P3425 code definition
When the powertrain control module (PCM) detects that the measured values it’s getting from the mass air flow (MAF) sensor, the manifold absolute pressure (MAP) sensor, and/or the throttle position (TP) sensor are out of range or somehow irregular when compared with the proper values for the cylinder 4 deactivation mode, it will store the P3425 code.
What the P3425 code means
When driving under normal conditions without a heavy load, the PCM for an eight-cylinder vehicle will improve the vehicle’s fuel efficiency by deactivating four of its cylinders, including cylinder 4 on the right engine bank, essentially allowing it to perform as a four-cylinder vehicle.
Through the use of specially designed valve lifters, the intake and exhaust valves of the deactivated cylinders will be prevented from opening. When a P3425 code is set, it indicates that the PCM is not receiving the proper values from the MAP, MAF, and TP sensors to enter four-cylinder mode and deactivate cylinder 4.
What causes the P3425 code?
The P3425 code may be saved due to a number of causes, including:
- Some restriction preventing the passage of oil.
- Oil pressure that’s below normal levels.
- A faulty or damaged cylinder deactivation solenoid.
- A problem with the mechanical condition of the engine.
- Poor electrical connection to the cylinder deactivation solenoid’s circuit.
- An open or shorted cylinder deactivation solenoid harness.
What are the symptoms of the P3425 code?
In most cases, the only symptom of a P3425 code (or any code involving the deactivation of a cylinder) will be the illumination of the Check Engine Light. In some instances, though, you may notice that the engine vibrates more than usual when attempting to go into four-cylinder mode.
How does a mechanic diagnose the P3425 code?
The first thing involved with diagnosing a P3425 code is using an OBD-II scanner to read the code from the PCM. After reading the code and ensuring that no other codes have been stored, the mechanic will inspect the vehicle. If any other deactivation codes or other related codes have been stored, these should be resolved before moving on. After these are addressed, the mechanic will ensure that the oil pressure is correct and that the engine has the proper amount of oil.
Then the mechanic will clear all existing codes and test-drive the vehicle to ensure that they have been properly addressed. If the P3425 code is stored again, they will continue taking diagnostic steps to find the problem that’s causing the code to store and resolve it.
Common mistakes when diagnosing the P3425 code
If the engine’s oil passageways are restricted in any way, it can cause the P3425 code to be stored, and the solution will be simply to clean out the passageways and ensure that there is proper oil pressure in the engine. If this is the case, replacing or repairing other parts will not help resolve the problem or clear the code.
How serious is the P3425 code?
While this problem may not be life-threatening to your engine, it can wreak havoc on your fuel economy, as your vehicle will not be able to effectively transition into four-cylinder mode when operating under light conditions. If left unresolved for long enough, it may also have lasting negative effects on your engine, as well.
What repairs can fix the P3425 code?
Some of the most common fixes for a P3425 code include:
- Clearing out restrictions in engine oil passageways.
- Adding more oil to the system and/or getting an oil change.
- Replacing a damaged cylinder deactivation solenoid.
- Repairing or replacing damaged or corroded wiring or connectors in the cylinder deactivation solenoid’s circuit.
- Ensuring that there are no shorts and that the circuit is not open at any point.
Additional comments for consideration regarding the P3425 code
Not only can it keep your vehicle from passing an OBD-II emissions test, but leaving a P3425 code and neglecting to resolve its underlying cause can create lasting damage for your vehicle.
Need help with a P3425 code?
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