The OBD-II code P0085 indicates a problem in the control circuit of the exhaust valve solenoid (VVT) for engine bank 2. This electrical fault, detected by the engine control module (ECM), disrupts variable valve timing and affects performance. Discover the causes, symptoms, and our comprehensive diagnostic guide.
Meaning of Code P0085 and VVT System Operation
The engine control module (ECM) continuously monitors the position of the exhaust camshaft via a VVT solenoid. This acts as a hydraulic valve, using pressurized engine oil to vary the timing angle. It is controlled by a PWM signal (Pulse Width Modulation) sent by the ECM.
- Code Trigger: The ECM detects an abnormally low voltage in the control circuit of the VVT solenoid for bank 2 (exhaust side).
- Related Codes: P0084 (Intake bank 2), P0086 (Exhaust bank 1), P0029 (Position fault).
Symptoms of Code P0085
- 🔴 Check Engine Light On (MIL)
- 🐌 Poor Acceleration and stumbling at low RPM
- ⛽ Increased Fuel Consumption
- 🚗 Unstable Idle or stalling
- 🔊 Clicking Noises from the rocker cover (in severe cases)
Possible Causes of Code P0085
| Cause | Explanation |
|---|---|
| Electrical Problem (Wiring) | Short to ground, chafed wires or damaged insulation, oxidized or loose connector. |
| Faulty VVT Solenoid | Internal coil shorted or resistance out of specifications (6-12 Ω). |
| ECM Signal Problem | Internal control module failure (rare). |
| Mechanical or Hydraulic Problem | Old or poor-quality engine oil, low oil level, insufficient oil pressure, faulty camshaft position sensor (CMP). |
Diagnosing Code P0085: Step-by-Step Guide
Step 1: Preparation and Tools
- Required Tools:
- Advanced OBD2 scanner (for reading live data, e.g., Autel, Launch).
- Digital multimeter (DVOM) or oscilloscope.
- Technical documentation (wiring diagram, reference values).
Step 2: Methodical Visual Inspection
- Turn the ignition OFF and disconnect the battery.
- Locate the VVT solenoid for bank 2 (exhaust side).
- Inspect the wiring harness and connector thoroughly: look for signs of burning, corrosion, exposed wires, or poor contacts.
Step 3: Electrical Tests (Multimeter)
- Power Supply Voltage Test:
- Disconnect the solenoid connector.
- Turn the ignition ON. Measure the voltage between the supply pin (+) and ground (-). Expected: ~12V. If 0V, check fuses and relays.
- Solenoid Resistance Test:
- Measure the resistance (Ω) between the two terminals of the solenoid.
- Normal value: 6-12 Ω. If < 5Ω: short circuit. If > 15Ω: open circuit. Replace the solenoid if out of specification.
Step 4: Control Signal Analysis (Oscilloscope)
- Reconnect the solenoid and start the engine.
- Using an oscilloscope, probe the solenoid’s control wire (signal).
- Check for the presence and shape of the PWM signal. Compare the duty cycle (typically between 20% and 80%) with manufacturer data.
Step 5: Checking Mechanical Aspects
- Check the engine oil level and quality. Dirty oil or a low level can prevent the solenoid from functioning correctly.
- If everything seems good electrically, check the oil pressure and the condition of the cam sensor.
Repair and Estimated Costs
| Identified Problem | Repair Solution | Estimated Cost (Parts + Labor) |
|---|---|---|
| Damaged Wiring Harness | Repair or replace the wiring harness | €50 – €200 |
| Faulty VVT Solenoid | Replace the faulty solenoid | €100 – €350 |
| Engine Oil Problem | Oil drain and refill with quality oil | €80 – €150 |
| Faulty ECM | ECU reprogramming or replacement | €500 – €1500 |
FAQ – Frequently Asked Questions about P0085
Q: Can I drive my car with a P0085 code?
A: It is strongly discouraged to drive for a long time. Performance is reduced, fuel consumption is higher, and you risk damaging the catalytic converter.
Q: Can a simple oil change clear the P0085 code?
A: Sometimes, yes. If the cause is degraded oil or a low level, putting in new oil can solve the problem. Then clear the code with a scanner to see if it returns.
Q: Does replacing the VVT solenoid require reprogramming?
A: Generally, no. But on some models, an adaptation procedure via the diagnostic tool may be necessary to calibrate the system.
Conclusion and Call to Action
The P0085 code is often the symptom of a simple electrical problem (solenoid, wiring) but can also reveal a maintenance issue (oil). Accurate diagnosis with the right tools is key to avoiding costly repairs.
Don’t feel comfortable performing these checks yourself?
⚠️ Entrust the diagnosis to a professional. Use our network of partner garages to get an accurate quote and guaranteed repair. Find an expert near you.