Toyota RAV4 Forums banner

1 - 2 of 2 Posts

·
Registered
Joined
·
15 Posts
Discussion Starter #1
About a year ago my vsc light and cel came on.

I did the reset by disconnecting the battery.. It was on a trip to Ga from Md.. It happens a few times, but didn't come on for a while and the dealer couldn't pull the codes while it was off... It eventually came on again, and I had to replace the thermostat.

Now a year later, it back on... The rub is the gas cap was not tight... I can reset it and wait to see if comes back on, but I have a trip scheduled in December.. If it's the charcoal canister or such, I'd rather replace it now...

However, if it's the gas cap, I'd rather not pay the dealer to tell me I'm a moron...

So, doesn't anyone know if the gas cap is off, and it's retightened, will go the lights go off by itself..

I'm gonna go to AutoZone tomorrow to see if I can get the codes..
 

·
Premium Member
Joined
·
1,427 Posts
Stop disconnecting the battery.

VSC is commanded when you have a CEL because the system is detecting an error and it does not "trust" the sensors.

CEL is triggered because there is a problem.
If you had an oil light would you just "reset" it? Of course not.
The CEL indicates a problem with your emissions or fuel control system. It MAY only impact emissions, but it will also likely impact power and fuel economy, and it COULD result in damage to the engine (example, mixture too lean).

There are two types of codes.
"Soft" codes do not trigger a light unless the fault is present for several restart cycles.
After triggering a light, soft codes will typically clear themselves within 2-3 restart cycles.

The EVAP system (gas cap) is one such system.
Beyond the gas cap, other things that can trigger an EVAP code would be if you are in the habit of "topping off" the tank, and the fuel has overflowed into the charcoal canister. The canister is not cheap. If it is only a small amount of fuel, it MAY be able to purge itself over a couple of weeks (you may experience rough running because the mixture will be rich when the purge valve is open)

Hard codes will typically trigger a CEL immediately. They will generally clear themselves within 10-20 restart cycles after the problem no longer manifests on startup.
Some of these codes can not be cleared by disconnecting the battery, but all codes can be manually cleared using Techstream.

AutoZone can generally read most codes. Some, such as the TPMS, ABS, and transmission, they can not read or clear.
Keep in mind that the typical AutoZone employee has the automotive educational level of a typical 7-11 employee. There's a few who have been wrenching for years and know their stuff, but not many.
Do not trust their interpretation of the code. A code for an O2 sensor MAY mean that the sensor is bad. This is typically how the code is interpreted, and you are sent on your merry way with a new sensor. A code for an O2 sensor MAY mean that the sensor is doing its job perfectly and there is a problem with a valve, spark plug, or injector that is causing one bank to actually run lean or rich.
This can not be fixed by replacing the sensor.

There is a reason AutoZone employees make minimum wage and dealer techs make 3x that.
In California, AutoZone (and other parts store) employees are prohibited from even touching your car or offering diagnostic advice. They can let you borrow the tool, but when you read a P0477, they are not allowed to make a diagnosis.
 
1 - 2 of 2 Posts
Top