This post contains affiliate links. This means I will make a commission at no extra cost to you should you click through and make a purchase [ “As an Amazon Associate, I earn from qualifying purchases.” ]. Read the full disclosure here.
P3448 Cylinder 6 Exhaust Valve Control Circuit High: Causes, Symptoms, and Repair Guide GuideMechanic.Com Modern engines are equipped with complex control systems that manage everything from fuel delivery to emissions.
One such system is cylinder deactivation, a fuel-saving technology that temporarily disables certain cylinders under light engine load.
When there is an issue with this system—specifically with the electrical control of the exhaust valve—a Diagnostic Trouble Code (DTC) such as P3448 may be triggered.
In this article, we will explore everything you need to know about the P3448 trouble code, including what it means, its symptoms, common causes, diagnostic steps, and possible repairs.
See Also: P3447 Cylinder 6 Exhaust Valve Control Circuit Low
P3448 Cylinder 6 Exhaust Valve Control Circuit High: Causes, Symptoms, and Repair Guide
What Is DTC P3448?
Code Definition: P3448 – Cylinder 6 Exhaust Valve Control Circuit High
This diagnostic trouble code indicates that the Powertrain Control Module (PCM) or Engine Control Module (ECM) has detected abnormally high voltage in the exhaust valve control circuit for cylinder 6.
This typically means that the ECM is receiving a voltage reading above the acceptable threshold, which can be due to wiring problems, a failing solenoid, or a faulty ECM.
The exhaust valve control system plays a vital role in cylinder deactivation systems like Active Fuel Management (AFM) or Displacement on Demand (DoD).
When the circuit malfunctions, the engine may lose its ability to deactivate or reactivate cylinder 6, leading to performance and fuel economy issues.
What Does the Exhaust Valve Control Circuit Do?
The exhaust valve control circuit is responsible for managing the operation of the exhaust valve lifter solenoid in cylinder 6. Here’s how it works:
- The ECM sends electrical signals to a solenoid (part of the Valve Lifter Oil Manifold – VLOM).
- The solenoid controls pressurized engine oil that collapses the lifters on the exhaust valve.
- When lifters are collapsed, the exhaust valve no longer opens, effectively deactivating the cylinder.
- When reactivation is needed, the solenoid stops sending oil pressure, and the valve resumes normal function.
- If the ECM detects voltage higher than expected in the control circuit, it will set P3448 and illuminate the Check Engine Light (CEL).
P3448 Cylinder 6 Exhaust Valve Control Circuit High
Common Symptoms of P3448
The presence of this code may or may not be immediately noticeable to the driver, but typical symptoms include:
- Check Engine Light is on
- Reduced fuel economy
- Rough idle
- Hesitation on acceleration
- Loss of power
- Engine misfires (sometimes)
- Increased tailpipe emissions
- Cylinder deactivation not working properly
Some drivers may not notice performance issues right away, especially if the failure is intermittent. However, over time, continued driving with this fault may cause damage to engine components or reduce efficiency.
What Causes Code P3448?
The “high” designation in this code usually points to an abnormal voltage spike or excess resistance in the electrical circuit. Common causes include:
1. Faulty Exhaust Valve Control Solenoid
An internal fault in the solenoid can cause voltage to exceed normal operating parameters.
2. Open Circuit or High Resistance in Wiring
A break in the wiring or excessive resistance due to corrosion can cause the voltage to read higher than expected at the ECM.
3. Short to Power
If a wire in the circuit comes into contact with a power source, it can cause higher-than-normal voltage levels.
4. Damaged or Corroded Connectors
Connectors exposed to moisture, oil, or engine heat may corrode or loosen, increasing electrical resistance and leading to abnormal voltages.
5. Malfunctioning ECM
While rare, a fault in the ECM can cause improper signal processing or voltage regulation.
Diagnosing P3448 – Step-by-Step
Step 1: Scan for DTCs
Use a high-quality OBD-II scanner to confirm the presence of P3448 and check for any other related codes (like P3445–P3447). Multiple codes may indicate a system-wide problem such as oil contamination or VLOM failure.
Step 2: Inspect the Wiring and Connectors
Look for chafed, frayed, or pinched wires near the cylinder 6 exhaust valve solenoid.
Check connectors for bent pins, corrosion, or oil contamination.
Step 3: Measure Voltage at the Solenoid
Disconnect the exhaust valve solenoid for cylinder 6.
With the ignition on, use a digital multimeter to measure voltage at the connector.
A normal reading should be around 12V (or as specified by the manufacturer). A significantly higher voltage may confirm a short to power.
Step 4: Check Solenoid Resistance
Test the solenoid’s resistance across its terminals.
Compare the result to manufacturer specifications (typically 6–10 ohms).
A reading significantly out of range indicates a faulty solenoid.
Step 5: Continuity and Ground Tests
Check for continuity between the ECM and the solenoid to ensure the wire is not open.
Verify that the ground circuit has minimal resistance.
Step 6: ECM Output Test
If all wiring and components check out, the ECM may need to be tested using an advanced scan tool that can command the solenoid on/off.
P3448 Cylinder 6 Exhaust Valve Control Circuit High
How to Fix Code P3448
Once the cause has been identified, one or more of the following repairs will resolve the issue:
Replace the Exhaust Valve Control Solenoid (Cylinder 6)
If testing confirms the solenoid is faulty or out of spec, replace it. These are often part of the VLOM and may require removal of the intake manifold.
Repair or Replace Damaged Wiring
Fix any frayed, broken, or shorted wiring. Be sure to use heat-shrink tubing and proper connectors to prevent future issues.
Clean or Replace Connectors
Corroded or loose connectors should be cleaned or replaced. Use dielectric grease to protect the new connection from moisture and corrosion.
Replace the ECM (If Necessary)
Only after all other possibilities are ruled out, the ECM may be the source of the fault and require replacement or reprogramming.
P3448 Cylinder 6 Exhaust Valve Control Circuit High
Is It Safe to Drive with Code P3448?
While the engine will likely still operate with code P3448, driving with this code for an extended period is not recommended. Risks include:
- Decreased fuel efficiency
- Improper engine operation
- Increased emissions
- Potential catalytic converter damage
- Worsening mechanical wear over time
It’s best to diagnose and repair the issue as soon as possible to avoid secondary damage and maintain performance.
Preventing P3448
Routine maintenance and inspections can help you avoid this and similar trouble codes:
- Use High-Quality Engine Oil – Dirty or incorrect oil can affect hydraulic components in the VLOM.
- Follow Recommended Oil Change Intervals – Oil sludge can clog solenoids and increase electrical resistance.
- Check Wiring During Service Intervals – Especially near high-heat areas.
- Respond Promptly to Engine Warning Lights – Ignoring codes can turn minor issues into major repairs.
Conclusion
P3448 – Cylinder 6 Exhaust Valve Control Circuit High is a fault that points to electrical problems in the system responsible for controlling the exhaust valve during cylinder deactivation.
While this may not immediately affect drivability, it can lead to poor engine efficiency, performance issues, and even damage over time.
By understanding the causes, symptoms, and proper diagnostic procedures, you or your mechanic can take prompt action to fix the problem. Whether the fault lies in the solenoid, wiring, or ECM, resolving P3448 ensures your engine runs smoothly, efficiently, and reliably.
- P3455 Cylinder 7 Exhaust Valve Control Circuit Low - June 4, 2025
- P3454 Cylinder 7 Exhaust Valve Control Circuit Performance - June 4, 2025
- Cylinder 7 Exhaust Valve Control Circuit/Open - June 4, 2025