Shannon75

Ok so I have the gascap light that keeps coming on at start up comes on about 10 seconds after start up no cel light and no codes stored it has been on for a few weeks I replaced the factory cap with a mopar factory cap but still no good. Looked at a bunch of forums but most have codes nothing any help please

ronjenx

The gas cap warning doesn't always mean there is a problem with the gas cap.

If the computer sees a leak in the evap system, and the test happened to run fairly soon after the tank was filled, it will give the gas cap warning. This is because it thinks it's possible the cap was not properly installed at the time of fill-up.

Here is some information about how the gas cap is monitored. Note that in the explanation it states the leak could be elsewhere in the system.

P0457-LOOSE FUEL CAP

Theory of Operation

Fuel level is recorded when the ignition key is turned off and is compared to the fuel level when the ignition key is turned back on. The PCM recognizes an increase in fuel level and will fail the Medium leak test because the fuel cap is broken or not installed properly. GAS CAP will be displayed in odometer to inform the owner that the cap is off of loose.

• When Monitored: Ignition on. Ambient Temperature between 4° C and 32° C (39° F and 89° F) Close Loop fuel system. Test runs after the medium leak test is inconclusive and the PCM has senses a fuel increase.
• Set Condition: If a leak greater than .090” is detected by the PCM for two consecutive cold start trips after a significant fuel level change, this DTC will set. One good trip turns off the MIL.

Here is some additional information from the '08 factory service manual:

• GasCap Message Display - On vehicles manufactured with a United States country code, each time the cluster receives an electronic message from the PCM indicating a monitored leak in the evaporative emissions system, the cluster replaces the displayed odometer/trip odometer value with the textual message, gascap. This message serves as a reminder to the vehicle operator to check that the gas cap is properly installed and tightened, but could also indicate another source of air leakage in the on-board evaporative and vapor recovery emissions systems. Unless the leak is corrected, this message will latch and remain displayed during the current and each subsequent ignition cycle until the trip odometer reset button is pressed and released momentarily, which will revert the display to the odometer/trip odometer information that was last displayed for the remainder of that ignition cycle. Once the source of a leak has been corrected, either momentarily pressing the trip odometer reset button or cycling the ignition switch will unlatch the message and return the odometer/trip odometer to normal operation.