Powertrain
Definition only
Lights the check engine lamp
P27A1: Electric/Auxiliary Transmission Fluid Pump A Stuck On
Standardized SAE J2012 code · P27xx — Transmission
What does P27A1 mean?
The first auxiliary transmission fluid pump runs even when no command is active.
The code tells you which monitor failed, not which part is broken. Test before replacing parts.
Symptoms
- Check engine or transmission warning light on
- Harsh, delayed, or missing shifts
- Possible limp mode (locked in one gear)
- Slipping or shuddering during gear changes
Common causes
- High TCM output driver stuck on
- Medium Control wire shorted to a permanent B+ supply
- Low Carbon or debris buildup preventing free movement
Likelihood is a general estimate across vehicles; your make and model may differ.
Add your car to see reports of P27A1 on the same make and model first.
P27A1 in the community
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