P0325 on GMC vehicles
Knock Sensor 1 Circuit Fault — what it means on a GMC, whether it's safe to drive, and the fixes by model and year.
P0325 on a GMC means knock sensor 1 circuit fault. Most vehicles stay drivable short-term, but diagnose it promptly. The most common cause is failed knock sensor element (typically $150–$600). Pick your GMC model below for its known failure patterns, recalls, and TSBs.
What does P0325 mean on a GMC?
P0325 is set when the engine control module does not receive a valid signal from the Bank 1 knock sensor — or the only knock sensor on engines that use one. The knock sensor is a piezoelectric vibration sensor that listens for the characteristic frequency of pre-ignition (detonation) so the ECM can pull timing to protect the engine. With no usable knock signal, the ECM defaults to conservative timing maps, which reduces power and fuel economy.
P0325 is a standardized OBD-II code, so its definition is the same on every GMC. What differs by model and engine is which cause is most likely — pick your GMC model below for a diagnosis tuned to its known failure patterns, recalls, and TSBs.
Is it safe to drive a GMC with P0325?
In most cases a GMC stays drivable for short trips with P0325 active, but diagnose and repair it promptly. This is a moderate-severity code — ignoring it can lead to further damage or a failed emissions test. Exact tolerance depends on the model and engine.
What causes P0325 on a GMC?
| Cause | Likelihood | Estimated repair (USD) |
|---|---|---|
| Failed knock sensor element — Most common at 100k+ miles. Some engines bury the sensor under the intake. | Most common | $150–$600 |
| Damaged or corroded knock sensor wiring or connector | Common | $80–$350 |
| Loose knock sensor mounting (sensor must be torqued correctly to "hear") | Common | $20–$100 |
| Rodent damage to knock sensor harness (parked vehicles) | Occasional | $80–$350 |
| Failed knock sensor sub-harness on GM L83/L86 truck V8s — Specific to GM 5.3 / 6.2 truck V8s — well-documented sub-harness failure. | Occasional | $200–$600 |
| Internal engine damage producing noise outside the knock sensor band | Rare | $2,000–$6,000 |
Repair costs are typical US ranges and vary by GMC model, model year, and labor rate. A diagnostic trouble code is a symptom, not a guaranteed failed part — confirm the root cause before replacing anything.
P0325 by GMC model
Select your GMC model and year for a P0325 diagnosis tuned to that vehicle's failure patterns, recalls, and TSBs.
GMC Sierra 1500
988 NHTSA owner complaints · 14 recalls on record across the years covered below.
Complaint and recall counts are NHTSA totals for the model years covered on this site, not counts specific to P0325.
P0325 on other makes
Other codes on GMC vehicles
P0325 on a GMC: frequently asked questions
What does diagnostic trouble code P0325 mean on a GMC?
P0325 is set when the engine control module does not receive a valid signal from the Bank 1 knock sensor — or the only knock sensor on engines that use one. The knock sensor is a piezoelectric vibration sensor that listens for the characteristic frequency of pre-ignition (detonation) so the ECM can pull timing to protect the engine. With no usable knock signal, the ECM defaults to conservative timing maps, which reduces power and fuel economy. P0325 is a standardized OBD-II code, so the definition is the same on every GMC — which cause is most likely varies by model and engine.
What are the symptoms of P0325 on a GMC?
Check Engine Light is illuminated. Reduced power and slower throttle response. Slight reduction in fuel economy. Engine may run cooler than normal under load. Possible audible engine ping or knock under hard acceleration. No drivability issue in normal driving
What causes P0325 on a GMC?
Failed knock sensor element (most-common). Damaged or corroded knock sensor wiring or connector (common). Loose knock sensor mounting (sensor must be torqued correctly to "hear") (common). Rodent damage to knock sensor harness (parked vehicles) (occasional). Failed knock sensor sub-harness on GM L83/L86 truck V8s (occasional). Internal engine damage producing noise outside the knock sensor band (rare)
Is it safe to drive a GMC with P0325?
In most cases a GMC stays drivable for short trips with P0325 active, but it should be diagnosed and repaired promptly — this is a moderate-severity code. Ignoring it can lead to further damage or a failed emissions test. Exact tolerance depends on the model and engine.