What does it mean?
P1627 is a Powertrain (engine, transmission, fuel system) fault code. It indicates: Control Module Long Term Memory Performance .
Symptoms
- MIL (check engine lamp) on, with the code usually returning soon after it is cleared
- Learned values lost, so the idle is rough and throttle response poor until the relearn completes
- Shift adaptation lost where the transmission shares this memory
- Readiness monitors will not set and the vehicle fails inspection
- Clock, radio presets and other stored settings lost on some vehicles
- Occasional no-start or unexplained stalling
Likely causes
- Constant battery feed to the module interrupted by a blown fuse, corroded terminal or broken wire
- Battery repeatedly run flat, or disconnected while the ignition was still on
- Voltage spike from jump starting or from a failing voltage regulator
- Poor or high-resistance module ground
- Internal memory device failed after years of heat and vibration
- Programming interrupted, leaving the memory only partly written
- Aftermarket accessory spliced into the constant power circuit
How to fix it
- Check the always-live fuse for the module and confirm voltage on that feed with the ignition off
- Voltage-drop test the constant supply and the module ground under load
- Load test the battery and check charging output; a tired battery causes most of these faults
- Look for previous repairs, corroded splices or accessories tapped into the constant circuit
- Clear the code, complete a normal drive cycle and see whether it returns on its own
- Reflash the module with the current calibration on a stable power supply
- Replace and program the module only if the memory fault stays with a verified supply, ground and battery