What it means
The transmission control module detected that eighth gear could not be engaged as expected. The code does not identify the cause or what gear the transmission will use instead.
At a glance
- Usually lights the check-engine light
How it works
The transmission control module commands eighth gear and checks speed signals to determine whether the ratio was achieved. P07D8 sets when eighth gear cannot be engaged as expected, which may happen if its shift solenoid does not open or the eighth-gear clutch element slips.
Common causes
Most likely first.
- Solenoid stuck closed
- Slipping clutch in 8th gear element
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
How to diagnose it
- Record freeze-frame data and compare commanded gear with actual gear and input/output speed readings to confirm the failed eighth-gear engagement.
- Check for related transmission codes and note which shift or driving conditions trigger the fault.
- Inspect transmission wiring and connectors serving the shift solenoids and speed sensors for damage or poor contact.
- Test the relevant solenoid circuit and command solenoid operation using the manufacturer's procedure.
- If electrical tests pass, check the hydraulic circuit and eighth-gear clutch element for failure to apply or for slip.
Common fixes
- Repair damaged wiring or connector faults in the relevant solenoid circuit.
- Replace a solenoid confirmed stuck closed or electrically faulty.
- Repair the hydraulic fault preventing eighth gear from applying if tests locate one.
- Repair or replace the slipping eighth-gear clutch element if internal diagnosis confirms it.
Can I keep driving?
Avoid high-speed travel or heavy loads if the transmission slips or cannot engage eighth gear, because continued slipping can overheat and damage internal parts. If it shifts unpredictably or loses a safe gear, stop driving and arrange recovery.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.