P0639 – Throttle Actuator Control Range/Performance (Bank 2)

What is P0639?

P0639 is a generic OBD-II diagnostic trouble code that indicates a problem with the throttle actuator control range or performance on bank 2 of the engine. This code applies to all makes and models of vehicles equipped with OBD-II.

Urgency and Severity

If your vehicle is displaying code P0639, it is important to diagnose and repair the issue as soon as possible. Driving with a malfunctioning throttle actuator can result in poor engine performance, reduced fuel efficiency, and potential safety issues. While it may be possible to continue driving short distances, it is recommended to have the vehicle inspected by a qualified mechanic promptly. Avoid driving long distances or under heavy load until the problem is resolved.

Technical Details

The throttle actuator is responsible for controlling the position of the throttle plate, which regulates the amount of air entering the engine. Code P0639 indicates that the powertrain control module (PCM) has detected a problem with the range or performance of the throttle actuator on bank 2 (the side of the engine opposite the number 1 cylinder).

This code is not specific to any particular make or model of vehicle, as it is a generic OBD-II code. However, the exact parts involved and the role they play may vary slightly between different vehicle manufacturers and engine configurations.

The throttle actuator system typically consists of only one throttle body to obtain a small volume and low manufacturing cost, and uses a DC servo motor for quick and accurate responses. When the throttle actuator is working correctly, it synchronizes with the fuel intake and accelerator pedal to allow the optimal amount of air to enter the engine.

Common Causes

Some common causes of code P0639 include:

• Damaged, burnt, shorted, corroded, or disconnected wiring and/or connectors
• Defective throttle actuator motor
• Faulty throttle position sensor
• Issues with the PCM or throttle actuator control module
• Throttle valve malfunction

Diagnosing P0639

To properly diagnose code P0639, follow these steps:

1. Scan for any additional trouble codes and make note of them.
2. Visually inspect the wiring and connectors related to the throttle actuator and throttle position sensor. Look for any damage, corrosion, or loose connections.
3. Test the throttle actuator motor and throttle position sensor using a multimeter or oscilloscope. Compare the readings to the manufacturer's specifications.
4. Check for any issues with the throttle valve such as dirt, carbon buildup, or mechanical problems.
5. If no issues are found, suspect a problem with the PCM or throttle actuator control module. These components may need to be reprogrammed or replaced.

Repair Solutions

The specific repair for code P0639 will depend on the root cause of the problem. Potential solutions include:

• Replacing damaged wiring or connectors
• Cleaning the throttle body and throttle valve
• Replacing a faulty throttle actuator motor, throttle position sensor, or throttle valve
• Reprogramming or replacing the PCM or throttle actuator control module

Prevention and Maintenance

To help prevent issues like code P0639 from occurring, follow these tips:

• Regularly inspect the throttle body and related components for buildup or damage. Clean the throttle body every 50,000-100,000 km (30,000-60,000 miles).
• Ensure all wiring and connectors are in good condition and properly secured.
• Have any related trouble codes promptly diagnosed and repaired by a qualified mechanic.

Repair Costs

The cost to repair code P0639 can vary widely depending on the specific cause and the make and model of the vehicle.

For some high-end vehicles like the BMW E60 M5, replacing both bank 1 and bank 2 throttle actuators can cost $3000-$3200 USD including labor. Used throttle actuators may be available at a lower cost.

In general, average repair costs for code P0639 range from $100-$600 USD (€90-€550 EUR) for diagnosis and repair. The cost of parts will depend on what needs to be replaced:

• Throttle actuator motor: $200-$500 USD (€180-€450 EUR)
• Throttle position sensor: $50-$200 USD (€45-€180 EUR)
• Wiring harness: $50-$300 USD (€45-€270 EUR)

Related Issues

Code P0639 may appear in conjunction with other throttle actuator or throttle position sensor related codes, such as:

• P0638 – Throttle actuator control range/performance
• P0122 – Throttle position sensor/switch A circuit low input
• P0123 – Throttle position sensor/switch A circuit high input

If any of these additional codes are present, they should be diagnosed and repaired along with P0639 for optimal results. A failing throttle actuator can also cause symptoms like:

• Lack of power
• Uneven or limited acceleration
• Abnormal idling (too high or too low)
• Poor fuel economy
• Check engine light illumination

When multiple of these symptoms occur together, it is a strong indication of a throttle actuator issue that requires immediate attention to prevent further damage to the engine and related components. Proper diagnosis and repair by a qualified mechanic is essential for resolving code P0639 and restoring optimal vehicle performance.

Frequently Asked Questions about P0639

What does the OBD-II code P0639 mean?

P0639 is a generic diagnostic trouble code (DTC) that indicates a problem with the throttle actuator control range or performance on bank 2 of the engine. It applies to all makes and models of vehicles equipped with OBD-II.

How serious is code P0639? Is it safe to drive with this code?

Code P0639 should be considered a serious issue that requires prompt diagnosis and repair. Driving with a malfunctioning throttle actuator can result in poor engine performance, reduced fuel efficiency, and potential safety concerns like lack of power or uneven acceleration. While it may be possible to drive short distances, it's best to have the vehicle inspected by a qualified mechanic as soon as possible and avoid driving long distances or under heavy load until the problem is resolved.

What are the common symptoms of code P0639?

Common symptoms that may accompany code P0639 include:

• Lack of power or poor acceleration
• Rough or unstable idle
• Reduced fuel economy
• Check engine light illumination
• Difficulty starting the engine

What are the possible causes of code P0639?

Some of the most common causes that can trigger code P0639 are:

• Damaged, corroded, or disconnected wiring and connectors related to the throttle actuator
• Faulty throttle actuator motor
• Issues with the throttle position sensor
• Malfunctions in the powertrain control module (PCM) or throttle actuator control module
• Throttle valve/plate problems like carbon buildup or mechanical failure

How do you diagnose code P0639?

To properly diagnose the root cause of code P0639, a mechanic should follow these general steps:

1. Scan for any additional trouble codes and note them.
2. Visually inspect the wiring, connectors, and components related to the throttle actuator system. Look for obvious damage, corrosion, or poor connections.
3. Test the throttle actuator motor and position sensor and compare the readings to manufacturer specifications.
4. Check for issues with the throttle valve/plate.
5. If no problems are found, suspect a failure with the PCM or throttle actuator control module.

How much does it cost to diagnose and fix code P0639?

The cost to diagnose and repair code P0639 can vary significantly depending on the root cause and the specific make and model of the vehicle. On average, expect to pay between $100-$600 for complete diagnosis and repair, with the cost of parts ranging from $50 for a wiring harness or sensor up to $500 or more for a throttle actuator motor or control module. Some high-end vehicles like a BMW M5 can cost over $3000 to replace the throttle actuators on both banks.

Can I diagnose and fix code P0639 myself?

Diagnosing code P0639 requires advanced knowledge of automotive electrical and computer systems, as well as special diagnostic equipment. It's not recommended for the average vehicle owner to attempt diagnosis and repair on their own. The throttle actuator is a critical component that directly impacts vehicle safety and performance. Incorrect diagnosis or repair could lead to further damage or unsafe driving conditions. It's best to have code P0639 professionally diagnosed and repaired by a qualified mechanic.

How long does it take to fix code P0639?

The time required to fix code P0639 depends on the specific cause and the necessary repairs. Simple issues like cleaning the throttle body or replacing a sensor could be done in under an hour. However, more involved repairs like replacing the throttle actuator or PCM could take several hours. Factor in additional time for proper diagnosis and testing. On average, expect a shop to spend 1-4 hours to fully diagnose and repair a vehicle with code P0639.

What happens if I ignore code P0639?

Ignoring code P0639 and continuing to drive the vehicle could result in progressively worse symptoms like lack of power, rough idle, stalling, or failure to start. Delaying repairs increases the risk of the vehicle becoming undrivable and could cause additional damage to the throttle system, engine, or other components. In a worst case scenario, an inoperable throttle actuator could leave you stranded or cause an accident if the vehicle loses power unexpectedly during driving. To avoid more costly repairs or unsafe driving conditions, it's strongly recommended to address code P0639 promptly.

What is a throttle actuator and what does it do?

The throttle actuator, also known as an electronic throttle body, is responsible for controlling the position of the throttle valve/plate which regulates the amount of air flowing into the engine. It consists of an electric motor, gears, and sensors that work together to open and close the throttle valve based on driver input from the accelerator pedal. The throttle actuator plays a critical role in engine performance, fuel efficiency, and emissions by ensuring the optimal air-fuel ratio for combustion.

What is the difference between code P0638 and P0639?

Both P0638 and P0639 refer to problems with the throttle actuator control system, but they apply to different engine banks. Code P0638 indicates an issue with the throttle actuator on bank 1, while P0639 points to bank 2. Bank 1 is the side of the engine that contains cylinder #1, and bank 2 is the opposite side. On inline 4-cylinder engines, there is only one bank. But on V6, V8, and other multi-bank engines, it's important to determine which bank is affected to locate the faulty throttle actuator.

Can low battery voltage cause code P0639?

While low battery voltage is not a direct cause of code P0639, it can potentially trigger a false code or contribute to throttle actuator problems. The throttle actuator motor and control module require adequate voltage to function properly. Low voltage could cause incorrect operation or communication faults that might be mistaken for a throttle actuator range or performance issue. However, if the code persists after ensuring proper battery voltage and charging system function, then the low voltage was likely not the underlying problem.

Can a bad throttle position sensor (TPS) cause code P0639?

Yes, a faulty throttle position sensor is one of the most common triggers for code P0639. The TPS measures the actual position of the throttle valve and sends that data to the PCM. If the TPS gives inaccurate readings, the PCM will detect a discrepancy between the expected and actual throttle positions, setting code P0639. A bad TPS can also cause symptoms like poor acceleration, rough idle, and stalling. However, a TPS problem is just one of several possible causes for P0639 and a thorough diagnosis is needed to isolate the fault.

Can a vacuum leak cause code P0639?

No, a vacuum leak would not directly cause code P0639. A vacuum leak allows unmetered air to enter the engine after the throttle body, throwing off the air-fuel ratio. This can trigger lean codes like P0171 or P0174, or cause a rough idle, but it does not affect the throttle actuator motor or control circuit. The only way a vacuum leak might contribute to P0639 is if the leak is so severe that it stalls the engine, which could theoretically set a false throttle actuator code. But in that case, the vacuum leak codes would be the primary issue.

Can a clogged catalytic converter cause code P0639?

No, a clogged catalytic converter is very unlikely to have any effect on code P0639. A catalytic converter is an exhaust system component located downstream of the engine. Its purpose is to reduce harmful emissions, not control the air intake. A severely clogged converter can cause loss of power or engine stalling, but that would be due to excessive backpressure, not a throttle actuator malfunction. Any potential link between a bad catalytic converter and code P0639 would be indirect and is not a common cause to suspect for this code.

Can a bad mass airflow sensor (MAF) cause code P0639?

No, a bad mass airflow sensor would not be a direct cause of code P0639. The MAF measures the amount of air entering the engine and is located before the throttle body. A faulty MAF can cause incorrect air-fuel mixture and trigger fuel trim codes (P0170-P0175), or lean/rich codes (P0171, P0172, P0174, P0175). But the MAF does not monitor throttle actuator performance or send any data that would set code P0639. Focus on the throttle actuator motor, wiring, and control module when diagnosing P0639.

Can a bad accelerator pedal position sensor (APPS) cause code P0639?

Yes, a faulty accelerator pedal position sensor (APPS) is a possible cause of code P0639, though not as common as a bad throttle position sensor or throttle actuator motor. The APPS tells the PCM the position of the accelerator pedal. If it gives an incorrect signal, the PCM may detect a mismatch between the pedal position and actual throttle position, potentially setting code P0639 in addition to APPS specific codes like P2135. However, APPS issues more commonly affect idle than throttle range.

What other codes may be related to P0639?

Code P0639 may appear along with other throttle actuator or throttle position sensor related codes such as:

• P0638 – Throttle actuator control range/performance (bank 1)
• P2135 – Throttle/pedal position sensor/switch A/B voltage correlation
• P0122 – Throttle position sensor/switch A circuit low input
• P0123 – Throttle position sensor/switch A circuit high input
• P0222 – Throttle position sensor/switch B circuit low input
• P0223 – Throttle position sensor/switch B circuit high input

What is the throttle actuator control range?

The throttle actuator control range refers to the normal operating range of motion of the throttle valve from fully closed to wide open. This range of motion is controlled by the throttle actuator motor based on signals from the accelerator pedal position sensor and PCM. The PCM monitors actual throttle position via the throttle position sensor. Code P0639 sets when the PCM detects that the actual throttle position is outside the expected control range for the given operating conditions, indicating a fault with the throttle actuator motor, control module, or related sensors and wiring.

What does "bank 2" refer to in code P0639?

"Bank 2" in code P0639 refers to the bank of the engine where the affected throttle actuator is located. On V6, V8, and other engines with two cylinder heads, bank 2 is the side of the engine opposite from the #1 cylinder. Bank 1 would be the side containing cylinder #1. Inline 4-cylinder and some inline 6-cylinder engines only have one bank. Knowing which bank is specified in the code helps locate the faulty component.

What is the difference between code P0639 and P0121?

Code P0639 indicates a problem with the throttle actuator control range or performance on bank 2, while P0121 refers to a fault in the throttle position sensor performance or circuit on bank 1. The throttle position sensor measures throttle blade angle, while the throttle actuator motor controls the throttle blade position. Both codes can cause similar symptoms, but P0121 is more likely to set due to wiring or sensor issues, while P0639 commonly points to throttle actuator motor or control module problems.