What it means
The transmission control module detected a fault during a 7-to-8 shift. The code does not identify a specific failed part.
At a glance
- Usually lights the check-engine light
How it works
During a commanded shift from 7th to 8th gear, the TCM checks shift timing and transmission speed changes to confirm the transition completed as expected. This code identifies a fault during that shift, but does not by itself name the failed component.
Common causes
Most likely first.
- Worn or damaged 8th-gear friction element
- Low or degraded transmission fluid
- Hydraulic pressure loss or valve body fault
- Shift solenoid sticking or malfunctioning
- Internal transmission wear or damage
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
- Save freeze-frame data and review commanded gear, actual gear, shift timing, and other transmission codes to see what happened during the 7-to-8 shift.
- Check the transmission fluid level and condition using the manufacturer’s procedure, and look for leaks that could reduce shift pressure.
- Inspect the wiring and connectors for the shift solenoids and speed sensors for corrosion, damage, or loose connections.
- Review live data during a safe road test to confirm whether 8th gear is commanded and whether input and output speeds respond as expected.
- If sensor signals are plausible, test the relevant solenoid and hydraulic pressure using manufacturer procedures, then assess the 8th-gear friction element if needed.
Common fixes
- Repair fluid leaks and restore the level using the specified fluid and procedure.
- Replace degraded or incorrect transmission fluid if service findings support it.
- Repair damaged wiring or connector faults in the solenoid or speed-sensor circuits.
- Replace a shift solenoid confirmed faulty by testing.
- Repair a confirmed valve-body pressure fault or worn 8th-gear friction element.
Can I keep driving?
If the 7-to-8 shift slips, shudders, or causes limp mode, avoid continued driving because additional slip can damage internal parts. With no severe symptoms, use gentle acceleration and avoid towing or sustained high speeds until it is checked.
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.