Sunday, June 10, 2012

Service engine soon Light Turned OFF after Jump Start?

The reason the light went out after the jump start, is because when the system loses battery voltage, the "clears" the trouble codes from the on-board computer. Once the computer "re-boots" itself, and re-checks all the systems, it will see the fault again, and re-set the Check Engine light. So, it's the same problem, it just took the on-board computer a little bit to re-evaluate the problem after the power loss.

Actually, When the Check Engine light comes on or Service engine soon light comes up, this is the Engine ECM way of telling you there is a problem in one of the monitored systems. Unfortunately, there are literally number of parts and sensors monitored in various systems, and to take a "guess" as to which part/sensor in which system is faulty, is virtually impossible.

However, if you are not experiencing any drivability issues such as skipping, stalling, shifting problems, etc, then more than likely, the problem is going to lie in the EVAP (emissions) system.

Very commonly in many such cases, this could be a faulty, loose or missing fuel cap or even putting fuel in while the vehicle is running.
So to test/inspect the problem

  • Check the cap for any cracks in the rubber o-ring on the underside.
  • Check the fuel filler neck for any signs of chips or debris. 
  • Check under the vehicle, around the area of the fuel tank and the EVAP canister looking for any vacuum lines that have dry-rot cracks, holes or loose/missing connections. 

If these all check out, then the best thing to do at this point is to have the "p-codes" read from the on-board computer. There are 4 digit P codes stored in vehicles computer.
These p-codes are what is used as a "starting point" for the diagnosis and will tell which part/sensor in which system has the fault.
There isn't a Mechanic on the planet that can tell you what is wrong with the vehicle just by "looking" at the Engine Light. Every single Mechanic's first course of action WILL be to obtain the p-codes. Once you get these p-codes you can more accurately and efficiently diagnose the problem and then make the repair. You can have these p-codes read FREE (except in California) at any local "big chain" part store (ie. AutoZone, PepBoys, Advanced, etc).

Once you receive the P-codes,you can troubleshoot the problem further with help of this P-codes.

This details will help.

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