CODE 172, 175 and `639

[briarhopper]

At work we have a 99 P40 Chevy Step Van with Codes
172,175 and 1639.I know 172 and 175 mean it is running to rich, but what about 1639. Anyone have any ideas what would cause these 3 codes. Any ideas would be greatly apreciated. All we have is a cheap Auto Zone code scanner.

 

[TheLoneRanger]

Briarhopper, the 1639 is a manufacturer specific code which means "VSBA circuit faulty".

Maybe someone will chime in with a VSBA circuit definition; I haven't a clue......

Since the other two codes mean both banks are rich, I'd look first at a bad FPR (fuel pressue regulator) sending raw fuel into the manifold through the vacuum hose.

 

[briarhopper]

Lone Ranger,
I changed the mass air flow sensor and the check engine light has been out for 3 days now. I just wanted to thank you for your suggestion anyway. The reason I tried the MAF sensor was I had these codes once before when I put a MAF sensor in backwards on another truck. I work in a fleet garage so I work on the same vehicles all the time. Makes it easier than working on something different every day.


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[TheLoneRanger]

Thanks for posting the results, Briarhopper, and congrats on fixing it. Good thinking on the MAF sensor.