P03C4
Cylinder 5 Pressure Variation Low
Generic OBD-II
Common symptoms
What you'll notice
- Check and replace the spark plugs in cylinder 5
- Inspect and clean the fuel injectors for cylinder 5
- Test and replace the ignition coil for cylinder 5
- Perform compression test on cylinder 5
Common causes
Most likely first
- Faulty spark plug or ignition coil in cylinder 5
- Clogged fuel injector in cylinder 5
- Low compression in cylinder 5
- Vacuum leak in cylinder 5
How to diagnose & fix
Work through it in order
- Rough idle or misfire
- Poor acceleration or reduced power
- Engine hesitation or stumbling
- Increased fuel consumption
- Engine running hot
Read & clear P03C4 yourself
Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.