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Greg A
Greg A, Master Troubleshooter
Category: Chevy
Satisfied Customers: 7952
Experience:  Working with Electronics & Cars for 25+ Years
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1998 Chevy Venture: Van..I have a P1665 Evap Circuit Code..OBD2..leak

Customer Question

1998 Chevy Venture Van 3.4 L, I have a P1665 Evap Circuit Code that reads 2 different messages on my OBD2 (Mfg Control )1: auxiliary input 2: auxiliary output. I have replaced all the components in the Evap circuit and checked every line for a vac leak. Yet the light comes back on even after I clear it with the same message.   New Parts I have installed solenoid control valve, vent valve and the charcoal canister. John Sovie Marietta, GA. 30064
Submitted: 7 years ago.
Category: Chevy
Expert:  Greg A replied 7 years ago.

Hi John & Welcome,


Let me give you the test chart for this particular code. If you have a multimeter, you should be able to do some of the tests listed and hopefully figure out what is happening here.


P1665 Chart


Here is an enlarged version of the schematic that is in the procedure.




Please let me know you find or if you have more questions.


Good Luck & Take Care, Greg A.

Greg A and 5 other Chevy Specialists are ready to help you
Customer: replied 7 years ago.



I'm out in left field on this, I have no idea on how to work a multimeter, even if I had one.


I will accept your answer and hopefully I can find someone who could do this for me.


In your opinon it is definitely an electrical problem.



Expert:  Greg A replied 7 years ago.

Hi John & Thanks for the accept.


After reviewing the procedure again, it looks like most of the entire test process is looking for open or shorted wires between the Powertrain Control Module (PCM) and the EVAP components.


If you have a friend that is familiar with basic electronics, they should be able to help you. But if you have been in there already, replacing everything that you have replaced, you may be able to do a careful inspection of the wiring and connectors and be able to find something loose or two things touching that are not supposed to be.


Thanks, XXXXX