What Does P1326 Mean?
P1326 indicates that cylinder 2's knock control has reached its maximum retard limit. The ECM has retarded ignition timing on cylinder 2 to the maximum allowed value to suppress detonation, but knock is still being detected. This means the root cause of the detonation is too severe for the knock control strategy to compensate.
Common Causes
25%
Carbon buildup in cylinder 2 combustion chamber increasing compression ratio
25%
Incorrect or low-octane fuel
20%
Cylinder 2 fuel injector delivering lean mixture
15%
Excessive engine coolant temperature not properly cooling cylinder 2
15%
Faulty knock sensor providing erroneous high-knock readings for cylinder 2 zone
Diagnostic Steps
1
Verify the fuel octane rating being used meets the manufacturer's minimum requirement.
2
Check coolant temperature with live data — elevated temperatures exacerbate knock conditions.
3
Perform a fuel trim analysis for cylinder 2 — a lean condition promotes detonation.
4
Inspect cylinder 2 for excessive carbon buildup using a borescope through the spark plug hole.
5
Verify knock sensor signal integrity — rule out a false high-knock reading before assuming mechanical issues.
6
Consider running a fuel system cleaner or performing a top-engine clean to remove carbon deposits.
Estimated Repair Cost
$100 - $600
Parts + labor, varies by vehicle and location
P1326 indicates that cylinder 2's knock control has reached its maximum retard limit. The ECM has retarded ignition timing on cylinder 2 to the maximum allowed value to suppress detonation, but knock is still being detected. This means the root cause of the detonation is too severe for the knock con...
The most common cause of P1326 (Cyl. 2 Knock Control Limit Attained) is: Carbon buildup in cylinder 2 combustion chamber increasing compression ratio
Typical repair costs for P1326 range from $100 to $600, depending on the vehicle, location, and whether you do it yourself or go to a shop.
When knock control is at its limit, the engine is operating with maximum timing retard on that cylinder, significantly reducing power. Continued detonation despite retard can cause piston crown damage, ring land failure, or rod bearing damage.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P1326 to identify the root cause.
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Quick Info
Category
Powertrain
System
Engine Knock Control / Ignition Timing
Difficulty
Type
Manufacturer
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