C0077: Low Tyre Pressure
What to do
Check all four tyre pressures with a gauge when the tyres are cold, including the spare if it is a full-size one. Inflate to the figure on the door pillar or in the handbook. Then reset the tyre pressure system — on many cars it learns from a baseline and will keep warning until told to. Look for a nail or a bulge while you are there, and if one tyre keeps going down, have it inspected rather than keep topping it up.
What this code means
The system has detected a low tyre pressure, or the circuit reporting it is faulty.
A tyre pressure code in the ABS block is not a filing mistake — on many cars the ABS sensors are the tyre pressure monitor.
A soft tyre has a smaller rolling radius, so it must turn faster to cover the same ground. The module already measures all four wheel speeds precisely; comparing them against each other reveals a deflating tyre without any sensor inside the wheel at all. That is indirect TPMS, and it is why this code lives here.
The method has consequences worth knowing. It detects difference, so four tyres losing pressure together are invisible to it — which is exactly what a winter does. It needs resetting after inflation or a tyre change, because it works from a learned baseline. And it cannot tell you which tyre or by how much: only that one is behaving differently.
Direct systems put a pressure sensor in each wheel instead, report actual figures, and bring their own failure modes — flat batteries after several years, and sensors that need programming to the car.
Either way, check the pressures with a gauge before assuming a fault. The system is usually right, and a cold morning is the commonest cause of all.
Likely causes
Start here
- Underinflated tyre · easy
- Tyre pressure system not reset after inflation · easy
- Faulty tyre pressure sensor · specialist
Less common
- Mismatched or incorrectly sized tyres · easy
- Faulty wheel speed sensor · 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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