'01 QX 4 died won't start

[AllTheTimeInTheWorld]

Having a terrible time here. My wife was driving at the time and says it just lost power. She pulled out of traffic and stopped. The engine was still running, but very rough so she turned it off and had it towed home. I tried to start it to see what it sounded like, but it didn't sound like it was even trying to hit.

I ran codes and the only one was P0505. I disconnected the IAC connector and checked harness coming in - 12 volts on #2 and 5 pins. The IAC itself read shorted, so I pulled it out of the housing and yes, coolant had got into it. Finally got around to replacing the IAC today, but it still won't start.

I don't know of a quick way to check the timing belt so I checked compression on #1 and got 95 PSI. Low, but should run right? Not all together sure my tester was tight because of the mile long run to the plug, but that tells me the belt isn't broken anyhow. Ideas?

[sroberts]

Sorry to pass along bad news, but it may be that your ECM (Engine Control Module, aka Car Computer) is damaged. It is a common problem, at least with the 2001 Pathfinder/QX4. It happened to me, I got a quote for $1600 for the ECM+IACV, so I also had my car towed home. But first make sure you check your fuses, especially the ECM related ones. If it is the ECM you probably have 4 choices on the repair:

1) Dealer repair - likely $1000+
2) Send yours out for repair to a place such as Circuit Board Medics, around $300
3) Replace the damaged IC (integrated circuit) in your ECM, $15+. See the last couple of posts in this thread, Idle Air Control Valve (IACV) Replacement DIY for 2001 Pathfinder
4) Find a used ECM. You may need to also reprogram your keys.

I sent my ECM to Circuit Board Medics last year and was satisfied with the service. Best of luck!

[AllTheTimeInTheWorld]

Well, I'd read the warnings about this is the reason I did the electrical checks first. Harness was, and is putting out proper voltage at the connector. My understanding is that if it had taken out the ECM there would be no voltage, but I still have 12 V on the correct pins. Guess I'll pull it apart and run checks again. Funny thing is I cleared the code after installing new IAC and then tried starting, code didn't come back. IDK.

[Buzzman]

You replaced the IACV? Did I get that right?
You may not get a P0505 orP0500 code with the new valve. Doesn't mean the ECM isn't damaged.
What happens if you hold the accelerator pedal down a bit when you try to start it?

[AllTheTimeInTheWorld]

Wasn't going to mess with it until this weekend, but you made me look. It just turns over. 505 code's back, looks like I burned it out. I'll pull the ECM this weekend and see what it looks like. Does anyone sell just the plunger assy for the IAC?

[TheReplay]

Its crazy how many threads are coming up with the IACV/ECM problem...