AT Check light after Code P0507 ISC?

Hello, there is a Technical Service Bulletin on this issue, which Ill post but the throttle body will not relearn if the rpm is even just 25 RPMs higher than it should be at idle, I'm not sure what that bang noise is, but it's extremely loud even in the video. I assume the vehicle might be in some Limp Mode or Reduced power mode right now. But I'll post this TSB, it actually has you unplug a fuel injector to lower the rpm so the throttle body can relearn.
But retrace your steps from the spark plug change and injector testing, make sure you don't have any loose hoses or lines that are causing a vacuum leak, which will raise the RPMs. I don't think the throttle body is the issue, with this spec of only 25 RPMs, that is not much of a range for it to be out of spec. You may consider putting the old throttle body back on and see if it will be ok without having to relearn the old one. You can also try a smoke test on the intake manifold and see if there are any air leaks, I probably wouldn't be driving it until you get throttle code taken care of, that noise sounds really bad. Do you have a scan tool that can scan other modules in the vehicle? Try doing a full system scan of the entire vehicle and see if there are trouble codes set in any other modules.
The AT module might be shifting like that if it doesn't know the correct rpm, the ECM may be sending it incorrect data.
Another issue with older vehicles like this is when you do any repairs which require moving the wiring harness around, there might be a connector that is not seated correctly right now, so retracing your steps and going back over everything you may have moved during the repair is a good idea, I run into this with older vehicles as well, the wiring harnesses get so brittle and due to so many years of being heated up and cooled down, the connectors expand and contract so much that when you go and unplug something to get it out of the way, you can end up with pin fitment issues when plugging them back in.
When a code sets that wasn't there before a repair, that's the first thing I go over, is what did I move or unplug that might have issues now. It has to be something you did if the issue wasn't there before, it happens all the time. So put the old throttle body back on with a good gasket and recheck the area you worked in.

https://www.2carpros.com/articles/engine-idles-too-high

https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge

Hello again,

Okay, this issue still exist.
I have replaced, Valve body with the TCM
Replaced throttle body, replaced pedal position sensor, Speed sensor (Crankshaft speed sensor) Camshaft position sensors. Airflow is fine
Pedal and Throttle along with air fuel programed successfully, TCM and ECM reset, no shorts and bad harnesses, But the AT Check light still comes on at near stop speed and when I brake when the car slows down right around 1st gear this happens.

Looks like my issue is out of this world I have no choice but to drive the car around until it explodes:)

Now we have no ECM or TCM codes everything looks fine, but the AT Check light still doesn't want to go away, and it comes on at low speeds (near stop) both in start moving and when breaking. And there's a large shock when the light is on, once the car starts moving, the light will go away, and the car goes fine with no issue.

Any other options would be helpful.

Hello,

Okay, so, when the warning light is on, it shifts hard to the next gear until you're at cruising speeds? Just trying to get an idea of what you mean by "large shock".

When you changed the spark plugs and this issue started, what brand plugs did you put in and what kind of testing did you do on the fuel injectors? I'm only asking because it looks like the TCM is going into failsafe mode for a short time (while the A/T lamp is on), and then coming out of failsafe mode. And if it is happening when you are coming to a stop, or slowing down, low speed and lower rpm, I may have an idea of what could be happening. I'm looking up some more info on why that warning light comes on right now, and I think we need to go back to when the problem started.
I can see why it's not setting any codes, with the light coming and going, the TCM or PCM is seeing the issue and then not seeing the issue, so it's not enough full drive cycles to set a code. Once you get moving again the problem disappears, so no code is triggered.

So, the AT light should come on for about 2 seconds at Ignition switch On, but does it happen to flash at all during the fault time, for about 8 seconds?
And it looks like the shock, or slam into gear you're experiencing is because when the TCM goes into its Fail Safe mode for that short period of time the TCM will stay fixed in whatever gear you happen to be in at that time, so when you accelerate and come out of Fail-safe mode, it might be going from that fixed gear into whatever gear it should currently be in for that speed and RPM.

Thank you for getting back to me.
Yes, the shifting seems like jumping from 1st to second gear and vice versa at low speeds. (Hard shifting - feels like a kick, from the bigfoot)
The previous spark plugs were single platinum spark plugs which i believe were the wrong ones, we replaced the single to double platinum spark plugs (NGK) and we tested the injectors (with the testing device) which is common in repair shops to make sure they work properly.
After assembling everything the car started acting crazy, AT Check light came on
rough idling and misfiring.
We have found out one of the coil harness was on the wrong piston.
Piston 2 to 4 piston 4.
We fixed that but since then the AT light is doing the same thing I mentioned before.
It's been 15 days with 4 different mechanics, still not a chance.

Okay, thanks for that info. I think what is happening is something (like an ignition coil) is interfering with one of the sensors in the transmission, (ie vehicle speed sensor, Turbine Revolution Sensor 1 or 2). Since this started happening when the plugs were changed, and the coils were disturbed. I have seen in many situations like this where some weird intermittent issue happens only a certain rpms or certain engine loads, that it seems to always be an ignition coil spiking the ground circuit and causing a glitch in a sensors signal that does this. And it's because the coils are the component on the vehicle that have the highest voltages when they are firing. Sometimes it doesn't even need to be a really bad coil, it can be just a little high resistance through a spark plug that causes the coil to end up firing outside the cylinder to ground.
It will usually show up when scoping the vehicles power feed and ground to the coils that a voltage spike will be seen. With no codes and this weird issue happening, that's what I would check, since the problem can be duplicated pretty easily it sounds.
Can you graph and transmission live data PIDs with your scan tool? And see if you notice a speed sensor either dropping out, or reading incorrectly when the fault occurs?

Unfortunately, I won't be able to get my hands on a decent scan tool for a while I'm out of the city but here i have a small garage with basic tools including a multimeter, But i have the car with me and I only have an aftermarket tiny OBD2 scan tool and I don't think that can do anything like that, It's a basic code reader with graphs and other options for ECM only and some sensors.
The last time I checked there's a slight difference between voltages on both grounds pin 10 and pin 5 on the harness at the top of the transmission (Valve body wiring harness)
I wonder what is causing that
I'm not sure about the drop of the voltage number but I'm pretty sure there were voltage drop in pin 10 in the exact same time when the AT CHECK light was coming on
I disassembled the transmission to get my hands on the valve body, started the car and checked the voltages in the wiring harness that's how I could see voltage drop in both pins (grounds only) That drop was happening when the AT CHECK came on
I checked and renewed every single grounding on the car from the engine to the transmission and body along with the battery terminals.

The problem is now 60% better than before but it's still there
I will check the coils and their wiring harness tomorrow if i can pinpoint any drop, short or find anything.
That's all I can do now until the end of the weekend
Any advice would be great.
Again, I really appreciate your efforts.

I was looking at the wiring going to the transmission today and I see pins 5 and 10 are grounds, so you're saying you measured voltage drop from pin 10 to Battery negative when the fault occurred? If that's the case and that ground location is F11 "Front of Engine" and both pin 5 and 10 ground there, Id check for voltage drop from the engine block to battery negative and then also from the transmission case itself to the engine block, and the trans case to battery negative and see how much there is during the fault, because the transmission housing itself acts as a ground as well, it's not just the wiring going into the valve body.
If I remember correctly, there was a case where the transmission and engine block had voltage drop between them even though they were bolted together. Very strange one, I can't recall what the actual fault was, but it seems like almost anything is possible sometimes. Here are the wiring diagrams for the transmission. Check the pin tension for the transmission connector as well, it strange to have voltage drop like that at lower rpm, or speed. And why after only changing plugs.

Hello again, this time I came with good news.
I finally fixed the car with the AT Check light was coming on in low speeds, hard shifting in first to second gear.

With your instructions i finally managed to pinpoint the problem and fix it entirely.
After replacing the spark plugs to a better ones and checked all the wiring for the coils. At the final step I decided to replace the wiring harness for the speed sensor (Crankshaft Speed Sensor) I've replaced the harness and I saw the group pin was a bit pulled out. I didn't tested the voltages there, I just decided to replace it to make sure everything is okay.
Now the car is running smoothly with no AT Check light and smooth shifting.

I really appreciate your help and accurate instructions to fix AT Check light on my infinity fx35.

I wanted to post the fix and again thank you for your support.

That's really great, so it was the connector for the crankshaft position sensor?

Yes exactly, the connector was looking good even when tested, But the problem was the ground wire right in the connector that was a bit pulled out due to previous oil leak, the oil inside the pin caused it to disconnect time to time or voltage drop from the sensor.

I replaced the connector with the wiring (soldered) and boom the problem is gone.

Good find, it's always strange what loose pins will, I'm surprised it didn't do anything at higher RPMs, but anyway glad it's fixed. That was a strange one for sure.