What this code means
P0325 may indicate that the engine computer is not seeing the knock sensor circuit signal the way it expects.
What the vehicle may do
- The check engine light may be on.
- The engine may feel less responsive because ignition timing can be reduced to help protect against knock.
- The concern may be intermittent if the fault is wiring or connector related.
Possible fault areas
- Possible knock sensor fault or sensor damage.
- Possible connector, terminal, or wiring issue between the knock sensor and engine control module.
- Possible sensor mounting or interference issue.
- Possible engine mechanical, accessory drive, fuel quality, or fuel pressure condition that can affect knock behavior.
Diagnostic path
Open and context
On this 2019 to 2025 Chevrolet Silverado 1500 with the 5.3 gas engine, P0325 points us toward the knock sensor circuit. In plain language, the engine computer may not be seeing the knock sensor signal the way it expects. The truck may have a check engine light, and because the system can retard ignition timing to protect the engine from knock, it may feel down on power or less responsive. The broad fault areas can include the knock sensor itself, its mounting and condition, the connector or wiring between the sensor and the engine control module, possible engine mechanical or accessory noise, and fuel or fuel pressure conditions that can affect knock behavior. We’re going to keep this focused on P0325 and use the related knock-system codes only as context.
Start with the basic checks
Before getting deep into the circuit, start with the basic system checks, then follow a structured diagnostic approach. Make sure you understand whether this is a current fault, an intermittent, or something that only showed up under a captured operating condition. If other codes are present, check what they mean first, because that can change the direction of the test path.
Initial verification
With the engine running, first verify whether P0325 is setting along with the knock sensor circuit group or the control-module knock-sensor processor group. If P0325 is the active direction, move into the circuit testing path. If the control-module processor direction is the only thing setting, the diagnostic path points at the engine control module instead.
Check the knock-detected data and stress the harness
If those codes are not set at that moment, watch the scan tool parameter for Cylinder 1–8 Knock Detected. The expected state is No. While watching that parameter, wiggle the knock sensor harness and connector, then the engine control module harness and connector. If the parameter changes from the expected state, repair the wiring, terminals, or connectors as needed. This is the intermittent check before you start condemning parts.
If performance-related knock codes are present
If the scan data is in the expected state, then make sure the related knock performance direction is not active. If that direction is active, inspect the knock sensor for installation problems, outside interference, and visible damage. Also look at nearby brackets, the accessory drive, belt-driven components, basic engine mechanical condition, fuel quality, and fuel pressure conditions. If you find a condition there, repair it as necessary. If those checks are normal, the path moves toward testing or replacing the knock sensor.
Reproduce the operating conditions
If none of the codes are setting during verification, operate the vehicle within the monitor gates for P0325, or reproduce the captured conditions from the stored data. Do not turn that running-condition list into a parts call. Use it to make the monitor run. The diagnostic formulas matter here too: an open signal circuit for greater than 5 s can set this direction, and the related signal-circuit checks also use greater than 5 s for short to ground and greater than 5 s for short to voltage. Then verify the DTC does not reset. If it stays gone, the check is okay at that time. If P0325 resets, go to circuit testing.
Circuit testing setup
For the circuit test, turn the ignition and vehicle off, then disconnect the knock sensor connector. Turn the ignition on with the vehicle in service mode. At this point you are checking what the control module and harness are providing on the two knock sensor signal circuits. The control-module input for terminal 1/A has internal resistance connected to 1.33 V, and terminal 2/B has internal resistance connected to 5 V, so the two circuits do not use the same expected voltage window.
Signal circuit terminal 1/A
Test between signal circuit terminal 1/A and ground. The expected reading is 1 to 2 V. If it is less than 1 V, turn the ignition and vehicle off, disconnect the engine control module connector, and test that circuit to ground for infinite resistance. Less than infinite resistance means repair the short to ground. If it is infinite resistance, check continuity end to end; the expected result is less than 2 Ω. If it is 2 Ω or greater, repair the open or high resistance. If it is less than 2 Ω, the path points to replacing the engine control module. If terminal 1/A is greater than 2 V, disconnect the engine control module, turn the ignition on in service mode, and check that circuit to ground for less than 1 V. If it is 1 V or greater, repair the short to voltage. If it is less than 1 V, the path points to replacing the engine control module.
Signal circuit terminal 2/B
If terminal 1/A is in the 1 to 2 V window, move to signal circuit terminal 2/B. Test between terminal 2/B and ground. The expected reading is 2 to 4 V. If it is less than 2 V, turn the ignition and vehicle off, disconnect the engine control module connector, and test that circuit to ground for infinite resistance. Less than infinite resistance means repair the short to ground. If it is infinite resistance, check continuity end to end; the expected result is less than 2 Ω. If it is 2 Ω or greater, repair the open or high resistance. If it is less than 2 Ω, the path points to replacing the engine control module. If terminal 2/B is greater than 4 V, disconnect the engine control module, turn the ignition on in service mode, and check that circuit to ground for less than 1 V. If it is 1 V or greater, repair the short to voltage. If it is less than 1 V, the path points to replacing the engine control module. If terminal 2/B is between 2 and 4 V, the circuit side has passed this part of the test, so move toward testing or replacing the knock sensor.
Component testing
For component testing, turn the ignition and vehicle off and disconnect the knock sensor connector. Test resistance between signal circuit terminal 1/A and signal circuit terminal 2/B. The expected result is infinite resistance. If it is less than infinite resistance, replace the knock sensor. If that test passes, test from each terminal of the sensor to the sensor housing. That result should also be infinite resistance. If either terminal is less than infinite resistance to the housing, replace the knock sensor. If both checks are infinite resistance, the component test is okay.
Verify the repair
After any repair, keep verification separate from the testing that found the fault. Verify the repair and confirm P0325 stays gone. The takeaway is simple: on P0325, do not jump straight to the sensor. Prove the scan data, stress the harness, inspect the sensor and surrounding conditions, then test both signal circuits before making the call. For more diagnostic training, visit stepdiagnostics.com.
Final check
P0325 is often best approached by verifying the code behavior, checking scan data and harness movement, inspecting the sensor and surrounding conditions, and then testing the two signal circuits.
For more guided automotive diagnostics, visit STEP Diagnostics.
