What is a throttle position sensor?
The throttle position sensor measures the opening and closing of the butterfly valve inside the throttle body. It is viewed as a feedback sensor to the on board computer in relation to driver command on the accelerator, idle control, and accessory demand (AC, power steering) on power. Many modern cars run on “fly by wire” technology, where the cable from the accelerator to the throttle has been eliminated and the computer now controls the opening and closing of the throttle in response to the accelerator position sensor.
What are the symptoms of a faulty throttle position sensor?
For most modern cars with drive by wire, when the on board computer either loses the throttle position sensor signal or feels it has become unreliable or erratic, the computer will place the engine in limp mode. Here, the engine will run only at very low RPMs and move only at slow speeds. It is a safety device to prevent catastrophic engine damage. The throttle position usually fails due to wear over time: the needle in the sensor sits on our favorite cruise speeds more than other positions, and over time these areas wear to the point of loss of contact (no voltage).
How severe is a faulty throttle position sensor?
Significant. Although this issue may not leave you stranded waiting for the tow truck, the car will be difficult to drive. Best to find a good mechanic, one who specializes in air induction/fuel management issues, and set an appointment as soon as possible, Most times this repair may be done same day, however some parts may only be available through special order, more time may be needed. Best to drop off the car, and plan for a couple of days of alternate driving.
What is the typical cost to replace the throttle position sensor?
- Estimated part(s) cost = $75 - $150
- Estimated labor cost= $70 - $175
- Estimated total cost = $145 - $325
This repair depends on how the manufacturer built the throttle position sensor into the throttle body. In a good portion of the vehicles, the sensor is replaceable. In this case, sensors will run in price from $75 to $150. Other vehicles, especially european models, the entire throttle must be replaced due a small computer embedded into the motor used to open and close the butterfly. Of course these assemblies will raise the price into the $300 to $500 range. Installation prices will be low due to the easy accessibility of the throttle, so look to pay in the $50 to $75. However, some sensors and almost all of the assemblies will need to be reprogrammed, and will add anywhere from $20 to $100 to the installation bill.
Keep in mind, pricing will vary by location and your vehicle make and model. If you're not already, save time by using Openbay to compare pricing and book an appointment with a qualified repair shop in your area.
Service article written by an ASE Master Technician