P0333 on 2014-2018 Chevrolet Silverado 2500: Knock Sensor Circuit Fixes

What's Unique About the 2014-2018 Chevrolet SILVERADO 2500

For this specific range of Silverado 2500 and its platform mates, P0333 is rarely a simple bad sensor. General Motors issued Technical Service Bulletin #20-NA-207 (which supersedes the older #PIP5576) identifying a common problem where voltage from the transmission's park/neutral signal circuit can bleed into the knock sensor circuit. This interference creates a false high voltage signal, often triggering the Check Engine Light right as you shift out of Park. 🎬 Watch: Understanding P0333 causes and high voltage circuit fixes. This makes inspecting the ECM's black X2 connector the most critical first step, saving you from a potentially unnecessary sensor replacement.

Diagnostic Flowchart

Tap your situation to follow the diagnostic path that matches what you're seeing on this vehicle.

Generation note: This range covers two Silverado 2500HD generations: the 2014 model year (the end of the GMT900 platform) and the 2015-2018 model years (the K2XX platform). The primary cause identified in TSB #20-NA-207 is known to affect vehicles from both generations, so the diagnostic advice applies to the entire 2014-2018 range.

Symptoms You May Notice

• Check Engine Light is on
• Reduced engine power and sluggish acceleration
• Noticeably lower fuel economy
• Engine may make a pinging or knocking sound, especially under load
• Code may appear immediately after shifting from Park to Drive

Most Likely Causes

1. Electrical Fault at ECM X2 Connector 🔴 High Probability Per GM TSB #20-NA-207, voltage from the transmission's park/neutral signal circuit can bleed into the knock sensor circuit within this specific connector, causing a false high signal. This is the most common cause for this code on this platform.
   How to confirm: Disconnect the battery, then locate the ECM in the engine bay. Disconnect the black X2 connector. Thoroughly inspect both sides of the connector for any debris, moisture, corrosion, or bent/backed-out pins. The issue is strongly indicated if the code sets right after shifting out of park.
   Typical fix: Clean the connector with electrical contact cleaner and compressed air. Apply a small amount of dielectric grease upon reassembly to prevent future moisture intrusion. Repair any damaged terminals or wires. Ensure a secure connection upon reassembly.
   Est. part cost: $0-$20
2. Faulty Bank 2 Knock Sensor 🟡 Medium Probability → Shop Ignition Knock (Detonation) Sensor Sensors can fail over time due to heat cycles and vibration. On these engines, the sensors are located on the lower sides of the engine block, exposing them to road debris and moisture, which can lead to failure. A crack in the sensor housing can allow moisture to enter and cause a short.
   How to confirm: After confirming the ECM connector is clean and secure, locate the Bank 2 knock sensor on the passenger side of the engine block, often near the starter motor. Test its internal resistance with a multimeter (compare to spec, often around 100k Ohms for GM vehicles) or check for an AC voltage signal while tapping on the engine block near the sensor.
   Typical fix: Replace the Bank 2 knock sensor. It is torqued to a specific value (typically 15-17 ft-lbs), so use a torque wrench to avoid damaging the new sensor.
   Est. part cost: $30-$80
3. Damaged Wiring or Sensor Connector ⚪ Low Probability The wiring harness can become brittle from engine heat or chafe against engine components, causing a short to voltage or an open circuit. The harness for the Bank 2 sensor is often routed near the starter and exhaust, making it susceptible to damage.
   How to confirm: Visually inspect the entire length of the wiring from the Bank 2 knock sensor back to the ECM. Check for breaks, chafing, or melted sections. Check the sensor's pigtail connector for corrosion or damage. One owner reported solving the code by replacing the pigtail, as an intermittent internal break was the cause despite no visible damage.
   Typical fix: Repair the damaged section of wire or replace the sensor's pigtail connector.
   Est. part cost: $10-$30

Rare But Worth Checking

• Faulty Engine Control Module (ECM): → Shop Engine Control Module (ECM) This is very rare. The ECM should only be considered as the cause after all other possibilities, including the TSB, wiring, and the sensor itself, have been definitively ruled out.

Diagnosis Steps

1. Read the trouble code with an OBD-II scanner to confirm P0333 is present.
2. IMPORTANT: Follow GM TSB #20-NA-207. Disconnect the battery. Locate the Engine Control Module (ECM) in the engine bay and carefully disconnect the black X2 connector. Inspect both the harness and ECM sides for any debris, corrosion, moisture, or damaged pins. Clean with electrical contact cleaner if necessary and ensure it is fully seated upon reconnection.
3. If the code returns, locate the Bank 2 knock sensor on the passenger side of the engine block, near the starter.
4. Inspect the sensor's connector and nearby wiring for any signs of damage, melting, or corrosion. Pay close attention to the harness routing near the exhaust manifold and starter.
5. Using a multimeter, test the sensor circuit for continuity and check for shorts to voltage or ground. Compare resistance readings of the sensor to the manufacturer's specification (typically 93-100k Ohms).
6. If the wiring is confirmed to be good, the knock sensor itself is the likely culprit. Replace the Bank 2 knock sensor, ensuring it is torqued to the correct specification.
7. If the problem persists after replacing the sensor and verifying all wiring, the issue may be with the ECM, which would require professional diagnosis.

Parts You'll Likely Need

• Knock Sensor (Bank 2) (OEM #ACDelco 213-3827 (GM 12623730)) — This is the component that generates the signal. It is the most likely part to be replaced if the TSB-related electrical issue is not the cause.
  Trusted brands: ACDelco, Delphi, Bosch, NTK
  OEM price range: $60-$90
  Aftermarket price range: $30-$50
• Knock Sensor Connector Pigtail (OEM #ACDelco PT2652 (GM 13580877)) — The connector at the sensor can become brittle and fail, causing a poor connection. Replacing the pigtail is often easier than repairing the old connector, and can solve intermittent issues from internal wire breaks.
  Trusted brands: ACDelco, Dorman
  OEM price range: $25-$40
  Aftermarket price range: $15-$25

Technical Service Bulletins (TSBs) & Recalls

• 20-NA-207: Malfunction Indicator Lamp (MIL) Illuminated - DTC P0333 Set. Advises inspection of the K20 ECM X2 electrical connector for an electrical concern, specifically voltage bleed-over from the transmission park/neutral circuit. Supersedes PIP5576.
• PIP5576: The original preliminary bulletin describing the same issue, now replaced by 20-NA-207.

Platform-Specific Known Issues

• TSB #20-NA-207: This is the most critical issue for this code. It documents that P0333 can be falsely triggered by voltage bleeding from the transmission park/neutral signal circuit. The fix involves inspecting and cleaning the ECM X2 electrical connector.

Mechanic-Grade Diagnostic Values

• Knock Sensor Internal Resistance — expected: 93 kOhms - 110 kOhms. Failure: A reading outside of this range indicates a faulty sensor.
• Knock Sensor Circuit Voltage (at ECM harness connector, Key On, Engine Off) — expected: 2-3 Volts. Failure: A reading less than 2V may indicate a short to ground or open circuit. A reading greater than 3V may indicate a short to voltage. A reading stuck high (above 4.5V-5V) is a direct trigger for the P0333 code.
• Knock Sensor AC Voltage Output (Dynamic Tap Test) — expected: A small, fluctuating AC voltage signal (e.g., > 1 Volt) should be generated when tapping the engine block near the sensor with a wrench (engine off).. Failure: Little to no AC voltage (e.g., less than 10 millivolts) when tapping indicates the sensor's internal piezoelectric element has failed.

Wiring & Ground Locations

• K20 ECM Connector X2, Pin 52 — The black multi-pin connector at the Engine Control Module (ECM) in the engine bay.. This is the specific signal circuit for the Bank 2 Knock Sensor, typically a Dark Blue wire. A high voltage reading on this pin triggers P0333.
• K20 ECM Connector X2, Pin 1 — The black multi-pin connector at the Engine Control Module (ECM) in the engine bay.. This is the Transmission Park/Neutral Signal 1 circuit on some models. Per TSB #20-NA-207, voltage can bleed from this pin to Pin 52 within the connector, causing a false P0333 code, especially when shifting out of Park.
• G103 — On the front of the passenger side cylinder head.. This is a primary engine ground point. A loose or corroded connection here can introduce electrical noise into sensor circuits, potentially interfering with the knock sensor signal and causing erratic readings.
• ECM/PCM Ground — A ground wire running from the main wiring harness to the top rear of the engine block.. This is the main ground for the computer and all its sensors. If this ground is compromised, it can cause a wide range of bizarre electrical issues and sensor-related codes, including P0333.

"I Checked Everything" — The Actual Cause

• A common scenario for P0333 on this truck involves a technician replacing the knock sensor and checking the wiring for continuity, finding no issues, yet the code persists. The root cause, as documented in TSB #20-NA-207, is not a simple open or short circuit that standard tests would find. Instead, it's a micro-voltage bleed-over between adjacent pins within the ECM X2 connector, often due to moisture or debris. This is why the TSB explicitly directs inspection and cleaning of this connector as the primary, non-obvious fix.

OEM Part Supersession History

• 12570125 → 12623730 — Part was updated by the manufacturer.
• 12623730 → 12739206 — Part was updated by the manufacturer.
  Heads up: Always verify the latest part number with a dealer using the vehicle's VIN, as supersessions can occur frequently.

Model Year Variations Within This Range

• 2014 vs 2015-2018: The 2014 model year is the last of the GMT900 platform, while 2015-2018 models are on the newer K2XX platform. Despite significant chassis and body differences, the core engine architecture and the specific electrical fault described in TSB #20-NA-207 (voltage bleed at the K20 ECM X2 connector) affects the entire 2014-2018 range, making the diagnostic procedure for P0333 consistent across these years.