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Hello,
my 06 Saturn Ion had being giving me (check gas cap) and check engine light came on. So, I changed the gas cap and reset the check engine light then took a 2400 miles road trip. 3 weeks from reseting the check engine light it came back on. with two codes P0106 & P0455 (MAP sensor & Large vapor leakage).
I noticed a new phenomena when I open the gas cap, I notice that the neck of the gas tank and the gas cap has gasoline on them, which was not happening before.
First question, are these two code related to each other? I am asking because (Saturn Engine Diagnostic parameters) for P0455 puts P0106 as the (secondary monitoring parameters and enable conditions). What does that mean? I am really interested in understanding this part.
My other question should I start fixing the first or second code first? I hear a mechanics says something about starting with the code with lower number, but not sure if I heard him right. please correct me.
Final question, what does the gasonline on the cap and the neck of the tank means? does it mean that the tank has problems? can it be the MAP sensor!! which I doubt.
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The MAP sensor should play a part in setting the code P0455. When the EVAP purge valve opens up to draw fuel vapors out of the vent canister, it’s essentially a built in vacuum leak. The MAP sensor is going to sense that vacuum leak as more atmospheric pressure getting into the manifold. However, you probably wouldn’t need to diagnose one code with any relevance to the other.
Diagnose the P0106 code first. This one could affect engine performance and fuel economy. That means checking power and ground circuits and, more importantly, apply a vacuum to the MAP sensor itself and make sure that the voltage changes proportionally with the vacuum applied. IIRC, every five inches of vacuum should about equal a change of roughly one volt out of the MAP signal circuit.
As far as the P0455 code goes, GM is notorious for EVAP vent valve problems. Dust and dirt gets into them and they don’t close right anymore. You might get away with shotgunning a new vent solenoid if you don’t want to pay for a smoke test at your local garage. (It’s a good gamble, but a gamble nonetheless.) I can’t remember where the vent solenoid is on that car. Part of me wants to say it’s up over the gas tank not too far from the right rear wheel. Another thing I can’t quite remember, is whether or not the gas tank has to come out entirely.
I don’t know what to say for fuel sloshing up the neck onto the cap. If you do have to drop the tank for the vent solenoid, you’ll have the opportunity to check the tank and the neck anyway.
Good luck.
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