Variable valve timing. VTEC, VVTI and VANOS — we’ve all heard these terms thrown around by mechanics for decades. Simply put, these systems all adjust the cam timing to improve how your engine functions.

However, we know as car owners that introducing more complexity means more components that can fail. The P0021 is the check engine light code for a failure in this system.

Here you’ll find how to diagnose and fix this trouble code. You’ll also find the most common causes, symptoms and any preventative measures you can take when encountering this issue. So, let’s get into it!

What is the P0021 Code, and What Does It Mean? 

The full error message for the P0021 code is, “Camshaft Position – Timing Over-Advanced or System Performance (Bank 2).” This means that the position of the camshaft in bank 2 is out of time. Timing is how the engine keeps all the components in the engine working together in unison.

This error code is specifically related to vehicles that use variable cam timing or (VCT). This technology allows the ECU to adjust cam timing at different engine speeds, improving both performance and fuel economy. Of course, if this system malfunctions, your engine will experience all kinds of issues. 

What Causes the P0021 Code?

Once you know the common causes of this trouble code, you’ll be one step closer to diagnosing what’s causing your problem. Most camshaft troubles are straightforward to diagnose. Here are the most common causes:

• Bad camshaft timing
• Faulty oil control valve
• Stuck camshaft phaser
• Dirty oil
• Wiring harness failure

Bad Camshaft Timing

This issue is fairly common after a timing belt service. The cam timing and belts need to be torqued to certain specifications. If this is not done correctly, you will get the P0021 code.

Faulty Oil Control Valve

An oil control valve or VVT solenoid uses oil pressure to adjust valve timing. It does this by pushing oil through a series of valves, either opening or closing the solenoid. This activates a cam phaser, which adjusts the camshaft timing. The P0021 code can be triggered by a faulty oil control valve on bank 2. 

Many manufacturers have moved to electronically controlled solenoids or use different systems, but there are still many that use this system. Consult your owner’s manual to check which system your vehicle uses.

Stuck Camshaft Phaser

A cam phaser is the major failure point of many engines. It’s the actual component that retards or advances cam timing. Different systems work in different ways, but most of them rely on the oil control valve to get the oil pressure needed to activate the phasing mechanism. Of course, we know that anything that uses oil can fail due to various oil related reasons. When this happens, it can cause the P0021 code. If you’re looking for a quality variable valve timing phasing parts, check our selection! 

Dirty Oil

Dirty oil or lack of oil can cause this trouble code. Contaminated oil, or old oil, can clog up the passages in the cam phasing mechanism and the oil control valve. The variable cam system uses oil pressure, a lack of oil can cause the system to malfunction and log the P0021 code.

Wiring Harness Failure

A wiring harness is the main connection between sensors and the ECU. Since the ECU regulates the oil control valve, you’ll find this trouble code in your logs if the connection with the sensor is no longer accessible.

What Are the Common Symptoms of P0021 Fault Code?

Correctly diagnosing these issues solely using the symptoms is difficult. These symptoms are common to most engine problems, but will still bring you closer to diagnosing your P0021 code. The common symptoms are:

• Check engine light
• Bad starting behavior
• Stalling

Check Engine Light

The check engine light is a common factor with all trouble codes. It’s the first indicator that something is wrong with your vehicle. A light that only illuminates means that there is an issue that will not cause immediate catastrophic damage to your engine or other vital components. With the P0021, the light will only illuminate.

Bad Starting Behavior

Poor starting behavior is a given when you have any sort of timing or camshaft issue. Your vehicle may not start at all if the oil valve system is too clogged. A rough idle or extended cranking can point to this trouble code.

Stalling

An engine stall while driving can occur if there is a failure while you’re driving. This is the worst-case scenario as it can destroy your camshaft and as well as other engine internals. Unfortunately, this is a common scenario for early vehicles that use VVT systems.

How to Diagnose and Fix the Cause of P0021 Code 

When you look at the diagnostic process for the P0021 code, it can be intimidating. Digging into your engine, and removing covers and components can be tedious. We will walk you through each process.

OBD-II Reader

To properly diagnose a P0021, you first need to know that you have a P0021. The only way to know for sure is by using an OBD-II reader. This will allow you to interface with your engine computer and read the error codes that it’s putting out.

Connect your scan tool to the connection port under the passenger side dash. Scan for trouble codes. Look for the P0021 code and any other camshaft-related codes.

Look for Obvious Signs of Damage

It is quite easy to notice major component failures in your vehicle. It is a bit more complicated to see the smaller failures that can cause inefficiency or larger components to malfunction.

First, you need to look for any oil under your vehicle. Even small oil leaks can cause the variable cam system to malfunction. Make sure that there is enough oil in your vehicle and that it is not contaminated. This check seems trivial but can cause major issues if ignored.

Check your wiring harness for any damage. There should be no fraying, corrosion or loose wires near the oil control valve. 

Once that’s done, you need to check your cam phaser and solenoid for damage. The location of the camshaft can differ from vehicle to vehicle, so be sure to check your owner’s manual before removing any components.

This process might require you to remove the timing cover and valve cover. This means you need new gaskets when replacing these covers. The cam phaser is under a timing guide cover, on either side of the camshaft.

When you have access to the cam phaser, check for a jelly-like substance. Overheated oil or oil that has mixed with coolant will turn into a gelatin-like consistency. If you have any sludge on the cam lobes and shafts, clean that off as well.

Wiring Harness Test

A wiring harness failure can cause your solenoid to malfunction. First, you need to check that the voltage is flowing into the solenoid. To test for voltage, you need a multimeter. Put your vehicle in the key on engine-off state. This means that your ignition is on, but the engine is not running.

Take your red multimeter probe and contact the positive connector terminal. The black probe should contact but because we have not ruled out a short to ground yet, we use the vehicle chassis as ground. Do this only if you know which of the terminals to test. 

The voltage output should be around 9 to 13V.

Oil Control Valve Test

Here, you will test your solenoid. The best way to do it is to remove the solenoid and bench test it using a car battery. First off, you need to test whether the solenoid is opening and closing. Connect your solenoid to a 12V power source. A car battery is useful for this purpose. Make sure you connect your positive terminal of the battery to the positive (red) terminal of the solenoid. 

Take your negative (black) wire, and contact ground and the solenoid terminal. You should hear an audible clicking noise. This means that your solenoid is functioning as it should. You can also test for resistance if you want more conclusive data on this problem.

Contact the solenoid tip with your red multimeter probe and ground with your black probe. You should get around 8-12 ohms of resistance. Remember that most manufacturers use a different form of variable cam timing. This means that the data, components and systems differ widely between manufacturer to manufacturer. Make sure you consult your owner’s manual.

How to Fix a P0021 code

There are a couple of quick fixes for this problem. A few changes of oil can clear up any contaminants clogging up the system. Engine cleaners are also helpful if you have excessive amounts of sludge or soot. Another option is to clean your cam phaser. Of course, it is easier to just replace the cam phaser, but if there is no scoring or external damage, cleaning it and putting it back in is definitely an option.

Does P0021 Clear Itself?

This code is one that clears itself because your engine is unlikely to start with this trouble code. Once you have your engine running smoothly, you no longer need to worry about the P0021 code. If you still have a check engine light, that should disappear within your vehicle’s drive cycle.

Is It OK to Drive with P0021 ?

If you can get your vehicle running with this trouble code, you should not be driving with it. A failed cam phaser or cam shaft will cause irreparable damage to your engine. This is a code where you should stop as soon as possible and get your vehicle towed.

Fix P0021 Codes with Quality Parts

Fixing a P0021 can require more than a few components and tools. Vehicle specific tools and parts are sometimes scarce if you pop in at your local parts store.

Luckily, we at eEuroparts.com, have you covered. We stock all the components that you need to fix a P0021 and more. All you need to do is select your vehicle and a comprehensive list of tailored components will be available to you. It’s that simple!