P0084, P0085, and P0086: Exhaust valve control solenoid circuit (Bank 2)

If you have a car with an engine that has variable valve timing (VVT), you may encounter some trouble codes that start with P008. These codes are related to the exhaust valve control solenoid, which is a device that controls the opening and closing of the exhaust valves in your engine. The exhaust valves are responsible for letting out the burned gases from the combustion chamber, and the VVT system adjusts the timing and duration of the valve operation to optimize the engine performance and efficiency.

However, if the exhaust valve control solenoid malfunctions, the engine may not work properly, and the check engine light may come on. In this article, we will explain what DTC codes P0084, P0085, and P0086 mean, what causes them, what symptoms they produce, and how to fix them.

What are DTC codes P0084, P0085, and P0086?

DTC codes P0084, P0085, and P0086 are diagnostic trouble codes that indicate a problem with the exhaust valve control solenoid circuit. The circuit consists of the solenoid, the wiring harness, and the engine control unit (ECU). The solenoid is an electromagnet that moves a plunger to open or close the exhaust valve. The wiring harness connects the solenoid to the ECU, which is the computer that controls the engine. The ECU sends signals to the solenoid to activate or deactivate it, depending on the engine speed and load. The ECU also monitors the solenoid’s operation and detects any faults or errors in the circuit.

The codes P0084, P0085, and P0086 have different meanings, depending on the bank and the cylinder of the engine. The bank refers to the side of the engine that contains the cylinders, and the cylinder refers to the individual combustion chamber where the fuel and air are burned. The codes are as follows:

• P0084: Exhaust Valve Control Solenoid Circuit Low (Bank 2)
• P0085: Exhaust Valve Control Solenoid Circuit Low (Bank 1)
• P0086: Exhaust Valve Control Solenoid Circuit High (Bank 1)

These codes mean that the ECU has detected a low or high voltage in the exhaust valve control solenoid circuit, which indicates a short or an open in the circuit. A short is when the circuit is accidentally connected to another circuit or to the ground, causing a low voltage. An open is when the circuit is broken or disconnected, causing a high voltage. These codes are usually accompanied by other codes that specify the cylinder number, such as P0301, P0302, P0303, etc.

What are the causes of DTC codes P0084, P0085, and P0086?

There are several possible causes of DTC codes P0084, P0085, and P0086, such as:

• Faulty exhaust valve control solenoid: The solenoid may be damaged, worn, or stuck, causing it to malfunction or fail. This may be due to dirt, debris, oil, or corrosion in the solenoid, or due to excessive heat or vibration in the engine.
• Wiring harness problems: The wiring harness may be damaged, loose, or corroded, causing it to short or open the circuit. This may be due to physical damage, moisture, or rodents in the wiring harness, or due to improper installation or modification of the wiring harness.
• Engine control unit (ECU) problems: The ECU may be faulty, corrupted, or programmed incorrectly, causing it to send or receive wrong signals to or from the solenoid, or to misinterpret the signals from the solenoid. This may be due to a power surge, a voltage spike, or a software glitch in the ECU, or due to a bad or incompatible update or tune of the ECU.

What are the symptoms of DTC codes P0084, P0085, and P0086?

DTC codes P0084, P0085, and P0086 may produce some noticeable symptoms, such as:

• Check Engine Light (CEL) illuminated: The CEL is a warning light on the dashboard that indicates a problem with the engine or the emission system. The CEL will come on when the ECU detects a fault or an error in the exhaust valve control solenoid circuit, and will store the code in its memory. The CEL may also flash or blink, which means that the problem is serious and may damage the engine or the catalytic converter.
• Reduced engine performance: The engine performance may be reduced due to the improper operation of the exhaust valves. The engine may have less power and torque, and may struggle to accelerate or maintain speed. The engine may also have poor fuel economy, and may consume more gas than usual.
• Rough idle: The engine may idle roughly or unevenly due to the improper operation of the exhaust valves. The engine may shake, vibrate, or stumble, and may make unusual noises or smells. The engine may also stall or die, especially when cold or warm.
• Fuel economy problems: The fuel economy may be affected due to the improper operation of the exhaust valves. The engine may use more fuel than necessary, and may emit more exhaust gases than normal. The engine may also fail the emission test, and may cause environmental problems.
• Engine misfires: The engine may misfire due to the improper operation of the exhaust valves. A misfire is when the fuel and air mixture in the cylinder does not burn completely or at the right time, causing a loss of power and a jerk in the engine. A misfire may also damage the engine or the catalytic converter, and may trigger other codes, such as P0300, P0301, P0302, etc.

How to fix DTC codes P0084, P0085, and P0086?

To fix DTC codes P0084, P0085, and P0086, you need to diagnose the problem using a scan tool, and repair or replace the faulty component in the exhaust valve control solenoid circuit. Here are some steps to help you do that:

• Diagnose the problem using a scan tool: You need to use a scan tool to read the code and the freeze frame data from the ECU, and to clear the code and the CEL after the repair. A scan tool is a device that connects to your car’s diagnostic port, usually located under the dashboard, and communicates with the ECU. A scan tool can display the code and the freeze frame data, which are the information about the engine’s condition and the parameters at the time of the fault. A scan tool can also perform some tests and functions, such as checking the voltage and the resistance of the circuit, and activating or deactivating the solenoid. You can buy a scan tool online or at an auto parts store, or you can borrow one from a friend or a mechanic.
• Repair or replace the faulty exhaust valve control solenoid: You need to locate the exhaust valve control solenoid, which is usually mounted on the cylinder head, near the exhaust manifold. You need to inspect the solenoid for any signs of damage, wear, or corrosion, and test it for proper operation. You can use a multimeter to measure the resistance of the solenoid, and compare it to the specifications in the service manual. You can also use a scan tool to activate or deactivate the solenoid, and listen for any clicking sounds. If the solenoid is faulty, you need to replace it with a new one, following the instructions in the service manual. You may also need to replace the gasket or the seal of the solenoid, if they are damaged or leaking.
• Repair or replace the wiring harness: You need to inspect the wiring harness that connects the solenoid to the ECU, and look for any signs of damage, looseness, or corrosion. You need to check the continuity and the voltage of the wires, and make sure they are not shorted or open. You can use a multimeter or a test light to check the wires, and compare them to the wiring diagram in the service manual. If the wiring harness is damaged, you need to repair or replace it, following the instructions in the service manual. You may also need to use some electrical tape, wire connectors, or soldering tools to fix the wires, if they are broken or disconnected.
• Repair or replace the ECU: You need to inspect the ECU, which is usually located under the dashboard, near the steering column. You need to look for any signs of damage, moisture, or corrosion, and test it for proper function. You can use a scan tool to communicate with the ECU, and check for any error codes or messages. You can also use a multimeter to check the power and the ground of the ECU, and make sure they are not interrupted or reversed. If the ECU is faulty, you need to replace it with a new one, following the instructions in the service manual. You may also need to reprogram or update the ECU, using a scan tool or a computer, if the software is corrupted or outdated.

Conclusion

DTC codes P0084, P0085, and P0086 are trouble codes that indicate a problem with the exhaust valve control solenoid circuit, which affects the operation of the exhaust valves and the performance and efficiency of the engine. These codes may be caused by a faulty solenoid, a wiring harness problem, or an ECU problem, and may produce symptoms such as a check engine light, reduced engine performance, rough idle, fuel economy problems, and engine misfires. 

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