So basically you're saying that unplugging the accelerator sensor didn't do me a damn bit of good
I assume that limp mode trumps everything and it doesn't really matter what bad input it's getting at that point?

I'm going to try and do some testing on the throttle body tomorrow. I haven't focused on that because the mechanic said he put a new one on just to see if that was the problem but it didn't do anything. I'll try to rule it out on my own though.
No cam or crank codes at all. I assume that side of things is good since it idles well with either the pedal sensor or throttle body disconnected. I assume it would still run like **** if timing was off or those sensors were bad.

 

Yes, it will default to a high idle, so you op won’t be able to control it, or check the sweep.
Have you tried the wiggle test yet? Checked for vacuum leaks?
For the record, a simple battery disconnect should never require a throttle relearn, I really think you have another issue here.
Is the idle your only issue now? Is it revving and driving fine?

 

I'll mess around with wiggling wires and vacuum today. At this point, I'm ready to try anything. And to be honest, I started ordering parts last night. I hate to do that but I'm getting very little evidence to go on. Starting with a new throttle body and MAF sensor. Simple stuff first. Want to do the pedal sensor too before hitting the ECU. Another thread I read had a guy with the exact same symptoms after he disconnected the battery to do his brakes. Same frustrations as me and it ended up being the ECU. I don't know...
To clarify, it doesn't drive fine. Yeah the idle is revving badly but the slightest tap of the accelerator rockets the RPMs up to over 5k. It's ultra sensitive . I followed the mechanic in my car while he drove it back to the house. He got it there without stalling but it wasn't a fun ride. He did say though that at one point on the ride there is a steep hill about 200 yards long and the car actually drove normally. I assume it was because the engine was under constant load but not sure how that relates to anything.

 

If it helps, here is a video of what it's doing.

 

Update (if anyone is even still reading this...)

Swapped out the throttle body and MAF for new parts and did the required relearn. Didn't help at all.

To quote Clint Eastwood, "A man has got to know his limitations". I've reached mine with my patience and ability to diagnose this. I scheduled a $150 appt to have the dealership use their computer to tell me what's wrong. If it's part related, I'll do the work. If it's software related, I'll let them fix it.

 

Every time something is fine, you do work an then it's no longer fine it's 99% chance you caused the issue. I don't believe in coincidence for this, there are some cases where replacing electronics might reveal further issues but that's it. FWIW I've had numerous dead batteries, disconnected batteries, different TBs, not once have I done a relearn and the car is always fine after.

 

I totally agree Dark. In this case, I truly believe the issue is electrical/computer related. Only thing they touched that could interface with that is the negative battery terminal and the disconnecting of plugs at the transmission. Crank position sensor already ruled out. Might be a harness issue? Maybe something in the computer got fried when power was reapplied? If they can isolate the issue for me in 1hr for $150 I'll gladly take that over me spending multiple days blindly poking around trying to find the problem.

 

I am still reading, but not here every day, I am interested in the result here though, so keep us posted.

 

Typically as long as the ground is the last connection you should be ok but who knows

 

Ok, here's the latest.
The Nissan dealership near me has had the vehicle now for 2 days. Bottom line, they have no f'n clue what is wrong. The guy working on it is supposedly their senior tech with 28 years experience and he has never seen anything like this. He even took the new throttle body I bought and installed it to see if that helped using his diagnostic systems. Dead end. He also tested all the relevant cabling/harnesses and no issues found. So, rather than leaving it with them to run up a troubleshooting bill I'm bringing it home and plan to go after the ECU. Although he highly doubted it was that at the beginning, he said that would be his next step too.

That all said, can you guys recommend a path/vendor to get a replacement ECU? I don't want any high end expensive racing ECU so don't say Haltech or Link. Here are the options I'm assessing:

• Buy a refurbished plug & play ECU for ~$340 that comes already flashed with the car's VIN. Possible vendor I've seen is Flagship One. Any others?
• Send in my existing ECU to be refurbished and returned for $190. They will repair if able. If it can't be repaired, you pay $90 for the test time and then must buy another ECU. Possible vendor I've seen is SIA Electronis. Any others?
• Buy an ECU off Ebay or salvage vehicle for $200ish and get it re-flashed at the dealer for $150.

Any input on the vendors I listed would be very helpful. I don't know anything about them.

 

That’s where I would start as well, there was a place in Florida that could repair ecms but I forget the name. If you get it out, take it apart and look closely at all the circuits, you may actually find a burn somewhere or something showing an issue.

 

That's just nonsensical to me that a clutch would lead to a bad ECM. I've never seen nothing like it, nor had any issues of that category in the 12+ years I've been a mechanic.

 

I hear ya Dark. Makes no sense to me either. I'm not a mechanic but do have a strong engineering background. I've never seen anything like this. Nor have all the trained mechanics that have looked at this so far. Short of dropping it off on the doorstep of Nissan's US headquarters to have their engineers tear into it, the ECU is my last hope. No idea what path to take if that doesn't fix it.

I called Flagship and that option is off the table. They don't have the ECU I need and want to charge $650 to refurbish the existing one.
I may give option 2 a shot. They don't touch the software but only repair the electronics. They said they can fix just about everything on the board except the microprocessor. If that's bad, it's toast.

 

It’s actually pretty common if there’s a weak ground, or a voltage spike to the ecm, like maybe from key on with a battery charger connected. Been a licensed tech for 20 years, and an apprentice for 4 before that, seen plenty of failed ecms in my years.
Actually I have a quick story that’s kinda related, but not really. About 8 years ago I had a 94 Ram I used every few months to do truck stuff, but it was very easy to steal, and not insured cuz I would use a dealer plate from work when I needed it. So despite living in a really good area I still always disabled it when parked on the street by pulling the ecm fuse. So one day I went to use it and it didn’t start, oops, forgot the fuse…so I plugged the fuse 8n and it still wouldn’t start, no spark. Checked everything myself (middle of winter) and couldn’t figure it out, threw a couple cheap parts at it out of desperation, and even had a friend who was a Chrysler tech for 15 years or so, he couldn’t figure it out either, it made no sense. Anyway, one day I decided to pull the ecm, and as I got it out I gave it a whiff and noticed a burning smell, tried taking it apart but it was gel-insulated so very hard to see anything failed inside. Regardless I grabbed a used one and slammed it in, same thing. Grabbed another and it fired up without issue, sold it to a buddy and he still has it.

 

I still have yet to see a ECM go like that. Seen crazy electrical issues as well, even wires grounding out and catching fire....no fried modules. I work on trucks but it's all nuts and bolts lol, most of my work is electrical as well.

 

Yeah, depends what kind of trucks I guess, cars are often quite a bit different, my 92 Regal had a pcm failure where it would start and run but not rev up and pop out the exhaust. This happened on my way to work, so I took it out (left it connected) and banged it on the fender…after a couple hits it ran mint, lol.
I’m not saying it’s a bad ecm, but it’s entirely possible, especially if there was a weak ground or power feed, it will burn other circuits trying to complete the connection.

 

Diesel trucks, and we do see a lot of other modules fail but it's all radar, ABS, powertrain controller, but not engine or trans controllers. I know all about weak grounds as I've owned 2 MR2s a loss of ground on those usually lead to fires as well, the engine would have no other alternative than to ground out on the shifter cables which are filled with grease and create a fire lol.

 

Drove the vehicle home last night. One thing I found interesting while driving it was how sensitive the accelerator is. The engine will run without surging until it goes to a near idle without a load. However, when I touch the accelerator with the lightest amount of pressure the RPMs jump like I smashed it to the floor. Since I haven't fully tested the pedal position sensor yet, I decided to pull the pedal assembly out of the car this morning and run a multimeter test on the sensor pins (no power applied). With the meter set to Ohms to measure continuity, I tested for continuity across all of the pins (power to ground, power to signal, ground to signal, etc.). I connected an alligator clip on one of the 6 pins and then touched the other probe to every other pin and moved the pedal up and down while doing so. I performed this cycle for each pin. I expected to see some continuity but got nothing. Every single pin to pin test yielded an open circuit. Doesn't seem right... Are these the expected results? Did I do it incorrectly?

 

Using this link (Pedal test procedure) I applied power to the sensor using a 5V power supply. Based on the voltage numbers in the instruction, it looks like I'm seeing what I'm supposed to.
On the sensor 1 circuit I'm seeing 0.85V with pedal out and 4.7V at WOT.
On sensor 2 circuit I'm seeing 0.43V with pedal out and 2.4V at WOT.
All of these reading are in line with the values listed in the article.

The part I don't get is why do I not get continuity when probing these same pins for resistance? I should see something, shouldn't I?

 

That’s not how they’re tested, they work off of voltage, as indicated in your test procedure. Personally I would think you should see a small resistance value on those wires, probably well under 1 ohm, but if you tested for voltage and it’s in line, then that’s the end of the test.