P26AC code meaning
Engine Coolant Bypass Valve B Control Circuit/Open
Powertrain system Generic code P26xx codes Check engine light
What P26AC means
Which valve carries the letter B depends on the maker. Ford names it in its gasoline OBD summaries for 2020–2023 and 2024–2025: valve B is the active transmission cooling valve, which sends engine coolant to the automatic transmission oil cooler, while valve A heats the transmission. P26AC is set when the smart driver in the PCM reports a fault on that output for 5 s; in 2024 Ford also files it under the extended code P26AC_13 for an open circuit. CARB lets makers combine open, low and high faults of an output into one code, which is why P26AC is often the only electrical code used. With the valve unpowered, transmission oil may run hotter or colder than intended.
P26AC at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modeNot expected
- Repair difficultyMedium
- Typical labor0.5 to 2.5 hours
- Clears after repairWhen cleared with a scanner
Symptoms of P26AC
- Check engine light
- Transmission fluid temperature higher than normal when towing
- Usually no change in normal driving
Common causes of P26AC
- Most likelyBroken wire or unplugged connector at valve B
- PossibleOpen solenoid or motor winding in the valve
- Less likelyFaulty output driver in the PCM
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Coolant bypass valve bSolenoidWiring harness
What each part of P26AC means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 2 | Generic code (second SAE range): it means the same on every make. |
| 6 | Area: computer (engine control module) and output circuits. |
| AC | The exact fault in that area. |
What to do next
- Note P26AC and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about P26AC
What does P26AC mean?
P26AC means "Engine Coolant Bypass Valve B Control Circuit/Open". Which valve carries the letter B depends on the maker. It is a generic code, so it means the same on every make.
Is it safe to drive with P26AC?
Usually yes, for a short time, if the check engine light is steady and the car drives normally. If the light flashes or the car runs badly, stop and have it checked.
Will P26AC fail an emissions test?
Yes, it can. P26AC is emissions-related, so most inspection programs fail a car while it is stored or while the check engine light is on.
How hard is P26AC to fix?
Difficulty: medium. A typical repair takes 0.5 to 2.5 hours of work. This is a job for a workshop.
Will P26AC clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.