What Does P2347 Mean?
Cylinder 12 Above Knock Threshold indicates the ECM detected persistent detonation on cylinder 12 exceeding the knock correction limit. Exclusive to V12 engines, this code means the last cylinder in the firing order is experiencing uncontrollable knock despite maximum ignition timing retard.
Common Causes
30%
Carbon accumulation in cylinder 12 combustion chamber
25%
Fuel injector 12 restriction or degraded performance
25%
Knock sensor or circuit fault for the bank monitoring cylinder 12
20%
Low-octane or contaminated fuel
Diagnostic Steps
1
Step 1: Check per-cylinder knock retard data. Compare cylinder 12 values against all other cylinders.
2
Step 2: Test fuel injector 12 flow rate and compare to specification and other injectors on the same bank.
3
Step 3: Compression test cylinder 12 and compare to other cylinders for evidence of elevated compression from carbon.
4
Step 4: Inspect the relevant knock sensor for proper mounting, resistance, and signal quality.
5
Step 5: Perform appropriate decarbonization if carbon buildup is confirmed as the root cause.
Estimated Repair Cost
$150 - $700
Parts + labor, varies by vehicle and location
Cylinder 12 Above Knock Threshold indicates the ECM detected persistent detonation on cylinder 12 exceeding the knock correction limit. Exclusive to V12 engines, this code means the last cylinder in the firing order is experiencing uncontrollable knock despite maximum ignition timing retard.
The most common cause of P2347 (Cylinder 12 Above Knock Threshold) is: Carbon accumulation in cylinder 12 combustion chamber
Typical repair costs for P2347 range from $150 to $700, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Knock on a V12 can lead to extremely expensive internal engine repairs. Reduce load immediately and schedule professional diagnosis.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P2347 to identify the root cause.
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Quick Info
Category
Powertrain
System
Ignition/Combustion System
Difficulty
Type
Generic (SAE)
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