P0027 Exhaust Valve Control Solenoid Circuit Range/Performance (Bank 1)

The P0027 diagnostic trouble code indicates that the engine control module (ECM/PCM) has detected a range or performance problem in the exhaust valve control solenoid circuit for Bank 1.

On many engines, this refers to the exhaust camshaft variable valve timing (VVT) control system. The ECM electrically controls an oil-control solenoid, which regulates engine oil flow to a camshaft phaser. The phaser then changes the exhaust camshaft timing.

The important part of P0027 is “Range/Performance.” This means the ECM is not necessarily detecting a simple open or short circuit. Instead, it has determined that the control system is not responding as expected.

The solenoid may be electrically functional while the actual camshaft timing fails to follow the commanded position.

Understanding Bank 1

Bank 1 is the cylinder bank containing cylinder number 1.

On an inline engine, there is normally only one cylinder bank, so the engine does not have a separate Bank 2.

On V-type and horizontally opposed engines, there are two banks. Bank 1 is identified by cylinder numbering and should not simply be assumed to be the left or right side of the engine.

The exact location of the Bank 1 exhaust control solenoid is therefore vehicle-specific.

What the Exhaust Valve Control Solenoid Does

Modern engines frequently use variable valve timing to change when the exhaust valves open and close.

A typical system works through several components:

ECM → exhaust valve control solenoid → engine oil flow → camshaft phaser → exhaust camshaft

The ECM determines the desired camshaft position based on factors such as:

• Engine speed

• Engine load

• Throttle position

• Coolant temperature

• Engine oil temperature

• Operating conditions

• Emissions requirements

The control solenoid regulates oil flow to the camshaft phaser.

The phaser changes the camshaft's angular position relative to the crankshaft.

The ECM then uses the camshaft position sensor to determine whether the requested timing change actually occurred.

What Does “Range/Performance” Mean?

P0027 is fundamentally a response or plausibility problem.

The ECM may command the exhaust camshaft to move to a particular position but observe that the actual position does not correspond to the command.

For example:

• The camshaft moves too slowly.

• The camshaft does not move far enough.

• The camshaft does not move at all.

• The camshaft moves but cannot maintain the requested position.

• The camshaft position changes inconsistently.

• The system responds outside the expected operating range.

This is different from simply finding a broken wire.

A solenoid can have an electrically normal coil and still cause P0027 if it cannot properly control oil flow.

Why Engine Oil Is a Major Part of the Diagnosis

The exhaust VVT system on many engines is fundamentally a hydraulic system controlled electrically.

The ECM controls the solenoid, but engine oil physically moves the camshaft actuator.

That means an apparently electrical VVT fault can actually be caused by a lubrication problem.

Potential problems include:

• Low engine oil level

• Incorrect oil viscosity

• Incorrect oil specification

• Old or degraded oil

• Sludge

• Restricted oil passages

• Blocked solenoid filter

• Low engine oil pressure

• Internal oil leakage

For this reason, replacing the solenoid immediately is not always the correct repair.

Common Causes of P0027

Faulty exhaust VVT control solenoid

The solenoid may be electrically defective, contaminated, internally restricted, or mechanically stuck.

Dirty or contaminated engine oil

VVT control passages can be sensitive to contamination. Sludge or debris can prevent the solenoid or phaser from responding correctly.

Incorrect oil level

Insufficient oil can reduce the hydraulic pressure available to the VVT actuator.

Incorrect oil viscosity

If the oil is substantially different from the manufacturer's specification, VVT response can be affected, particularly during cold operation.

Low engine oil pressure

A worn oil pump, restricted pickup, excessive internal engine wear, or another lubrication problem can prevent the camshaft actuator from reaching its commanded position.

Restricted oil passage

A restriction between the control solenoid and camshaft phaser can limit actuator movement.

Sticking camshaft phaser

The phaser itself may be mechanically stuck or slow to respond because of contamination, wear, or internal damage.

Damaged wiring

The solenoid's electrical circuit can have damaged insulation, broken conductors, excessive resistance, or intermittent connections.

Connector problem

Corrosion, loose terminals, oil contamination, or poor terminal tension can affect solenoid operation.

Camshaft position sensor problem

The VVT system may actually move correctly while the sensor provides incorrect feedback to the ECM.

Crankshaft position signal problem

Because the ECM calculates camshaft position relative to the crankshaft, an inaccurate crankshaft signal can also interfere with VVT control.

Timing-chain or timing-belt problem

Mechanical timing that is incorrect or unstable can produce a mismatch between commanded and actual camshaft position.

Worn timing components

A stretched timing chain, weak tensioner, or damaged timing components can cause camshaft timing to vary from the expected position.

ECM problem

An ECM control-driver failure is possible but should generally be considered only after the external components and circuits have been tested.

Symptoms of P0027

P0027 can produce very different symptoms depending on the severity of the fault.

Possible symptoms include:

• Check Engine Light

• Rough idle

• Hesitation

• Reduced acceleration

• Loss of engine power

• Poor throttle response

• Reduced fuel economy

• Difficult starting

• Extended cranking

• Engine misfires

• Unstable idle

• Increased emissions

• Poor performance at certain engine speeds

Some vehicles may show almost no noticeable drivability symptoms.

This can happen when the VVT system is still functioning partially and the problem occurs only under particular engine-speed, temperature, or load conditions.

Why the Problem Can Appear Only at Certain RPM

A VVT system does not necessarily behave the same way across the entire operating range.

For example, a partially restricted oil passage may allow the camshaft to move adequately at low RPM but fail to provide the required response when the ECM requests a rapid timing change.

Similarly, a weak solenoid may work when the engine is warm but respond slowly when the oil is cold.

This means a vehicle can idle normally while setting P0027 during acceleration.

The operating conditions stored in the freeze-frame data can therefore be very useful.

How to Diagnose P0027

The best diagnostic strategy is to determine whether the failure is electrical, hydraulic, mechanical, or related to position feedback.

1. Scan the vehicle completely

Read all stored and pending diagnostic trouble codes.

Record the freeze-frame information associated with P0027.

Useful information includes:

• Engine RPM

• Engine load

• Coolant temperature

• Oil temperature, if available

• Throttle position

• Vehicle speed

• Commanded exhaust camshaft position

• Actual exhaust camshaft position

Other VVT, camshaft, crankshaft, or oil-pressure codes may provide important clues.

2. Check the engine oil

Start with the basics.

Verify:

• Oil level

• Oil condition

• Correct viscosity

• Correct manufacturer specification

If the oil is heavily contaminated or the engine has a history of poor maintenance, the VVT oil-control system should receive particular attention.

3. Locate the correct Bank 1 exhaust solenoid

Confirm the component using the manufacturer's service information.

Do not assume that the first VVT solenoid you see is the one associated with the code.

Some engines have separate intake and exhaust solenoids, and some use more complicated multi-solenoid arrangements.

4. Inspect the solenoid and surrounding area

Look for:

• Oil leakage

• Physical damage

• Contamination

• Incorrect installation

• Damaged connector

• Wiring damage

If the solenoid has an oil filter or screen, inspect it according to the manufacturer's procedure.

5. Inspect the wiring

Follow the circuit from the solenoid toward the ECM.

Look for:

• Broken wires

• Chafing

• Melted insulation

• Corrosion

• Oil contamination

• Poor previous repairs

• Loose connectors

The wiring near the cylinder head and exhaust components can be exposed to substantial heat.

6. Test the electrical circuit

Use the vehicle-specific wiring diagram to identify the power and control circuits.

Depending on the design, the ECM may operate the solenoid using a switched ground or PWM control.

Check for:

• Correct power supply

• Correct control signal

• Excessive resistance

• Short circuits

• Open circuits

• Poor terminal connections

Do not assume a generic voltage value applies to every VVT system.

Testing the Solenoid

A resistance test can be useful, but it should not be the entire diagnosis.

Compare the measured resistance with the manufacturer's specification.

An open or severely shorted coil can indicate an obvious solenoid fault.

However, a solenoid can have correct resistance and still fail because it is:

• Mechanically stuck

• Contaminated

• Internally restricted

• Slow to respond

• Unable to control oil flow properly

Where supported, a scan-tool actuator test can provide additional information by commanding the solenoid and observing the system's response.

Compare Commanded and Actual Camshaft Position

For a range/performance code, this is one of the most informative diagnostic checks.

The ECM may request a specific exhaust camshaft angle.

The technician should compare:

Commanded camshaft position vs. actual camshaft position

If the command changes but the actual position barely responds, possible causes include:

• Faulty solenoid

• Insufficient oil pressure

• Restricted oil passage

• Stuck camshaft phaser

• Mechanical timing problem

If the camshaft moves but overshoots or fluctuates excessively, investigate oil control, phaser operation, and mechanical condition.

The live-data pattern can often tell you more than simply measuring the solenoid's resistance.

Checking the Camshaft Position Signal

If the mechanical VVT system appears to operate correctly but the ECM continues to report a performance problem, verify the feedback signal.

Inspect:

• Camshaft position sensor

• Sensor power

• Sensor ground

• Signal wiring

• Connector

• Camshaft target wheel or reluctor, where applicable

A faulty position signal can make a correctly operating VVT mechanism appear incorrect to the ECM.

Timing-Chain Problems Should Not Be Overlooked

If P0027 is accompanied by other camshaft or crankshaft correlation codes, the mechanical timing system deserves close attention.

Potential problems include:

• Stretched timing chain

• Incorrect timing installation

• Weak chain tensioner

• Damaged timing guides

• Incorrect camshaft timing

• Damaged camshaft phaser

If the mechanical timing is incorrect, changing the VVT solenoid may not solve the problem.

Could Low Oil Pressure Cause P0027?

Absolutely.

The electrical solenoid may be functioning perfectly while the hydraulic system fails to move the camshaft.

Low oil pressure can result from:

• Low oil level

• Incorrect oil

• Worn oil pump

• Restricted oil pickup

• Excessive bearing clearance

• Internal oil leakage

• Restricted oil passages

If low oil pressure is suspected, it should be measured using the manufacturer's specified procedure.

The P0027 code alone cannot prove that oil pressure is low.

Why Continuity Testing Is Not Enough

A wiring harness can pass a basic continuity test and still cause P0027.

Continuity does not necessarily reveal:

• Excessive resistance

• Poor terminal tension

• Intermittent connections

• Voltage loss under load

• Wiring faults that appear only during engine movement

When an electrical connection is suspected, voltage-drop testing under load can be much more informative than simply checking whether a wire has continuity.

P0027 After an Engine or Timing Repair

If P0027 appeared after:

• Timing-chain replacement

• Cylinder-head repair

• Camshaft replacement

• Engine replacement

• VVT solenoid replacement

• Wiring repair

inspect the recently disturbed areas first.

Check for:

• Incorrect mechanical timing

• Disconnected connectors

• Damaged wiring

• Incorrect solenoid installation

• Contaminated oil passages

• Incorrectly installed camshaft phaser

• Missing components

A VVT fault that appears immediately after a repair should not automatically be treated as an unrelated component failure.

Should You Replace the VVT Solenoid?

Not solely because P0027 is stored.

The solenoid should be replaced when testing demonstrates that it is defective or cannot control the oil circuit correctly.

If the electrical circuit is good and the solenoid responds correctly, the investigation should move toward:

Oil pressure → oil passages → camshaft phaser → cam/crank feedback → mechanical timing

This prevents unnecessary parts replacement.

Can P0027 Damage the Engine?

P0027 itself does not necessarily mean that engine damage is occurring.

The cause of the code is what determines the risk.

A damaged connector is very different from low engine oil pressure or a failing timing-chain system.

Particular caution is warranted if the engine also has:

• Low oil pressure

• Timing-chain rattling

• Severe misfires

• Hard starting

• Significant power loss

• Multiple cam/crank correlation codes

• Unusual mechanical engine noise

In those circumstances, continuing to drive without determining the underlying cause may be unwise.

Is It Safe to Drive With P0027?

If the vehicle runs normally and only the Check Engine Light is illuminated, limited driving may be possible.

However, the fault should be diagnosed rather than ignored.

Avoid continued operation if there is severe power loss, persistent misfire, hard starting, loud timing noise, or an oil-pressure warning.

Those symptoms may indicate a deeper mechanical or lubrication problem.

Final Diagnostic Perspective

P0027 is best viewed as a failure of the Bank 1 exhaust valve-control system to achieve the expected performance or operating range.

The code does not identify the VVT solenoid as the only possible culprit.

A reliable diagnosis follows the complete control chain:

ECM command → wiring → exhaust VVT solenoid → oil flow → camshaft phaser → camshaft position feedback → mechanical timing

If the solenoid is commanded correctly but the camshaft does not follow the command, the next question should be why the camshaft cannot respond.

That could be a restricted oil passage, low oil pressure, a sticking phaser, incorrect mechanical timing, or inaccurate position feedback—not necessarily a failed solenoid.