P26AE: Engine Coolant Bypass Valve B Control Circuit High

With P26AE the valve B drive output sees voltage where it expects none, typically a short to battery. GM's 2016 Volt table again applies it to the second drive line of the one bypass valve: the VICM sets it when driver 2 flags a short to high while the valve is stopped or commanded low, after 16 failures in 20 samples at 100 ms, Type B. Ford's 2024–2025 gasoline summary lists P26AE as the short-to-battery case of the active transmission cooling valve, also filed as P26AC_12, detected when the smart driver reports a fault for 5 s. A pinched harness touching a supply wire or an internally shorted valve motor are the main causes; drivers often protect themselves by switching off, so the valve stops moving.

Symptoms

• Check engine light
• Valve stays in its last position
• Transmission or cabin temperature control off target

Most likely causes

• Drive wire shorted to a battery-voltage wire
• Internally shorted valve motor or solenoid drawing excess current
• Damaged output stage in the control module

What to check, in order

Start with the simplest. You can tick off each step.

1. With the engine cold, check the coolant level; never do this when the system is hot
2. Check the sensor's ground and make sure the signal wire is not receiving voltage from another circuit.
3. Check the actual temperature in live data
4. Make sure the fan comes on when it should
5. Check the thermostat and connector
6. Measure the sensor and replace it if its readings do not make sense

Good to know

• Repair difficulty: medium
• It affects emissions.

What each character of P26AE means

• P: Powertrain: engine and transmission
• 2: Generic code: same on every make
• 6: Control modules and outputs
• AE: Specific fault in that system

Frequently asked questions

Can I keep driving with code P26AE?

Watch the temperature gauge. If it climbs or a warning appears, stop the car in a safe place and turn off the engine: overheating can cause serious damage.

What causes code P26AE?

The most common causes are: drive wire shorted to a battery-voltage wire; internally shorted valve motor or solenoid drawing excess current; damaged output stage in the control module.

Related codes

• P26ADEngine Coolant Bypass Valve B Control Circuit Low
• P26ACEngine Coolant Bypass Valve B Control Circuit/Open
• P2683Engine Coolant Bypass Valve A Control Circuit High
• P26A9Engine Coolant Bypass Valve A Position Sensor Stop/Minimum Stop Performance

Sources

• gsi.ext.gm.com: 16OBDG01 Hybrid Diagnostics
• fordservicecontent.com: OBDSM2400OUTPUT 16Jul2024 WSM final V2 MCS7001

Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.