P0018 on 2020-2023 Cadillac XT6: Crankshaft/Camshaft Correlation Causes and Fixes

What's Unique About the 2020-2023 Cadillac XT6

The 3.6L V6 LGX engine in the XT6 is used across many GM vehicles and relies on oil pressure to operate its camshaft phasers (part of the Variable Valve Timing system). While the LGX features an improved timing system over its predecessors (LY7/LLT), it is not immune to timing-related faults. GM has issued several Technical Service Bulletins (TSBs) relevant to this code. TSB #PIP5730B points to a sticking 'Intake Camshaft Position Actuator Park Lock Solenoid Valve' as a potential cause that may not trigger other drivability issues. TSB #23-NA-091 warns that P0018 can appear after engine repairs if the wiring connectors for the camshaft actuator and park lock solenoid are swapped, as they are identical. This highlights the need for careful diagnosis beyond just assuming a stretched chain.

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 is on.
• Rough or erratic idle.
• Reduced engine power and poor acceleration.
• Engine may hesitate or stall.
• Decreased fuel economy.
• Rattling or slapping noise from the engine, especially on a cold start, near the timing cover.

Most Likely Causes

1. Low, Dirty, or Incorrect Viscosity Engine Oil 🔴 High Probability The camshaft phasers that adjust timing are hydraulically operated by engine oil. If oil pressure is low or passages are clogged with sludge from dirty or degraded oil, the phaser cannot adjust correctly. This is often the first and easiest thing to check.
   How to confirm: Check the engine oil level on the dipstick and examine its condition. If it's low, black, sludgy, or past its service interval, this is a likely contributor. An oil change is a low-cost first diagnostic step.
   Typical fix: Perform an oil and filter change using the manufacturer-specified oil viscosity (e.g., ACDelco dexos-approved 5W-30 synthetic oil). Clear the code and test drive.
   Est. part cost: $50-$100
2. Failed Camshaft Position Actuator Park Lock Solenoid Valve 🔴 High Probability → Shop Engine Camshaft GM TSB #PIP5730B specifically identifies this component as a cause for P0018 on the LGX engine. The solenoid can stick or come apart internally, causing a correlation code without other obvious symptoms. This is a known issue across multiple vehicles with this engine.
   How to confirm: A technician can remove the solenoid (located on the front of the engine) to inspect for damage or sticking. Swapping the Bank 2 solenoid with the Bank 1 solenoid is a key diagnostic step; if the code changes to P0016, the solenoid is confirmed as the fault.
   Typical fix: Replace the faulty Intake Camshaft Position Actuator Park Lock Solenoid Valve for Bank 2.
   Est. part cost: $40-$80
3. Stretched Timing Chain 🟡 Medium Probability → Shop Engine Timing Chain While improved in the LGX V6, timing chain stretch can still occur, especially with extended oil change intervals or high mileage. A stretched chain creates slack, altering the mechanical timing between the crank and cams. The 3.6L engine family has a history of this issue.
   How to confirm: This is a mechanical issue requiring physical inspection. A technician will remove the timing cover to measure chain deflection and check timing marks. A rattling noise from the front of the engine is a common symptom. A lab scope can also be used to compare cam/crank sensor waveforms to a known-good pattern to confirm stretch without disassembly. 🎬 Watch: How to use a lab scope to test for timing chain stretch.
   Typical fix: Replacement of all three timing chains, tensioners, and guides. This is a very labor-intensive job, often costing over $2,500.
   Est. part cost: $400-$800
4. Failed Camshaft Phaser / Actuator Solenoid (VVT Solenoid) 🟡 Medium Probability → Shop Engine Camshaft The main oil control solenoid (separate from the park lock solenoid) can fail or its filter screens can become clogged with debris, preventing proper oil flow to the phaser.
   How to confirm: A technician can use a high-level scan tool to command the phaser position and observe if it responds. If it doesn't, the solenoid can be removed, cleaned, and tested for resistance. Swapping with the Bank 1 solenoid is also a valid diagnostic test.
   Typical fix: Replace the Bank 2 intake camshaft oil control solenoid (actuator).
   Est. part cost: $30-$70
5. Incorrect Wiring After a Previous Repair ⚪ Low Probability
   How to confirm: Visually inspect the connectors on the front of the engine. The wire colors must be verified against the service manual schematic to ensure they are plugged into the correct components.
   Typical fix: Swap the connectors to their correct positions and clear the codes.
   Est. part cost: $0 (labor only)
6. Faulty Camshaft Position Sensor ⚪ Low Probability → Shop Engine Camshaft Position Sensor While sensors can fail, it's far less common for a correlation code like P0018 than oil-related or mechanical timing issues. This is often misdiagnosed as the primary cause.
   How to confirm: A simple diagnostic step is to swap the Bank 2 intake camshaft sensor with the Bank 1 intake sensor. If the trouble code changes to P0016 (the Bank 1 equivalent), the sensor is faulty.
   Typical fix: Replace the faulty camshaft position sensor.
   Est. part cost: $40-$90

Rare But Worth Checking

• Damaged or Slipped Crankshaft Reluctor Wheel: → Shop Engine Crankshaft The reluctor wheel is what the crankshaft position sensor reads. In some GM 3.6L engines, it has been known to physically slip or rotate on the crankshaft. This causes a persistent correlation code even with perfect mechanical timing, as the ECM receives an incorrect crank signal. This is a catastrophic failure. The only fix is crankshaft replacement.
• Faulty Engine Control Module (ECM): → Shop Engine Control Module (ECM) This is extremely rare, but a software glitch or internal failure in the ECM could theoretically cause it to misinterpret sensor data. This should only be considered after all other possibilities, including wiring and mechanical faults, have been exhaustively ruled out.

Diagnosis Steps

1. Verify the engine oil level and condition. If low or dirty, perform an oil and filter change with full synthetic 5W-30 oil. Clear codes and re-test.
2. Use a professional OBD-II scanner to check for any other related trouble codes and view live data. Observe the desired vs. actual camshaft position angles for Bank 2.
3. If the code appeared after a recent repair, inspect the wiring connectors for the Bank 2 camshaft actuator solenoid and park lock solenoid per TSB #23-NA-091 to ensure they are not swapped.
4. Following TSB #PIP5730B, remove and inspect the Bank 2 Intake Camshaft Position Actuator Park Lock Solenoid. Check if it is sticking or has come apart. Swap it with the Bank 1 solenoid, clear codes, and see if the fault moves to Bank 1 (P0016). If it does, replace the solenoid.
5. Test the Bank 2 intake camshaft actuator solenoid (VVT solenoid). Command it with a scan tool and check for response. Consider swapping it with the Bank 1 solenoid to see if the code follows.
6. Swap the Bank 2 intake camshaft position sensor with the sensor from Bank 1. Clear the codes and see if the fault moves to Bank 1 (P0016). If it does, the sensor is bad.
🎬 Watch: A step-by-step guide to testing and fixing the P0018 code.
7. If the above steps do not identify the issue, a mechanical timing issue is highly likely. A lab scope can be used to compare cam and crank sensor signals to a known-good waveform to confirm a timing chain issue without disassembly.
8. If a scope is unavailable or results are inconclusive, perform a mechanical inspection. This involves removing the engine timing cover to check for a stretched timing chain, worn guides, or incorrect timing marks.

Parts You'll Likely Need

• Engine Oil and Filter — Incorrect or degraded oil is a primary cause of VVT system faults that trigger this code.
  Trusted brands: ACDelco, Mobil 1
  OEM price range: $50-$100
  Aftermarket price range: $40-$80
• Intake Camshaft Position Actuator Park Lock Solenoid Valve (OEM #12697027) — This specific solenoid is called out in a TSB as a common cause for P0018. It can stick or break internally.
  Trusted brands: ACDelco (GM Genuine)
  OEM price range: $40-$80
  Aftermarket price range: $25-$50
• Camshaft Position Actuator Solenoid (VVT Solenoid) (OEM #12679529) — This solenoid controls oil flow to the phaser. It can get clogged or fail electrically, preventing the cam from adjusting its timing.
  Trusted brands: ACDelco, Delphi
  OEM price range: $30-$70
  Aftermarket price range: $20-$50
• Timing Chain Kit — If the chain has stretched, the entire system of chains, guides, and tensioners must be replaced to restore correct mechanical timing. This is a major, labor-intensive repair.
  Trusted brands: ACDelco (GM Genuine), Cloyes
  OEM price range: $500-$800
  Aftermarket price range: $300-$600
• Camshaft Position Sensor (OEM #12703620) — Though less common, a failed sensor can provide incorrect data to the ECM, causing a correlation fault. It's often misdiagnosed but can be the culprit.
  Trusted brands: ACDelco, Bosch, NTK
  OEM price range: $60-$110
  Aftermarket price range: $40-$90

Related Codes That Often Appear With This One

• P0016 — This is the equivalent correlation code for Bank 1. If both P0016 and P0018 are present, it strongly suggests a problem with the primary timing chain or crankshaft position, as this affects both banks of the engine.
• P0019 — This code relates to the exhaust camshaft on Bank 2. If seen with P0018, it points to a timing problem affecting the entire bank, likely a secondary timing chain or phaser issue on Bank 2.
• P0008 — A general Engine Position System Performance code for Bank 1. On GM 3.6L engines, this is very commonly associated with stretched timing chains and may appear alongside P0018.
• P0009 — The equivalent of P0008 but for Bank 2. Seeing this with P0018 reinforces a timing issue on Bank 2.

Technical Service Bulletins (TSBs) & Recalls

• 23-NA-091: Warns that P0016/P0018 can set after engine repairs due to swapped electrical connectors for the camshaft actuator and park lock solenoid.
• PIP5730B: Provides diagnostic aid for P0016/P0018, pointing to a sticking or broken Intake Camshaft Position Actuator Park Lock Solenoid Valve as a likely cause.
• 20-NA-085: Notes that on some 2019-2020 engines, a missing timing chain guide insert could cause chain wear and codes P0018/P0019.

Platform-Specific Known Issues

• Swapped Connectors Post-Repair: A unique and frustrating issue specific to the LGX engine is that the electrical connectors for the VVT solenoid and the park lock solenoid are identical. TSB 23-NA-091 was issued because technicians were inadvertently swapping them during reassembly, causing an immediate P0018 code. Always verify wire colors if the code appears after service.
• Park Lock Solenoid Failure: Unlike a simple sensor or general VVT solenoid failure, GM specifically calls out the 'Intake Camshaft Position Actuator Park Lock Solenoid' in TSB PIP5730B as a common culprit for P0018. This part can stick or break apart without causing other noticeable symptoms, making it a key component to inspect early in the diagnosis.

Mechanic-Grade Diagnostic Values

• Camshaft Oil Control Valve (VVT Solenoid) Resistance — expected: 6.9 to 7.9 Ohms at 68°F (20°C). Failure: A reading outside this range, or an open loop (OL) or short (0 Ohms), indicates a faulty solenoid coil.
• VVT Solenoid Connector Voltage — expected: Battery voltage on the power supply pin with ignition on, engine off.. Failure: No voltage points to a problem in the wiring or the power supply relay.
• Camshaft Position Sensor (CMP) Low Reference Circuit Resistance to Ground — expected: Less than 5.0 ohms. Failure: A reading greater than 5.0 ohms indicates high resistance or an open in the ground circuit, which can cause incorrect sensor readings.
• Scan Tool Camshaft Position Variance — expected: Near 0 degrees at idle.. Failure: A significant, persistent deviation from 0 degrees at idle, especially one that exceeds 9 degrees, points to a mechanical timing or phaser problem.

Scan Tool Commands That Help

• GDS2 (GM Dealer Scan Tool): Camshaft Position Actuator Solenoid Control — This bidirectional command allows a technician to manually activate and deactivate the VVT solenoid while the engine is running. A noticeable change in engine idle quality or RPM confirms the solenoid is mechanically responding, helping to distinguish a stuck solenoid from a wiring or ECM driver issue.
• GDS2 (GM Dealer Scan Tool): Data Display > Engine > Engine Control Data — Used to monitor the desired vs. actual camshaft position angles for Bank 2 in real-time. A large and consistent variance between the desired and actual values is a strong indicator of a mechanical timing fault (stretched chain) or a stuck cam phaser.

Wiring & Ground Locations

• G102 (or similar designation) — Typically located at the left rear of the engine block or cylinder head on GM V6 engines.. This is a common ground point for ignition coils and other engine sensors. A loose or corroded connection here can introduce electrical noise or faulty reference voltages for the camshaft position sensors, potentially contributing to correlation codes.
• Cylinder Head Grounds — On some GM V6 engines, small ground wires are located on the back of the cylinder heads.. These grounds are critical for engine sensor data. A poor connection on the Bank 2 cylinder head ground could directly impact the camshaft position sensor circuit for that bank.

OEM Part Supersession History

• 12633123 → 12681018, which is now superseded by 12734067 — This part number trail applies to the Camshaft Position Actuator Park Lock Solenoid Valve, a key component mentioned in TSB #PIP5730B. Part revisions often address reliability or performance issues.
  Heads up: While these parts are for the GM V6/V8 family, fitment can vary. Always verify the correct part number by VIN. The part listed as 12681018 is specified for the LGX V6 among other engines.