P27A6: Electric/Auxiliary Transmission Fluid Pump B Stuck On
The second auxiliary transmission fluid pump runs even when no command is active.
What P27A6 means
P27A6 is a generic OBD-II powertrain code in the transmission group. In plain English: the part isn’t responding the way the computer expects when it is commanded.
- Check engine light
- Usually on
- Emissions-related
- No
- Limp mode possible
- Not typical
- Drive cycle to clear
- Not required
Get it fixed
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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
- 01TCM output driver stuck onMost likely
- 02Control wire shorted to a permanent B+ supplyPossible
- 03Carbon or debris buildup preventing free movementLess likely
Can I drive with P27A6?
Usually yes, for a short time.
The car will often drive normally, but get it diagnosed soon. If you notice rough running, warning lights flashing, overheating or a burning smell, stop driving.
Why we rate it moderate
- Turns on the check engine light
Severity is our rule-based rating from the code’s flags in OBDex and the system it affects, not an inspection of your car. If the check engine light is flashing, or you notice overheating, low oil pressure, or brake or steering problems, stop driving and get help.
How to diagnose P27A6
- 1
Confirm the code and save freeze-frame data
Read the codes with an OBD-II scan tool and note every code, not just P27A6. Save the freeze-frame data (speed, load, temperature when the fault set) before clearing anything; it tells you when the fault happens.
- 2
Check for related codes first
Look for P27A1. Related codes often share a cause; a circuit or sensor code usually needs fixing before a performance code like this one.
- 3
Check live data
Watch the related sensor and actuator readings in live data (Aux trans pump B, Control module, Wiring harness) and compare them with expected values in the service information for your vehicle.
- 4
Test the likely causes in order
Start with the most likely cause and work down: TCM output driver stuck on; control wire shorted to a permanent B+ supply; carbon or debris buildup preventing free movement. Test before replacing parts.
- 5
Check for recalls and service bulletins
Look up recalls for your exact vehicle with its VIN, and ask a dealer about technical service bulletins (TSBs). Manufacturers sometimes issue software updates or extended warranties for known faults.
- 6
Clear the code and verify the repair
After the repair, clear the code and drive the car under the conditions in the freeze-frame data to confirm it does not return.
P27A6 repair cost estimate
Estimate, not a quote. Labor times are typical ranges for this code from OBDex, and $125/hr is an assumed rate. Shop rates and labor times vary by vehicle and region. Diagnosis time may be billed separately.
- DIY difficulty
- Moderate
- Good DIY job?
- Usually a shop job
Needs a scan tool and some experience with testing.
Parts and systems involved
- Aux trans pump B
- Control module
- Wiring harness
P27A6 FAQ
What does P27A6 mean?
P27A6 means “Electric/Auxiliary Transmission Fluid Pump B Stuck On”. The second auxiliary transmission fluid pump runs even when no command is active.
Is P27A6 serious? Can I keep driving?
We rate P27A6 as moderate severity. Usually yes, for a short time. The car will often drive normally, but get it diagnosed soon. If you notice rough running, warning lights flashing, overheating or a burning smell, stop driving.
What causes P27A6?
The most common causes, from most to least likely: TCM output driver stuck on; Control wire shorted to a permanent B+ supply; Carbon or debris buildup preventing free movement. Test before replacing parts, because several causes can set the same code.
How much does it cost to fix P27A6?
Typical labor is about $100–$440 at an assumed $125/hour shop rate, plus parts. That is an estimate, not a quote: labor times and rates vary by vehicle and region, and diagnosis may be billed separately.
Can I fix P27A6 myself?
DIY difficulty is moderate. Most owners leave this to a shop because it needs involved testing or specialist tools. Always confirm the cause before buying parts.
Will P27A6 clear itself?
If the fault was intermittent, the warning may go off once the computer stops seeing it, but the code stays in memory. Fix the cause; clearing the code alone doesn’t repair anything.