P1325

What it means

On Volkswagen, P1325 means the knock control for cylinder 1 has reached its limit of adjustment. The engine control unit has retarded the ignition on that cylinder as far as it is allowed because it keeps detecting knock, and it cannot reduce the knock any further. It is a fault about combustion on cylinder 1, not a knock sensor circuit fault.

Symptoms

• Engine management light on
• Reduced power or flat performance, especially under load
• Pinking or knocking noise on acceleration
• Slightly higher fuel consumption
• Rough running or hesitation on cylinder 1

Possible causes

• Poor quality, wrong octane or contaminated fuellikely
• Worn, faulty or incorrect spark plug or ignition coil on cylinder 1likely
• Carbon build-up in the combustion chamber raising compression or creating hot spotspossible
• Knock sensor loose, wrongly torqued or giving a false signal, or wiring and connector damagepossible
• Mechanical engine noise picked up as knock, such as piston slap, a loose component or valve train noisepossible
• Lean mixture on cylinder 1 from an intake leak or faulty injectorpossible
• Engine overheating or a cooling system faultrare

How to diagnose

1. Read all stored and pending codes and the freeze frame data, noting load, engine speed and coolant temperature when the fault set
2. Ask about the fuel used recently and any recent refill, and check that it meets the specification for the engine
3. Inspect the knock sensor wiring and connector for damage, corrosion or chafing, and check the sensor is secure and torqued correctly
4. Check the spark plugs and coils, paying particular attention to cylinder 1, for wear, correct type and heat range
5. Check live data for ignition retard per cylinder, misfire counters and fuel trims to see whether cylinder 1 stands out
6. Check for intake air leaks and injector faults on cylinder 1, using smoke testing and fuel trim readings
7. Listen for abnormal mechanical noise and check the cooling system and coolant temperature
8. Inspect cylinder 1 with a borescope and check compression for carbon build-up or mechanical damage; the exact procedure depends on the engine

How to fix

• Drain and replace poor or wrong fuel with the correct grade, then clear the code and monitor
• Replace worn spark plugs with the correct type and renew a faulty ignition coil on cylinder 1
• Renew a faulty knock sensor or repair damaged wiring and connectors, and refit the sensor to the correct torque
• Repair intake leaks or replace a faulty injector causing a lean mixture
• Clean carbon deposits using a method approved for the engine, or repair the mechanical fault if one is found
• Repair any cooling system fault found

Can I keep driving?

This code for other makes

• P1325LexusIgniter Circuit Malfunction No 6
• P1325SubaruKnock Sensor Circuit Low Input

Nearby codes

• P1324VolkswagenKnock Sensor 4 Circuit High Input
• P1326VolkswagenCylinder 2 Knock Control Limit Attained