P0802: Transmission Control System Malfunction Indicator Lamp Request Circuit/Open
What to do
Nothing will feel wrong, and that is exactly the problem: this fault means future transmission problems will not light the warning lamp. Worth repairing on those grounds alone, even though the car drives normally.
What this code means
The wire by which the transmission module asks for the warning lamp is open. On vehicles where that request is a discrete wire rather than a message on the data bus, this fault has a consequence worth stating plainly: the transmission can no longer warn the driver about anything.
Every future transmission fault will still be stored, and the transmission will still protect itself, but no lamp will come on to say so. A driver could accumulate a serious fault and drive on it for months with a dashboard that looks perfectly normal. That makes this a fault about the warning system rather than about the gearbox — inconsequential today and potentially expensive later, which is an unusual and easily dismissed combination.
Likely causes
Start here
- Open circuit in module wiring · moderate
- Corroded or loose connector · easy
Less common
- Poor module ground connection · moderate
Rare
- Faulty transmission control module · specialist
Symptoms
Components involved
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.
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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