OBD-II code · Powertrain (generic, extended)
P2340 Cylinder 5 Above Knock Threshold
The knock-sensor evaluation reports cylinder 5 above the knock threshold over a sustained window. The ECU retards ignition for that cylinder; persistent knock indicates poor fuel quality, carbon deposits or cooling issues.
Is it safe to drive with P2340?
Usually safe to drive in the short term. Get it diagnosed when convenient, sooner if the car drives differently.
Common causes
- Most likelyLow octane or contaminated fuel
- PossibleCarbon deposits raise compression locally
- Less likelyLocal cooling issue at cylinder 5
Repair at a glance
- Difficulty
- Medium
- DIY friendly
- Often, with basic tools
- Typical labour
- 0.5–4 h
- Emissions test
- Likely to fail
- After the fix
- A drive cycle is needed before the light stays off
- Parts involved
- Knock Sensor, Cylinder 5
Related codes
- P2336Cylinder 1 Above Knock Threshold
- P2337Cylinder 2 Above Knock Threshold
- P2338Cylinder 3 Above Knock Threshold
- P2339Cylinder 4 Above Knock Threshold
- P2341Cylinder 6 Above Knock Threshold
- P2342Cylinder 7 Above Knock Threshold
- P2343Cylinder 8 Above Knock Threshold
- P233DFuel Pressure Regulator B Solenoid Supply Voltage Control Circuit Open
- P233EFuel Pressure Regulator B Solenoid Supply Voltage Control Circuit Low
- P233FFuel Pressure Regulator B Solenoid Supply Voltage Control Circuit High
Code data: OBDex open dataset (CC0). Labour times are typical ranges, not a quote.