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 2003 AmTran DT466E Codes 121 & 123
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Airdirect
Active Member

15 Posts

Posted - 02/17/2019 :  7:34:01 PM  Show Profile  Visit Airdirect's Homepage  Reply with Quote
We are having a problem with our 2003 AmTram bus. There has been 3 occasions when the check engine light comes on and the engine derates. The bus smokes terribly and has no power in this mode, but will allows the bus to limp between 15 and 40 mph. When the warning light goes out, the engine resumes normal operation. Codes are 121 (MAP Manifold Absolute Pressure Frequency Out of Range) and 123 (MAP Manifold Absolute Pressure (MAP) above spec. level at low idle).

Have replaced the MAP sensor (intake manifold), new fuel filter, and checked the air filter. Searching the forum other folks have suggested this problem is caused by the "fuel inlet strainer". Where is this and how is it replaced or cleaned?

Any help would be appreciated Thanks.

Edited by - Airdirect on 02/17/2019 7:36:28 PM

Airdirect
Active Member

15 Posts

Posted - 02/18/2019 :  08:53:28 AM  Show Profile  Visit Airdirect's Homepage  Reply with Quote
Ok, I have been Google searching and have figured out the fuel strainer is below the hand primer pump. I have also learned about the check ball issue. I will check both of these.
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Airdirect
Active Member

15 Posts

Posted - 02/19/2019 :  08:57:12 AM  Show Profile  Visit Airdirect's Homepage  Reply with Quote
Inspected the check ball, it is the black variety and appears to be in good condition. I went ahead and replaced it with the newer yellow check ball. Also pulled the inlet fuel screen and will replace it. Neither of these items appear to be the problem. The turbo outlet boot has a small hole in it, ordered a replacement unit. The hole is slightly smaller than a pencil, could this be causing the problem?
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Bluenozer
Senior Member

Canada
103 Posts

Posted - 02/19/2019 :  10:11:22 AM  Show Profile  Reply with Quote
turbo actuator working and free, air filter clear , a little hole would leak boost not sure if it would be enough to log code , EGR valve operation is ok, is it closing all the way might not log a code

OEM trained in wiring and all engine platforms for 20 years
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Airdirect
Active Member

15 Posts

Posted - 02/20/2019 :  11:37:10 AM  Show Profile  Visit Airdirect's Homepage  Reply with Quote
I installed new coupling hose for the turbo outlet, cleared all codes, drove it 20 plus miles with no engine warn lamp and no codes set. It goes on the route tonight, will see if any codes re-appear.
Thanks.
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