Drive and idle is normal but suddenly check engine, pcs and vsc light come up. mechanic have checked. they said this car have few code. p0420, p0430, c1734, b2090, c1a40

Your VSC system doesn't have anything to do with your gas cap, unfortunately. You're going to either need an OBD2 Scanner to read the messages for your check engine light or take it to a mechanic/dealership to read the code and reset that light. You can also go to Autozone if memory serves and borrow a scanner to see the codes. You can pick up scanners from amazon for 10-50 USD, or about 40 USD from Autozone. Your VSC system not working means that you're not going to have optimal stability while driving until you can get the system operational again. Note that since it's Toyota Proprietary, you will not be able to read the VSC codes with the scanner, just the standard check engine codes. If your vehicle's braking system still seems to work, it could be a sensor malfunction, but I would recommend you take your vehicle to a Toyota dealership (unfortunately) to see if they can find the fault. Don't let them BS you either... http://www.greenhybrid.com/forums/f49/check-vsc-system-warning-dealer-says-normal-display-20826/index2.html

P0420 & P0430 You need new catalytic converter
The P0430 check engine light code, like P0420, means the catalyst system efficiency is below the required threshold. Simply put, this means your car is adding more pollution into the air than it's supposed to.

A p0420 sets after Engine and catalyst are warmed up, vehicle driven within set vehicle engine speed range and waveforms of heated O2 sensors bank 1 sensor 1 and bank 1 sensor 2 have the same amplitude.
Catalytic convertor and O2 sensors need to be tested

Battery was diconnected for 1 minute and then reconnected. All lights are off.

The check engine light ,trac control light and VSC light are on. Does this normally represent a serious problem on a 2004 toyota solara?

You need a scan tool to retreive the diagnostic trouble code in the VSC system

You Definatelly got some Bad Fuel. Get a can of B-12 Chemtool from any Auto Parts Store or Wal-Mart and Pour it in the Gas Tank then Let it Run for a While. Should help Dramatically! Let me know!

First thing I would do is clean the throttle body if nothing changes check your mass air sensor if still nothing. change (or clean) your oxygen sensors can normally be found on the exhaust manifolds. also it couldn't hurt to give it an oil change and use a fuel additive to get rid off all the nasty build up in the engine I use BG 44K

That's all the information I have good luck!

Often when the battery is disconnected or replaced the computer will lose it's learned idle settings. You could try letting the engine idle in park until the engine temperature comes up to normal and leave it like that for a few minutes, then put the Air con on and let it idle again for a few minutes, then switch the air con off and put it into drive. If it does not stall, let it idle in drive for 2 minutes or so, and then do the same with the Air con on. This should relearn the base idle settings and stop it from stalling on you. Before you carry out this procedure you should make sure that when you replaced the battery you didn't remove any other plugs or knocked anything that may be causing the fault. If you try this procedure and it still stall when you select drive, you will need to get a Mechanic to check the vehicle over.

Hope this helps,
Mark.

As compgeek09 stated, yes the DTC (diagnostic trouble code) should be found out first. And yes, AutoZone or Advance Auto Parts should be able to retrieve the code for you. Then you should be able to tell how severe the problem is.

Yes, you should still be able to drive the vehicle. When the check engine light starts flashing is when you should stop driving the vehicle. Also, if your city/state require smog emissions, the vehicle will probably fail the test. Then you'll be required to repair the problem.

Lastly, Vehicle Stability Control. That light is probably related to the check engine light since it sounds like they both came on at the same time. The VSC controls engine power. Thus, if there is a problem with the engine (check engine light), the VSC can't do it's job.

Once the check engine light problem is repaired, the VSC light should go off as well.