Cause
Internal transmission failure
Mechanical failure inside the transmission — a clutch pack, a planetary set, a bearing or a shaft — as opposed to a control, sensor or hydraulic fault outside it. It is the conclusion of last resort and belongs there, because it is the most expensive answer available and almost everything cheaper produces the same codes.
Ratio codes are what it usually announces itself with, since the module compares input and output speeds and finds a ratio the gearbox should not be able to produce. But a solenoid, low fluid, a stuck valve or a worn valve body will all give the same reading. Rule those out first, in that order — they are cheaper, commoner, and each is a genuine repair when found.
The evidence that distinguishes it is physical. Debris in the pan and on the magnets — clutch material, metal, or bronze from a bushing — is the strongest indicator available, and burnt-smelling fluid supports it. Drop the pan before quoting, because it converts a suspicion into a finding. A gearbox slipping in one gear and correct in others points at a specific clutch pack rather than at general wear, which is worth knowing before deciding between repair and replacement.
Typically specialist work. Needs equipment or training most home workshops do not have.
Some of these codes mean you should stop driving
1 of the 4 codes this can cause indicate a fault where continuing to drive risks damage or is unsafe. Which one you have matters more than the cause does — read the code's own page before deciding.
Codes this can cause (4)
Codes where this is a likely explanation first, rather than merely a possible one.
Information, not instruction
CarGeek is a reference, not a service manual. Its pages are written from public sources and from what other people have found, never from a manufacturer's own service information, so they can be wrong or incomplete for your particular vehicle. Some of what they describe carries real risk: high voltage, fuel under pressure, stored energy, hot and moving parts.
Have anything you intend to act on checked by a trained person against the manufacturer's own procedure for your vehicle. Nothing here replaces that procedure.
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What makes one worth reading:
- The car — make, model, year and engine. The same fault behaves differently on each.
- What you measured, not only what you replaced.
- What actually fixed it — or that nothing did, which is worth knowing too.
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