Alrighty, so I did a check on my ECU and found 4 new codes along with the already existing code that was on there. Joy.

The only code I am confused with is the 0205: Idle Speed Control

For the longest time I thought this was referring to the TPS sensor, but after trying 3 different TPS sensors, I figured out that wasn't my problem.

So basically I want to know exactly what it means by "Idle Speed Control?"

I'm guessing IACV, but after me searching on google and here I can't get a straight enough answer to be completely sure. Thanks to all!

 

Not sure on your code issues although there is an external manual idle control near the throttle body. I had been advised my IACV was behind some starting and spuratic low rpm concerns and should either be dismantled and cleaned or replaced. I ran a full tin of SeaFoam with a full tank and all was good within the first 50 miles. If you do do that, be sure and change your oil after the full tank is spent as the SeaFoam brings a lot of residue down to the oil pan.

 

seafoam or chevron tecron. If that dont work then replace IACV

 

Really, the only thing that's going to throw P0505/0205 is a bad IACV, or the wiring harness between it and the ECU. You could test it per the FSM, but most likely it's a bad unit. Cleaning it won't restore it's electrical functionality.

 

Cleaning wont restore electronic functionality, I am not so sure. I have heard tales of guys cleaning old 02 sensors with a torch to restore functionality and also not-cleaning the IACV can bog things down to where the ecu throws a fault code even though the part may be ok.

 

The difference there being that O2 sensors can develop a layer over the sensor over time, inhibiting it's ability to sense the presence of oxygen in the exhaust. Torching them burns this off.

In this case, the code is specifically for an electrical fault in the IACV or harness. If this were a P1506 or P1507 (idle speed overrun/underrun), then cleaning an IACV may very well fix the problem.

 

That's what I thought, but how likely do you think it would be the wiring harness?

 

Rather unlikely, if it came up suddenly. You can test continuity from the IACV back to the ECU while shaking the wiring harness, specifically around the right side strut tower (there's a TSB for harness breakage in this area).

 

Honestly, I have had this problem for almost 3 years. The only thing I have ever tried was replacing the TPS sensor. I idle at about 200-400 so that's why I went to the TPS.

 

A low idle is less of a TPS problem than it is an IACV one, assuming no other driveability issues.

Test the IACV itself as well as doing a continuity check on the wiring harness, but chances are it's your IACV.

 

Thanks a bunch! I will test it tomorrow and give the results.

And no, there are no other driveability issues at all. I took care of the other codes minus the 0205 code just a few hours ago.

 

Not to sway from the subject, but this is pretty cool.

http://www.lyberty.com/car/tsb-nissan-maxima-1996.html

 

If you need the Factory Service Manual, FSM, download it from Fallenone's signature.

 

Thanks!

 

I had this code come up on me once and then never came back. But now im noticing that when i cycle the ac on and off the idle dips dangerously low and almost stalls sometimes.
That being the case, is it common for these IACV units to fail ?

 

That being the case, is it common for these IACV units to fail ?[/QUOTE]

I don't know the actuarial number of IACV failures per 10,000 cars but doubt it is high with 4th generation. I cleaned up what I thought was part replacement time with a tin of SeaFoam cleaner to a full tank and likely could have done just as good a job with 1/2 tin in 1/2 tank. All rpm dips and hard starts ceased immediately. Good idea to change your oil after once you have had one new fill up after the treatment. SF is under 10$.