P27E1 code meaning
Electric/Auxiliary Transmission Fluid Pump A Pressure Too Low
Powertrain system Generic code P27xx codes Check engine light
What P27E1 means
P27E1 is a hydraulic verdict, not a wiring one: electric auxiliary pump A was running on command, yet the pressure it built stayed below what the module expected. No manufacturer documents this exact code publicly. GM shows how such a check works on its CVTs (2025 TCM tables): during an engine auto-start, with more than 400 kPa requested, both pulley pressure sensors reading under 200 kPa for over 0.525 s set the broader performance code P2797, Type B. Wiring faults on the pump belong to P2796 and its siblings, leakage to P0B0C, and pump B has P27E2. Worn pump gears, a clogged intake screen, low fluid or a leaking check valve are typical. Stop-start is usually blocked, and restarts after a stop may engage harshly.
P27E1 at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modePossible
- Repair difficultyHard
- Typical labor1 to 6 hours
- Clears after repairAfter a drive cycle
Symptoms of P27E1
- Stop-start function disabled
- Jerky or delayed engagement when the engine restarts after a stop
- MIL or transmission warning lit
Common causes of P27E1
- Most likelyWorn pump gears or internal leakage inside pump A
- PossibleLow or aerated transmission fluid, pump draws air
- PossibleIntake screen of the pump partly blocked by debris
- Less likelyCheck valve in the pump circuit not sealing
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Aux transmission pump aTransmission fluidValve body
What each part of P27E1 means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 2 | Generic code (second SAE range): it means the same on every make. |
| 7 | Area: transmission. |
| E1 | The exact fault in that area. |
What to do next
- Note P27E1 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 P27E1
What does P27E1 mean?
P27E1 means "Electric/Auxiliary Transmission Fluid Pump A Pressure Too Low". P27E1 is a hydraulic verdict, not a wiring one: electric auxiliary pump A was running on command, yet the pressure it built stayed below what the module expected. It is a generic code, so it means the same on every make.
Is it safe to drive with P27E1?
Drive gently and only to a workshop. With P27E1 the car can go into limp mode (reduced power) to protect itself.
Will P27E1 fail an emissions test?
Yes, it can. P27E1 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 P27E1 to fix?
Difficulty: hard. A typical repair takes 1 to 6 hours of work. This is a job for a workshop.
Will P27E1 clear itself after the repair?
After the repair the car has to complete a drive cycle (a mix of city and highway driving) before the test runs again. Until then the readiness monitor shows "not ready", which can fail an inspection.