Hi, I started out with a 'P0037 - H02S Heater Control Circuit Low (Bank 1, Sensor 2)' that I let sit for a while as I wasn't driving the car that much. Code eventually disappeared, and I was advised to forget about it, until a P0507 - 'Idle Air Control System RPM Higher Than Expected' came on. I cleaned Throttle Body followed by an Idle Re-Learn on my mechanic friends pricey console unit, but as I have read on countless accounts, the re learn does not complete and goes back to a high idle at the end of the procedure.

I purchased a new Hitachi Throttle body , reset codes, did another idle - relearn BUT the P0507 returned quickly after so I am back to trouble - shooting.

I am now wondering If It was perhaps that air sensor all along. Not sure if this is normal or not, but as I was checking out info from my OBD device on ' Nissan Data Scan' I saw that one of my air sensors had a constant reading while I was parked, while all other sensors had a reading of 0.0.

Besides that, I have read about ECM re-call and re-flashing at the dealer, ECM replacement, unplugging fuel injectors, and MAF sensor replacement.

If anyone has any leads for me, I would appreciate it.

 

I don't think MAF impacts idle- issues with MAF are at higher RPM power loss (IIRC).

What year is your max? Have you checked for vacuum leaks?

 

You replaced the TB that mustve been pricey.

Did you reset the TPS too?
Theres a procedure for that illustrated in the EC section of the Nissan workshop deal.

It involves twisting it while probing pins 4 & 5 for continuity. If its not done i can not tell you if youd get an IACV code but its going to affect your fuel dilivery if its not set right.

 

This is 2003. No vacuum leaks to be found. Thank you for your input regarding the MAF. I appreciate it.

I got a Hitachi for about 140 I think from rockuato, although the way it was packed it seemed as if it was open already, which I did not like. Wondering If I bought it for nothing now.

I don't believe that was done. I looked online into this and I saw a vid of a guy adjusting his idle manually, as you describe, but on older Max's. I am not seeing too much on this regarding 5.5 gens specifically, but I will take a look under the hood. Your input is appreciated my friend.

 

Here is a link to the FSM for the P0507 code. Go to page 433.
http://boredmder.com/FSMs/Nissan/Maxima/2003/EC.pdf

On page 434 it says to do 3 adjustments that are referenced on page 72.
Perform “Accelerator Pedal Released Position Learning”, EC-72.
Perform “Throttle Valve Closed Position Learning”, EC-72.
Perform “Idle Air Volume Learning”, EC-72.

This is kind of s long shot, but check the PSP (Power Steering Pressure) switch. Its purpose is to increase engine idle when turning the wheels, but if the switch is putting out a false signal - who knows.

 

Thank You so much Dennis. Performing the instructions you you referred me too produced better results then just hooking up a computer and doing an idle air relearn ( which 3 different experienced mechanics said "that should have done it" ) but for some reason it just won't stick. I was not able to locate the PSP switch I am looking more into that now.

The RPM's increase little by little when in idle after I perform the procedures and when I turn the car off and on it is a hit or miss as to whether the RPM's get stuck at 1100 - 1200. I tried for hours, unhooking the battery, attaching back, then going through all the procedures manually. It just won't stick. Starting to wondering if my ECM is malfunctioning. One of my mechanics told me to exchange the hitachi throttle body i just got for another and see if I got a dud. I'm getting drained from all this and I'm starting to think about taking her to the dealer.

Any last ditch effort thoughts here?

 

Took it to the dealer. Told me it was gonna be 140 to run diagnostics. All they did was an idle air control relearn... I guess this required Nissan's computer to fix. Oh well. Thanks to everybody who tried to help me out.

 

Well it looks like I've got the same code "PO507" and I can't get any relearn procedure to stick. What a mess. What triggered my high idle "PO507" was cleaning the throttle body. Big mistake.

So are you telling me the only way to fix this is to have the dealer or someone with a consult 2 to perform a relearn? I was trying to avoid a $140 stealership charge, but might have to it looks.

Has anyone else found other alternatives? I've checking for vacuum leaks and any disconnected wires/sensors and I seem to be good.

 

It's not a good situation.

I had a high idle even before i tried cleaning the throttle body. Not sure if when I cleaned it it messed it up, but when I installed my new Hitachi throttle body, it still didn't work. In the end, I am not sure if I needed the new throttle body...perhaps a reset from the Nissan computer with the original was all that was needed. I just don't have the knowledge or experience to know.

I was thinking of switching out the old one to test , but realized that I better not mess with this sh*t. I was scared the dealer was gonna sell me a story and fleece me in this situation and I'm not looking to test it.

 

Resetting the idle is a b^tch and a half on these cars. I read a bunch of old threads on this once and a lot of people said it's due to a flaw in the ECM. You can change the TB, do the pedal dance, disconnect the battery, reset with a scan tool, blah blah, and the ECM just doesn't take the new idle. There was supposedly a TSB back when these cars were newer to address this issue via an ECM reflash.

One thing that worked for some was artificially bringing the idle down before doing the reset procedure. The ECU seems to have a threshold for how high of an idle it can reset; if you're getting a P0507, it's safe to say you're past that threshold. I read one guy ran the engine with a disconnected fuel injector, which decreased the idle to 700ish. With the engine off, he then plugged it back in, did 2 resets and the new idle saved successfully. Maybe try that.

 

You could try looking into:
http://www.nissandatascan.com/

Not sure if it does idle relearns, but if you try it out let us know