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ENGINE and TRAC lights in a 2000 LEXUS

I have a problem with ENGINE and TRAC lights in my ES300. When the gas tank is full, the lights are off. When the gas tank is about half to 3/4 full, both ENGINE and TRAC lights turn on. I have taken the car to a mechanic and he tried to diagnose the problem with his special device that he connected in the car. He looked up the codes and said it is the PCV valve and he changed it. The lights were off for maybe a couple of weeks and then they came back on. As soon as I filled up the tank a few days later, the lights went off. And this cycle repeats itself. Any help to fix this is much appreciated. Thanks.

When you say, “engine” light, I am going to assume that you are referring to the Check Engine Light (CEL). Going on that assumption, I can tell you that I have observed that this combination of lights (CEL + Traction Control) is frequently an indicator of a problem with the car’s Evaporative Emissions System.

Yes, I know that this seems counter-intuitive, but this is what I have observed, and the fact that you can relate the lights to the level of gas in the tank is probable support for my theory that you have a problem with the Evaporative Emissions System.

So, I would suggest that the next step is for your mechanic to check the functioning of the carbon canister, the lines, and the valves that comprise the evap emissions system. If this area is the source of the problem, hopefully you only need to have the vent control solenoid valve replaced, which is a relatively cheap and fast repair. If you are not so lucky, you may need to have the carbon canister replaced, and this will probably cost somewhere in the neighborhood of $400.

Incidentally, if you or someone else who drives this car is in the habit of continuing to put gas into the tank after the gas pump first clicks off, then you are the likely source of the problem. If you are setting out on an expedition across the Gobi Desert, it might make sense to put that extra 50 cents worth of gas into the tank, but if you are driving on normal roads in the US, all you are accomplishing is adding greatly to your potential repair costs.

Please report back to us on your findings.

Thanks very much. As soon as I know something, I’ll report back.