P0122 on 2012-2017 Hyundai Accent: Throttle Position Sensor Causes and Fixes

What's Unique About the 2012-2017 Hyundai Accent

For the 2012-2017 Hyundai Accent with the 1.6L Gamma GDI engine, the throttle position sensor (TPS) is not sold as a separate, replaceable part. It is permanently integrated into the electronic throttle body assembly. This is a critical distinction, as it means a confirmed TPS failure requires the replacement of the entire throttle body, not just a small sensor. This design is common on many modern vehicles to simplify assembly but increases the cost of repair for this specific fault.

Symptoms You May Notice

• Check Engine Light is on
• Poor, hesitant, or sluggish acceleration
• Engine goes into 'limp mode' (reduced power, won't rev past ~3000 RPM)
• Rough or unstable idle
• Engine stalling, especially when coming to a stop or at idle
• Harsh or erratic automatic transmission shifting
• Engine surges or randomly slows down and accelerates

Most Likely Causes

1. Failing Throttle Body Assembly (Integrated TPS) 🔴 High Probability The internal electronic components of the throttle position sensor wear out over time, leading to erratic or low voltage signals. Since it is integrated into the throttle body on this model, the entire unit is the most common point of failure for code P0122. 🎬 Watch: A detailed breakdown of P0122 causes and symptoms.
   How to confirm: Use a scan tool to monitor the live data for 'TPS Voltage' (or TPS1). With the key on and engine off, the voltage should increase smoothly from ~0.5V to ~4.5V as you slowly press the gas pedal. If the voltage is stuck low (e.g., under 0.2V), drops out, or the reading is erratic and jumpy, the sensor has failed. A lab scope can also be used to visualize the signal and confirm dropouts.
   Typical fix: Replace the entire throttle body assembly. After replacement, a throttle relearn procedure is required to calibrate the new part with the ECM.
   Est. part cost: $150-$250
2. Wiring or Connector Issue 🟡 Medium Probability The wiring harness to the throttle body is subject to engine bay heat and vibration. A common issue on this platform is the harness rubbing against a transmission bracket, which can wear through the insulation and cause a short to ground. Corrosion or loose pins in the connector can also cause a low input signal.
   How to confirm: Visually inspect the wiring harness and the 6-pin connector going to the throttle body. Pay close attention to the area where the harness is secured to a bracket near the transmission. Use a multimeter with the key on to check for a 5V reference wire, a good ground, and a signal wire at the connector. Wiggle the harness while monitoring TPS voltage on a scan tool to see if the reading fluctuates.
   Typical fix: Repair the damaged section of the wiring harness or clean/replace the connector. Secure the harness away from any sharp edges to prevent future damage.
   Est. part cost: $5-$50

Rare But Worth Checking

• Faulty Powertrain Control Module (ECM): This is extremely rare and should only be considered after the throttle body and all related wiring have been definitively ruled out. An ECM failure is the least likely cause.

Diagnosis Steps

1. Read the trouble codes with an OBD-II scanner. Confirm P0122 is present and note any other codes like P0123, P0222, or P2135, which strongly suggest a throttle body failure.
2. Use the scanner's live data function to observe the Throttle Position Sensor 'A' (TPS1) voltage. With the Key On, Engine Off (KOEO), the reading should be around 0.5V at closed throttle and sweep smoothly up to about 4.5V at wide-open throttle.
3. If the voltage is stuck below ~0.2V, is erratic, or does not change with pedal input, the sensor or its circuit is faulty.
4. Perform a thorough visual inspection of the throttle body connector and its wiring harness. Look for any chafed wires, loose pins, or signs of corrosion, especially where the harness is bracketed to the transmission.
5. If the wiring appears okay, disconnect the connector and use a multimeter to test the circuit at the harness plug (Key On, Engine Off). You should find a 5-volt reference wire, a ground wire (check for continuity to battery negative), and the signal wire.
6. If the 5V reference and ground are present at the connector, the issue is almost certainly the throttle body assembly itself.
7. If reference voltage or ground is missing, the wiring fault must be traced back toward the ECM and repaired.
8. After replacing the throttle body, perform a throttle relearn procedure.

Parts You'll Likely Need

• Electronic Throttle Body Assembly (OEM #35100-2B300, superseded by 35100-2B340) — This is the most common cause of code P0122 on this vehicle, as the throttle position sensor (TPS) that fails is integrated into this assembly and not sold separately.
  Trusted brands: Hyundai (OEM), Bosch, Cardone (Remanufactured), Mando
  OEM price range: $180-$250
  Aftermarket price range: $120-$200

Related Codes That Often Appear With This One

• P0123 — Throttle Position Sensor 'A' Circuit High Input. If the sensor is failing erratically, it might send signals that are both too high and too low, causing both codes to appear.
• P2135 — Throttle/Pedal Position Sensor/Switch 'A'/'B' Voltage Correlation. This code appears when the ECM detects a disagreement between the two internal TPS circuits (TPS1 and TPS2), which is a very common result of a failing sensor assembly.
• P0222 — Throttle Position Sensor 'B' Circuit Low Input. This indicates the secondary TPS circuit is also reading low, further pointing to a failure of the complete throttle body unit.

Platform-Specific Known Issues

• A throttle body replacement on a Hyundai/Kia requires a 'throttle relearn' procedure. This can often be done without a scan tool. A common DIY method is to turn the ignition to 'ON' (without starting the engine) for 10-15 seconds, then turn it 'OFF' for 10-15 seconds, and repeat this cycle 3-5 times. You may hear the throttle body motor cycling. Alternatively, disconnecting the battery for 30 minutes can reset the ECM, which will then relearn the new throttle body parameters during the first few minutes of idling and driving.
🎬 Watch: Four ways to perform a throttle body relearn.
• The engine wiring harness has a known chafe point where it is secured by a bracket on the transmission. Over time, vibrations can cause the bracket to rub through the wire loom and short out the TPS signal wire, causing P0122.

Mechanic-Grade Diagnostic Values

• TPS1 Signal Voltage (KOEO) — expected: Approx. 0.5V at closed throttle, sweeping smoothly to approx. 4.5V at wide-open throttle.. Failure: Voltage is stuck below 0.176V for more than 0.14 seconds.
• ECM Fault-Setting Threshold — expected: TPS1 voltage > 0.176V. Failure: If TPS1 voltage < 0.176V for 0.14 seconds, the ECM will log DTC P0122.
• Throttle Body Connector Pin 6 (5V Reference) — expected: Approx. 5.0V with key on, engine off.. Failure: Voltage significantly lower than 5.0V or 0V indicates a wiring or ECM issue.
• Throttle Body Connector Pin 4 (Sensor Ground) — expected: Near 0V, with good continuity to chassis ground.. Failure: Voltage present or high resistance to ground indicates a bad ground connection.

Scan Tool Commands That Help

• Hyundai GDS (or equivalent advanced scan tool): Throttle Position Sensor Adaptation / Reset Adaptive Values — This function should be used after replacing the throttle body assembly. It forces the ECM to erase its learned throttle plate values and recalibrate to the new sensor's closed and wide-open positions, ensuring proper idle and throttle response.

Wiring & Ground Locations

• Throttle Body Connector (6-Pin) — On the electronic throttle body assembly, located between the air intake hose and the intake manifold.. This connector provides all power, ground, and signal lines for the integrated TPS. P0122 is caused by a low signal on Pin 5. The pinout is: Pin 1 (Motor +), Pin 2 (Motor -), Pin 3 (TPS2 Signal), Pin 4 (Sensor Ground), Pin 5 (TPS1 Signal), Pin 6 (5V Reference).
• GGG04 / GGG05 — On the right rear of the engine compartment, near the ECM.. These are primary engine compartment ground points. A loose or corroded connection at these locations can create a floating ground, causing erratic voltage readings for multiple sensors controlled by the ECM, including the TPS. This can mimic a sensor failure.
• Primary Engine Ground — A large ground cable or braided strap connecting the engine block/cylinder head to the chassis or firewall. On many Hyundais, the main battery ground cable attaches to the transmission case, which serves as the primary engine ground.. This is the main return path for the entire engine's electrical system. A compromised primary ground can cause widespread, intermittent electrical issues and incorrect sensor readings, including a P0122 code.

Real Owner Repair Stories

• Hyundai-Forums user (2013 Hyundai Accent 1.6L) — Check engine light with code P0122, car going into limp mode with poor acceleration.
  ❌ Tried (didn't work) Replacing the throttle body assembly with a new OEM part did not fix the issue.
  ✅ What actually fixed it The user traced the wiring harness from the throttle body and found a spot where it was rubbing against a metal bracket for the transmission. The insulation on the signal wire had worn through, causing it to short to ground. Repairing the wire and securing the harness away from the bracket permanently resolved the code.
• NHTSA ODI #11292479 — While involving a different Hyundai model, an owner reported that even after painting ground points, the problem persisted with a cascade of codes including P0122, P0222, and P0123, eventually requiring the vehicle to be limped to a shop.

OEM Part Supersession History

• 35100-2B300 → 35100-2B340 — Likely an internal revision for improved reliability or manufacturing process change.
  Heads up: The parts are generally interchangeable for the 2012-2017 Accent. No software updates are typically required for this specific supersession.

Diagnostic Flowchart

Other Known Issues on This Vehicle

Issues unrelated to this code that are worth knowing about as an owner of this generation:

• Wiring Harness Chafing 🟠 Medium — Commonly reported. A wiring harness near the brake master cylinder can rub against a transmission bracket, wearing through insulation and causing shorts for ignition coils or other sensors.
• Faulty Canister Purge Valve (CPV) 🟡 Low — A frequent failure item. The valve sticks open, causing a rough idle, difficulty starting after refueling, and EVAP-related check engine lights. It's a relatively cheap and easy part to replace.
• Failing VVT Solenoids 🟠 Medium — Can fail due to age or infrequent oil changes, leading to rough running, poor acceleration, stalling, and timing-related codes.
• High-Pressure Fuel Pump (HPFP) Failure 🔴 High — A known weakness on the 1.6L GDI engine. The pump can leak fuel internally into the crankcase, diluting the engine oil and causing rich running conditions (like code P2188) and potential for engine damage.
• Engine Bearing Wear / Engine Failure 🔴 High — While more prominent on the larger Theta II engines, the 1.6L Gamma GDI can also suffer from premature connecting rod bearing wear, leading to knocking noises and eventual engine seizure. This was part of a larger series of Hyundai/Kia engine issues. (Ref: Related to Hyundai Service Campaign T6G (TSB 22-01-023H-2))

Used vs. New Parts: Buying Guide for This Vehicle

When a used part is the smart pick: A used throttle body is generally NOT recommended for this repair. The failure is due to electronic wear on the internal TPS tracks. A used part from a junkyard has unknown mileage and wear, and may fail shortly after installation, wasting time and money.

Donor-vehicle mileage cap: roughly under 40000 miles for the part to have meaningful remaining life.

What to inspect on the donor part:

• Verify the part number (35100-2B300 or 35100-2B340) matches exactly.
• Inspect the 6-pin connector for any bent, corroded, or broken pins.
• Check the throttle plate for excessive carbon buildup, which might indicate a high-mileage or poorly maintained donor vehicle.
• Avoid parts with any visible cracks or damage to the plastic housing.

OEM-only on this vehicle (don't cheap out):

• While not strictly 'OEM-only', using a new OEM (Hyundai) or OEM-supplier (e.g., Mando, Bosch) throttle body provides the highest probability of a long-lasting repair.

Aftermarket brands forum-validated for this vehicle:

• Bosch
• Hitachi
• Standard Motor Products (SMP)

Brands owners have reported issues with on this vehicle:

• Remanufactured units from brands like Cardone can be a gamble; while they may function, some mechanics report a higher failure rate compared to new units. Unbranded, low-cost options from online marketplaces are also a significant risk.

Real Owner Stories

Aggregated from forums and TSBs cited above. Mileages and costs reflect what owners reported in those sources.

Related OBD-II Codes

• P0123 — Often appears alongside P0122 when the integrated throttle body sensor fails or has circuit issues.
• P0222 — A companion code for throttle/pedal position sensor circuit low input, strongly suggesting a throttle body assembly failure.
• P2135 — Indicates a voltage correlation issue between the throttle position sensors, frequently occurring with P0122 on this vehicle's integrated system.
• P2188 — A 'system too rich at idle' code that can occur on this 1.6L GDI engine due to high-pressure fuel pump failure, which may share similar driveability symptoms.

Frequently Asked Questions