P079B
Transmission Friction Element B Slip Detected
Transmission — internal clutch/band
Generic OBD-II
Medium
What it means
P079B means the control module has detected that internal friction element "B" — a clutch pack or band inside the transmission — is slipping when it should be fully applied. That shows up as the engine revving without matching acceleration, delayed shifts, and heat build-up. It won't stop the engine from starting, but a slipping element wears quickly, so it needs prompt attention.
Medium
Can I keep driving? Drive as little as possible — a slipping internal clutch or band overheats and wears quickly, and continued driving can turn a repair into a rebuild.
Common symptoms
What you'll notice
- Transmission slipping or jerking (engine revs climb without matching acceleration)
- Delayed or erratic shifting
- Loss of power or acceleration
- Transmission running hot
- Check-engine light on
Common causes
Most likely first
- Worn or damaged friction element B (clutch pack or band)Likely
- Low, dirty, or contaminated transmission fluidCommon
- Low apply pressure from a faulty solenoid or valve bodyCommon
- Sensor or wiring fault causing incorrect apply commandsLess often
- Internal mechanical failure of the transmissionLess often
How to diagnose & fix
Work through it in order
- Read freeze-frame data and note which gear/element the slip occurred in.
- Check transmission fluid level and condition first; low or degraded fluid is a common, cheap cause of slippage.
- Perform a line-pressure test to confirm the element is receiving enough apply pressure.
- Inspect solenoids and the valve body for faults that reduce pressure to element B.
- If pressure is correct and the element still slips, the clutch pack or band is worn and the transmission needs teardown/repair.
FAQ
Quick answers
Is it safe to drive with P079B?+
Not really — a slipping friction element generates heat and wears fast. Keep driving to a minimum and get it diagnosed promptly to avoid a full rebuild.
Can I just clear P079B?+
Clearing won't fix mechanical slippage. The code returns as soon as the element slips again; address the fluid, pressure, or worn clutch.
Related codes
Often seen with P079B
Read & clear P079B yourself
Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.
✓ Verified name — SAE J2012 / ISO 15031-6Guidance reviewed by OBD DashX