P0123: TP Sensor A Circuit High Input

P0123: TP Sensor A Circuit High Input

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P0123: TP Sensor A Circuit High Input - What You Need to Know

Look - OBD2 code P0123 means your Throttle Position (TP) Sensor A is sending a high voltage signal. This isn't just a glitch; it can lead to poor performance, increased emissions, or a completely unresponsive throttle. You need to pay attention to this, because ignoring it could result in more extensive engine issues.

Before you start throwing parts at the problem, understand that it's not always the TP sensor itself at fault. Wiring issues or a faulty Engine Control Module (ECM) can also trigger this code. Start diagnosing systematically to avoid unnecessary expenses.

Symptoms

  • Check Engine Light illuminated
  • Rough idling or stalling
  • Unresponsive throttle during acceleration
  • Increased fuel consumption
  • Erratic engine behavior
  • Difficulty maintaining speed
  • Engine misfires
  • Loss of power during acceleration

Diagnostic order

  1. Check for any visible damage to the TP sensor wiring and connector. Look for frayed wires or corrosion.
  2. Measure the voltage at the TP sensor connector. You should see a reference voltage around 5 volts. If it's above 4.5 volts, the sensor may be faulty.
  3. Verify ground connections. Test resistance between the ground pin of the sensor and the battery negative; it should be close to 0 ohms.
  4. Check the output voltage of the TP sensor at idle. It should be around 0.5 volts. If it's above 0.8 volts, the sensor needs replacing.
  5. Inspect the ECM for any stored codes or updates that might affect the TP sensor operation.

Common questions

  • What does the TP sensor do?

    The TP sensor measures the position of the throttle plate, sending this information to the ECM to adjust fuel delivery.

  • Can I drive my car with P0123?

    While you can drive it, it's not advisable due to potential performance issues and increased emissions.

  • How do I clear the P0123 code?

    You can use an OBD2 scanner to clear the code, but addressing the underlying issue is crucial first.

  • How much does it cost to replace a TP sensor?

    Costs range from $50 to $200 depending on the vehicle and labor involved.

  • Will cleaning the TP sensor work?

    Cleaning may help if there's dirt buildup, but if the sensor is faulty, replacement is necessary.

  • What other codes might I see with P0123?

    You might also see codes like P0122 or P0222.

  • Can a bad TP sensor affect my transmission?

    Yes, it can lead to shifting issues since the ECM relies on throttle position for proper transmission operation.

  • How do I know if the ECM is faulty?

    Look for multiple sensor codes and erratic behavior; consider testing the ECM with a professional.

Vehicle-specific notes

  • Ford EcoBoost engines may experience wiring issues due to heat exposure near the turbo.
  • The Honda K-series often has a known issue with the harness connector corrosion, affecting sensor readings.
  • Toyota 2GR-FE V6 engines have been reported to have issues with the throttle body itself, not just the sensor.
  • GM 3.6 LFX engines can show P0123 due to faulty software in the ECM, which might require a reflash.
  • Hyundai/Kia Theta II engines have been known to have premature sensor failures under high mileage (>100,000 miles).
  • The Chrysler 3.6 Pentastar may throw this code if the throttle body is dirty or carbon-fouled.
  • BMW N20/N54/N55 engines can also trigger P0123 due to faulty wiring harnesses that are prone to wear.
  • VW/Audi 2.0T TSI engines often see issues with the throttle body assembly failing, causing high input codes.
  • Subaru EJ20/FA20 engines may have throttle position issues due to improper installation of aftermarket parts.
  • Nissan VQ35 engines can have inconsistent readings if the throttle body is not calibrated correctly after a service.

Parts and cost ranges

  • Throttle Position Sensor: $50 - $150
  • Wiring harness repair kit: $15 - $50
  • Engine Control Module (ECM): $300 - $1,500
  • Throttle body assembly: $200 - $600
  • Labor costs for diagnostics and replacement: $75 - $150/hour

What people get wrong

  • Assuming the TP sensor is the only issue without checking wiring or connectors.
  • Ignoring other related codes that could point to a broader problem.
  • Clearing the code without fixing the underlying issue, leading to future recurrences.
  • Replacing the sensor without verifying the voltage and ground integrity first.
  • Not considering the possibility of a faulty ECM affecting sensor readings.

Related codes

If you're dealing with P0123, you might also encounter codes like P0122 (TP Sensor A Circuit Low Input) or P0222 (TP Sensor B Circuit Low Input). These can provide additional insight into the problem.

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-- Hank, Master Mechanic at Mobile Master Mechanic

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