If your Nissan or Infiniti has triggered the P1170 diagnostic trouble code, your vehicle’s knock sensor system has detected a problem. The knock sensor is a critical component that monitors engine detonation (knock) and allows your engine to run at optimal timing. When this sensor fails to communicate properly with the engine control module (ECM), you’ll see this code stored in your vehicle’s memory.
What Does P1170 Mean?
P1170 is a manufacturer-specific code used by Nissan and Infiniti vehicles. It stands for “Knock Sensor Signal Issue” and indicates that the ECM is not receiving a valid signal from the knock sensor circuit. This code is specific to Nissan’s diagnostic system and differs from the generic knock sensor codes used by other manufacturers.
The knock sensor uses piezoelectric technology to detect vibrations caused by engine knock (pre-ignition or detonation). When the sensor detects knock, it sends a signal to the ECM, which then retards the ignition timing to prevent engine damage. If the ECM cannot read this signal—whether due to sensor failure, wiring issues, or connector problems—the P1170 code is triggered.
Common Symptoms
- Check Engine Light: The primary indicator that code P1170 has been stored
- Engine Knocking or Pinging: A metallic pinging sound under acceleration, especially when using low-octane fuel
- Reduced Engine Performance: The ECM may enter a safe mode, limiting power output to protect the engine
- Poor Fuel Economy: Inefficient combustion due to incorrect ignition timing
- Rough Idle: Unstable idle quality caused by timing issues
- Difficulty Starting: In some cases, the vehicle may be hard to start or hesitate during cold starts
- Transmission Shifting Issues: Some models may experience delayed or harsh shifts if the knock sensor signal affects fuel trim calculations
Possible Causes
- Faulty Knock Sensor (Most Common): The sensor itself has failed or degraded over time, preventing proper signal transmission. This is the most frequent cause in vehicles with higher mileage.
- Damaged or Corroded Wiring Harness: The wiring connecting the knock sensor to the ECM may be corroded, pinched, or damaged, interrupting the signal.
- Loose or Corroded Connector: The connector at the knock sensor or ECM end may be loose, corroded, or improperly seated, causing intermittent signal loss.
- Engine Carbon Buildup: Excessive carbon deposits in the combustion chamber can cause false knock signals or prevent the sensor from detecting real knock events.
- Defective ECM or PCM: In rare cases, the engine control module itself may have failed, preventing it from reading the knock sensor signal properly.
- Incorrect Fuel Octane Rating: Using fuel with an octane rating lower than recommended can cause excessive knock, overwhelming the sensor’s ability to communicate properly.
- Timing Chain or Belt Issues: Problems with the timing system can cause irregular combustion, confusing the knock sensor signal.
Diagnostic Steps
Step 1: Verify the Code and Check for Related Codes
Use an OBD-II scanner to confirm P1170 is present and check for any related codes such as P0325 (knock sensor circuit malfunction). Multiple codes may point to a specific component failure.
Step 2: Inspect the Knock Sensor and Wiring
Locate the knock sensor (typically mounted on or near the engine block). Visually inspect the wiring harness for signs of damage, corrosion, or pinching. Check that the connector is fully seated and free of corrosion. Clean any corroded connectors with electrical contact cleaner.
Step 3: Test the Knock Sensor Connector
Disconnect the knock sensor connector and use a multimeter to check for proper resistance. Consult your vehicle’s service manual for the correct resistance specification (typically 200-900 ohms depending on the sensor type). If the reading is outside the specification, the sensor is faulty.
Step 4: Check the Wiring Harness Continuity
With the connector disconnected, use a multimeter in continuity mode to test the wiring between the sensor connector and the ECM. There should be no breaks in the circuit. If continuity is lost, the wiring is damaged and needs repair or replacement.
Step 5: Perform a Voltage Test
With the engine running, use an oscilloscope or advanced multimeter to measure the knock sensor signal voltage. The signal should show a varying waveform as the engine operates. A flat or absent signal indicates sensor failure.
Step 6: Check Fuel Quality and Engine Condition
Verify that you’re using the correct octane fuel for your vehicle. Consider having a fuel sample analyzed if contamination is suspected. Inspect the engine for carbon buildup, which may require fuel system cleaning or intake valve cleaning.
Step 7: Clear the Code and Test Drive
After repairs, clear the code using your scanner and perform a test drive to ensure the code does not return. Monitor the check engine light for at least 100 miles to confirm the fix.
Repair Cost Estimates
Knock Sensor Replacement: $150–$400
- Parts: $50–$150
- Labor: $100–$250 (varies by engine accessibility)
Wiring Harness Repair/Replacement: $100–$300
- Parts: $30–$100
- Labor: $70–$200
Connector Cleaning/Replacement: $50–$150
- Parts: $10–$50
- Labor: $40–$100
ECM Reprogramming or Replacement (Rare): $400–$1,200
- Parts: $200–$800
- Labor: $200–$400
Fuel System Cleaning (if carbon buildup is the cause): $100–$300
Can I Still Drive?
P1170 is a moderate severity code. You can typically continue driving, but with caution:
- Short-term: It’s generally safe to drive to a repair facility, though you may notice reduced performance and fuel economy.
- Long-term: Continued driving with a faulty knock sensor can lead to engine damage due to uncontrolled detonation. The ECM cannot properly adjust timing without valid sensor input.
- Avoid aggressive acceleration: Do not drive hard or tow heavy loads until the issue is resolved, as this increases the risk of engine knock damage.
- Use premium fuel: If you normally use regular fuel, switch to premium (higher octane) to reduce the likelihood of knock while the sensor is malfunctioning.
We recommend having this code diagnosed and repaired within a few days to prevent potential engine damage.
Frequently Asked Questions
What is the difference between P1170 and P0325?
P1170 is a Nissan/Infiniti-specific code indicating a knock sensor signal issue, while P0325 is a generic code for knock sensor circuit malfunction. Both point to similar problems, but P1170 is manufacturer-specific and may have different diagnostic procedures. If you see P0325 on a Nissan, it indicates the same problem as P1170.
Can a bad knock sensor cause my engine to run rough?
Yes. A faulty knock sensor can cause rough idle, hesitation, and poor acceleration because the ECM cannot properly adjust ignition timing. Without valid sensor input, the engine may run with incorrect timing, leading to rough operation and reduced performance.
Is it safe to drive with the P1170 code?
You can drive short distances to a repair shop, but extended driving is not recommended. A faulty knock sensor prevents the ECM from protecting the engine against detonation. Continued driving, especially under load or with hard acceleration, risks serious engine damage. Repair this code promptly.
How much does it cost to fix a P1170 code?
Most commonly, replacing the knock sensor costs $150–$400 including labor. If the problem is a wiring issue, costs may range from $100–$300. In rare cases where the ECM needs replacement, costs can exceed $1,000. Get a diagnostic scan and visual inspection to determine the exact cause before authorizing repairs.
Can I replace the knock sensor myself?
Knock sensor replacement difficulty varies by vehicle model and engine layout. On some Nissan/Infiniti models, it’s accessible and can be a DIY job for someone with mechanical experience. On others, significant disassembly is required. Consult your vehicle’s service manual and consider professional help if you’re unsure. Improper installation can cause the code to return.