# P0327: Knock Sensor 1 Circuit Low (Bank 1 or Single Sensor)

**Verdict:** Drive to a shop this week

Engine sensors - Generic OBD-II code, applies to all gasoline cars and light trucks sold in the US since 1996.

- **Typical cost:** $150-$1,200
- **Urgency:** This week
- **Most likely:** Failed knock sensor or broken wire
- **DIY?:** Depends on sensor location

## Quick answer

P0327 means the engine computer sees a signal from knock sensor 1 that is lower than it should be, or missing altogether. This usually points to a failed sensor, a broken wire, or a corroded connector rather than any real engine knock. The computer retards ignition timing to stay safe, so you may lose a little power and fuel economy.

## What does P0327 mean?

Knock sensor 1 is the first or only knock sensor, mounted on the engine block or head on bank 1, the side with cylinder 1. It contains a piezoelectric element that turns engine vibration into a small voltage. The engine computer listens to that voltage for the sharp frequency of detonation, and pulls back ignition timing if it hears it. That lets the engine run more spark advance for power and economy the rest of the time.

P0327 is a "circuit low" code. The computer sets it when the knock signal stays below a minimum level, which often means an open wire, a short to ground, a poor connection or a dead sensor. Some computers apply a small bias voltage to the circuit and watch for it to drop. The test usually runs once the engine is warm and above a certain rpm, and many makers turn on the light after the fault repeats on a second drive cycle.

## What are the symptoms of P0327?

- Check engine light on
- Slightly sluggish acceleration, most noticeable under load
- Fuel economy a little lower than usual
- Engine may ping on hot days or with heavy loads

## What causes P0327?

Ranked from most to least likely. Check them in this order: the cheap, common causes first.

1. **Failed knock sensor** (most common). After many heat cycles the sensor's crystal or internal connection can crack or open, so it no longer produces a usable voltage. This is a common age-related failure on higher-mileage engines, and the car often feels almost normal. A shop confirms it by measuring resistance where the maker lists a value, or by seeing a flat signal on a scope.
2. **Corroded connector or water in the engine valley** (common). On many V6 and V8 engines the sensor and its connector sit in the valley under the intake manifold, where water, coolant or oil can collect. Corroded pins or a soaked connector drag the signal low. Some GM trucks with V8 engines are known for this, and the code often appears together with P0332 for bank 2.
3. **Broken, chafed or rodent-damaged wiring** (common). The knock sensor wire is thin and routed near hot engine parts, so heat can crack the insulation and vibration can break the conductor. Rodents also chew engine wiring in cars parked outdoors. An open or grounded wire anywhere between the sensor and the computer reads as a low signal and sets P0327.
4. **Engine computer fault** (rare). The engine computer supplies the circuit and filters the knock signal internally, and that input can fail from water intrusion or electrical damage. Because this is rare, a shop first proves the sensor and wiring good, often by checking continuity from the sensor to the computer connector. Only then is a software update or computer replacement considered.

## How do you diagnose P0327?

1. Read all codes and check whether P0332 for the bank 2 knock sensor is also stored.
2. Unplug and inspect the sensor connector for corrosion, oil, coolant or bent pins.
3. Check the wiring between the sensor and the engine computer for opens and shorts to ground.
4. Measure the sensor's resistance against the specification, or watch its output on a scope with the engine running.

## How do you fix P0327, and what does it cost?

| Fix | Typical cost | What it involves |
| --- | --- | --- |
| Repair knock sensor wiring or connector | $150-$400 | Often a replacement pigtail or small knock sensor harness. |
| Replace knock sensor (easy-access location) | $200-$450 | For sensors on the side or front of the block. |
| Replace knock sensor and harness under the intake | $500-$1,200 | Common on V6 and V8 engines; replacing both sides at once saves repeat labor. |

Full price breakdowns: [knock sensor replacement cost](/cost/knock-sensor-replacement).

## Is it safe to drive with P0327?

> **Drive to a shop this week.** Generally safe to drive for a while, since the computer runs retarded timing to protect the engine. Avoid low-octane fuel and heavy towing until it is fixed, and stop if you hear loud knocking.

## Will P0327 fail an emissions test?

A car with P0327 and the check engine light on fails an OBD-based emissions inspection in most states. The comprehensive component monitor watches the knock sensor circuit, and clearing the code just before a test resets the other readiness monitors. Repair it first, then drive normally for several days so all monitors report complete.

## After the repair: clearing P0327

Clear the code and drive once the engine is fully warm, including some moderate acceleration, since the circuit test runs above idle. On a scan tool, the knock sensor signal should respond as rpm rises. If the light stays off through a week of normal driving and power returns, the repair worked.

## How to prevent P0327

- Fix intake and coolant leaks that can let fluid pool around valley-mounted knock sensors.
- Use rodent deterrents if the car is parked outdoors or stored for long periods.
- Replace the knock sensor harness along with the sensor when its connector is brittle or corroded.
- Keep engine wiring clipped in place and away from exhaust heat after any repair work.

## P0327 by make

| Make | What to know |
| --- | --- |
| Chevrolet | Many GM trucks and SUVs with V8 engines mount both knock sensors in the engine valley under the intake, so P0327 and P0332 often appear together. |

## Codes often seen with P0327

- [P0325](/codes/p0325): Knock Sensor 1 Circuit (Bank 1 or Single Sensor)
- [P0326](/codes/p0326): Knock Sensor 1 Circuit Range/Performance (Bank 1 or Single Sensor)
- [P0332](/codes/p0332): Knock Sensor 2 Circuit Low (Bank 2)
- [P0300](/codes/p0300): Random/Multiple Cylinder Misfire Detected

## Frequently asked questions

### Can I drive with a P0327 code?

Yes, in most cases you can drive for a short time, because the engine computer retards timing to protect the engine. Power and fuel economy may drop slightly. Use the octane your manual recommends, avoid heavy towing, and plan the repair within a few weeks.

### What does knock sensor circuit low mean?

It means the voltage coming from the knock sensor is weaker than the engine computer expects, or absent. The usual causes are a failed sensor, an open or grounded wire, or a corroded connector. It does not mean the engine is knocking; the computer simply cannot trust the sensor.

### How much does it cost to fix P0327?

Expect $150 to $1,200 at an independent shop. A wiring or connector repair runs about $150 to $400, and an easy-to-reach sensor $200 to $450. Sensors in the valley under the intake manifold cost $500 to $1,200, mostly in labor to remove and reinstall the intake.

### Why do I have both P0327 and P0332?

Both knock sensors reading low at once usually points to something they share, such as a common harness, connector or ground. On many V8 engines both sensors sit in the valley under the intake, where water or coolant can corrode them together. Replacing both sensors and the harness in one visit is common.

### Can I replace the knock sensor myself?

You can if the sensor is on the side of the block and easy to reach with basic tools. If it sits under the intake manifold, removing the intake takes time, new gaskets and care, so many owners use a shop. Torque the new sensor to specification and use no washers unless specified.

### Will a bad knock sensor cause a misfire?

A bad knock sensor does not normally cause a misfire by itself. The computer retards timing, which can make the engine feel flat but not shake. If you also have misfire codes, those usually have a separate cause, such as spark plugs, coils or a vacuum leak, and need their own diagnosis.

### Is P0327 a serious problem?

It is a moderate problem rather than an emergency. The car usually drives normally with slightly less power, and the computer protects the engine with safer timing. The risk is that genuine knock, from bad fuel or heavy loads, may go undetected, so do not ignore the code for months.

### Will P0327 pass inspection?

No, P0327 with the check engine light on fails an OBD-based emissions test in most states. Clearing the code right before a test does not help, because the readiness monitors reset. Fix the circuit, then drive several days of normal trips so the monitors complete before you go.

### Can a bad ground cause a knock sensor code?

Yes, on some engines a poor engine ground or a corroded connector pin can drag the knock signal low enough to set P0327. Some sensors ground through their mounting bolt, so rust or paint under the sensor matters. A shop checks grounds and connectors before condemning the sensor.

### Does P0327 mean the engine is knocking?

No, P0327 means the computer is getting too little signal from knock sensor 1, not that knock was detected. Real knock is more likely to show as retarded timing or a range/performance code. Even so, use proper fuel, because the computer cannot listen for knock reliably until the circuit is fixed.

## Sources

- [SAE J2012: Diagnostic Trouble Code Definitions](https://www.sae.org/standards/content/j2012_201812/)
- [EPA: On-Board Diagnostics (OBD)](https://www.epa.gov/state-and-local-transportation/vehicle-emissions-board-diagnostics-obd)

## Other engine sensors codes

- [P0316 Engine Misfire Detected on Startup (First 1000 Revolutions)](https://diagxcar.com/codes/p0316)
- [P0320 Ignition/Distributor Engine Speed Input Circuit](https://diagxcar.com/codes/p0320)
- [P0325 Knock Sensor 1 Circuit (Bank 1 or Single Sensor)](https://diagxcar.com/codes/p0325)
- [P0326 Knock Sensor 1 Circuit Range/Performance (Bank 1 or Single Sensor)](https://diagxcar.com/codes/p0326)
- [P0332 Knock Sensor 2 Circuit Low (Bank 2)](https://diagxcar.com/codes/p0332)
- [P0335 Crankshaft Position Sensor "A" Circuit](https://diagxcar.com/codes/p0335)
- [P0336 Crankshaft Position Sensor "A" Circuit Range/Performance](https://diagxcar.com/codes/p0336)
- [P0339 Crankshaft Position Sensor "A" Circuit Intermittent](https://diagxcar.com/codes/p0339)
- [P0340 Camshaft Position Sensor "A" Circuit (Bank 1 or Single Sensor)](https://diagxcar.com/codes/p0340)
- [P0341 Camshaft Position Sensor "A" Circuit Range/Performance (Bank 1 or Single Sensor)](https://diagxcar.com/codes/p0341)

## Symptoms

- [Why does my car lose power when accelerating?](https://diagxcar.com/symptoms/car-loses-power-when-accelerating)
- [Why is my car getting bad gas mileage?](https://diagxcar.com/symptoms/poor-gas-mileage)
- [Why is my engine knocking?](https://diagxcar.com/symptoms/engine-knocking-noise)

## Repair costs

- [Knock sensor replacement cost](https://diagxcar.com/cost/knock-sensor-replacement): $180-$950

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Source page: https://diagxcar.com/codes/p0327
Updated: 2026-11-03
General information, not a substitute for a qualified mechanic.