Typically with an aftermarket gauge that connects to the OBD-II port. Scangauge is very popular, ultra-gauge is about 1/2 price. It doesn't have as many abilities but it will read and clear codes. Now if you are talking service codes (oil change reminders), they can be done manually without any special devices.
You can also take the car (assuming it's drivable) to most major auto parts stores and the can read the code with their readers for free. You can then search the web or here for explanations. NOTE: there are some toyota/hybrid specific codes they can't "see" and I'm not sure if they can or will clear codes for you though.
If all you want to do is to clear the codes without reading them, disconnect the 12V battery for a few minutes and then reconnect it.
My 12V died and my car wouldn't run even after I replaced it. I took it to the dealer and they said all they did was "clear the codes" and it runs fine. They said there was a failsafe code because it said it was out of gas (it had 5 gallons), so they may just be full of it. Anyway, I'm posting this because simply disconnecting the battery may not be enough, apparently.
I haven't had all that much experience with clearing the Gen1 codes and intially I did have a few that caused me some problems, briefly. Each time it involved the the Tiangle of Death and and some obscure 3000 series codes. And each time is seened to come back to the 12v battery or the connections. Firsst OEM battery, passed my load tests but failed the dealers diagnostic test. So to be on the safe side, until I could order in a Yellow Top Optima I kept a jumper battery in the trunk, just in case. If I got a Code or Warning, I would just hook up the spare battery and drive on and the code would go away. For about a week I just left it hooked up to see if my mileage would improve and it did. So I went ahead and installed the Yellow Top when it came in. No problem since, and I eventually sold the care with some confidence that the problem had gone away. So say that dirty or corroded therminals or connecter can cause grief and I believe that as well when it comes to the Prius. Steve
I should mention that once, early in my experience with my used Gen1, I got the Red Triangle a few blocks from home and the ICE wouldn't run, so I did the "switch-4-times" thing to get it to run on battery and managed to get to within a block of home, did the switch routine again and got into the drive way with only a couple read bars showing. Hooked up the Jumper battery, Cleared what code that were still evident. But I still had the Red Tiangle. Called the dealer, because they had just been working on a recall item and they said to bring it in. I managed to get the ICE to run this time and started the 10 mile trip to the dealer, intially it wouldn't make highway speed, until the battery bars came up into the blue, then all was fine and by the time I got to the dealer I turn it off and on again and the Red Triangle went off and every thing was fine. That is when the dealer tested and recommended replacing the 12v battery. Steve
Got it back from the dealer, and here is the sequence of events for my Gen 2 (2005) 12V died while driving (had problems with it in the past, and it was 8 years old) engine died due to 12V being gone ran on HV battery to get off the road and it ran low (this is key) "Problem" error displayed Verified sufficient gas in the car replaced 12V, but ICE still would start, then stop Dealer found codes P3190 and P0A0F and said it was "Limp Mode" which happens when the battery is discharched too much. They cleared the codes and it ran fine (because I had replaced the 12V) So my conclusion is that disconnecting the battery does not clear all codes, particularly if the code is due to the HV battery running low, even if you've corrected the condition that would prevent it from charging. The dealer said (as expected) that there is no way I, as a user, could clear the code myself, even with a code scanner. Take that with a grain of salt.
Another conclusion: Don't run your HV battery low if your engine dies and you might still be able to fix it yourself.
Cleared all trouble codes in 2002 Prius--after replacing 12V sec. bat. However, I also cleared "Headlight" indicator lamp symbol in dash display. Any idea how to "Re-Install"??????
There is also another way to clear the codes, without the mini VCI, offered by nh7o elsewhere on this sight. In reference to what he is saying below, I need to figure for myself just which pins are #'s 4 and 13. 1. Short pins 4 and 13 of the OBDII port and then make car Ready. 2. Press the brake pedal 8 times within 5 seconds. 3. lights should go off if no problems remain. These brake codes are stored in nonvolatile memory and can't be cleared by removing the 12V. Read more: http://priuschat.com/threads/vsc-abs-brake-light-on.134873/#ixzz2xOoiQ3MT Follow us: @PriusChat on Twitter | PriusChat on Facebook
That's one of the non-scantool ways to clear codes - that's the one that only clears codes stored in the antilock-brake computer, not any of the other computers that run the car. There's a different set of steps to clear only codes in the steering computer, and another different set to clear codes in the airbag system, for example. You can find them all in the service manual ... along with pin diagrams of the OBD-II connector so you know which pins CG, Tc, and Ts are, and also how to translate the blinking dash lights into equivalents of the codes a scanner could read. (Unfortunately, two of the most interesting computers, the Hybrid Vehicle and the Battery computers, do not have lights to blink, so a Prius-aware scanner is the only way to know what they're fussing about. The steering computer can blink a light, but you have to bring your own light.) -Chap
I am getting a new main (not 12 volt) battery and am installing it my self. When I am finished installing the battery will I have to take it to dealer to clear all the triangles ect from the display ?
No. As part of the traction battery installation process, one of the first things you should do is to disconnect the 12V battery. When you remove power, the DTC logged by the hybrid vehicle ECU, traction battery ECU and engine ECU will all be cleared.
An ELM327 (via USB) plus any Windows-based diagnostic program on a laptop should read engine trouble codes and be able to clear the codes. You will not be able to read the prius-specific hybrid codes this way. You can only clear them. I assume the engine codes should still be readable since OBD-II is a standard requirement in the United States. You need a Mini-VCI cable (J2534) with TechStream (Windows required, I recommend 32-bit XP) and the correct driver for the cable to read the hybrid trouble codes and also perform some special Toyota functions.
Disconnect the 12V battery for a few minutes, then reconnect. However the more interesting question is why that DTC appeared to begin with. One reason might be that the traction battery interlock switch is not correctly installed.
