P0123 – Throttle Position Sensor Circuit High

Understanding and Troubleshooting the P0123 Diagnostic Trouble Code

The P0123 diagnostic trouble code (DTC) indicates a "Throttle/Pedal Position Sensor/Switch 'A' Circuit High Input" issue. When this code appears, it means the throttle position sensor (TPS) is sending a signal to the engine control module (ECM) that exceeds the expected voltage range. While the vehicle may still be drivable, it's crucial to diagnose and address the problem promptly to prevent further damage and ensure optimal performance.

Detailed Code Information

The P0123 code is a generic powertrain code that applies to OBD-II equipped vehicles. The TPS is a potentiometer mounted on the throttle body that detects the throttle blade angle. It typically has three wires: a 5-volt reference from the ECM, a ground from the ECM, and a signal return to the ECM.

When the throttle is closed, the TPS signal voltage should be around 0.45 volts. At wide open throttle (WOT), the voltage approaches 5 volts. If the ECM detects a voltage higher than the normal upper limit, it sets the P0123 code.

Common Causes

Several factors can trigger the P0123 code, including:

• Faulty TPS
• Wiring issues (shorts, open circuits, frayed wires)
• Poor electrical connections
• Throttle body problems
• Faulty ECM (less common)

Related fault codes that may appear alongside P0123 include P0120, P0121, P0122, and P0124.

Step-by-Step Diagnosis

1. Visual Inspection: Check the TPS and its wiring for visible damage, corrosion, or loose connections.

2. Check Wiring: Use a multimeter to test for continuity and shorts in the TPS wiring harness. Repair any damaged wires or connectors.

3. Test TPS: With the key on and engine off, use a multimeter to measure the TPS signal voltage. It should be around 0.45 volts with the throttle closed and approach 5 volts at WOT. Replace the TPS if the voltage is out of spec.

4. ECM Diagnosis: If the TPS and wiring check out, the issue may lie with the ECM. This requires professional diagnostic equipment and expertise.

Repair Solutions

Depending on the diagnosis, repairs may include:

• Replacing the TPS: Expect to pay around $100-$200 (€85-€170) for parts and labor.
• Repairing wiring: Costs vary based on the extent of the damage.
• Cleaning the throttle body: This can be done DIY or professionally for about $75-$150 (€65-€130).

Prevention Tips

• Regularly inspect and clean the throttle body and TPS.
• Use high-quality replacement parts.
• Address any related issues promptly to prevent cascading problems.

Frequently Asked Questions (FAQ) about P0123 Diagnostic Trouble Code

What does the P0123 code mean?

The P0123 code indicates a “Throttle/Pedal Position Sensor/Switch ‘A’ Circuit High Input.” This means the throttle position sensor (TPS) is sending a signal voltage to the engine control module (ECM) that exceeds the normal upper limit.

Is it safe to drive with a P0123 code?

While the vehicle may still be drivable, it’s crucial to diagnose and address the problem promptly to prevent further damage and ensure optimal performance. The code can cause drivability issues like poor acceleration and decreased fuel efficiency.

What are the common symptoms of a P0123 code?

Common symptoms include an illuminated check engine light, hesitation during acceleration, rough-running engine, high idle, limited power, and potential stalling.

What are the potential causes of a P0123 code?

Potential causes include a faulty throttle position sensor, damaged wiring or connectors, a dirty throttle body, or in rare cases, an issue with the ECM.

How do you diagnose a P0123 code?

Diagnosis involves visually inspecting the TPS wiring and connectors, testing the TPS signal voltage with a multimeter, and using a scan tool to check live data from the TPS. More advanced steps may require checking the ECM.

Can a P0123 code cause limp mode?

Yes, when the P0123 code is detected, the ECM may put the vehicle into a failsafe or “limp home” mode to prevent further damage. This limits engine performance and throttle response.

How much does it cost to diagnose a P0123 code?

Expect to pay between $60-$100 for a professional diagnostic check at a repair shop. Alternatively, you can use an advanced scan tool like Carly to run manufacturer-level diagnostics yourself.

What is the estimated cost to repair a P0123 code?

The repair cost depends on the root cause. Replacing a faulty TPS typically costs around $100-$200 for parts and labor. Wiring repairs vary based on the extent of the damage.

Can a bad throttle position sensor cause a P0123 code?

Yes, a failing or defective throttle position sensor is one of the most common causes of a P0123 code being triggered.

How do you test a throttle position sensor?

Testing a TPS involves measuring its output voltage with a multimeter at different throttle positions. With the key on, engine off, the voltage should be around 0.45V at closed throttle and approach 5V at wide open throttle.

Can a P0123 code clear itself?

While it’s possible for intermittent issues to allow the code to clear itself, it’s likely to reappear if the underlying problem is not addressed. Properly diagnosing and repairing the issue is important.

What are some other common TPS-related codes?

Other throttle position sensor-related trouble codes include P0120, P0121, P0122, and P0124. These indicate various range and performance faults.

Can a dirty throttle body cause a P0123 code?

Yes, a dirty or clogged throttle body can cause the throttle plate to stick, leading to incorrect TPS readings and a potential P0123 code. Cleaning the throttle body may resolve the issue.

Is a P0123 code the same on all vehicles?

P0123 is a generic code that applies to all OBD-II equipped vehicles. However, the specific repair steps may vary somewhat depending on the vehicle make and model.

Can a wiring issue cause a P0123 code?

Absolutely. Damaged, shorted, or corroded wiring and connectors can disrupt the TPS signal, leading to a high input voltage and triggering the code.

What should I do if I get a P0123 code?

If you’re not experienced with vehicle diagnostics, it’s best to have the issue checked by a professional mechanic. Continuing to drive with the code present risks further damage.

How do you clear a P0123 code?

After properly diagnosing and repairing the underlying issue, the code can be cleared using an OBD-II scanner. However, if the problem persists, the code will likely reappear.

Can a P0123 code affect fuel economy?

Yes, issues with the TPS can lead to incorrect fuel trim adjustments, causing the engine to run rich or lean. This can decrease fuel efficiency.

What preventive measures can be taken to avoid a P0123 code?

Regular vehicle maintenance, including inspecting the throttle body and TPS, can help prevent issues. Addressing any wiring problems promptly and avoiding aggressive driving habits also reduce risk.

Is it possible to diagnose a P0123 code myself?

While some basic diagnostic steps like visual inspections can be done DIY, accurately diagnosing the issue often requires professional knowledge, tools, and experience. It’s recommended to consult a mechanic for a comprehensive diagnosis.