Tpms

It could be a number of issues; it's hard to say:

1) Tire pressure problem

2) Failing sensor unit.

3) Failing receiver unit.

4) Failing ECU.

Tom

 

My bet is on #2, because I think one of the TPMS sensor batteries is failing.

What do I win if I'm right? :madgrin:

 

It could also be interference from another sensor, such as his "other car", the 2010, parked closely.

 

The service manual says "When the tire pressure warning light circuit is open, the tire
pressure warning light flashes for 1 minute and then illuminates." It blinks at a rate of once per second (on for half a second, off for half a second).

The troubleshooting says to first check for DTC B1247 (Tire Pressure Monitor Receiver Communication Stop). The first step on this is to check the fuse marked 'ECU-IG' in the driver side junction box (next to the steering column), so you might as well do that before taking it in - though I would expect a lot more to have failed if this is the case. (This fuse carries the 'ignition ON' signal to the Body ECU, Gateway ECU and Power Steering ECU among a number of others.)

After that it's checking one or more wire harnesses and connectors leading between the Tire Pressure Warning ECU and the combination meter (dashboard panel), and from the Certification ECU (if you have Smart Key)/Transmission Control ECU (if you don't) to the Tire Pressure Warning ECU. It might require replacement of one or more harnesses or, if no problem is found, the Tire Pressure Warning ECU itself.

If the DTC is not recorded, the fault could be in the dashboard assembly itself. This can be tested by connecting an active tester (Mastertech/TechStream laptop) and telling the combination meter to turn the light on. If it doesn't, you need the dashboard assembly replaced.

If the Tire Pressure Warning ECU needs to be replaced, the valve transmitter IDs should be read from the old ECU before it's disconnected, using the active tester. They then need to be programmed into the new ECU once it's installed.

 

I think I'm having the same problem: 2008 Prius and the tire pressure light blinks for a minute whenever I start the car and then stays on. Tires are properly inflated, pushing the reset button does nothing.

What's my play here? Do I take it to the dealer or will a regular mechanic be able to tackle the job? About how expensive is it to get all the TPMS sensors replaced? I like having the warning light, but it's not a huge hassle for me to manually check tire pressure from time to time.

 

One difference, between your problem and the original poster, is seven and a half years. The TPMS sensors have batteries, that don't last forever, and 2008 sounds about right for failures to start happening.

Where in the world are you? In the 'States? And if so: which state? Some States will fail you at an annual inspection, some won't:

Tire Tech Information - State TPMS Regulations

I believe at (US) federal level there is regulation, that tire shops are legally obligated to send you on your way with functional TPMS system. There may be workarounds though, for example if you show up with loose rims, and maybe some shops are more lax?