You need a short piece of wire, bear both ends, open the diagnostic cover and 'bridge' terminals TE1 and E1
Then turn on the ignition and watch the CEL, it will flash, if it is constant then you have no fault codes if not then count the flashes, there will be a pause and it will start again, keep counting, the idea is if the first sequence flashes three times (for example) then write down three then after the pause if it flashes six times then the code is 36.
Check out http://www.troublecodes.net and follow the trouble code link to Toyota for more info, a diagram and a list of what the codes mean, if you ever have any trouble with the abs and the abs light comes on then you can try and diagnose the fault in a similar way by bridging Tc and E1 but you first have to remove the short pin in DLC1 (inside the diagnostic cover lid there is a 'map' showing you the terminal numbers) .
