Blink (a/k/a Flash) Codes – How to. - Historical

While the preferred, and only complete, way to get diagnostic trouble codes (DTCs) from the car is to use a scan tool with Toyota-specific capabilities to query all of the electronic control units (ECUs) in the car, sometimes you have one or more warning light(s) showing and no good scan tool handy, and you still want to know what the trouble codes are.

When that happens, you have another option, for some, but not all, of the ECUs in the car: you can use a short piece of wire between two specific pins of the car's diagnostic port, and trigger some of those ECUs to use the warning lights they control on the dash to blink out their trouble codes, and you can count out the blinks to get two-digit codes.

This is a feature carried over from pre-OBD-II days, and the number of ECUs in the car that can do this trick has been decreasing over the Prius generations. In Gen 1, a lot of the car's ECUs could do it. In Gen 2, not as many, but still several, can do it. In Gen 3, it may just be down to the skid ECU (responsible for braking, stability, and traction control), the tire pressure monitor ECU, and the airbag ECU.

In all three of those early generations, the skid ECU is one of the ECUs capable of blinking codes. That's good news, because when there are warning lights from the brake system, it's always good to know what the codes are without delay.

Some of the description on this page assumes you are interested in codes from the skid ECU (the brake warning lights, or VSC or skid lights, are on). The same procedures apply to reading blink codes from other ECUs that can give them. It's just a matter of which dash lights you count the blinks of.

The skid ECU makes the most interesting example, because most other ECUs in the car might control just one warning light on the dash. The skid ECU controls several. In Gen 3, for example, it controls the lights that say BRAKE, ABS, the VSC or skiddy-car traction light, and the ((!)) light (known as the ECB light, for electronically-controlled braking).

When trouble codes from the skid ECU are being blinked out, there can be codes blinking on more than one of those lights. Be sure to keep track of which codes flashed on which lights. Some of the two-digit code numbers overlap, and you need to know which ones blinked on which light to look up the right meanings in the repair manual.

To get started, you need nothing more than a short wire or paper clip. With the car turned off, short pins 4 and 13 on the OBD2 connector using the wire/clip, then put the car in IG-ON (press the POWER button twice with your foot off the brake).

Now observe the blinking patterns of whatever lights are blinking on the dash. If there are multiple codes, they will blink out in ascending order. Each of the indicators may blink out a different code so note that carefully. The two-digit codes obtained correspond to full DTCs that can be looked up in the repair manual.

This doesn't show historical codes, though. And again, only some of the ECUs in the car can do this. A scan tool like Techstream is needed to get trouble codes from the rest.

This Prius Wiki page has been created so that there is a convenient place to direct people, rather than regurgitate the same information over hundreds of posts.

The original thread (with thanks to Mr. F) from which this information was taken can be found here:

Check Hybrid System | Post #8 |PriusChat