P0829: 5-6 Shift Malfunction
What to do
You may notice nothing at all, or only a slight hesitation at motorway speeds. If a garage reports that it drove fine, ask whether the test drive was long enough to reach and hold top gear — this change does not happen around town.
What this code means
The change from fifth to sixth did not complete correctly. The flare-versus-tie-up distinction set out under P0781 applies unchanged and is the most useful thing a driver can observe about it.
What is particular to 5-6 is when it happens. This is a cruising shift, taken at low torque and steady speed, so it is both the gentlest change the transmission makes and the one least likely to be noticed going wrong. Like P0784 before it, the code usually arrives before the complaint does — and it will not reproduce on a short test drive that never reaches top gear.
Likely causes
Start here
- Low or degraded transmission fluid · easy
- Low transmission line pressure · specialist
- Failed shift solenoid · moderate
Less common
- Worn valve body · specialist
- Worn clutch packs · specialist
Symptoms
Components involved
Information, not instruction
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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.
Community experience
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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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