P2118 Code: Here's How to Solve It Fast

The P2118 diagnostic trouble code (DTC) is related to the throttle actuator control system in modern vehicles equipped with electronic throttle control (ETC). This code indicates that the powertrain control module (PCM) has detected an issue with the throttle actuator control motor's current range or performance. When this code is triggered, it typically means that the PCM is detecting an abnormally high current draw from the throttle actuator motor, which could lead to various drivability issues and potentially leave you stranded.

P2118 Code Meaning	P2118 Code Common Causes
Throttle Actuator Control Motor Current Range/Performance Issue	Faulty throttle body assembly
Excessive current required to operate the throttle actuator control motor	Damaged or corroded wiring in the throttle control circuit
PCM detects higher than normal current to move the throttle plate	Failed throttle position sensor
Throttle actuator control system performance out of specification	Obstructed throttle plate movement
Electronic throttle control system malfunction	Defective accelerator pedal position sensor

Faulty Throttle Body Assembly

The throttle body is a critical component of the engine's air intake system, controlling the amount of air flowing into the engine based on driver input and engine requirements. In vehicles with electronic throttle control, the throttle body contains an electric motor that operates the throttle plate.

Symptoms

• Illuminated check engine light
• Rough or unstable idle
• Hesitation or stumbling during acceleration
• Engine stalling or failing to start
• Reduced engine power or "limp mode" activation

Technical Explanation

When the throttle body assembly fails, it can cause the throttle plate to stick, move erratically, or require more force to operate. This increased resistance results in higher current draw from the throttle actuator motor, triggering the P2118 code.

Diagnosis Steps

1. Visually inspect the throttle body for carbon buildup or physical damage.
2. Check the throttle plate for smooth operation throughout its range of motion.
3. Use a scan tool to monitor throttle position sensor readings and actuator commands.
4. Perform a throttle relearn procedure if applicable to the vehicle model.

Solution

If the throttle body is determined to be faulty, replacement is typically necessary. Some vehicles may allow for cleaning and recalibration, but this is less common with modern electronic throttle bodies.

Cost Estimate

Throttle body replacement can cost between $200 to $600, depending on the vehicle make and model. Labor usually accounts for 1-2 hours of work.

Warnings and Recommendations

Never attempt to manually force the throttle plate open, as this can cause damage to the delicate electronic components. Always follow manufacturer-specific procedures for throttle body cleaning and replacement.

Damaged or Corroded Wiring in the Throttle Control Circuit

Wiring issues can cause erratic signals or increased resistance in the throttle control circuit, leading to the P2118 code.

Symptoms

• Intermittent check engine light
• Erratic throttle response
• Loss of throttle control
• Engine performance issues that come and go

Technical Explanation

Corroded or damaged wiring can increase the electrical resistance in the circuit, causing the PCM to detect higher than normal current draw. Intermittent connections can also cause erratic throttle behavior.

Diagnosis Steps

1. Visually inspect all wiring and connectors in the throttle control circuit.
2. Check for signs of corrosion, fraying, or physical damage.
3. Use a multimeter to test for continuity and proper resistance in the wiring.
4. Perform a voltage drop test across suspicious connections.

Solution

Repair or replace any damaged wiring or connectors. In some cases, entire wiring harnesses may need replacement if corrosion is extensive.

Cost Estimate

Wiring repairs can vary widely in cost, from $50 for a simple connector replacement to $500 or more for a complete harness replacement.

Warnings and Recommendations

Always disconnect the battery before working on electrical systems to prevent short circuits or electrical shock. Use manufacturer wiring diagrams to ensure proper routing and connection of any replaced wires.

Failed Throttle Position Sensor

The throttle position sensor (TPS) provides crucial feedback to the PCM about the throttle plate's position. A faulty TPS can cause the PCM to misinterpret throttle position, leading to incorrect actuator control.

Symptoms

• Erratic idle
• Sudden unintended acceleration or deceleration
• Poor fuel economy
• Difficulty starting the engine

Technical Explanation

When the TPS fails, it may send incorrect or no signal to the PCM. This can cause the PCM to command more current to the throttle actuator motor in an attempt to achieve the desired throttle position, triggering the P2118 code.

Diagnosis Steps

1. Use a scan tool to monitor TPS voltage output throughout the throttle range.
2. Compare TPS readings with the accelerator pedal position sensor readings.
3. Check for any correlation between TPS readings and engine performance issues.
4. Perform a wiggle test on the TPS wiring to check for intermittent connections.

Solution

If the TPS is determined to be faulty, it will need to be replaced. In many modern vehicles, the TPS is integrated into the throttle body assembly and cannot be replaced separately.

Cost Estimate

TPS replacement costs can range from $100 to $400, depending on whether it's a standalone sensor or part of the throttle body assembly.

Warnings and Recommendations

Ensure that the replacement TPS is correctly calibrated after installation. Some vehicles require a specific relearn procedure to be performed using a scan tool.

Obstructed Throttle Plate Movement

Physical obstructions can prevent the throttle plate from moving freely, causing the actuator motor to draw more current as it attempts to overcome the resistance.

Symptoms

• Rough idle
• Reduced engine power
• Stalling
• Difficulty accelerating

Technical Explanation

Debris, carbon buildup, or mechanical issues can cause the throttle plate to stick or move irregularly. This increased resistance requires more force from the actuator motor, resulting in higher current draw and triggering the P2118 code.

Diagnosis Steps

1. Remove the air intake duct to visually inspect the throttle plate.
2. Check for carbon buildup, debris, or signs of physical damage.
3. Manually (with the engine off and cool) attempt to move the throttle plate, feeling for any binding or resistance.
4. Use a scan tool to command the throttle open and closed, observing for smooth operation.

Solution

If an obstruction is found, carefully clean the throttle body using an approved throttle body cleaner. For mechanical issues, the throttle body may need to be replaced.

Cost Estimate

Professional throttle body cleaning can cost between $50 to $150. If replacement is necessary, costs can range from $200 to $600.

Warnings and Recommendations

Never use abrasive materials or unapproved solvents to clean the throttle body, as this can damage sensitive components. If you're uncomfortable with this procedure, seek professional assistance.

Defective Accelerator Pedal Position Sensor

The accelerator pedal position sensor (APPS) tells the PCM how much the driver is pressing the gas pedal. A faulty APPS can cause the PCM to misinterpret driver input, leading to incorrect throttle actuator commands.

Symptoms

• Unresponsive or overly sensitive accelerator pedal
• Engine revving without pressing the pedal
• Difficulty accelerating or maintaining speed
• Vehicle entering "limp mode"

Technical Explanation

When the APPS fails, it may send erratic or incorrect signals to the PCM. This can cause the PCM to command inappropriate throttle positions, potentially leading to increased current draw from the throttle actuator motor and triggering the P2118 code.

Diagnosis Steps

1. Use a scan tool to monitor APPS voltage output as the pedal is depressed.
2. Check for smooth and consistent voltage change throughout the pedal's range of motion.
3. Compare APPS readings with throttle position sensor readings for proper correlation.
4. Inspect APPS wiring and connectors for damage or corrosion.

Solution

If the APPS is determined to be faulty, it will need to be replaced. In many vehicles, this involves replacing the entire accelerator pedal assembly.

Cost Estimate

APPS replacement can cost between $150 to $400, depending on the vehicle make and model.

Warnings and Recommendations

After replacing the APPS, a relearn procedure may be necessary to calibrate the new sensor with the vehicle's PCM. This often requires a professional-grade scan tool.

Frequently Asked Questions About P2118

Frequently Asked Questions About P2118

• Can I drive my car with a P2118 code?
  It's not recommended to drive with a P2118 code. The vehicle may enter "limp mode" or experience sudden loss of power, which can be dangerous.
• How urgent is it to fix a P2118 code?
  P2118 should be addressed as soon as possible. It affects a critical system that controls engine power and could lead to stalling or other serious drivability issues.
• Will a P2118 code clear itself?
  The code may clear temporarily if the issue resolves, but it will likely return if the underlying problem isn't fixed. Proper diagnosis and repair are necessary for permanent resolution.
• Can a bad battery cause a P2118 code?
  While unlikely, a weak battery can cause various electrical issues. However, P2118 is typically related to the throttle control system rather than general electrical problems.
• How do I perform a throttle relearn procedure?
  Throttle relearn procedures vary by vehicle make and model. Generally, it involves a specific sequence of key cycles and pedal movements, often requiring a scan tool.
• Is it safe to clean the throttle body myself?
  If you're comfortable working on your vehicle, cleaning the throttle body can be a DIY task. However, use caution and follow manufacturer guidelines to avoid damaging sensitive components.
• Can weather conditions trigger a P2118 code?
  Extreme temperatures or moisture can exacerbate existing issues in the throttle control system, potentially triggering P2118. However, weather alone is rarely the root cause.
• How long does it take to fix a P2118 code?
  Repair time can vary from 1-3 hours for simple fixes like cleaning or sensor replacement, to 4-6 hours for more complex issues requiring throttle body or wiring harness replacement.

In conclusion, the P2118 code indicates a potentially serious issue with your vehicle's throttle control system. While some causes can be addressed by DIY enthusiasts, many require specialized tools and knowledge for proper diagnosis and repair. Always prioritize safety and don't hesitate to seek professional help if you're unsure about any aspect of the repair process. Regular maintenance, including keeping the throttle body clean and addressing any performance issues promptly, can help prevent P2118 and related problems from occurring.