P0882: Transmission Control Module Power Input Signal Low
What to do
This code changes how every other transmission fault on the car should be read. Insist that the electrical supply and earth connections are repaired and the codes cleared before any transmission work is quoted — a module short of voltage reports faults in healthy parts, and those parts are expensive ones. Ask specifically for a voltage drop test on the supply and earth paths rather than a static battery voltage reading, which will look normal.
What this code means
The transmission module's supply voltage is below what it needs. This is the most expensive misreading available in the whole transmission range, and the reason is that modules do not fail cleanly when starved of voltage — they misbehave.
A module with insufficient supply does not stop. It carries on, badly. Solenoid drivers cannot hold their valves fully open, so shifts are slow or incomplete and the module records them as solenoid performance faults. Sensor references drift, so speeds and pressures read wrong and the module records ratio errors and pressure faults. Adaptation values get written using bad measurements, so shift quality degrades even after the supply is fixed until they are reset. Every one of those recorded faults names a perfectly healthy part, and because they are transmission parts, the quotations that follow are transmission-sized.
The corpus makes this argument twice already — under P0562, where low system voltage generates faults across the whole vehicle, and under P0641, where one reference supply feeds several sensors so they all report faults and none is faulty. This is the same argument in its costliest form, because the components being wrongly implicated here are inside a gearbox.
What is genuinely wrong is usually cheap: a corroded earth strap, a battery terminal that looks clean under its cover, a tired battery, or a relay whose contacts have burnt. The fix is often under twenty minutes and the alternative quotation is four figures.
The procedure matters as much as the diagnosis. Repair the supply, clear every stored code, drive the vehicle through a full range of gears, and read it again. Faults that return are real. Faults that do not were the supply talking.
Likely causes
Start here
- Poor module ground connection · moderate
- Corroded battery terminals · easy
- Failing battery · easy
- Faulty transmission control module power relay · easy
- Damaged module supply wiring · moderate
Less common
- Faulty alternator · moderate
- Corroded or loose connector · easy
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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