Air & Fuel Mixture ControlOBD2 Codes

P0122 – Meaning, Causes, Symptoms, & Fixes

What Does Code P0122 Mean?

  • P0122 definition: Throttle Position Sensor/Switch (TPS) A Circuit Low Input
  • Issue Severity: SEVERE – Stop driving immediately 
  • Repair Urgency: Fix this code immediately (same day if possible) to avoid unsafe driving conditions.
  • Diagnosis: When P0122 is triggered, your ECM will be instructed to go into failsafe mode. When this happens, your vehicle will have substantial trouble with acceleration, exhibit limited speeds, and possibly even stall. We recommend that you confront this issue as soon as possible.

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Code P0122 is triggered when your vehicle’s Engine Control Module (ECM) detects that your Throttle Position Sensor (TPS) circuit A is reporting an output voltage that is below its expected voltage. Depending on your vehicle, your TPS lower output voltage limit should be around .17 to .20 volts, and if the ECM detects that it has dipped below that, then it will trigger Code P0122.

P0122 Causes

There are many potential causes of code P0122.

  • TPS Mounted Incorrectly
  • Faulty or Frayed TPS Wiring
  • TPS Circuit Short to Ground
  • Faulty TPS

P0122 Symptoms

  • Check Engine Light
  • High Idle
  • Possible Stalling or Surging
  • Hesitation upon acceleration

How Do I Fix Code P0122?

With a TPS fault, the first step is to get it diagnosed to figure out what is causing the problem. 

If your vehicle has this fault and you’re not comfortable diagnosing this issue at home, we recommend finding a RepairPal certified shop nearby to pinpoint the problem and give an accurate estimate for repairs. 

These shops can not only help you figure out what’s going wrong before you waste time and money on the wrong parts, but they also offer a minimum 12-month, 12,000-mile warranty and stand behind all their estimates with guaranteed fair pricing.

> Find a RepairPal Certified Shop Near You

How Much Does It Cost to Fix Code P0122?

P0122 can be caused by anything from a faulty TPS to damaged wiring to improper TPS installation. It’s impossible to give an accurate estimate without properly diagnosing the issue first. 

If you take your car to a shop for diagnosis, most shops will start with an hour of “diag time” (the time spent in labor diagnosing your specific issue). Depending on the shop’s labor rate, this typically costs somewhere between $75-$150. Many, if not most, shops will apply this diagnosis fee to any required repairs if you have them perform the repairs for you. From there, a shop will be able to give you an accurate estimate for repairs to fix your P0122 code.

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Possible Repair Costs for P0122

For error code P0122, one or more of the below repairs may be needed to solve the underlying issue. For each possible repair, the estimated cost of repair includes the cost of the relevant parts and the cost of labor required to make the repair.

  • Throttle position sensor: $157 to $201
  • Throttle body: $489 to $600

DIY Steps to Diagnose Code P0122

Engine code P0122 could be caused by a number of things, including a faulty TPS, damaged wiring, or improper TPS installation. If you’d like to try to fix code P0122 at home without throwing money at parts, you’ll want to follow the steps below for proper diagnosis. Keep in mind this is an intermediate-level diagnosis and repair and not recommended for beginners. Diagnosis requires more specialized equipment beyond what the FIXD Sensor can provide and it can be a time and labor-intensive process for inexperienced DIYers.

DIY difficulty level: Intermediate

This repair requires mechanical knowledge and is not recommended for beginners.

Tools/parts needed (our top picks from Amazon):

STEP 1: USE FIXD TO ENSURE NO OTHER ENGINE CODES ARE PRESENT.

Use FIXD to scan your vehicle to verify P0122 is the only code present. If not, make a note of the additional codes, as they help diagnose the problem.

STEP 2: USE FIXD TO VERIFY THROTTLE POSITION DATA.

Using FIXD Live Data, look at your throttle position data. This provides a live readout from the throttle position sensor. If this data is erratic or incorrect, it’s a sign of a problem with the sensor or related wiring.

STEP 3: CHECK TPS WIRING.

Conduct a visual inspection of wiring around the TPS for possible wire fraying or disconnection. If any wiring issues are found, repair them, clear your codes with FIXD, and re-scan to see if P0122 still shows up.

STEP 4: CHECK TPS MOUNTING.

Make sure the TPS is mounted correctly. If it is not in the correct position, it can give out inaccurate voltage levels. Adjust TPS if you think it is out of position.

If after all of these steps Code P0122 is still present, you may need to replace your TPS.

Common P0122 diagnosis mistakes

A common diagnosis mistake made when dealing with code P0122 is replacing the TPS before visually inspecting the wiring or connectors. Oftentimes frayed or damaged wiring is the issue, and replacing the TPS isn’t actually necessary.

Still Need Help Fixing Code P0122?

If you’ve followed the steps above and are still experiencing check engine code P0122, please contact the FIXD Mechanic Hotline if you’re a FIXD Premium subscriber or find a RepairPal certified shop near you to get the right repairs at a fair price.

Justin-Hughes

Recovering autocross and track day enthusiast. Once turned a VW Jetta into a pickup truck. Lives in a van down by the river. Dream car: 2001 Subaru WRC rally car.

Justin Hughes
Recovering autocross and track day enthusiast. Once turned a VW Jetta into a pickup truck. Lives in a van down by the river. Dream car: 2001 Subaru WRC rally car.

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    9 Comments

    1. I cleaned the throttle body and position sensor . Checked spark plugs and wires , cleaned and replaced air filter. No more codes and engine running smooth.

      1. How and what did you clean the position sensor with

    2. had BATTERY CHECKED not good.put NEW battery.

    3. I am still having trouble with idle, it is high and it varies. Just before this code came up I was and am having a problem with high coolant temperature so I looked around at and moved some of the wires near the thermostat. Some of those wires go to the TPS. I might have a wiring problem of some kind….and I also still have a problem with my coolant gauge reading way too high but that does not seem to turn on any lights…I don’t know what’s up.

      1. Karl ..there are 2 coolant sensors. They build up with sink-rust looking stuff. One has a thicker sensor that goes into the water. Clean the bigger one.
        One sensor goes to your dash. The other goes to the computer.

    4. Toyota Ractis 2006 model. After changing the gearbox (transmission), often times the car just goes into limp mode. In the morning when you start it, its normal with normal raves. But after driving it for few kms, limp mode comes back. What should I do?

    5. My Chev Spak, is shaking at idle and hasitating when eccelarating it sometimes shows up the engine light.

    6. After replacing dead battery in a 2013 VW jetta SE 2.5l L5 with 155k miles, ECP and Check engine light came on. The car shifted roughly and transmission released with a clunk at stops. Codes PO122 and PO638. Erased the codes with FIXD and drove again, and the same codes came up. Drove a couple more times then looked up codes. One site said check wires to the accelerator pedal. They seemed tight. I operated the accelerator through its full range with engine off, started the car again and no lights, car drove like normal. Besides a few electrical quirks, this has been a great car.

    7. I replaced my tps sensor and it’s still acting the same. The plug that goes to it looked fine. Any suggestions on what to do now?

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