Low, degraded or contaminated transmission fluid reducing clutch apply pressure; Worn or burnt friction plates in element B; Faulty shift solenoid or pressure control solenoid for element B, sticking or electrically failed; Valve body wear, sticking valves or internal hydraulic leaks, including worn seals or sealing rings; Wiring or connector fault between the gearbox and control module, or poor earth or supply; Faulty speed sensor or pressure sensor giving false slip readings; Outdated gearbox control software where the manufacturer has issued a fix.

P07A4

Transmission Friction Element B Performance/Stuck Off.

Generic
Powertrain
Generic code
High severity

How this code is built

P: SystemPowertrain
0: Defined bySAE, the same on every car
7: AreaTransmission
A4: FaultThe specific fault in that area

What it means

P07A4 means the transmission control module has detected that friction element B, a clutch or brake pack inside the automatic gearbox, is not engaging when commanded (stuck off or slipping). It sets when input and output shaft speeds do not match the expected ratio for the commanded gear, or when slip is seen while that element should be applied. Which clutch or brake is 'element B' depends on the manufacturer and gearbox, so the exact gears affected vary.

Symptoms

Engine revs rise without matching acceleration (flare or slipping) in certain gears
Harsh, delayed or missed shifts
Gearbox stuck in a single gear or limp mode
Gearbox warning light or malfunction message on the dash
Loss of a gear or no drive in forward or reverse
Burnt smell from the gearbox fluid

Possible causes

Low, degraded or contaminated transmission fluid reducing clutch apply pressurelikely
Worn or burnt friction plates in element Blikely
Faulty shift solenoid or pressure control solenoid for element B, sticking or electrically failedlikely
Valve body wear, sticking valves or internal hydraulic leaks, including worn seals or sealing ringspossible
Wiring or connector fault between the gearbox and control module, or poor earth or supplypossible
Faulty speed sensor or pressure sensor giving false slip readingspossible
Outdated gearbox control software where the manufacturer has issued a fixrare

How to diagnose

Read all stored codes and freeze frame data, noting gear, fluid temperature and speed when the fault set, and check for related solenoid, speed sensor or ratio codes
Check transmission fluid level, condition and smell, following the manufacturer's procedure for that gearbox as some are sealed or need a set temperature
Inspect the gearbox wiring, connector and harness for damage, fluid ingress, corrosion or chafing
Check the battery and charging voltage, as low voltage can cause false shift faults
Use live data to compare input and output shaft speeds, commanded gear and slip, and check solenoid duty and line pressure against specification
Test solenoid and sensor resistance and signals against the manufacturer's values
Carry out a line pressure or clutch apply pressure test where the model allows
Check for available software updates or technical bulletins for the specific model and gearbox

How to fix

Correct the fluid level or replace degraded fluid and filter using the specified type
Repair or replace damaged wiring, connectors or poor earths
Replace the faulty solenoid or speed or pressure sensor once confirmed
Overhaul or replace the valve body or worn seals where hydraulic leaks or sticking are found
Rebuild or replace the gearbox if friction element B is worn or burnt
Update the transmission control software where an outdated calibration is a known cause for that model

Can I keep driving?

High severity

Avoid driving beyond a short trip to a workshop, as slipping clutches can quickly burn out and cause costly internal damage. If the gearbox is in limp mode, slipping or has lost drive, stop and arrange recovery.

Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.