P0325 GMC Sierra 1500
Knock Sensor 1 Circuit Malfunction (Bank 1) · Powertrain Code · Medium
What is P0325?
The knock sensor 1 on bank 1 is not functioning properly. The ECM cannot detect engine knock/detonation.
When the GMC Sierra 1500 triggers code P0325 (knock sensor 1 circuit malfunction (bank 1)), it typically points to an issue in the powertrain system. Below you'll find the most common causes, symptoms, and repair options specific to the GMC Sierra 1500.
Diagnostic data on this page is compiled from publicly available repair resources and technical service bulletins. Always have a qualified mechanic confirm the diagnosis before authorizing repairs on your GMC Sierra 1500.
Common Causes on GMC Sierra 1500
- Failed knock sensor 1 (common failure on GM V8s due to heat and age)
- Corroded knock sensor wiring harness under the intake manifold
- Intake manifold gasket leak allowing coolant to reach knock sensor connector
- Loose or improperly torqued knock sensor
Symptoms
- Check Engine Light on
- Engine may retard timing, causing reduced power
- Slight decrease in fuel economy
- Engine may ping or knock under load if sensor is ignored
Notes for GMC Sierra 1500
On GM V8 trucks, knock sensor replacement requires intake manifold removal — always replace the wiring harness at the same time as the sensor.