P277B: Electric/Auxiliary Transmission Fluid Pump B Driver Circuit Performance
The driver stage for the second auxiliary transmission fluid pump does not respond to commands within tolerance.
What P277B means
P277B is a generic OBD-II powertrain code in the transmission group. In plain English: the signal is within electrical limits but doesn’t make sense compared with other readings, so the part or system isn’t performing as expected.
- 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
- 01Aged driver shows degraded switching behaviourPossible
- 02Current feedback loop noisyPossible
Can I drive with P277B?
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 P277B
- 1
Confirm the code and save freeze-frame data
Read the codes with an OBD-II scan tool and note every code, not just P277B. 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 P0C29. Related codes often share a cause; a circuit or sensor code usually needs fixing before a performance code like this one.
- 3
Test the circuit
Inspect the wiring and connector at the aux trans pump b driver and control module for damage, corrosion or chafing. With a multimeter, check supply voltage, ground and signal against the specifications in the service manual for your vehicle.
- 4
Test the likely causes in order
Start with the most likely cause and work down: Aged driver shows degraded switching behaviour; current feedback loop noisy. 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.
P277B 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
- Hard
- Good DIY job?
- Usually a shop job
Involved testing or major parts. Most owners use a shop.
Parts and systems involved
- Aux trans pump B driver
- Control module
P277B FAQ
What does P277B mean?
P277B means “Electric/Auxiliary Transmission Fluid Pump B Driver Circuit Performance”. The driver stage for the second auxiliary transmission fluid pump does not respond to commands within tolerance.
Is P277B serious? Can I keep driving?
We rate P277B 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 P277B?
The most common causes, from most to least likely: Aged driver shows degraded switching behaviour; Current feedback loop noisy. Test before replacing parts, because several causes can set the same code.
How much does it cost to fix P277B?
Typical labor is about $190–$625 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 P277B myself?
DIY difficulty is hard. Most owners leave this to a shop because it needs involved testing or specialist tools. Always confirm the cause before buying parts.
Will P277B 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.