What this code means
P0325 means the PCM may be seeing a Knock Sensor 1 circuit signal that is outside the expected range.
What the vehicle may do
- The MIL may illuminate.
- The vehicle may run normally, or drivability may change depending on PCM response.
Possible fault areas
- Possible knock sensor signal circuit issue.
- Possible sensor return circuit issue.
- Possible connector, terminal, or harness issue.
- Possible knock sensor issue.
- Possible PCM issue after other checks are complete.
Diagnostic path
Opening and code meaning
On this Ram 1500 with the 5.7 HEMI, P0325 is a Knock Sensor 1 circuit code. In plain terms, the PCM may be seeing a knock sensor signal that is outside the range it expects. The truck may only show a MIL, or it may have drivability changes depending on how the PCM responds. The broad fault areas can include the knock sensor signal circuit, the sensor return circuit, connector or terminal issues, the knock sensor itself, and, after the rest of the path is proven, the PCM. Start with the basic system checks, and if other codes are present, check what they mean first so you do not chase this circuit out of context.
Monitor gate and setting logic
Before testing, understand what has to happen for this code to run and set. The monitor gate is engine speed above 2000 rpm, battery voltage between 7.5 volts and 15.8 volts, and barometric pressure above 75.2 kPa. The PCM sets this fault when Knock Sensor input voltage is above 4.8 volts, or less than 0.2 volts when engine speed is above 2000 rpm. Use those conditions, along with the recorded data, to reproduce the operating conditions instead of testing at random.
Confirm the code returns
First, use the scan tool to read DTCs in all electronic control units and record what is there. Save the vehicle scan report and the related recorded data. Then erase all DTCs, turn the ignition off for a minimum of 10.0 seconds, turn the ignition back on, and operate the vehicle under the conditions that set the code. Read DTCs again. If P0325 does not return, handle it as an intermittent condition. If it does return, move into the circuit checks.
Check the signal circuit for a short to another circuit
With the ignition off, isolate the Knock Sensor 1 signal circuit by disconnecting the ECU and every component connector that contains the circuit being tested. Leave the in-line connectors connected at this point, and use the wiring diagram to follow the circuit path. Connect one DVOM lead to the signal circuit at the ECU harness connector, then probe the other circuits at that connector with the other lead. If a PCM harness terminal must be accessed, use Adapter, GPEC Diagnostic 10436. With the circuit isolated, there should be no continuity between the signal circuit and any other circuit. If continuity is present, repair the short between the circuits, using in-line connectors to help isolate the location, then verify the repair and confirm the code stays gone. If there is no continuity, the available branch sends you to the connection checks. If the path you are following does not clearly take you into the next electrical check, pause, recheck the earlier diagnostic path, and avoid guessing.
Open and high-resistance checks
When the path calls for the open and high-resistance checks, keep the ignition off. For the Knock Sensor 1 signal circuit, isolate the circuit by disconnecting the ECU and the component connector. Before measuring the circuit, touch the DVOM leads together and note the meter lead resistance, because the leads can add resistance to the reading. Measure from the component connector to the circuit at the GPEC adapter. The GPEC Diagnostic Adaptor can add up to 1.5 Ohms of resistance to the circuit. The signal circuit decision point is below 3.0 Ohms. If it is not below 3.0 Ohms, repair the open or high resistance in that circuit, then verify the repair. Next, perform the same style of check on the Knock Sensor 1 return circuit. The return circuit also has to be below 3.0 Ohms. If it is not below 3.0 Ohms, repair the open or high resistance in the return circuit, then verify the repair. Do not probe the PCM harness connectors. Probing those connectors can damage PCM terminals and create a poor terminal-to-pin connection, so use the GPEC Diagnostic Adaptor for this diagnosis.
Short checks between circuits and to ground
Next, with the ignition off, isolate the Knock Sensor 1 signal circuit and check for a short to the sensor return circuit. Disconnect the ECU and every component connector containing the circuit being tested, then check continuity between the signal circuit and the return circuit at the component connector. There should be no continuity. If continuity is present, repair the short between those circuits, then verify the repair. If there is no continuity, check the signal circuit for a short to ground. Keep the ignition off, connect the negative DVOM lead to a known good ground, and use the positive lead on the signal circuit at the component connector. There should be no continuity between ground and the signal circuit. If continuity is present, repair the short to ground, using the wiring diagram and in-line connectors to help isolate the location, then verify the repair.
Sensor retest, connection checks, and final verification
If the circuit checks lead you there and the signal circuit is not shorted to ground, turn the ignition off and replace Knock Sensor 1. Reconnect the component and ECU harness connectors, turn the ignition on, erase all DTCs, turn the ignition off for a minimum of 10.0 seconds, then turn it back on. Operate the vehicle under the conditions that set the code and read DTCs again. If P0325 does not return, verify the repair and confirm the code stays gone. If it does return, check the related PCM and component connections. Perform any applicable service bulletins. Disconnect the PCM harness connectors, related in-line connectors if equipped, and related component connectors. Inspect the connectors and terminals for proper installation, damaged locks, corrosion, water intrusion, weather seal damage, bent terminals, discoloration from overheating, pushed-back terminals, spread terminals, and proper terminal tension. Repair any conditions found, then reconnect everything fully seated with the locks engaged. Erase DTCs, operate the vehicle under the monitor conditions, and read DTCs again. If the code does not return, the wiring or poor connection problem has been repaired. If the code still returns after that connection work, replace and program the PCM, then verify the repair and confirm the code stays gone. Bottom line: prove the monitor conditions, prove the circuit, protect the PCM terminals, and verify the final result. For more diagnostic training, visit stepdiagnostics.com.
Final check
For P0325, confirm the code under the right operating conditions, test the signal and return circuits cleanly, protect the PCM terminals, and verify the repair.
For more guided automotive diagnostics, visit STEP Diagnostics.
