knock sensor code P0325

[Ray Thomas]

Ok I have a 1995 Subaru Legacy with a P0325 code. I got a used sensor from the junk yard that got rid of the code for about a week. After getting the code again I watched Eric’s video that he made on his 97 Subaru. I did the voltage drop test and it seemed to test ok. It had the 5volt reference from the computer and then I hooked it up and got the 2.5volts. I think the old one was good too but I had thrown it away after a couple of days thinking it was fixed.
Anyone have any ideas on what to do next.
Thanks, Ray

Topic

[Richard Kirshy]

P0325:
Possible Causes ……
Defective Knock Sensor Considering you’ve replace this and still having the issue
Broken or frayed wires that connects to the sensor circuit C onsidering you’ve apparently tested this and still have the issue
That would lead to possibly one of these …..
Faulty EGR (Exhaust Gas Recirculation) system
Lean air-fuel ratio
Defective cooling system

[Ray Thomas]

I’ll go back and try to trace the wires all the way back to the computer. I took the egr valve off and cleaned it and it seems to functioning ok when I put vacuum to it the plunger is moving. How does the cooling system affect the knock sensor? The engine seems to run fine but I noticed the gas mileage dropped 2 miles/gal.
Thanks for responding.
Ray

[Richard Kirshy]

How to Check

The PCM (Powertrain Control module) controls the ignition system spark advance and help it achieve maximum power with good fuel economy. The error code is triggered when the Knock Sensor informs the PCM about the knocking on the engine. The PCM then automatically changes the amount of timing advance by delaying it in measured increases. It continues to change until the knock sensor stops sending signal about the pinging or knocking to the PCM.
Error Code P0325 is triggered as the PCM identifies the signal from the Knock Sensor circuit, sensor #1.

To diagnose, take note of the freeze frame data so you will have an idea what operational conditions caused the PCM to trigger the error code.

Next, conduct a visual inspection on the engine and its cooling system, particularly the coolant level or the condition and oil level. This is to verify whether the error code was caused by a failure in the mechanical system or not.

Then, start the engine and make a few revolutions to see if it works normally. This is to ensure there are no severe mechanical errors that may affect the drivability of the vehicle and may cause further damage.

Then, test drive your vehicle. Bring a data streaming scanner with you and pay attention to the #1 Knock Sensor PID as well as the PID for timing advance. How is the sensor #1 working? Is it sending the signal to the engine when it pings? If not, then you should find out why. Sometimes, people tap the engine using a small hammer and observe the knock sensor PID, along with the PID for timing advance.

[Ray Thomas]

Thanks for the information. I don’t have any type of scan tool or any equipment like that so I bought a new knock sensor. I installed it and then got the p0325 plus a p0400 code too. That pertains to the egr system so took all of that stuff apart and cleaned it. There was a tube from the manifold to the bottom of the transducer that was totally plugged with carbon. Cleaned that, cleared the codes, started the engine and haven’t gotten codes codes for 3 days I’ll keep my fingers crossed.
Thanks for all the help.
Ray

[Richard Kirshy]

Glad to hear you got it sorted out.

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