P0325 on GMC
Knock Sensor 1 Circuit Malfunction (Bank 1)
P0325 on GMC vehicles indicates knock sensor 1 circuit malfunction (bank 1). Au7o has documented this code across 1 GMC model — most commonly on Sierra 1500. This code indicates a fault in the knock sensor 1 circuit on Bank 1. The knock sensor listens for the vibrations of detonation (pinging/spark knock) and lets the computer retard ignition timing to protect the engine. When the sensor's signal is missing, out of range, or the circuit is open/shorted, P0325 sets. With knock detection compromised, the computer may run more conservative timing, causing reduced power and slightly lower fuel economy, and the engine is less protected against damaging knock. Typical repair costs on GMC range from $400 to $900, depending on the specific model and root cause.
Common Causes of P0325
- •Failed knock sensor
- •Corroded or loose knock sensor connector
- •Damaged, open, or shorted sensor wiring
- •Improperly torqued or loosely mounted sensor
- •Moisture or corrosion in the connector
- •Wiring harness chafing near the engine
- •Faulty PCM/ECM (rare)
P0325 on GMC by Model
GMC Sierra 1500(1 issue)
- Knock Sensor Water Intrusion Under Intake Causing Check Engine Light and Reduced Performance2000-2006
The 4.8L, 5.3L, and 6.0L Vortec engines used in early GMT800 Sierra trucks place the knock sensors in wells beneath the intake manifold, where water can collect and corrode the sensors or harness. Owners frequently report recurring check-engine lights, timing retard, and reduced power, especially after washing the engine bay or driving in wet conditions. GM issued service information addressing knock sensor corrosion and revised sealing practices.
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View P0325 across all makes →Frequently Asked Questions
What does P0325 mean on GMC?▼
P0325 stands for "Knock Sensor 1 Circuit Malfunction (Bank 1)." This code indicates a fault in the knock sensor 1 circuit on Bank 1. The knock sensor listens for the vibrations of detonation (pinging/spark knock) and lets the computer retard ignition timing to protect the engine. When the sensor's signal is missing, out of range, or the circuit is open/shorted, P0325 sets. With knock detection compromised, the computer may run more conservative timing, causing reduced power and slightly lower fuel economy, and the engine is less protected against damaging knock. On GMC specifically, this code is documented across 1 model.
What causes P0325 on GMC vehicles?▼
Common causes on GMC: Failed knock sensor, Corroded or loose knock sensor connector, Damaged, open, or shorted sensor wiring, Improperly torqued or loosely mounted sensor, Moisture or corrosion in the connector. Specific causes vary by model and year — see the per-model sections below.
How much does it cost to fix P0325 on a GMC?▼
Repair costs on GMC range from $400 to $900, depending on the specific model and root cause.
Which GMC models have P0325 documented?▼
Au7o has documented P0325 on 1 GMC model: Sierra 1500.