P2681 on Lexus: How to Diagnose & Fix
Engine Coolant Bypass Valve Control Circuit/Open
1 Lexus model · 1 documented issue
P2681 on Lexus by model: symptoms, diagnosis and fix
The M20A-FKS in the UX 200 uses an electrically actuated coolant flow shut-off valve (also called the coolant bypass or control valve) that blocks flow through the block during warm-up to speed the engine to operating temperature. On 2019-2021 UX 200 vehicles the valve develops a small external coolant seep and the internal actuator circuit fails, setting P268111 (bypass valve circuit short to ground) or P268115 (circuit short to battery or open) and posting an 'Engine Maintenance Required' message in the multi-information display. The leak is slow and often mistaken for a non-issue, but coolant dripping onto surrounding components has been documented to cause A/C system malfunction as well. Lexus issued TSB L-SB-0051-24 (Toyota's parallel bulletin is T-SB-0112-24) directing replacement with an updated valve, superseding part 16671-F2010 with 16671-F2030. This is a UX 200 issue tied to the Dynamic Force gasoline engine family - the UX 250h hybrid uses a different cooling architecture and is not listed in the bulletin's applicability.
Common Symptoms
- 'Engine Maintenance Required' message in the multi-information display
- Check engine light
- Small coolant seep/drip near the front of the engine
- Low coolant level over time
- Slow warm-up or erratic temperature gauge behavior
- Air conditioning performance loss from coolant contamination of adjacent components
How to Fix
Replace the coolant flow shut-off valve with the updated part (16671-F2030, superseding 16671-F2010) and refill/bleed the cooling system per TSB L-SB-0051-24. Critically, 2019-2020 UX 200 vehicles are covered by Lexus Customer Support Program 24LE02 (Toyota's version is 24TE04), which pays for the repair regardless of mileage - call any Lexus dealer with the VIN and ask them to check 24LE02 before paying out of pocket. Do not simply clear the code: the valve does not recover.
Sources for this issue (3)
P2681 code reference
General diagnostic-code context. The code alone does not confirm a cause for your vehicle; use the applicable issue card and its sources.
Frequently asked questions
What does P2681 mean on a Lexus?
P2681 stands for "Engine Coolant Bypass Valve Control Circuit/Open." The engine coolant bypass valve routes coolant flow (e.g., to control warm-up or flow paths). The PCM commands it and detects an open in its control circuit, so the valve cannot be operated. On Lexus it is documented across 1 model: UX.
What are the most common causes of P2681?
The most common causes of P2681 are: Open/broken wiring in the bypass valve circuit, Faulty coolant bypass valve/actuator, Corroded or disconnected connector, Blown fuse, PCM driver fault. The specific cause varies by vehicle.
How much does it cost to fix P2681 on a Lexus?
Repair costs vary widely with the root cause and Lexus model; each issue on this page carries its own estimate where one is published.
Looking for P2681 on a different make?
View P2681 across all makes →Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.