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Old 09-22-2009, 08:06 PM   #1
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OBD_II Fault codes PO451, PO455, PO456

Seems like the evaporative/pollution system. Anybody know the fix on the G500 2002?

Should be covered under the emission warranty?

Any advice gratefully received esp. how to approach the dealer. I have the MB CPO warranty.
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Old 09-23-2009, 05:46 AM   #2
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Check the gas cap, maybe it's not on tight? Did you put gas in it with the engine running?
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Old 09-23-2009, 09:32 AM   #3
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Good catch

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Originally Posted by guardrail View Post
Check the gas cap, maybe it's not on tight? Did you put gas in it with the engine running?
I had the "red gas cap loose" indicator come on. The check engine light came on after this but the engine run strong and all fluids and temps are normal.

According to the owner's manual the system is supposed to reset itself after several cycles of driving.

I will fill the car with gas and see what happens. I do shut off the engine while filling.

Otherwise these codes seem to indicate tears in the evaporative system or defective sensors in fuel delivery or pollution. I got a free OBD2 check at Autozone but they don't have MB codes but all the brands seem the same as far as the messages go.
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Old 09-23-2009, 09:46 AM   #4
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Could be a bad gas cap also
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Old 09-23-2009, 11:53 AM   #5
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It's going in Monday so I'll have them check that cap!
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Old 09-24-2009, 08:51 AM   #6
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Originally Posted by ivanj View Post
It's going in Monday so I'll have them check that cap!
I don't know what Autozone's problem was with you -- those are generic codes: 0451 is the fuel tank pressure sensor is sending the wrong reading back to the ECM; 0455 is a large leak (0.040"); 0456 is a small leak (0.020"). Most EVAP systems can only be tested by the ECM when the fuel tank is 15-85% full. It is also a 2-drive cycle code but should clear, when fixed, on the next drive cycle if all the prerequisites are met (like the fuel level). EVAP problems tend not to cause any driveability issues unless it's something crazy, like the purge valve opening when at idle.

Regards,
paul...
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Old 09-24-2009, 02:40 PM   #7
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Thank you very much

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Originally Posted by paulv View Post
I don't know what Autozone's problem was with you -- those are generic codes: 0451 is the fuel tank pressure sensor is sending the wrong reading back to the ECM; 0455 is a large leak (0.040"); 0456 is a small leak (0.020"). Most EVAP systems can only be tested by the ECM when the fuel tank is 15-85% full. It is also a 2-drive cycle code but should clear, when fixed, on the next drive cycle if all the prerequisites are met (like the fuel level). EVAP problems tend not to cause any driveability issues unless it's something crazy, like the purge valve opening when at idle.

Regards,
paul...
Great advice!

I will fill up the car and see if the codes/check engine light goes away.

I have an appointment with the dealer Monday. If the EVAP is defective is this a warranty or emissions issue that would be covered, do you reckon?

Autozone does not list MB as a brand. That's I suppose why they were confused. Lots of Kias and Mitsubishis though.
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Old 09-24-2009, 03:11 PM   #8
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Quote:
Originally Posted by ivanj View Post
Great advice!

I will fill up the car and see if the codes/check engine light goes away.

I have an appointment with the dealer Monday. If the EVAP is defective is this a warranty or emissions issue that would be covered, do you reckon?

Autozone does not list MB as a brand. That's I suppose why they were confused. Lots of Kias and Mitsubishis though.
Don't fill it all the way -- just 50% to play it safe, and make sure the engine is totally warmed up before taking it for a ride to accomplish the drive cycle. I believe that emission components are warrantied for 80,000 miles in most states -- don't know about the labor (diagnostics and R&R) costs. Check your warranty booklet.

AZ uses a service by Wells Mfg who makes engine mgt systems for GM and others. Like I said, those are generic codes (P0xxx) and are the same for all cars. I would think that it will take the dealer 1 hr to diagnose the components, and if there is a leak in the plumbing somewhere, another 1-2 hrs smoking/searching the system to find the leak and repair it. Hopefully, there aren't any wiring problems. best of luck.

Regards,
paul...
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Old 09-28-2009, 11:19 AM   #9
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Problem solved, thank you!

Quote:
Originally Posted by paulv View Post
I don't know what Autozone's problem was with you -- those are generic codes: 0451 is the fuel tank pressure sensor is sending the wrong reading back to the ECM; 0455 is a large leak (0.040"); 0456 is a small leak (0.020"). Most EVAP systems can only be tested by the ECM when the fuel tank is 15-85% full. It is also a 2-drive cycle code but should clear, when fixed, on the next drive cycle if all the prerequisites are met (like the fuel level). EVAP problems tend not to cause any driveability issues unless it's something crazy, like the purge valve opening when at idle.

Regards,
paul...
I followed your advice. Saturday I drove 10 mile to a gas station, first put in Techron, and then filled the tank 50%. (I examined the cap and it looked ok and had a tight seal - I compared the cap to other cars.) I drove the truck around doing errands. It was started and stopped several times

Sunday I started the car and the "check engine" light had disappeared.

Paul, you were exactly right! Thank you Paul!

PS
I have been advised of some "disturbing" trends with the CPO warranty. I hate to be evasive but frankly I want to verify this myself before I divulge any details. Paul has set a high standard for knowledge and I want to at least approach this bar.
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Old 09-29-2009, 08:53 AM   #10
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Quote:
Originally Posted by ivanj View Post
I followed your advice. Saturday I drove 10 mile to a gas station, first put in Techron, and then filled the tank 50%. (I examined the cap and it looked ok and had a tight seal - I compared the cap to other cars.) I drove the truck around doing errands. It was started and stopped several times

Sunday I started the car and the "check engine" light had disappeared.

Paul, you were exactly right! Thank you Paul!

PS
I have been advised of some "disturbing" trends with the CPO warranty. I hate to be evasive but frankly I want to verify this myself before I divulge any details. Paul has set a high standard for knowledge and I want to at least approach this bar.
Thanks for the kind words and I'm glad your problem is solved -- that's what these forums are all about!!

Having some knowledge of these systems is a big help, especially when talking to a pro -- I've found that they have a higher level of respect for you when you can speak some of their lingo!! Best wishes.

Regards,
paul...

Last edited by paulv; 09-29-2009 at 08:54 AM. Reason: spelling
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Old 09-29-2009, 08:53 AM
 
 
 
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Tags
0455, 85, cel, code, codes, cycle, drive, engine, evap, fault, fuel, g500, gm, po451, po455, po456



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