What is the P0084 Code?
The P0084 trouble code is a generic OBD-II (On-Board Diagnostics) code related to the powertrain. It indicates an electrical problem in the “B2” circuit of the exhaust valve control solenoid. This code applies to most vehicles (from 1996 onwards), although repair steps may vary from model to model.
Function and Symptoms of the P0084 Fault
On vehicles equipped with a Variable Valve Timing (VVT) system, the Engine Control Module (ECM/PCM) controls the camshaft position by regulating engine oil flow via a solenoid. This solenoid is activated by a Pulse Width Modulated (PWM) signal. If the ECM/PCM detects an out-of-specification or intermittent voltage in the circuit, it records the P0084 code and illuminates the Malfunction Indicator Lamp (MIL).
The designation “B2” (or Bank 2) refers to the side of the engine that does not contain cylinder number 1. Always consult the manufacturer’s documentation to identify it with certainty. The exhaust valve control solenoid is typically located on the exhaust manifold side of the cylinder head.
Common Symptoms
- Illuminated Malfunction Indicator Lamp (MIL)
- Poor acceleration and engine performance
- Reduced fuel economy
- Rough idle
- The vehicle may enter limp mode
Potential Causes of the P0084 Code
- Faulty or clogged VVT control solenoid
- Poor electrical connection, corroded terminals, or damaged wiring harness
- Short circuit to ground or power in the circuit
- Engine oil level or quality issue
- Engine Control Module (ECM/PCM) failure
Diagnostic Procedure for the P0084 Code
⚠️ Caution: These steps are generic. Refer to your vehicle’s repair manual for specific procedures and specification values.
1. Visual and Connection Inspection
Inspect the solenoid connector and wiring harness. Look for signs of corrosion, damage, loose wires, or burning. Disconnect and reconnect the connectors to ensure good contact.
2. VVT Control Solenoid Test
With the connector disconnected, use a multimeter (DVOM) in Ohms (Ω) mode to measure the resistance between the solenoid terminals. Compare the reading with the manufacturer’s specifications. An infinite resistance (open circuit) or zero resistance (short circuit) indicates a faulty solenoid.
3. Electrical Circuit Testing
- Continuity: Disconnect the connectors at the solenoid and the ECM. Check for continuity (resistance ~1 Ω or less) on each wire of the circuit. Excessive resistance indicates corrosion or a damaged wire.
- Short to Ground: With the PCM connector disconnected, check that no wire in the solenoid circuit has continuity to the chassis ground.
- Short to Power: With the engine off, check that no wire in the circuit shows voltage (test with the multimeter in Volts mode).
4. Control Signal and ECM Testing
Reconnect all connectors. Using an advanced scan tool, activate the solenoid and observe the commanded duty cycle. Using an oscilloscope or a multimeter capable of measuring duty cycle, probe the control wire at the solenoid to verify that the signal sent by the ECM matches the command. If the wiring and solenoid are functional but no signal is detected, the ECM/PCM may be faulty.
5. Additional Checks
Check the engine oil level and quality. Dirty oil or a low level can prevent the proper operation of the VVT system and generate trouble codes.
Conclusion and Call to Action
Diagnosing the P0084 code requires a methodical approach, starting with the simplest checks (connections, oil) before moving on to complex electrical tests. If you are not comfortable with these procedures, consult a professional mechanic for an accurate diagnosis. An incorrect diagnosis can lead to unnecessary replacement of expensive parts.
Need help diagnosing your vehicle? Use our online scan tool or consult our database to find wiring diagrams specific to your model.