What is the P0028 code?
The error code P0028 indicates a malfunction in the Variable Valve Timing (VVT) system on Bank 2 (the side opposite cylinder number 1). The ECM/PCM (Engine Control Module) detects that the actual position of the intake camshaft does not match the target position when it commands the VVT solenoid. This generic OBD-II code applies to many brands such as Toyota, Ford, Volkswagen, Honda, Hyundai, Kia, and others.
Symptoms of the P0028 code
- Check Engine Light (MIL) illuminated on the dashboard.
- Noticeable power loss during acceleration.
- Unstable idle or abnormal vibrations.
- Increased fuel consumption.
- Sometimes, a metallic knocking sound coming from the engine.
Possible causes of the P0028 fault
| Category | Details |
|---|---|
| Engine oil problems | Low level, contaminated oil, incorrect viscosity, or clogged circuit (clogged filter). |
| Mechanical failures | Stuck or faulty VVT solenoid, worn camshaft actuator (or eccentric), loose timing chain, or faulty tensioner. |
| Electrical problems | Damaged wiring, oxidized or loose connector, poor PWM control signal sent by the ECM. |
Diagnosis and solutions to fix the P0028 code
1. Engine oil check
- Level and quality: Check the level with the dipstick. Top up if necessary with the recommended viscosity oil (e.g., 5W-30). Replace the oil and filter if it is black, contaminated with soot, or metal particles.
2. Inspection and testing of the VVT solenoid (Bank 2)
- Location: Usually on the intake manifold side of the cylinder head (Bank 2). Consult the repair manual specific to your vehicle.
- Electrical test:
- Measure the resistance across the solenoid terminals with a multimeter. A value outside the 5–20 Ω range indicates a faulty solenoid.
- Check the PWM control signal with an oscilloscope. An irregular or missing square wave signal points to a wiring or ECM problem.
- Cleaning: Remove and clean the solenoid with a specific degreaser to remove carbon deposits that could block it.
3. Actuator and oil pressure check
- Oil pressure: Use a pressure gauge. Pressure below 2 bars at idle may prevent proper VVT system operation.
- Mechanical condition of the actuator: Check the camshaft actuator for internal oil leaks, broken springs, or clogged channels.
4. Timing system examination
- Chain tension: Check the automatic tensioner and guides. Replace them if worn.
- Timing: Ensure the timing marks on the camshafts and crankshaft are perfectly aligned according to the manufacturer’s specifications.
5. Advanced ECM/PCM diagnosis
- Control signal: With an advanced diagnostic tool (e.g., Autel MaxiCOM or Launch X-431), check the consistency of the PWM signal sent by the ECM based on engine RPM.
- Related codes: Look for the presence of codes related to oil pressure (P0081, P0082, P0083) and prioritize their resolution.
Average repair costs for the P0028 code
| Component | Part price (€) | Labor (€) |
|---|---|---|
| VVT Solenoid | 80 – 150 | 50 – 100 |
| Camshaft Actuator | 200 – 400 | 200 – 400 |
| Timing chain replacement (full kit) | 300 – 600 | 500 – 900 |
| ECM electronic diagnosis | – | 100 – 200 |
Best practices and tips
- Always use an advanced OBD2 diagnostic tool to clear the code and confirm that the repair was effective.
- Strictly follow the manufacturer’s Technical Service Bulletins (TSB) (e.g., Toyota TSB-EG-0032) to avoid common mistakes.
- Use high-quality engine oil and adhere to oil change intervals to prevent system clogging.
FAQ – Frequently Asked Questions about P0028
Q: Can I continue driving my car with a P0028 code?
A: It is not recommended to drive for long. The performance loss and increased consumption can damage the catalytic converter, a very expensive part.
Q: Why does the P0028 code return after changing the VVT solenoid?
A: The root cause is not resolved. Check the oil pressure, the condition of the actuator, or a timing system issue. A clogged oil circuit is also a common cause.
Q: Is the P0028 code serious?
A: Yes, it should not be ignored. Prolonged operation can lead to more significant and costly engine damage.
Conclusion and call to action
The P0028 code is a serious problem that requires a methodical investigation, starting with the simplest checks (oil, solenoid). 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? Share your error codes in the comments below!