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P3470 Cylinder 9 Exhaust Valve Control Circuit Performance GuideMechanic.Com Modern internal combustion engines rely on increasingly complex electronic control systems to balance performance, fuel economy, and emissions.
Among these is cylinder deactivation technology, which temporarily disables select cylinders under light load to improve fuel efficiency. This system requires precise control over valve timing and actuation.
When the Powertrain Control Module (PCM) or Engine Control Module (ECM) detects abnormal behavior in one of these systems, it triggers a Diagnostic Trouble Code (DTC). Code P3470 points to a performance-related problem with the exhaust valve control circuit for cylinder 9.
This article will explore what DTC P3470 means, how the system works, its symptoms, causes, diagnostic process, and how to resolve it.
See Also: P3469 Cylinder 9 Exhaust Valve Control Circuit/Open
P3470 Cylinder 9 Exhaust Valve Control Circuit Performance
What Is Code P3470?
The full definition is: P3470 – Cylinder 9 Exhaust Valve Control Circuit Performance
This code indicates that the ECM/PCM has detected irregular performance in the exhaust valve control system for cylinder 9.
Unlike an “open” or “high/low” voltage fault, a performance code suggests that while the electrical circuit may be complete, it is not functioning as expected. The actuator may be responding too slowly, inconsistently, or in an unexpected pattern that affects the valve operation.
In essence, this means the exhaust valve on cylinder 9 isn’t behaving correctly when the ECM attempts to activate or deactivate it—often during transitions between full-cylinder and partial-cylinder modes.
Understanding Cylinder Deactivation
Cylinder deactivation—known as Displacement on Demand (DoD) or Active Fuel Management (AFM) in General Motors (GM) vehicles—is a technology that turns off specific engine cylinders under light-load conditions (such as cruising) to conserve fuel.
Here’s how it works:
- The intake and exhaust valves for selected cylinders are deactivated.
- This is achieved using special hydraulic lifters, solenoids, and oil pressure.
- The ECM controls oil flow to these components, using sensors and actuators to command lifter collapse and reactivation.
The system requires:
- Clean oil at proper pressure.
- Functional control solenoids.
- Accurate sensor data.
- Complete and properly timed electrical signals.
A performance issue (P3470) occurs when the ECM notices a delay, inconsistency, or inefficiency in how the cylinder 9 exhaust valve operates, even if the circuit is technically complete.
P3470 Cylinder 9 Exhaust Valve Control Circuit Performance
Affected Vehicles
Code P3470 is commonly found in GM V8 engines using cylinder deactivation. Affected vehicle models may include:
- Chevrolet: Silverado, Suburban, Tahoe, Avalanche, Camaro
- GMC: Sierra, Yukon
- Cadillac: Escalade
- Buick and other GM brands using 5.3L, 6.0L, or 6.2L V8 engines with AFM
Other automakers may also implement similar systems, but the cylinder number and DTC specifics may differ.
Symptoms of P3470
When P3470 is stored, the driver may or may not experience noticeable changes. Typical symptoms include:
- Illuminated Check Engine Light (CEL)
- Reduced Engine Performance
- The ECM may disable cylinder deactivation entirely.
- Rough Idle or Hesitation
- Especially when switching between V4 and V8 modes.
- Increased Fuel Consumption
- Due to deactivation being turned off as a precaution.
- Misfire-like Symptoms
A weak or inconsistent exhaust valve may cause a misfire on cylinder 9.
Unusual Engine Noise
Ticking or tapping noises due to lifter or actuator delay.
P3470 Cylinder 9 Exhaust Valve Control Circuit Performance
Common Causes of P3470
Several problems can contribute to a performance issue in the exhaust valve control circuit:
1. Sticky or Failing Exhaust Valve Lifter
The hydraulic lifter may be slow to engage/disengage due to varnish buildup, oil contamination, or mechanical wear.
2. Low or Dirty Engine Oil
AFM solenoids and lifters rely on oil pressure. Contaminated or low oil can interfere with operation.
3. Weak or Clogged Solenoid
A partially functioning solenoid may activate the lifter inconsistently or with delay.
4. Electrical Problems
Wiring or connectors that intermittently lose contact can cause poor solenoid actuation, even without a complete circuit failure.
5. Oil Pressure Problems
Oil pressure regulators, faulty sensors, or sludge buildup may prevent proper hydraulic actuation.
6. Faulty ECM/PCM
In rare cases, the control module may misinterpret sensor data or send incorrect signals.
Diagnosing P3470
To accurately diagnose this code, follow a structured diagnostic process:
1. Check for Additional DTCs
Use a diagnostic scanner to check for other codes, particularly:
P3469 (Circuit/Open)
P3471 (Circuit Low)
P3472 (Circuit High)
These may provide context about whether the issue is electrical or mechanical.
2. Visual Inspection
Inspect wiring and connectors related to the exhaust valve solenoid for cylinder 9.
Look for pinched, frayed, or oil-soaked wires.
3. Check Engine Oil
Inspect oil condition and level.
Dirty or degraded oil can directly affect valve timing performance.
4. Test the Solenoid
Use a multimeter to check resistance.
Typical solenoid resistance is 5–15 ohms.
Perform actuation tests using a scan tool, if available.
5. Monitor Live Data
With a bi-directional scan tool, observe cylinder deactivation behavior.
Check if cylinder 9 is activating/deactivating at appropriate times.
6. Perform Oil Pressure Test
Ensure proper oil pressure, especially in the AFM circuit.
Low oil pressure can cause actuator delays.
P3470 Cylinder 9 Exhaust Valve Control Circuit Performance
How to Fix P3470
The proper fix depends on identifying the root cause. Common repairs include:
1. Replace the Cylinder 9 Exhaust Valve Solenoid
If performance testing shows a sluggish or inconsistent solenoid, replace it.
2. Change Engine Oil and Filter
Use manufacturer-recommended oil grade. If oil is dirty or broken down, it can cause timing issues.
3. Clean or Repair Wiring
Fix any damaged wires or corroded connectors to ensure strong, uninterrupted electrical flow.
4. Replace Faulty Lifter (Advanced Repair)
If the hydraulic lifter is failing mechanically, it may need to be replaced. This involves removing cylinder heads and is labor-intensive.
5. Update or Replace ECM/PCM
In rare situations, a faulty or outdated control module may require reprogramming or replacement.
Preventing P3470
You can prevent performance issues in the exhaust valve control circuit by following these best practices:
- Regular Oil Changes: Use the correct viscosity and high-quality oil to maintain hydraulic lifter function.
- Avoid Short Trips: Frequent short drives can prevent the oil from reaching operating temperature, leading to sludge buildup.
- Use Fuel and Oil Additives Sparingly: Only use additives approved by the manufacturer.
- Monitor Engine Performance: Address early signs of rough running or oil pressure fluctuations.
- Inspect Wiring Periodically: Especially in high-mileage vehicles or after engine work.
Conclusion
DTC P3470 – Cylinder 9 Exhaust Valve Control Circuit Performance indicates a problem where the exhaust valve for cylinder 9 is not operating as expected.
Though not as direct as an open or short circuit, this performance issue can affect engine efficiency, cause drivability problems, and disable the fuel-saving cylinder deactivation system.
By understanding the role of the AFM system and following a methodical diagnostic approach—including inspecting oil condition, electrical components, solenoids, and lifters—you can resolve this issue effectively.
If you’re not confident in your ability to perform these diagnostics, consult a professional technician with experience in cylinder deactivation systems. Catching and correcting the issue early can save you from more expensive repairs down the road.
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