P26A5 Engine coolant bypass valve position sensor range or performance fault

Engine coolant bypass valve "A" position sensor circuit range/performance (Subaru thermo control valve)

Severity not verified — if the car runs badly, have it inspected

Owners report the check engine light and disabled driver-assist features, and one warns of possible overheating, but no maker document read for this page rates the severity.

It gets more serious if:

  • Inspect soon: Get it inspected soon if the temperature gauge or an oil temperature warning shows high, as one Outback owner warned the car may overheat if not stopped.

Source: how we rate severity

P26A5 in short

P26A5 means the computer sees the engine coolant bypass valve position sensor reading out of range or performing poorly. On 2019 to 2021 Subarus the cause reported by dealers and owners is a failing thermo control valve. It can turn on the check engine light and disable EyeSight and cruise features.

Some engines route coolant through an electronically controlled valve that sends it through or around the radiator to hold the right engine temperature. The valve carries a position sensor so the computer knows where it is.

P26A5 is set when that position reading is out of range or does not match what was commanded. On the 2019 to 2021 Subaru Forester, Outback and Crosstrek, owners and dealers tie it to the thermo control valve, which Subaru calls the TCV, and Subaru extended its warranty for the valve in bulletin 09-119-24.

Several owners report that EyeSight, adaptive cruise and lane assist turn off while the code is stored. That is an owner report, not something confirmed in the bulletin.

Most likely causes

  1. Failing thermo control valve (coolant bypass valve) on 2019 to 2021 Subarus

    Supported by vehicle data
    Why it ranks here
    Subaru dealers in two complaints named the thermo valve for this code, and Subaru extended warranty on the TCV in 09-119-24 for the same models.
    What would change this
    Raises if the valve position reading is stuck or erratic in live data; lowers if the valve moves as commanded and the reading is normal.

What to test first

Start at step 1. Each result tells you what it means and where to go next.

  1. Read the stored codes and note whether other cooling or valve codes are stored with P26A5, and whether the engine temperature behaves normally.

    Low riskTool: OBD-II scan tool

    • IfP26A5 is stored on a 2019 to 2022 Forester, Outback, Legacy or Crosstrek

      It meansAsk the dealer whether warranty extension 09-119-24 applies to your VIN.

      Go to step 2

    • IfOther vehicle or other codes

      It meansThe cause may differ; the sourced evidence here is Subaru-specific.

      Go to step 2

  2. Have a shop read the coolant bypass valve position in live data and compare it with the commanded position.

    Best left to a shopTool: scan tool with live data

    Warning:The cooling system is hot and under pressure after driving; do not open the radiator or coolant reservoir cap on a warm engine. The valve sits in the coolant circuit, so replacing it means draining coolant.

Symptoms

  • Check engine light, sometimes with the cold or oil temperature lights staying on
  • EyeSight, adaptive cruise and lane assist switched off (reported by owners)
  • Temperature gauge climbing or an overheating warning Gets more serious: stop and have it checked.

How to fix

On your vehicle

Subaru

  • 2019–2021 · Forester

    Supported by vehicle data

    Owners report P26A5 with a failed thermo control valve on the 2019 to 2021 Forester, and Subaru bulletin 09-119-24 extends warranty on the valve. The bulletin does not name the code. Status not verified.

  • 2020–2022 · Outback

    Supported by vehicle data

    An owner reports P26A5 with EyeSight disabled on a 2021 Outback; bulletin 09-119-24 covers the valve on the 2020 to 2022 Outback. Status not verified.

  • 2021 · Crosstrek

    Supported by vehicle data

    A 2021 Crosstrek owner reported P26A5 after about 200 miles; bulletin 09-119-24 covers the valve on the 2021 Crosstrek. Status not verified.

  • 09-119-24Status unverified

    Extended warranty coverage for the Thermo Control Valve

    2019–2022forester, outback, crosstrek · issued · NHTSA 10253930

    Extends warranty on the thermo control valve to 15 years or 150,000 miles. The NHTSA summary does not name a trouble code, so it applies to P26A5 only as context.

    We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.

No curated relationships for P26A5 yet.

All Engine cooling (thermostat) codes

P26A5 questions

Is P26A5 covered by Subaru warranty?

Subaru bulletin 09-119-24 extends coverage on the thermo control valve to 15 years or 150,000 miles on 2019 to 2022 models listed in it. One owner was refused for mileage, so ask a dealer to check your VIN.

Sources and review

  1. NHTSA complaint ODI 2204503: 2021 Subaru Outback, P26A5 and EyeSight disabled — NHTSA (owner complaint)
  2. NHTSA complaint ODI 1923655: 2020 Subaru Forester, P26A5 and a failed thermo control valve — NHTSA (owner complaint)
  3. NHTSA complaint ODI 1907235: 2019 Subaru Forester, P26A5 with EyeSight failure — NHTSA (owner complaint)
  4. TSB 09-119-24, 2022 Subaru Outback — CarComplaints.com
  5. Subaru 09-119-24: extended warranty for the Thermo Control Valve (2019-2022 Forester, Outback, Legacy, Crosstrek) — Subaru of America / NHTSA ,
  6. NHTSA complaint ODI 1843898: 2019 Subaru Forester, P26A5 and a cold engine light — NHTSA (owner complaint)
  7. Subaru Outback sensors problems — StartMyCar
Last reviewed
Written by
Saurabh K.
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