P237D concerns the same drive line as P237C, the one that operates bypass flap A of an exhaust heat recovery unit, but here the module measures a voltage that sits too low – the usual picture of a control wire touching ground or an actuator shorted internally. Moisture in a connector under the car can produce exactly that. Ford names P237D in two full-hybrid bulletins: SSM 51921 for 2.5L Maverick hybrids built for model years 2022–23, where water inside the heat exchanger is the cause and the unit is renewed, and SSM 53003 for the PowerBoost F-150 hybrid of model years 2021 to 2023, which points to the heat exchanger actuator and supplies a replacement kit. Both bulletins describe a lit MIL. Unlike P237E, the short goes to ground; with the flap uncontrolled, warm-up can take longer.
Medium severity. Can I keep driving?You can usually keep driving in the short term. If you smell exhaust fumes in the cabin, stop driving and ventilate the car.
Symptoms
- Check engine light on
- Slower heater response after a cold start
- Car otherwise drives normally
Most likely causes
- Water in the heat exchanger or its actuator shorting the drive (Maverick)
- Actuator internally shorted to ground
- Control wire chafed through against the body or exhaust bracket
What to check, in order
Start with the simplest. You can tick off each step.
Good to know
- Repair difficulty: hard
- It affects emissions.
What each character of P237D means
- P: Powertrain: engine and transmission
- 2: Generic code: same on every make
- 3: Ignition and misfires
- 7D: Specific fault in that system
Frequently asked questions
Can I keep driving with code P237D?
You can usually keep driving in the short term. If you smell exhaust fumes in the cabin, stop driving and ventilate the car.
What causes code P237D?
The most common causes are: water in the heat exchanger or its actuator shorting the drive (Maverick); actuator internally shorted to ground; control wire chafed through against the body or exhaust bracket.
Related codes
- P237CExhaust Heat Exchanger Exhaust Bypass Valve A Control Circuit/Open
- P237EExhaust Heat Exchanger Exhaust Bypass Valve A Control Circuit High
- P237FExhaust Heat Exchanger Exhaust Bypass Valve A Control Performance
- P23A3Exhaust Heat Exchanger Exhaust Bypass Valve B Control Circuit Low
- P2C22Exhaust Heat Exchanger Exhaust Bypass Valve A Position Sensor Circuit
Sources
- static.nhtsa.gov: MC 10243534 0001
- static.nhtsa.gov: MC 11008695 0001
- en.wikipedia.org: Exhaust heat recovery system
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.