P2720 on 2018-2019 Chevrolet Colorado: Transmission Solenoid Causes and Fixes

What's Unique About the 2018-2019 Chevrolet COLORADO

For the 2018-2019 Chevrolet Colorado (and other GM vehicles with the 8L45 8-speed transmission), this code has a very specific and well-documented cause. General Motors issued a Technical Service Bulletin (TSB #N182193520) because a number of these trucks left the factory with the main electrical connector to the valve body solenoids not fully seated. This simple physical issue is the most likely culprit, making the diagnosis more direct than on other vehicles. It is important to differentiate this specific electrical fault from the more widely known 'Chevy Shudder' issue that also affects these 8L45/8L90 transmissions, which is typically related to contaminated transmission fluid and torque converter problems.

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
• Transmission enters "limp home" mode with limited gear selection
• Harsh or delayed shifting
• Transmission may feel stuck in one gear
• Increased fuel consumption
• Transmission may not shift properly
• Stabilitrak light may illuminate

Most Likely Causes

1. Transmission Valve Body Solenoid Electrical Connector Not Fully Seated 🔴 High Probability → Shop Transmission Valve Body This is a known factory assembly issue documented by General Motors in TSB #N182193520 for 2018-2019 Colorados and several other GM models with the 8L45/8L90 automatic transmission. 🎬 Watch: A deep dive into the GM 8-speed transmission internals.
   How to confirm: A technician must remove the transmission fluid pan to access the valve body and physically inspect the two main solenoid connectors, pressing firmly to ensure they are fully seated.
   Typical fix: Reseat the loose connector(s). The transmission pan gasket will need to be replaced and the fluid refilled to the correct level.
   Est. part cost: $50-$100 for gasket and fluid.
2. Faulty Pressure Control Solenoid 🟡 Medium Probability → Shop Transmission Clutch Pressure Control Solenoid Solenoids can fail over time due to electrical issues or internal wear. Note that this solenoid may be referred to as 'E', 'S1', or 'Clutch Pressure Control Solenoid 4' in various service documents.
   How to confirm: After confirming the connector is seated, a technician can test the solenoid's internal resistance with a multimeter. A reading outside the manufacturer's specification (4.5-5.5 ohms) 🎬 See how to test a transmission solenoid with a multimeter. indicates a failed solenoid.
   Typical fix: Replace the individual solenoid. This requires removing the transmission pan and valve body. Note that replacing solenoids may require a 'Transmission Adaptive Values Learn' procedure using a GM-specific scan tool.
   Est. part cost: $60-$110 for an OEM part.
3. Damaged or Corroded Wiring ⚪ Low Probability
   How to confirm: Visually inspect the external transmission wiring harness for any signs of chafing, breaks, or corrosion. Check for continuity from the TCM connector to the transmission connector.
   Typical fix: Repair or replace the damaged section of the wiring harness.
   Est. part cost: $20-$500 depending on the extent of damage.
4. Low or Contaminated Transmission Fluid ⚪ Low Probability → Shop Transmission Assembly The original fluid fill in some 8L45 transmissions was found to be hydroscopic (absorbs moisture), leading to shuddering and other issues, though this is less likely to directly cause a P2720 circuit code.
   How to confirm: Check the transmission fluid level and condition. The fluid should be at the correct level, bright red, and free of debris or a burnt smell. Dark or milky fluid indicates a problem.
   Typical fix: Perform a transmission fluid and filter change. Some TSBs for other issues recommend a triple fluid flush.
   Est. part cost: $100-$200 for fluid and a filter kit.

Rare But Worth Checking

• Faulty Transmission Control Module (TCM): → Shop Transmission Assembly While less common, the TCM itself can fail, causing it to send incorrect signals or falsely report a circuit low voltage. This is typically diagnosed only after all other possibilities (wiring, connectors, solenoids) have been ruled out. Some owners have reported extensive issues with communication between the TCM, ECM, and other modules, leading to complex and expensive diagnostic challenges.
• Internal Valve Body Issue: → Shop Transmission Valve Body A blockage or crack in the hydraulic passages of the valve body can mimic a solenoid failure. If replacing the solenoid doesn't fix the issue, the valve body itself may be the problem. One owner of a 2019 Colorado reported a valve body replacement costing over $2,500.

Diagnosis Steps

1. Scan the vehicle's computer system to confirm P2720 is the active code and check for any other related codes, like P2718.
2. Check the transmission fluid level and condition. Dark, burnt, or low fluid can indicate other problems and should be addressed.
3. Reference TSB #N182193520. The most probable cause is a loose connector inside the transmission.
4. Gain access to the transmission valve body by removing the transmission pan.
5. Locate the two valve body solenoid connectors and press firmly on each to ensure they are fully seated, as per the TSB instructions.
6. If connectors are secure, test the resistance of Pressure Control Solenoid 'E' (S1). It should be between 4.5 and 5.5 ohms.
7. If the solenoid tests good, inspect the wiring harness both inside and outside the transmission for any signs of damage, shorts to ground, or corrosion.
8. If all wiring and components test good, the issue may lie with the Transmission Control Module (TCM) or the valve body itself, which requires more advanced diagnostics.

Parts You'll Likely Need

• Automatic Transmission Fluid Pan Gasket (OEM #24260071) — Required for re-sealing the transmission pan after inspecting the internal connectors and solenoids.
  Trusted brands: ACDelco, Fel-Pro
  OEM price range: $30-$50
  Aftermarket price range: $15-$30
• Pressure Control Solenoid (PCS) (OEM #24272282) — If the solenoid itself has failed electrically, it will need to be replaced. This is also known as Solenoid S1 (E).
  Trusted brands: ACDelco, Bosch
  OEM price range: $60-$110
  Aftermarket price range: $40-$90
• Dexron VI Automatic Transmission Fluid (OEM #19355656) — The transmission fluid must be drained to access the internal components and will need to be refilled with the correct type of fluid. Note: The 8L45 actually specifies ATF DEXRON HP fluid.
  Trusted brands: ACDelco
  OEM price range: $10-$15 per quart
  Aftermarket price range: $8-$12 per quart

Related Codes That Often Appear With This One

• P2718 — This code, for Pressure Control Solenoid 'D' Control Circuit Range/Performance, is also mentioned in TSB #N182193520 as being caused by the same loose connector issue.

Technical Service Bulletins (TSBs) & Recalls

• N182193520: States that a loose electrical connector to the transmission valve body solenoids can cause DTC P2720 and P2718, resulting in a 'limp home' mode. The fix is to access the valve body and fully seat the connectors. 🎬 Watch: A quick video on fixing common Colorado transmission issues. This TSB applies to a range of GM vehicles including the 2018-19 Colorado/Canyon and Camaro, and 2019 CTS, Corvette, Silverado, and Sierra.

Platform-Specific Known Issues

• A GM Technical Service Bulletin (TSB #N182193520) was issued for 2018-2019 Chevrolet Colorados with the 8L45 8-speed automatic transmission due to the electrical connector to the transmission valve body solenoids not being fully seated from the factory, which directly causes codes P2720 and P2718. This TSB also applies to the GMC Canyon, Chevy Camaro, and other GM models.
• The 8L45 and 8L90 transmissions are also the subject of class-action lawsuits for separate issues, including a prominent shudder or vibration, harsh shifting, and hesitation, often linked to contaminated fluid or torque converter failure. While P2720 has a specific electrical cause, owners may experience these other symptoms concurrently.

Mechanic-Grade Diagnostic Values

• Pressure Control Solenoid (S1, S2, S3, S4, S5, S6, S7) Coil Resistance — expected: 4.5 - 5.5 Ohms. Failure: A reading outside this range indicates an internal fault in the solenoid.
• Default Control Solenoid (S8) and Boost Control Solenoid (S9) Coil Resistance — expected: 11 - 13 Ohms. Failure: A reading outside this range indicates a fault. Note that these are different from the other solenoids.
• Solenoid Power Wire Voltage — expected: ~12V (Battery Voltage). Failure: A reading below 9V can indicate a low-circuit condition. This should be tested with the key on, engine off.

Scan Tool Commands That Help

• GDS2 (GM Global Diagnostic System 2): Transmission Adaptive Values Learn — This procedure is required after replacing the transmission, valve body, or individual solenoids to reset adaptive values to baseline and ensure proper shifting. The transmission fluid must be between 167°F and 185°F to perform the learn.
• GDS2 (GM Global Diagnostic System 2): Solenoid Data Characterization (MCVM Operations) — Required when replacing the transmission assembly. This process uses the Transmission Unique Number (TUN) from the new transmission to program the TCM with the specific mechanical and electrical characteristics of the new unit's solenoids.
• GDS2 (or similar professional scan tool): Shift-Solenoid Test — Used to command a specific solenoid on and off to verify its electrical function and listen for an audible click, helping to isolate a faulty solenoid from a wiring issue.

Wiring & Ground Locations

• TCM Location — For the 8L45/8L90 transmission, the Transmission Control Module (TCM) is mounted externally, away from the transmission itself, not inside it like on older 6-speed models.. Knowing the TCM is external is crucial for testing the wiring harness continuity between the module and the transmission's main connector.
• Ground Splice Packs (SP105/SP106) — On first-generation Colorados, these were notorious failure points under the hood. SP105 is near the battery (driver's side) and SP106 is behind the engine airbox (passenger side). While for a different generation, poor grounds can cause widespread electrical issues, including TCM and sensor problems.. A poor ground connection can cause low voltage conditions throughout the vehicle's electrical system, potentially triggering a circuit low code like P2720 even if the transmission components are fine.
• Main Transmission Connector — The main external harness connector for the 8L45/8L90 transmission.. This is the primary point for testing voltage and continuity from the TCM to the transmission. A poor connection or corrosion here can cause P2720.

OEM Part Supersession History

• 24272282 → 24044716 — Part update or manufacturer change.
  Heads up: One source indicates this supersession, but it should be verified with a dealer as part information from third-party sellers can be unreliable.

Model Year Variations Within This Range

• 2018-2019: The internal transmission wiring harness may differ depending on whether the vehicle is equipped with Engine Start/Stop (ESS). GM issued service information (PIP5700C) detailing different part numbers for the pass-thru and valve body harnesses based on ESS and the type of internal mode switch (4-pin vs. 10-pin).