P0021 Code: 'A' Camshaft Position - Timing Over-Advanced (Bank 2)

P0021 OBD-II Trouble Code: 'A' Camshaft Position - Timing Over-Advanced (Bank 2)

Quick answer

• What the code means: The P0021 code means that the engine control module (ECM) has detected that the intake camshaft on Bank 2 is more advanced than it should be.
• Severity: Get this checked out as soon as possible. While you can likely drive home, ignoring it can lead to serious engine damage.
• Most common cause: The most common cause of a P0021 code is a faulty oil control valve (OCV), also known as a variable valve timing (VVT) solenoid.

What the P0021 code means

The official OBD-II definition for P0021 is "'A' Camshaft Position - Timing Over-Advanced or System Performance (Bank 2)." In plain English, this means your car's computer has noticed a problem with the timing of the intake camshaft on Bank 2 of the engine.

Your engine uses a system called variable valve timing (VVT) to adjust when the intake and exhaust valves open and close. This helps to improve engine performance and fuel economy. The "A" camshaft is the intake camshaft, and "Bank 2" refers to the side of the engine that does not contain cylinder number 1.

The ECM uses signals from the camshaft and crankshaft position sensors to monitor the timing of the camshafts. If the ECM sees that the intake camshaft on Bank 2 is advanced more than it's commanding it to be, it will set the P0021 code.

Common symptoms

You may notice one or more of the following symptoms if your car has a P0021 code:

• Check Engine Light: The most common symptom of any DTC is an illuminated Check Engine Light.
• Rough idle: The engine may run rough or stall when idling.
• Poor fuel economy: You may notice that you're getting worse gas mileage than usual.
• Reduced engine performance: The engine may feel sluggish or lack power.
• Engine rattling or knocking noises: In some cases, you may hear a rattling or knocking sound from the engine, especially at idle.
• Hard starting: The engine may be difficult to start.

Common causes

The most common causes of a P0021 code, in order from most likely to least likely, are:

1. Faulty oil control valve (OCV): The OCV is responsible for controlling the flow of oil to the VVT system. If the OCV is stuck open or not functioning correctly, it can cause the camshaft to become over-advanced.
2. Low or dirty engine oil: The VVT system relies on clean oil to function properly. If the oil level is low or the oil is dirty, it can cause problems with the VVT system and trigger a P0021 code.
3. Faulty camshaft phaser: The camshaft phaser is the component that actually adjusts the timing of the camshaft. If the phaser is damaged or stuck, it can cause the camshaft to become over-advanced.
4. Timing chain or belt issues: A stretched timing chain or a worn timing belt can cause the camshafts to be out of time, which can trigger a P0021 code.
5. Wiring issues: Damaged wiring or a poor connection to the OCV or camshaft position sensor can cause problems with the VVT system.
6. Faulty camshaft position sensor: While less common, a faulty camshaft position sensor can send an incorrect signal to the ECM, causing it to set a P0021 code.
7. Faulty ECM: In rare cases, a problem with the ECM itself can cause a P0021 code.

How a technician diagnoses it

A technician will use a systematic approach to diagnose a P0021 code. Here are the typical steps they will take:

1. Scan for codes: The technician will first connect a scan tool to the vehicle's OBD-II port to confirm the P0021 code and check for any other related codes. They will also look at the freeze-frame data, which is a snapshot of the engine's operating conditions at the time the code was set.
2. Check the oil: The technician will check the engine oil level and condition. If the oil is low or dirty, they will recommend an oil change.
3. Inspect the wiring: The technician will inspect the wiring and connectors for the OCV and camshaft position sensor for any signs of damage or corrosion.
4. Test the OCV: The technician will use a scan tool to command the OCV on and off to see if it is functioning properly. They may also use a digital multimeter to check the resistance of the OCV. A good OCV will typically have a resistance of around 10-15 ohms.
5. Test the camshaft position sensor: The technician will use a scan tool to monitor the signal from the camshaft position sensor. A good sensor will produce a clean, square waveform.
6. Inspect the timing components: If the above tests do not reveal the cause of the problem, the technician may need to inspect the timing chain or belt and the camshaft phaser for any signs of wear or damage. This is a more involved process that may require removing the engine's timing cover.

Typical repair cost

The cost to repair a P0021 code can vary widely depending on the cause of the problem. Here are some typical repair costs:

• Oil change: $50 - $150
• Oil control valve (OCV) replacement: $150 - $500
• Camshaft position sensor replacement: $100 - $300
• Camshaft phaser replacement: $800 - $2500+
• Timing chain or belt replacement: $1000 - $3000+

Can I keep driving with this code?

It is not recommended to continue driving with a P0021 code. While you may be able to drive the vehicle, ignoring the problem can lead to more serious and expensive engine damage down the road. An over-advanced camshaft can cause the pistons to come into contact with the valves, which can result in catastrophic engine failure.

Related codes

Here are some codes that are related to P0021:

• P0011: 'A' Camshaft Position - Timing Over-Advanced (Bank 1)
• P0020: 'A' Camshaft Position Actuator Circuit (Bank 2)
• P0022: 'A' Camshaft Position - Timing Over-Retarded (Bank 2)
• P0345: Camshaft Position Sensor 'A' Circuit (Bank 2)
• P0346: Camshaft Position Sensor 'A' Circuit Range/Performance (Bank 2)

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