Ignition and pre-heatingGeneric OBD-II codeUrgency: Garage soon
Code P0325: knock sensor 1 circuit (bank 1)
P0325 means: knock sensor 1 circuit (bank 1 or single sensor): malfunction.[1][2][3] The ECU has detected a fault in the circuit of the knock (detonation) sensor on bank 1 (the side of the engine where cylinder 1 is) or in the only sensor, if the engine has just one. According to TroubleCodes.net, the sensor uses a piezoelectric crystal that generates a voltage when it detects knock, and the ECU uses it to adjust the ignition and protect the engine. Autodoc Club says it is mounted on the engine block or on the intake manifold.[1][3][4]
What code P0325 means
The ECU has detected a fault in the circuit of the knock (detonation) sensor on bank 1 (the side of the engine where cylinder 1 is) or in the only sensor, if the engine has just one. According to TroubleCodes.net, the sensor uses a piezoelectric crystal that generates a voltage when it detects knock, and the ECU uses it to adjust the ignition and protect the engine. Autodoc Club says it is mounted on the engine block or on the intake manifold.[1][3][4]
Without the sensor's signal, the ECU cannot retard the ignition to prevent knock. Carista explains that for this reason it adopts a more conservative ignition, with less power, especially uphill or on lower-octane petrol, and with somewhat higher consumption.[5]
P0325 is the code for the circuit itself. For the same sensor, P0326 indicates a range or performance fault, P0327 a low input and P0328 a high input. In Saab's workshop manual for a 2.0 petrol, P0325 is set with the signal circuit open, P0327 with the circuit shorted to earth and P0328 with the circuit shorted to voltage, in all three cases for more than 8 seconds.[4][6][7][8]
It is a generic OBD-II code (it starts with P0), so it means the same on any make; what changes from one engine to another is the most likely cause.[9]
Original definition (SAE J2012): Knock Sensor 1 Circuit (Bank 1 or Single Sensor)[1][2][3]
Codes from the same family
They indicate the same problem in a specific cylinder, bank or sensor. Causes, symptoms and diagnosis are those on this page.
Causes of P0325 and its family
From most to least likely, according to the sources.
- 1Faulty knock sensor. Carista considers it the most common cause and MechanicBase, TroubleCodes.net, Autodoc Club and Saab also cite it.[1][2][3][5][6]
- 2Poor wiring or connectors on the sensor: broken, worn, shorted or open wires, corroded connectors or failed connections.[1][2][3][5][6]
- 3Sensor loose, badly tightened or overtightened, or badly fitted or physically damaged.[5][6]
- 4ECU fault (uncommon).[2][3][6]
- 5A fault in the exhaust gas recirculation (EGR) system, which only Autodoc Club mentions.[1]
Symptoms
- Engine warning light on. TroubleCodes.net notes that in many cases it is the only symptom.[1][2][3][5]Engine warning light: faults that cause it
- Loss of power and reduced performance, especially on hills.[1][3][5]Less power: faults that cause it
- Slow response when accelerating or hesitation.[2][3]Jerking: faults that cause it
- Increased fuel consumption.[2][5]Uses more fuel: faults that cause it
- Knocking or pinking noise from the engine, especially when accelerating and going uphill.[1][2][3]
How to diagnose P0325
In order: from the most likely and cheapest to check to the most expensive.
- 1Read all the codes with a diagnostic tool and see whether, alongside P0325, other codes for the sensor (P0326, P0327, P0328) or for a second sensor (P0330, P0332, P0333) appear.[2][3][6]
- 2Visually inspect the sensor, its wiring and its connectors: broken or chafed wires, corrosion, loose connections.[1][2][3][6]
- 3Check that the sensor is properly tightened, to the torque the manufacturer specifies: Carista cites a loose or badly tightened bolt as a cause, and Saab asks you to verify the tightness and warns that it can also cause problems if overtightened.[5][6]
- 4Look at the sensor's signal in live data: MechanicBase measures it as voltage, Carista advises watching it during a road test and Saab gives, for its 2.0, between 1 and 4 V at the ECU connector.[2][5][6]
- 5Test the sensor with a multimeter: TroubleCodes.net suggests measuring its output and Carista cites about 90-100 kΩ of resistance as a typical value. It depends on the sensor, so use the manufacturer's value.[3][5]
- 6Check the continuity of the wiring between the sensor and the ECU. On engines with two sensors, Saab suggests swapping the connectors of the two to see whether the fault stays with the circuit or goes with the sensor.[3][6]
- 7Replace the sensor if the wiring is fine and tighten it to the specified torque. Leave the ECU until last.[2][3][5]
Can I keep driving with P0325?
Garage soon
The sources do not agree on the severity. Autodoc Club says driving with this code is not considered especially serious or dangerous, but that it must be fixed before it causes more serious faults; MechanicBase classes it as low severity, with the car still driveable, and Carista as medium severity. Autodoc Club, however, in the pages for the sister codes P0326, P0327 and P0328, recommends repairing them quickly and warns that uncontrolled detonation can damage the engine. It is best not to put the repair off.[1][2][4][5][7][8]
Documented faults related to P0325
Known faults of specific engines and cars, with their repair cost, the affected years and their sources.
Engine sensors: the most serious faults by engine and car
- High severityFrequency: Occasional2.0 DTI and 2.2 DTIVP44 injection pump and air mass meter failureGerman Wikipedia documents recurring failures of the Bosch VP44 injection pump and the air mass meter in the early years of this engine. An owner testimony for this engine describes the pump being replaced at 192,500 km, at a cost the owner calls «prohibitive».
- Medium severityFrequency: Common2.0 TDIClogged particulate filter or faulty pressure sensorThe 2.0 TDI's particulate filter clogs if the car mostly makes short journeys, because it never gets to regenerate; sometimes the fault is just the differential pressure sensor. Cleaning it costs around €200 and replacing it, €800 to €3,000.Repair (garage): €800–€3,000
- Medium severityFrequency: Common1.4 and 1.6 8vCrankshaft position sensor failure (TDC sensor)The crankshaft position sensor (capteur PMH, or TDC sensor) appears repeatedly in the reliability sources for the Clio II, the Kangoo I and the Dacia Logan I with this engine, with hard cold starting or stalling as the main symptoms. It is a cheap part, but the failure can leave you stranded.
- Medium severityFrequency: Common1.4 and 1.6 16vCrankshaft position sensor failureThe crankshaft position sensor (capteur PMH) appears repeatedly in the reliability sources for almost every generation with this engine, with hard cold starting, stalling or the car cutting out unexpectedly. It is a cheap part, but the failure can leave you stranded.
Wiring, connectors and short circuits: the most serious faults by engine and car
- Critical severityFrequency: OccasionalBMW N62 / N63Additional turbo coolant pump with a risk of short circuit and fireIn 2011 BMW recalled 5, 6 and 7 Series, X5 and X6 models built between 2007 and 2011 because of the additional turbo coolant pump: moisture, a short circuit and, in extreme cases, a fire. In 2012 there was another campaign for a crack in the pump, with a more robust version.
- High severityFrequency: Occasional1.3 TCeBlown fuel pump fuseOn the Renault Captur II and Clio V with the 1.3 TCe engine, a 20-amp fuse can blow and leave the car without an engine. According to L'argus, in April 2021 this fault still had no factory fix; the official service centre's diagnosis includes checking, and sometimes replacing, the catalytic converter.
- High severityFrequency: OccasionalM264/M254Poorly tightened 48 V earth wiring in the mild-hybrid system (fire risk)Mercedes-Benz has issued several recalls (2022-2025) because the 12 V and 48 V earth connections of some cars with a 48 V system may be poorly tightened: resistance rises, the connection heats up and a fire cannot be ruled out. The official workshop checks them and repairs them if necessary in an hour or more.
- High severityFrequency: Occasional1.9 TDIUnit injector tappet wear and injector wiring damageOn the unit injector system, the tappets that operate the injectors can wear if the oil is not changed on time, and the injector wiring can be damaged by contact with oil, causing misfires or loss of power.
- Critical severityFrequency: CommonRover 75Seat SRS connector fault with airbag and seatbelt warning light onAuto Express warns that the Rover 75's seat SRS connector can cause the airbags to fail, and dealers were fixing it with revised connectors. The Dutch APK inspection puts the airbag or seatbelt fault warning among the most frequent defects across almost all series.
- Critical severityFrequency: OccasionalAlfa Romeo GiuliettaShort circuit from badly routed wiring that can prevent gear shifting (KBA campaign, 2010-2015)Yes: according to Germany's KBA, on Alfa Romeo Giulietta cars built between 2010 and 2015 inadequate cable routing could cause a short circuit and, as a result, gear-shift failure.
Frequently asked questions
Can I drive with code P0325?
The sources do not entirely agree. Autodoc Club says it is not considered especially serious or dangerous, but that it must be fixed before it causes more serious faults; MechanicBase classes it as low severity and says the car remains driveable. Autodoc Club does warn, though, that uncontrolled detonation that the sensor does not detect can damage the engine, so it is best to repair it soon.[1][2][4][7][8]
What does the knock sensor do?
It detects the vibrations of abnormal combustion (knock or detonation) and alerts the ECU, which retards the ignition to protect the engine. According to TroubleCodes.net, it uses a piezoelectric crystal; according to Autodoc Club, it is mounted on the engine block or on the intake manifold.[1][3]
What is the difference between P0325, P0326, P0327 and P0328?
All four refer to the same bank 1 knock sensor (or the only sensor). P0325 indicates a circuit fault; P0326, a range or performance fault; P0327, a low input, and P0328, a high input. In Saab's workshop documentation, P0327 corresponds to a circuit shorted to earth and P0328 to a circuit shorted to voltage.[4][6][7][8]
Does the knock sensor have to be tightened to a specific torque?
Yes. Carista lists a loose or badly tightened bolt among the causes and advises tightening it to the manufacturer's torque after replacing the sensor; Saab's documentation asks you to verify the tightness and cites loose or overtightened sensors among the causes.[5][6]
Does P0325 mean the same on all makes?
Yes. Codes starting with P0 are generic OBD-II codes and have the same definition for all manufacturers.[9]
Will I pass the MOT with code P0325?
If the code has switched on the engine warning light, no: with that light on, the inspection records a serious defect, and on Euro 5 and Euro 6 cars the ITV (Spain's roadworthiness inspection, similar to the MOT) also reads the OBD diagnostic system. Repair the fault before you go; clearing the code just before the inspection does not help either, because it counts as a serious defect.[11]
Not sure what is wrong with your car? Describe what you notice in the symptom diagnosis or see all fault codes.
Sources
Every fact on this page links to its source. If you find an error, let us know.
- Código OBD2 P0325: causas, síntomas y cómo corregirloAutodoc Club · Technical documentation · consulted 4 October 2026 · in Spanish
- P0325 Code – Meaning, Causes & How to fix itMechanic Base · Technical documentation · consulted 4 October 2026
- P0325 – Knock sensor (KS) 1, bank 1 -circuit malfunctionTroubleCodes.net (BAT Auto) · Technical documentation · consulted 4 October 2026
- Código OBD2 P0326: causas, síntomas y cómo corregirloAutodoc Club · Technical documentation · consulted 4 October 2026 · in Spanish
- P0325: OBD-II code P0325 means the PCM has detected a fault in the bank 1 knock sensor circuitCarista · Technical documentation · consulted 4 October 2026
- DTC P0325, P0327, P0328, P0330, P0332, or P0333, Saab 9-5 (9650) 2011, motor de gasolina de 2.0 l (copia del manual de taller de Saab)Saab WIS Online (Saab Workshop Information System) · Technical documentation · consulted 4 October 2026
- Código OBD2 P0327: causas, síntomas y cómo corregirloAutodoc Club · Technical documentation · consulted 4 October 2026 · in Spanish
- Código OBD2 P0328: causas, síntomas y cómo corregirloAutodoc Club · Technical documentation · consulted 4 October 2026 · in Spanish
- On-board diagnosticsWikipedia · Other source · consulted 4 October 2026
- P0326 – Knock Sensor (KS) 1, bank 1 -range/performance problemTroubleCodes.net (BAT Auto) · Technical documentation · consulted 4 October 2026
- Desmontando mitos: ¿puede pasar mi coche la ITV con el testigo de «avería motor» encendido?Diariomotor · Motoring press · published 8 March 2021 · consulted 2 October 2026 · in Spanish