Hey Folks,
I just purchased a 2009 Aspen. The day after buying it the gascap warning comes on and engine light. Codes are 0456 and 0457 I believe. Loose or missing gascap and small EVAP leak detected.

The question is can a shop mechanic force a code reset so it goes away for a while? I ask because when we test drove it there were no trouble indications. However, there was a nearly flat tire. It has the TPMS and no warning was present. After the gascap warning appeared I tested the TPMS my deflating a tire partially. Of course I get a warning right off the bat. So I guess we were taken by a crooked dealer who cleared the codes before the test drive.

What do you think?

Thanks,
JT

 

Starting with the introduction of 2005 model year vehicles a new diagnostic trouble code (DTC) P0457 - Evap System - Loose Fuel Cap was introduced. Also added to some vehicles was an instrument cluster message in the odometer display or message center (EVIC) that alerts the driver that the gas cap is loose.

The PCM monitors the fuel level for a "significant" change in either direction and remembers that this has recently occurred. A loose fuel cap DTC, cluster message or message center message matures when the check for the EVAP system large leak condition fails after the fuel level change event. If a leak of greater than 0.090" is observed after a fuel level change, a loose cap diagnostic single trip failure is stored and the cluster message or message center message is displayed even though a DTC may not yet be present. DTC P0457 - Evap System - Loose Fuel Cap is stored and the MIL illuminated after 2 cold start failures of the large leak diagnostic checks following a fuel change event.

Only the passing of one of the 3 EVAP system diagnostic routines large leak, small leak or loose gas cap) by the PCM will validate that the cap is no longer loose and turn off the MIL light or message.

DTC P0457 - Evap System - Loose Fuel Cap will be stored and the MIL illuminated after 3 cold starts.

To temporarily clear the gas cap loose message from the odometer or message center press the reset button on the odometer or message center while the message is being displayed. This clears the message for the current key cycle only.

To clear the gas cap loose message from the odometer or message center ensure the gas cap is tight and let the vehicle run the small leak diagnostic routine. The small leak diagnostic routine will pass a sealed system after an 8 hour soak and a negative 3° C change in fuel temperature from the last key cycle.

NOTE: A heated garage may effect the small leak diagnostic routine.

To clear the gas cap loose message from the odometer or message center and matured DTC (MIL light) diagnose and repair the leak and then erase DTC's with the DRB IIIŽ/StarSCAN™ scantool

NOTE: The DRB IIIŽ/StarSCAN™ scantool may be used to reset the Loose Cap message. Select the PCM Reset function on StarSCAN™ (version 6.05_SP1 or higher) or the Clear PCM Batt Disconnect function on DRB IIIŽ.

Disconnecting and reconnecting the battery will also clear the message.

If a gas cap loose message is displayed or DTC P0457 - Evap System - Loose Fuel Cap is set without P0455 - Evap System Large Leak then ensure the gas cap it tight, no further service action is required.

 

I unhooked the battery yesterday to clear the code. Today I have been writing down all events such as cold start, warm start, add fuel...etc. No code or gascap message has appeared yet so far.

Here is what has happened today after battery disconnect...

Cold start
Cold start
Warm start
Cold start
Warm start
Add fuel
Warm start

We'll see what happens next.

 

Very Nice!

I hope it was a simple fault code and that a simple resetting resolves this issue for you.

Please keep us posted on the results.

 

Today there has been a few cold starts, a few warm starts, and a fuel fillup. No codes. I'm keeping my fingers crossed it doesn't happen again. We'll see.

Thanks!

 

Gascap warning came back. Here's exactly what has occurred since I did the battery disconnect...CS = Cold Start, WS = Warm Start

8/31
CS, CS, WS, CS, WS, 3.99 Gal fuel added while low fuel lamp lit, WS.

9/1
CS, CS, WS, 21.275 Gal fuel added (fill up), WS, WS, WS, WS, WS, CS.

9/2
CS - Gas Cap Warning appears, again!

I don't get it.