P26AB Engine coolant bypass valve stuck: the valve that steers coolant to the heater core is not moving as commanded

Engine coolant bypass valve stuck

Monitor

Owners report the code with a failed three-way coolant valve that controls heat to the heater core and defrost; the engine usually keeps running, but loss of defrost and heat affects visibility in cold weather.

It gets more serious if:

  • Inspect soon: Get it inspected soon if the windshield will not defrost or the temperature gauge reads high, since the valve also steers heat to the heater core.

Source: how we rate severity

P26AB in short

P26AB means the engine coolant bypass valve, also called the three-way cooling valve, is stuck. On 2014-2016 Ram 1500 3.0L diesels, owners report it with a failed valve that controls heat to the heater core and defrost. Chrysler also has a computer flash that lists the code. Get it checked.

Some engines use a valve to send coolant either through the engine only or through the heater core and other circuits. The computer commands the valve and sets P26AB when it does not move as expected.

Chrysler bulletins for the 3.0L Ram 1500 list P26AB-00, engine coolant bypass valve stuck, in a powertrain computer flash for bucking under hard acceleration. Three owners report the code on 2014-2016 trucks; one had the three-way cooling valve replaced with an OEM part.

We do not have a bulletin that states a repair for the valve. Treat the owner reports as leads, and test the valve and wiring before replacing it.

Most likely causes

  1. Stuck or failed three-way coolant (bypass) valve

    Supported by vehicle data
    Why it ranks here
    Three Ram 1500 owners report P26AB with the coolant bypass or three-way valve faulty, and one had it replaced with an OEM part to restore heat and defrost.
    What would change this
    Rises if cabin heat or defrost is weak and the valve does not move when commanded. Falls if the valve moves freely when commanded.

  2. Powertrain control module software (2014-2016 Ram 1500 3.0L)

    Supported by vehicle data
    Why it ranks here
    Chrysler bulletin 18-001-16 Rev C lists P26AB-00 in a computer flash for the 2016 3.0L; the 2014 bulletin 18-021-15 Rev F is a similar flash. The summaries do not give a repair for the code.
    What would change this
    Rises if other codes from the same bulletin are stored. Falls if no flash applies.
    How to test the engine control module (ecm / pcm)

  3. Valve wiring or connector fault

    Possible — needs testing
    Why it ranks here
    A stuck-valve code can also come from a circuit problem, but we did not find a source that documents it for this valve, so it needs testing.
    What would change this
    Rises if the connector is damaged or the valve works when powered directly. Falls if wiring tests good.

What to test first

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

  1. Read all codes and note other codes from Chrysler's list (P206D, P050E, U3017), and whether cabin heat and defrost are weak.

    Low riskTool: OBD-II scan tool

    • IfHeat or defrost is weak

      It meansThe valve is likely stuck.

      Go to step 2

    • IfHeat is normal

      It meansAsk about the software flash.

      Go to step 3

  2. Command the valve with a scan tool and check that it moves, and inspect the valve connector.

    Use cautionTool: scan tool with output controls

    Warning:Do not open the cooling system when hot; pressurised coolant can burn.

  3. Ask a dealer whether the 3.0L computer flash applies to your VIN.

    Best left to a shop

    Warning:This needs specialist tools and vehicle service information. Leave it to a shop.

Symptoms

  • Check engine light on
  • Weak cabin heat
  • Windshield defrost weak Gets more serious: stop and have it checked.
  • Bucking under hard acceleration (Chrysler flash)

How to fix

  1. Check the coolant level only when the engine is cold.

On your vehicle

Ram

  • 2014–2016 · 1500

    Supported by vehicle data

    Three owners report P26AB on 2014-2016 Ram 1500 3.0L trucks, one with the three-way cooling valve replaced; Chrysler lists the code in a 2016 computer flash. Whether the bulletin is still current is not verified.

  • 18-001-16 Rev CStatus unverified

    3.0L powertrain flash listing P26AB

    20161500 · NHTSA 10181469

    A computer flash for bucking under hard acceleration and the MIL; its code list includes P26AB-00 engine coolant bypass valve stuck.

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

  • 18-021-15 Rev FStatus unverified

    2014 3.0L powertrain flash

    20141500 · NHTSA 10160010

    A computer reprogramming for the 3.0L with oxygen sensor and exhaust temperature sensor work as needed; the code list is truncated in the flat file.

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

No curated relationships for P26AB yet.

All Engine cooling (thermostat) codes

P26AB questions

Will P26AB leave me without heat?

Owners report weak heat and defrost when the valve fails. It is worth fixing before winter.

Sources and review

  1. NHTSA complaint ODI 11433204: Ram 1500 2015, P26AB three-way cooling valve replaced — NHTSA Office of Defects Investigation
  2. NHTSA complaint ODI 11386672: Ram 1500 2016, P26AB coolant three-way valve malfunctioning — NHTSA Office of Defects Investigation
  3. NHTSA complaint ODI 11184246: Ram 1500 2014, P26AB engine coolant bypass valve — NHTSA Office of Defects Investigation
  4. Chrysler bulletin 18-001-16 Rev C (NHTSA 10181469): 3.0L powertrain flash with P26AB — Chrysler Group
Last reviewed
Written by
Saurabh K.
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