What is the P0084 Code?
P0084 is a powertrain-related OBD-II (On-Board Diagnostics) generic diagnostic trouble code. It indicates an electrical issue in the “B2” circuit of the exhaust valve control solenoid. This code applies to most vehicles (manufactured after 1996), but repair procedures may vary by model.
Function and Symptoms of the P0084 Code
In vehicles equipped with a Variable Valve Timing (VVT) system, the Engine Control Module (ECM/PCM) regulates engine oil flow through the solenoid to control camshaft position. This solenoid operates via a Pulse Width Modulation (PWM) signal. When the ECM/PCM detects voltage outside the specified range or intermittent voltage in the circuit, it records the P0084 code and illuminates the Malfunction Indicator Lamp (MIL).
The designation “B2” (Bank 2) refers to the engine side that does not include cylinder number one. Always refer to the manufacturer’s documentation for accurate identification. The exhaust valve control solenoid is typically located on the exhaust manifold side of the cylinder head.
Common Symptoms
- Illuminated Engine Warning Light (MIL)
- Poor acceleration and reduced engine performance
- Decreased fuel efficiency
- Irregular idling
- Vehicle may enter limp mode (reduced performance mode)
Potential Causes of the P0084 Code
- Faulty or contaminated VVT control solenoid
- Poor electrical connections, corroded terminals, or damaged wiring
- Short to ground or short to power in the circuit
- Engine oil level or quality issues
- Faulty Engine Control Module (ECM/PCM)
Diagnostic Procedure for the P0084 Code
⚠️ Note: These procedures are general guidelines. Always consult your vehicle’s repair manual for precise steps and specification values.
1. Visual Inspection and Connection Check
Inspect the solenoid connector and wiring. Look for signs of corrosion, damage, loose connections, or burn marks. Disconnect and reconnect the connector to ensure proper contact.
2. Testing the VVT Control Solenoid
With the connector disconnected, set a multimeter (DVOM) to ohms mode (Ω) and measure the resistance between the solenoid terminals. Compare the reading with the manufacturer’s specifications. Infinite resistance (open circuit) or zero resistance (short circuit) indicates a faulty solenoid.
3. Testing the Electrical Circuit
- Continuity Check: Disconnect the solenoid and ECM connectors. Check for continuity (resistance ~1Ω or less) in each wire of the circuit. Excessive resistance indicates corrosion or wiring damage.
- Short to Ground: With the PCM connector disconnected, verify that no wire in the solenoid circuit has continuity with the chassis ground.
- Short to Power: With the engine off, ensure no voltage is present in any wire of the circuit (test with a multimeter in voltage mode).
4. Testing Control Signal and ECM
Reconnect all connectors. Use an advanced scan tool to activate the solenoid and observe the commanded duty cycle. Probe the control wire on the solenoid side using an oscilloscope or a multimeter capable of measuring duty cycle to confirm the signal from the ECM matches the command. If no signal is detected despite functional wiring and solenoid, the ECM/PCM may be faulty.
5. Additional Checks
Check the engine oil level and quality. Dirty oil or low levels can hinder proper VVT system operation and generate fault codes.
Conclusion and Call to Action
Diagnosing the P0084 code requires a systematic approach—start with the simplest checks (connections, oil) before tackling complex electrical tests. If you are unfamiliar with these procedures, consult a professional mechanic for accurate diagnosis. Incorrect diagnosis may lead to unnecessary replacement of expensive components.
Need help with vehicle diagnostics? Use online scan tools or refer to databases to find wiring diagrams specific to your model.