have 2 amps to my stereo . Tested it again by turning on the AC, same result

My car has 120000 miles.
My car has an automatic transmission.

If you have the electronic type throttle that has no cable to the throttle body, then you will need to check to make sure that battery voltage is not dropping below 12.5 volts when your A/C is turned on. You will need to have the charging system checked to make sure it is putting out above 13.2 volts at idle and the amperage at 1500 is within specified range of 87 amps and that the voltage does not drop below 13.5 with no load.

You may be overloading the alternator with the stereo amps you have and causing the battery voltage to drop too low at idle causing the throttle actuator to not work correctly. The A/C takes about 20 amps of power to run and if you are already taking more than the alternator can put out at idle, then the only place to get the power is from the battery. The battery is rated in AMPs not volts. You put a heavier duty battery that has more amp capacity and if the alternator cannot replace the power taken away, then the voltage will drop in the battery until it gets below the 12 volts needed to power the electronics in the car and there’s where you will start to have problems. If you want to have this diagnosed in person, a technician from YourMechanic can inspect your Check Engine Light and let you know exactly what will need fixing.

Was this answer helpful?
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details
  1. Home
  2. Questions
  3. When the AC is turned on my Check engine light comes on , code reading throttle position sensor, not enough voltage.

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: Engine seized in 2005 Acura TL

Hi. An engine replacement in your vehicle will cost between $2,000 and $4,000. This Depends on where the engine is installed and where the replacement engine is ordered from. The engine itself can range from $500 to $2,000. The labor...

Q: Whining noise, parts keep going out

Hello. If the air compressor is faulty this will cause the engine to work harder and that may result in lower mpg. The whining noise could be caused by a bad serpentine belt, pulley, or a bad serpentine belt tensioner....

Q: My Camry is starting at 2000 rpm's.

Sounds like there is a vacuum leak that is causing the engine to rev up high. If there is no vacuum leak, then the Idle Air Control Valve could be stuck causing the engine idle to fluctuate on startup. I...

Related articles

How Do Power Car Windows Increase Passenger Safety?
Power windows are responsible for approximately 2,000 emergency room visits every year. When a power window closes, it exerts enough force to bruise or break bones, crush fingers, or restrict an airway. Though...
P0052 OBD-II Trouble Code: HO2S Heater Control Circuit High (Bank 2 Sensor 1)
P0052 code definition HO2S Heater Control Circuit High (Bank 2 Sensor 1) What the...
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...