IACV wire harness issue. Help! Yes I've read the threads.

[jonnydclark]

Hello,

I recently bought 2001 Maxima SE 5 speed. Replaced MAF (which it needed) but still had a bad idle problem. I replaced the IACV, tried the idle relearn, then gave up and took it to the dealership. At this point they said it is a wire harness issue and they want a blank check to just trace it down without knowing how long it will take. Should I let them?

Can I trace it down? I am a mechanical engineer with decent electrical knowledge. I looked at the ECM board and couldn't see any burnt traces. I understand that IACV can hurt the ECM or visa versa and if I have to have to replace the ECM I will have to reprogram the key chips. What would I look for if I was to trace it myself? Where could I find wireing diagrams?

Any help would be appreciated. Even just sending condolences. I need to get it fixed to pass inspection although it is quite driveable now.

Jon

[maxhopper]

The easiest way to find a harness issue is to do the "wiggle test." With the car running grab different sections of the wiring harness and wiggle them. If you find a section or spot that makes the idle change, you've narrowed it down.

This is the FSM for the 2001 Maxima. http://www.nicoclub.com/FSM/maxima/2001/Start in section EL.

[jonnydclark]

Hey Thanks. This link looks like a great resource. I'll try to get my car back if they don't find it after 4 labor hours and see what I can find myself.

Jon

[NutriaforBreakfast]

I probably dont need to tell you this since your an engineer,but it doesnt take long to run up a bill at the dealership forservice work. I think they are at about $160/hr now? What aripoff!

I certainly vote for some coolheaded "circuit analysis" by the owner.The FSM shows the electrical connectors (I think toward the backof the EL section). Maybe there is some dirt and water in the connectoror some static electricity stopping the current. I would unplug and cleanthese connections. Might wipe with Armor All to keep the plastic fromcracking.

Also get Haynes or Chiltons from the local library and see if you canmultimeter the connections and see what the resistances and voltagesare and compare them to the specs. The FSM will have wiring diagrams.

I unplugged my ECU to release any static electricity and had no problemsafter unhooking.

Another thing about the IACV is that the electrical spec can come out righteven though carbon/gunk in the device is present. I remember mine specdok but it was so clogged up it wasnt working. I know u said it was new butsome little thing might be stopping it up mechanically.

[jonnydclark]

The dealership just called and said they found two wire harness issues... one at the fire wall (probably as you described) and one by the computer. I'll pick it up this after noon and hope the $400 was not wasted. Next time I'll look into it more before taking it to them. As stated I needed to get a key programmed and thought this would be simpler than it was.

Thanks for the help.

[jonnydclark]

Ok. So I get the car back and it runs and drives like it should. Before all of the monitors clear the check engine light comes on and I have 0420 0430 and P1126. These are Catalyst System Efficiency below threashold (banks 1 and 2) and Thermostat Function respectively. I read on OBDcodes.com that one cause for 0420 and 0430 is "The engine coolant temperature sensor is not working properly." Has anybody ran into this? With the recenty history of wire harness issues I wonder if I now have a poor connection on the temperature sensor. Also how likely is it that by running with a bad MAF and idle setting I gunked up both CATS?

I bought the OBD pro and just now hooked it up. I am not able to read the sensors while it is running but hopefully I can soon.

Jon