PontiacBonnevilleClub.com

I am having chk engine light for evap (loose gas cap) , it was on every once in a while, now it is on all the time. Unfortunately here in PA we have emission inspection and if your chk engine light is on it will not pass.

Since most sensor in any car are operated through applying so many volts (lets say 5 volts) to the sensor at one leg and then the icm reads the voltage on the other leg coming out. Doesn't this mean that most sensor such as the evap sensor is just a resister. So is it possible to unhook the wire harness at the evap sensor insert a resister in to the wire harness so that we can achieve a voltage that is within range that the computer will accept so that a Chk engine light will not come on.

I saw some post about gas cap issue. But i wanted to repost so everyone could here my brilliant idea.

Brandon

You could also spend that time figuring out what the problem is....

00Beast you are right and i thought about that as i typed it. But i was more of just wondering if that would work. I guess I always tend to see if there is a way around it.

It actually seems like it would be a 2 minute fix as long as I new what a good operating voltage was.
I could figure out the correct resistor to use.

I'm more curious to see if it would work, then actually doing it.

Well you have to figure out WHICH sensor of the evap system is throwing the code.....at that point you may as well just replace the faulty sensor.

if you figure out what the sensor is, you should be able to get the specs for the sensor to show you what the correct reading is. then that will tell you if you can use a resistor and if so what ohm you would need. OR if you have someone local to you on like Club GP with DHP Powrtuner you can just disable the CEL for that code and it will never come one again.

S

I would never suggest bypassing a sensor or code just so you do not have to replace something. It seems like a lot more work to bypass it than to just find the fault and then fix the issue.

What is the actual code you are getting? Have you actually checked the cap, replaced it and verified there is no rust on the sealing surface and you are getting a good seal? Let's try to fix the issue first and that would be by starting with the actual code setting the SES light.

Also have to remember that voltage and resistance are two different things. If you wire in a resistor on a system that works off of adjusting voltage, then all you're going to do is create a bigger headache. Resistance is measured in ohms, and symbolizes electrical losses through a system, voltage is the measurement of the "pressure" a system sees, and amperage is the "flow" a system has/needs.

Thanks for everyone's help. I was more interested in the idea of if it would work or if anybody has attempted. With a degree in electrical engineering i already kinda had an answer but since i don't specialize in electrical systems in cars only hospital equipment, i thought i would ask. knowing that the majority of the sensor within the engine do adjust with the changing conditions of the car it would be hard to over ride any of them. But occasionally some of us out there get that pesky CEL to pop up on the dash and i thought i would throw the idea out there.

I will chk for rust around the filler neck. I will also pick up a new gas cap probably needs a new one anyway. I will chk evap solenoid and vent valve. i will report back friday afternoon with results. Thanks everyone

I had the Check Gas Cap come on in the DIC a year or so ago. Bought an aftermarket one and the message hasn't come back since. Note that I could not see anything visually wrong with the original gas cap, but the PCM sure could when it did the evap testing.

Good luck.

xdhd350 wrote:I had the Check Gas Cap come on in the DIC a year or so ago. Bought an aftermarket one and the message hasn't come back since. Note that I could not see anything visually wrong with the original gas cap, but the PCM sure could when it did the evap testing.

Good luck.

The gas cap is vented so to speak.