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  #1  
Old 10-08-2010, 08:27 PM
brooksv4
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Default Engine surges, 505 Code for IACV

Engine surges at idle and while driving. Idle fluctuates between about 1400 and 1700. Getting 505 code, idle relearn procedure not working. Trying to troubleshoot IACV and am on page EC-422 of manual. Can't figure out how to disconnect ECM harnish to check.

Skipped above section. Checked vacuum hose from air control valve (from power steering not the IACV) to air duct next. It takes a minute or so to build only 1-
2 inches of vacuum; jumps to 15 when turn steering wheel a little. Manual says slight vacuum before turning wheel so I am going to assume air control valve is ok.

Next step was to disconnect the IACV plug and measure the stepper motor winding resistance at the male plug; suppossed to get 20-24. It was very difficult to do because of location and not being able to see but did get 1 ohm on one measurement so decided to take it off. Had to remove the throttle body/IACV as a unit to get to the IACV. The 4 ohm readings were 24, 10, 1, and 1 so motor is bad.
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Old 10-13-2010, 09:23 AM
swifty2
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I feel your pain. I've got a post for a similar code, 0506 low idle, with the same cause. The stepper motor on my IACV shorted out and got hot enough to begin to melt the plastic on the connnector. Fortunately, I still have continuity from the ECM to the IACV connector, but no signal from the ECM. The harness disconnects from the ECM by pulling on the release handle on the ECM connector, after pushing a small locking tab out of the way. It has a lever action that removes the connnector from the ECM as you pull the lever.
I'm pretty sure my ECM was damaged by the shorted motor, which is a common problem with Maximas. I may try one of the ECM repair shops mentioned in the Maxima posts.
I bought a good stepper motor from a wrecking yard for $75; I'll just change it out with the old one and leave the IACV housing and throttle body in place, and exchange the soft phillips head screws for socket heads.
I'll update my post when I get my ECM back.
Good luck.
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  #3  
Old 10-13-2010, 07:14 PM
brooksv4
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I found the valve/motor on line for 197. I didn't realize the motor was availible separate until I had already removed the entire throttle body to get to the valve. The 4 screws attaching the valve were very difficult to get loose without stripping the heads; had to push as hard as could on heads and use a small wrench to turn the screwdriver blade. Could have replaced the motor alone like you did without taking anything else off. Valve should be here tomorrow; I'll find out then wheather the ECM was damaged.

Good luck with your ECM. How much will the repair cost?
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  #4  
Old 10-18-2010, 04:54 PM
brooksv4
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Unhappy

I installed the new IACV Sunday. Unfortunately it did not fix the problem, the tach fluctuates about 100 rpm every second, up down, up down. I drove it about 2 miles; it doesn't surge under load and the rpm still never drops below about 1500. I tried disconnecting the plug, the needle fluctuated between 1400 and 2200 rpm. I finally disconnected the battery and will let it set until next weekend. Probably will not do any good and I'll get the book out again.
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  #5  
Old 10-24-2010, 03:40 PM
brooksv4
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Default ECM pulled

Continuity of harness checked OK between the ECM and IACV. I then ran all the diagnostic checks I could with the harness in place. The only thing that looked odd was the voltage at pin 17 to the IACV. The voltage jumped around between 6 and 10.7 volts. The other 3 pins (6,7,8) were between 13.8 and 14 volts and steady.

I removed the two 10mm nuts and pulled the ECM. I also removed the mounting brackets from the ECM case. The next step is figuring out what to do with it. I will first check on the repair sites. I'm hoping that sending it for repair will save having to have new keys or remotes programmed.
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  #6  
Old 11-05-2010, 04:05 PM
brooksv4
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Default Finally fixed

I bought a used ECM for $135 from autocomputerwholesalers. Installed original with one hand tight bolt and drove it to the dealer. They had me pull it into the sign-in bay. I switched them out in about 3 minutes. The technician programmed the replacement with 2 keys in about 5-10 minutes and I was on my way. Kudos to Fort Wayne Nissan, they were very courteous and charged me only like $43.
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