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P3459 Cylinder 8 Deactivation/Intake Valve Control Circuit Low GuideMechanic.Com Modern internal combustion engines use sophisticated systems to enhance fuel efficiency, improve emissions, and increase performance.
One such innovation is cylinder deactivation technology, commonly found in V6 and V8 engines. While this feature offers clear advantages, it also adds complexity that can result in diagnostic trouble codes (DTCs) when components malfunction. One of these is P3459, which indicates a problem with the intake valve control circuit on cylinder 8.
In this article, we’ll explore everything you need to know about the P3459 code—what it means, what causes it, how to diagnose it, and how to fix it.
See Also: P3458 Cylinder 8 Deactivation/Intake Valve Control Circuit Performance
P3459 Cylinder 8 Deactivation/Intake Valve Control Circuit Low
What Is DTC P3459?
P3459 is a generic OBD-II powertrain code that indicates the intake valve control circuit for cylinder 8 is showing a low voltage condition or signal.
This circuit is part of the cylinder deactivation system, which allows the engine to shut down selected cylinders under low-load conditions, like highway cruising, to save fuel.
When the Powertrain Control Module (PCM) attempts to deactivate cylinder 8 but detects that the control circuit voltage is lower than expected, it stores code P3459. This could be due to wiring problems, a faulty solenoid, or electrical issues preventing the solenoid from engaging correctly.
Understanding Cylinder Deactivation
Cylinder deactivation works by turning off fuel delivery and disabling valve movement in selected cylinders, typically during light engine loads. In a V8 engine, the PCM can deactivate up to four cylinders by:
- Disabling fuel injectors
- Deactivating valve operation using special lifters and solenoids
- Controlling oil pressure to collapse hydraulic lifters
When the intake valve control system fails in cylinder 8, the deactivation process doesn’t occur as intended, which can affect performance and fuel economy.
P3459 Cylinder 8 Deactivation/Intake Valve Control Circuit Low
What Does “Circuit Low” Mean?
The phrase “circuit low” refers to the voltage level detected in the control circuit. In this case, the intake valve control solenoid for cylinder 8 is not receiving the expected amount of voltage. This could be because of:
- A grounded or shorted wire
- Corrosion or a loose connection
- A faulty solenoid that is drawing too much current or has failed internally
Low voltage means the PCM cannot properly control the solenoid, which disrupts the deactivation process.
Common Causes of P3459
Several issues can lead to a low voltage condition in the control circuit. The most common causes include:
Faulty Intake Valve Control Solenoid (Cylinder 8)
A failed solenoid may draw excess current or short internally, causing voltage to drop.
Damaged or Corroded Wiring/Connectors
Faulty wiring can cause resistance in the circuit or short to ground.
PCM Driver Circuit Failure
The internal transistor (driver) that controls the solenoid may be defective.
Oil Pressure Issues
Low or dirty oil can prevent proper operation of the hydraulic lifters and solenoids.
Poor Ground Connection
A weak ground can result in unstable or insufficient voltage to the solenoid.
Battery or Charging System Problems
Weak battery voltage or alternator failure can reduce system voltage across multiple circuits.
P3459 Cylinder 8 Deactivation/Intake Valve Control Circuit Low
Symptoms of the P3459 Code
The symptoms associated with code P3459 may vary in severity depending on whether cylinder 8 is stuck in an active or deactivated state. Common symptoms include:
Illuminated Check Engine Light (CEL)
The most immediate indication is the CEL appearing on the dashboard.
Reduced Fuel Economy
With cylinder deactivation disabled, the engine consumes more fuel.
Rough Idle or Engine Vibrations
If cylinder 8 is not operating as expected, engine smoothness is affected.
Engine Misfire
Cylinder 8 may misfire, especially under light throttle conditions.
Poor Acceleration or Hesitation
You may notice sluggish response when accelerating.
Ticking or Tapping Noise from the Engine
Faulty lifters or solenoids may cause audible valve train noise.
P3459 Cylinder 8 Deactivation/Intake Valve Control Circuit Low
Diagnosing P3459
Accurate diagnosis of P3459 involves both electrical and mechanical inspections. Below is a step-by-step guide:
1. Retrieve the Trouble Code
Use an OBD-II scanner to verify that P3459 is active. Look for related codes such as:
P3457 (Open Circuit)
P3458 (Circuit Performance)
Other P34xx-series codes
2. Inspect Wiring and Connectors
Check the wiring harness leading to the cylinder 8 intake valve control solenoid.
Look for broken wires, chafing, corrosion, or loose connectors.
Use contact cleaner and reconnect securely.
3. Test the Solenoid
Disconnect the solenoid and use a multimeter to measure resistance.
Normal range is typically between 10–20 ohms.
Infinite resistance or zero ohms may indicate an internal short or open.
You can also test solenoid activation using a scan tool with active test functionality (if available).
4. Measure Circuit Voltage
With the ignition on, test the control wire to verify voltage.
A low or no voltage reading confirms the low signal condition.
Trace the circuit back to the PCM to isolate the fault.
5. Inspect Engine Oil
Check oil level, cleanliness, and viscosity.
Dirty or old oil can clog oil passages and affect hydraulic lifters.
Replace with manufacturer-recommended oil if necessary.
6. Check PCM Operation
If no mechanical or wiring issues are found, the PCM driver circuit may be faulty and not supplying proper voltage to the solenoid.
P3459 Cylinder 8 Deactivation/Intake Valve Control Circuit Low
Repair Options for P3459
Once the issue has been correctly diagnosed, the following repairs may resolve the code:
Replace the Cylinder 8 Intake Valve Control Solenoid
This is often the root cause and the most effective repair.
Repair or Replace Wiring/Connectors
Any damaged or corroded wiring should be repaired or replaced.
Clean or Reseat Electrical Connectors
Poor contact can lead to voltage issues.
Perform Oil and Filter Change
Dirty or degraded oil can impair solenoid and lifter operation.
Replace PCM (if necessary)
In rare cases, the PCM itself may need to be repaired or replaced if it fails to deliver proper control signals.
Preventive Maintenance Tips
To avoid reoccurrence of code P3459 or similar valve control issues, follow these best practices:
Change Engine Oil Regularly
Use the correct oil grade and change at intervals recommended by the manufacturer.
Use OEM or Quality Aftermarket Parts
Especially when replacing solenoids or PCM components.
Inspect Electrical Connectors During Routine Maintenance
Check for corrosion and secure all connections.
Monitor Engine Performance
If you notice unusual engine vibrations or fuel economy loss, investigate early.
Conclusion
The P3459 trouble code indicates a low voltage condition in the intake valve control circuit for cylinder 8, which is crucial to the cylinder deactivation system. While this may not cause immediate engine failure, it compromises fuel efficiency, performance, and emissions.
Fortunately, diagnosing and repairing this issue is typically straightforward—especially when addressed early. Whether it’s a faulty solenoid, degraded engine oil, or a wiring issue, prompt action can restore your engine’s proper function and prevent long-term damage.
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