P0021 on 2018-2019 Buick Enclave: Causes, Fixes & ECM Reprogram TSB

What's Unique About the 2018-2019 Buick ENCLAVE

For the 2018-2019 Buick Enclave and its platform mates with the 3.6L LGX engine, this code is uniquely and strongly tied to a known software issue. Multiple Technical Service Bulletins (TSBs) from GM acknowledge that P0021, often with other timing codes, can appear due to incorrect ECM logic, especially "immediately following an auto-start and while the vehicle is stopped." The official fix is an ECM reprogram, not a mechanical part replacement. This makes checking for applicable TSBs the most critical first step, potentially saving hundreds of dollars on unnecessary repairs. The NHTSA complaint database includes reports from owners who had dealers find these codes but initially had no fix until GM issued the software update.

Diagnostic Flowchart

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

Symptoms You May Notice

• Check Engine Light illuminated
• Engine runs rough, especially at idle or after a cold start.
• Reduced engine power.
• Engine may stall, particularly when stopped or during a stop/start event.
• Increased fuel consumption.
• Hesitation during acceleration.
• Rattling noise from the engine (in cases of mechanical timing failure).

Most Likely Causes

1. Engine Control Module (ECM) Software Update Needed 🔴 High Probability → Shop Engine Control Module (ECM) Documented in GM Technical Service Bulletin #N192266190, which specifically addresses DTCs P0011, P0021, P0014, and P0024 setting after a stop/start event and causing drivability issues.
   How to confirm: Contact a GM dealership with your vehicle's VIN and ask if Service Update #N192266190 is open for your Enclave. The dealer can check the GM Global Warranty Management system.
   Typical fix: Dealer reprograms the Engine Control Module (ECM) with updated software using the Service Programming System (SPS).
   Est. part cost: $0 (if covered under warranty or service campaign)
2. Low or Dirty Engine Oil 🟡 Medium Probability The LGX engine's Variable Valve Timing (VVT) system is hydraulic and extremely sensitive to oil pressure and cleanliness. Sludgy, low, or incorrect viscosity oil can clog the small passages in the actuator solenoids, causing them to stick or respond slowly.
   How to confirm: Check the engine oil level on the dipstick and inspect the oil's color and consistency. Ensure the correct oil viscosity (SAE 5W-30) is being used per the owner's manual.
   Typical fix: Perform an oil and filter change using a high-quality, full-synthetic oil meeting GM's dexos1 specification.
   Est. part cost: $50-$120
3. Faulty Intake Camshaft Position Actuator Solenoid (Bank 2) 🟡 Medium Probability → Shop Engine Camshaft These solenoids control oil flow to the camshaft phasers and are a common failure point. They can become clogged with debris from dirty oil or fail electronically over time.
   How to confirm: A common diagnostic technique is to swap the Bank 2 intake solenoid (firewall side) with the Bank 1 intake solenoid (radiator side). Clear the codes and drive the vehicle. If the code changes to P0011 (the Bank 1 equivalent), the solenoid is confirmed faulty.
   Typical fix: Replace the Bank 2 intake camshaft position actuator solenoid. 🎬 Watch: How to test and fix a P0021 Bank 2 code. It is held in by a single 10mm bolt.
   Est. part cost: $30-$80

Rare But Worth Checking

• Faulty Camshaft Position Sensor: → Shop Engine Camshaft Position Sensor This sensor tells the ECM the camshaft's position. While less common to fail than the solenoid, it can send incorrect data, leading to the code. Usually, a sensor failure will trigger other specific sensor circuit codes.
• Stretched Timing Chain or Failed Phaser: → Shop Engine Timing Chain While a more serious mechanical issue, a stretched timing chain or a camshaft phaser stuck in the advanced position can cause this code. This is usually accompanied by rattling noises from the engine, especially on startup. While the LGX has an improved timing system over the older LLT/LY7 engines, neglect and poor oil quality can still lead to premature wear.
• Faulty Intake Camshaft Park Lock Solenoid: → Shop Engine Camshaft The LGX engine has additional 'park lock' solenoids that lock the intake cams in a default position for startup. A sticking or damaged park lock solenoid can cause timing correlation issues. GM TSB #PIP5730B discusses this for related codes (including P0021) on the V6 engine, noting it's a cause that normal diagnosis might miss.

Diagnosis Steps

1. Scan the vehicle for all stored trouble codes. Note if P0021 appears with P0011, P0014, or P0024, as this is a key indicator for the TSB.
2. CRITICAL FIRST STEP: Contact a GM dealer with your VIN to see if TSB #N192266190 is applicable and outstanding for your vehicle. If so, have the ECM reprogrammed before any other repairs.
3. If no TSB applies, perform a thorough check of the engine oil. Verify the level is correct and the oil is clean and of the proper viscosity (dexos1 5W-30).
4. Inspect the wiring and connectors for the Bank 2 (firewall side) intake camshaft position sensor and actuator solenoid for any damage, corrosion, or oil contamination.
5. Using a professional scan tool like GDS2, monitor the live data for 'Camshaft Position Variance'. A variance over 4 degrees is considered suspect and indicates a fault in the actuator system.
6. Locate the intake actuator solenoids for Bank 1 (radiator side) and Bank 2 (firewall side). They are mounted vertically in the front of the valve covers and held by a 10mm bolt. Swap them 🎬 Watch this walkthrough for replacing the camshaft position actuator solenoid. and clear the codes. If the code returns as P0011, the solenoid you moved is faulty and needs replacement.
7. If the code remains P0021 after the swap, the issue is likely not the solenoid. Further diagnosis of the sensor, wiring, or mechanical timing components (phaser, timing chain) is needed, which may require a professional technician. Consider investigating the Intake Camshaft Park Lock Solenoid as per TSB PIP5730B.

Parts You'll Likely Need

• Intake Camshaft Position Actuator Solenoid (OEM #12687964 (Note: Often superseded by 12687167 or similar. It's reported that all four VVT solenoids on the LGX engine may be the same part number. Verify with dealer.)) — This is the most common mechanical part to fail or clog, causing this code when it's not a software issue.
  Trusted brands: ACDelco (OEM), Delphi, Dorman
  OEM price range: $50-$80
  Aftermarket price range: $30-$60

Related Codes That Often Appear With This One

• P0011 — This is the same 'over-advanced' code but for Bank 1. If both appear, it strongly suggests a systemic issue like oil pressure/quality or the ECM software glitch mentioned in TSBs.
• P0014 — This is for the exhaust camshaft timing on Bank 1. Its appearance with P0021 is specifically mentioned in TSB N192266190 as part of the group of codes fixed by the ECM reprogram.
• P0024 — This is for the exhaust camshaft timing on the same bank (Bank 2). If P0021 and P0024 appear together, it points to an issue affecting the entire Bank 2 cylinder head, such as oil flow or a mechanical timing problem on that bank.

Technical Service Bulletins (TSBs) & Recalls

• N192266190 / N192266190 02: States that DTCs P0011, P0021, P0014, and P0024 may set, causing rough running or stalling after a stop/start event, and the fix is to reprogram the ECM.
• PIP5568E / PIP5568B: Documents a GM engineering investigation into these same codes (P0011, P0014, P0021, P0024) setting together and causing drivability concerns, which led to the creation of the software update.
• 17-NA-317: Lists P0021 among codes that can set with symptoms like MIL illumination, transmission shudder, and low idle/stall, corroborating the symptoms.
• PIP5730B: Details an edge-case cause for P0021 (and related codes) where the Intake Camshaft Position Actuator Park Lock Solenoid sticks or fails, which may not be found through normal diagnostics.

Platform-Specific Known Issues

• A primary issue for the 2018-2019 model years is an ECM software problem that can cause P0021 to set, often after a cold start or stop/start event. The fix is a dealer-installed software update under TSB #N192266190.
• The 3.6L LGX engine has four VVT actuator solenoids (intake/exhaust for each bank) plus two camshaft park lock solenoids. Misidentifying the correct solenoid during diagnosis is a common pitfall. For P0021, the target is the 'A' (Intake) solenoid on Bank 2 (firewall side).

Mechanic-Grade Diagnostic Values

• Camshaft Position Actuator Solenoid Coil Resistance — expected: Generally between 5 and 20 Ohms, with some sources specifying 6.9-7.9 Ohms. Always check the service manual for the exact specification.. Failure: A reading of infinite resistance (Open Loop) or very low resistance (short circuit) indicates a failed solenoid.
• Camshaft Position Variance (Live Data) — expected: Under 4 degrees during normal operation.. Failure: A variance consistently over 4 degrees indicates a suspect fault in the camshaft actuator system.

Scan Tool Commands That Help

• GDS2 (GM Techline): Camshaft Position Actuator Solenoid Test — Use this bidirectional control to manually command the solenoid on and off. This verifies if the solenoid is mechanically clicking and if the wiring from the ECM is functional, helping to isolate a bad solenoid from a wiring or mechanical phaser issue.
• GDS2 (GM Techline): Camshaft Position Variation Learn — This reset procedure should be performed after replacing a camshaft, phaser, or timing chain to allow the ECM to learn the new baseline positions of the valvetrain components.

Real Owner Repair Stories

• Camaro6 Forums user (2016+ Chevrolet Camaro 3.6L V6 LGX (same engine family)) — Check Engine Light with code P0014 (Bank 1 Exhaust equivalent), with no noticeable driveability issues.
  ❌ Tried (didn't work) Initially misidentified the bank, disconnecting the driver's side (Bank 2) sensor first.
  ✅ What actually fixed it The user correctly identified Bank 1 (passenger side on RWD Camaro) and replaced the exhaust VVT solenoid (GM Part #12687167). After replacement and driving, the permanent and pending codes cleared on their own.

OEM Part Supersession History

• 12687964 → 12687167 — Standard part revision/update by GM.
  Heads up: The parts are generally considered interchangeable. A parts clerk informed one user that all four VVT solenoids (intake/exhaust, bank 1/2) on the LGX engine may use the same part number, simplifying replacement.