# Nissan Sentra 1.8L IACV Failure Car wont start error 505



## masihano1 (Feb 28, 2010)

Hi 

i just wanted to share my story as i have read through many threads that have helped me understand my problems through the advice of many experts here after reading many of the threads on this site

I have a Nissan Sentra 1.8L which was running fine until last week friday night. After waking up on a firday morning i turned my car on and all was well. 
I drove it to work 20K and on my way to work I noticed the Check Engine Light that appeared

i decided to ignore it for a bit as i have know that this light could be a loose gas cap or something small. 

After work when i tried to start my car all i heard was the engine cracking but wont start

i read the fourms and realized that if i can hear my fuel pump while in the ON position then fuel is not the issue 
to further confirm i bought some carb cleaner (O2 sensor safe) and sprayed some in my throttle and surely the engine didnt start even for a seconds as it would have if my issue was fuel related

I check my check engine light and it turns out to be error 505 which is a IACV ACC malfunction. 

i used the haynes manual and read that the IACV valve is a stepper motor.

Since i am a Electrical Engineer i know the basic pricinple of stepper motor operations and i check out the power to the IACV motor (middle two pins) which was not there at any time

basically for this motor to run there should be a voltage present 12V on the middle two pins for nissan sentra 2002. the side four pins are the control pins for the motor. They are PCM (pulse code modulated) for the whole thing to turn. 

once i realized there was no power i looked at the sch in the haynes manual and realized that the poewer must be comming from the ECM. (this is still my assumption as i didnt see a relay or fuse for this directly)
I wanted to rule out a ECM issue so i did a connectivity test from one of the control pins to the IACV motor and GND. Basically when the ECM tries to run this motor it grounds out each pin in a sequence so what you would hear while doing a continuity test to GND form one of the contorl pins is a series of beeps on all four side pins while trying to turn the car on

what this means is that the ECM module is properly controlling the motor but without power to the motor there is no movement as no current flows from the middle power pins to the control pins causing the motor to move

what i ended up doing is wiring my horn power to the motor power wire and disabling my horn temporarily until i get a more permanent solution

the car lives  270,000 Km

The symptoms of my problem

the Car cranks but wont turn on
Got a Check engine light 505 code
fuelpump was fine along with all the relays
i had no issues with idling that i know of
the car just died on me after being parked for a while

in conclusion the IACV motor can cause the car to not turn on as it my prevent air flow to the engine.


Hope this helps anyone looking for help with IACV no power issue


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