Cause
Transmission fluid leak
Fluid escaping from the transmission, lowering the level until pressure cannot be maintained. Low fluid is the commonest cause of almost every transmission complaint, so a leak is the thing to find before anything internal is suspected.
The symptoms follow the level: slipping under load, delayed engagement, harsh or missing shifts, all worse when hot and worse on gradients. The usual leak points are the pan gasket, the output and input seals, the cooler lines and the case connector — that last one also wicks fluid into the module's harness, which is a separate and expensive fault from the same leak. Check the level by the manufacturer's procedure, since most modern units have no dipstick and read meaningfully only at a specified temperature.
Typically a moderate job.
Some of these codes mean you should stop driving
1 of the 1 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 (1)
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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