P0327 on GMC
Knock Sensor 1 Circuit Low Input (Bank 1)
P0327 on GMC vehicles indicates knock sensor 1 circuit low input (bank 1). Au7o has documented this code across 2 GMC models — most commonly on Sierra 1500, Yukon XL. This code means the knock sensor on engine bank 1 sent a voltage signal that was lower than the expected range. The knock sensor is a small vibration microphone bolted to the engine block that listens for the 'pinging' of abnormal combustion (detonation), letting the computer retard ignition timing to protect the engine. A low-input reading usually points to an electrical problem — a fault in the sensor, its wiring, or connector — rather than actual knock. With the sensor compromised, the engine may run with safer, less efficient timing, causing slightly reduced power or fuel economy. Typical repair costs on GMC range from $400 to $1,100, depending on the specific model and root cause.
Common Causes of P0327
- •Faulty knock sensor (Bank 1, Sensor 1)
- •Damaged, shorted-to-ground, or corroded sensor wiring
- •Loose or corroded sensor connector
- •Improperly torqued/loose sensor mounting
- •Open or high-resistance signal circuit
- •Wiring shielding or grounding problem
- •Faulty engine control module (PCM) — rare
P0327 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.
GMC Yukon XL(1 issue)
- Knock Sensor Water Intrusion Under Intake Causing Check Engine Light2000-2006
The 4.8L, 5.3L, and 6.0L Vortec engines used in this generation commonly develop knock sensor faults because moisture collects in the valley beneath the intake manifold. Corrosion at the sensors or harness causes persistent P0327/P0332 codes, reduced spark advance, and occasional drivability complaints. This is a well-known GMT800 issue documented in GM service bulletins and owner forums.
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View P0327 across all makes →Frequently Asked Questions
What does P0327 mean on GMC?▼
P0327 stands for "Knock Sensor 1 Circuit Low Input (Bank 1)." This code means the knock sensor on engine bank 1 sent a voltage signal that was lower than the expected range. The knock sensor is a small vibration microphone bolted to the engine block that listens for the 'pinging' of abnormal combustion (detonation), letting the computer retard ignition timing to protect the engine. A low-input reading usually points to an electrical problem — a fault in the sensor, its wiring, or connector — rather than actual knock. With the sensor compromised, the engine may run with safer, less efficient timing, causing slightly reduced power or fuel economy. On GMC specifically, this code is documented across 2 models.
What causes P0327 on GMC vehicles?▼
Common causes on GMC: Faulty knock sensor (Bank 1, Sensor 1), Damaged, shorted-to-ground, or corroded sensor wiring, Loose or corroded sensor connector, Improperly torqued/loose sensor mounting, Open or high-resistance signal circuit. Specific causes vary by model and year — see the per-model sections below.
How much does it cost to fix P0327 on a GMC?▼
Repair costs on GMC range from $400 to $1,100, depending on the specific model and root cause.
Which GMC models have P0327 documented?▼
Au7o has documented P0327 on 2 GMC models: Sierra 1500, Yukon XL.