P0327: Knock/Combustion Vibration Sensor A Circuit Low
What Does P0327 Mean?
P0327 is a diagnostic trouble code indicating: Knock/Combustion Vibration Sensor A Circuit Low. This code relates to the ignition system system. It has been reported in NHTSA complaints across 2 different vehicle models.
Engine misfires are detected by monitoring crankshaft rotational speed variations. Each cylinder's power stroke produces a characteristic acceleration pattern. When a cylinder fails to fire, the crankshaft decelerates during that cylinder's stroke. The ECM identifies which cylinder misfired and how often. P0313-P0399 codes cover extended misfire monitoring including lean misfire detection, knock-related ignition faults, and secondary ignition monitoring. A flashing check engine light during active misfires is an emergency — raw unburned fuel enters the catalytic converter, potentially destroying it.
Symptoms of P0327
- ⚠️ Check engine light on (may flash during active misfire)
- ⚠️ Engine misfiring — rough idle, stumbling, shaking
- ⚠️ Loss of power during acceleration
- ⚠️ Increased emissions and fuel consumption
- ⚠️ Catalytic converter damage if ignored
- ⚠️ Possible engine vibration at idle
Common Causes
- 🔍 Worn or fouled spark plugs
- 🔍 Faulty ignition coil
- 🔍 Vacuum leak causing lean misfire
- 🔍 Fuel injector issue (clogged, leaking, or electrical)
- 🔍 Low compression (worn rings, burned valve, head gasket)
- 🔍 Incorrect ignition timing
P0327 Reports by Year
Real Owner Reports
From NHTSA complaint database — actual owner descriptions.
"Service Engine Soon light came on while driving. Code P0327 - Knock Sensor 1, Circuit Low Input (Bank 1) shown on code reader. Took vehicle to local service station and had both knock sensors and wiring harness replaced. Mechanic said that the rear knock sensor was corroded due to water getting t"
— Chevrolet Silverado owner, 05/09/2023
"I bought my 2010 GMC Terrain SLE at 160,000. It had a rough start up but the dealer said it was because it was an older car and been sitting for a while. The rough start up never stopped even after replacing the catalytic converter because of code P0420. The mechanic informed of this specific vehicl"
— Gmc Terrain owner, 11/14/2021
Source: NHTSA Complaints Database
Most Reported Vehicles for P0327
Based on NHTSA owner complaint data.
| # | Vehicle | Reports |
|---|---|---|
| 1 | CHEVROLET SILVERADO | |
| 2 | GMC TERRAIN |
Diagnostic Tips
- Check misfire counters in Mode 6 data — identifies which cylinder(s) are misfiring most
- Swap ignition coil to another cylinder — if misfire follows, coil is bad
- Check spark plugs — worn electrode, fouled with oil or carbon, cracked insulator all cause misfires
- Perform compression test on affected cylinder(s) — low compression means mechanical issue
Common Mistakes to Avoid
- ❌ Replacing coils without checking spark plugs — a worn plug will kill a new coil
- ❌ Ignoring a flashing check engine light — this means severe misfire that's damaging the catalytic converter NOW
- ❌ Replacing ignition parts when the misfire is caused by a vacuum leak or low compression
Frequently Asked Questions
What does a flashing check engine light mean?
Can misfires damage my engine?
Why does my car misfire only when cold?
What To Do Next
Possible Fixes
- 🔧 Replace spark plugs
- 🔧 Replace ignition coil(s)
- 🔧 Repair vacuum leak
- 🔧 Clean or replace fuel injector
- 🔧 Engine mechanical repair (valves, rings, gasket)
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Find your vehicle above
Click your make and model for real owner reports and common causes specific to your vehicle.
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Check for recalls
Go to nhtsa.gov/recalls and enter your VIN. Free repairs if covered.
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Get a professional diagnosis
A code alone doesn't identify the exact failed part. A diagnostic ($50–$150) pinpoints the root cause.