2009 Chevrolet Cobalt LT 2.2L, 4T45E automatic (non turbo and FWD) = P0717

Maintenance/Repairs
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1st off, this is a father (disabled) - son (dummy) slow project (I am a full time care taker for my mom that can’t do much for herself, so not much time to work on it) that I am the money man and he is the labor. I (we) have already replaced the fuel lines (pressure/return full length), new Firestone tires, not econos, and a few other things… Did the ECM/TCM ground hack to fix a few other issues and works great…

The P0717 is the turbine/input shaft speed sensor low or no voltage, It has a labor rate of 8.5 hour job to replace, really don’t want to have to pull the transaxle again on jack stands (easy on a lift), yes again then remove the valve body and a few more things to replace the input shaft sensor again, yes again (5 years ago with 0 miles driven until a month ago when we started messing with it again)… long story…

Anyway, I need a wiring diagram for the transmission and TCM so I know what wires to check and try to back prob… I would almost burn this car to the ground before I have a shop try sell me a transmission over a wire or sensor… (no insurance on it so no ins fraud if burned… lol)… Reset the computer and the 1st drive around the house area and it shifts normal, turn off/restart the 2nd or 3rd drive cycle and the CEL comes on and it starts hunting gears etc…

My buddy’s Pro scanner doesn’t get to deep into transmissions so all we can see is the input shaft speed in RPM’s out of range, and glitching…

No fluid leaks on the wiring harness or plug areas, no leaks anywhere, have removed the trans harness plug and TCM and confirmed no corrosion or bent damaged pins in either…

Possible issues are a bad input shaft speed sensor and or the wiring harness inside the transmission, damaged wire in harness going from the trans to the TCM, or the TCM…

One issue is my son doesn’t remember where he bought the sensor, much less if he bought the encono one or better one, so not sure if I didn’t install a junk or possible defective sensor… I would just replace the sensor if it wasn’t behind the chain drive in the transaxle…

If anyone has the diagnostic tree to check this out that would be a bonus also…

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I don’t know if any of this helps?

Tester

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not sure if this helps any but, late last night I was looking online and remember reading something about someone who had the same car and was having shifting problems. they said there is a ground wire or harness (I can’t remember which) that runs by the oil filter, and it is common for those wires to get burnt or worn through. Might be a good idea just to give it an eyeball. sorry, I can’t help much, but good luck. I hope it is something easy to fix.

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There’s probably two wires from the transmission input speed sensor to the TCM, wiring diagram should tell you the colors. If you can find them, with any luck maybe something wrong with one of those wires outside the trans. The sensor itself looks to be inside the trans apparently, which is why it takes so long to replace. It is probably just be a simple magnetic pickup sensor, magnets rotating by induce voltage pulses in a pickup coil. Maybe you can measure the resistance of the pickup coil (should be less than 100 ohm I expect) or if you have the equipment, view the pulses on an o’scope. The pulses should increase in voltage and frequency as the input rpm increases.

My guess, the problem is inside the trans, likely a bad connection at the sensor connector.

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Thank you for the info link Tester, I ordered the J-44152 jumper harness, so I am on hold until I get it and then have to wait for my buddy’s scanner… Hopefully this will narrow it down, time will tell…

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Thank you W-W, I will defiantly check that out, I am open to any help I can get…

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Yes, I have already replaced the ISS inside the transmission once, 5 years ago, hope I don’t have to again… I am thinking/hoping it is in the external wiring or TCM, even the ECM vs having to pull the trans out again… Yes it is a simple 2 pin sensor that GM buried inside the trans…

And yes, the wiring harness would/might help…

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ISS wiring
ISS wiring1920×2657 155 KB

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iss document
iss document1920×2657 370 KB

@davesmopar Hopefully, this will help

fwiw . . . as per Identifix direct hit, the most common cause of P0717 is that internal wiring

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Thank you db4690, I am sure it will help, and I am thinking the internal wiring also, just really don’t want to go back into it again, but what do you do?.. lol
Does it show you by any chance the bulletin for the diagnostic or repair process such as the resistance and air gap specs etc??

I am waiting on the jumper harness to do some better tests as well as have use to the pro scanner…

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3-19-2024 b
3-19-2024 b1920×2657 312 KB

3-19-2024 a
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@davesmopar I wasn’t able to find those sensor resistance or air gap specs

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Thank you again db4690, I think some of that overlaps with Testers link, but that is OK, better to be safe than sorry… lol

I just asked about the specs on a FB trans group I am in, just hate asking anything their cause of all the BS answers you get sometimes… I honestly don’t remember any movement/adjustability for the sensor anyway…

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Well after playing the waiting game, we finally did the testing today… The ISS (input speed sensor) was dropping off while reading live data making it look as if the ISS was bad, or wiring inside the transmission… We checked the TCM main ground at the connector and it showed an open circuit (infinite resistance/ohms), found a group of ground wires at the starter with some damaged wires and one broken one, the TCM ground, repaired and still kicking the P0717 code… Did all the test Tester posted the link to and it passed everything showing a bad TCM…

So we even checked the ISS with the engine running with the jumper harness plugged into the trans and since the magnetic coil in the ISS produces a small electrical signal, we were able to read that small amount of voltage it was producing and it was varying smoothly with the increase/decrease in engine rpms confirming the ISS and wiring harness inside the transmission is good and all the other test confirmed the wiring harness is good, the only thing left is the TCM is at fault…

So where can I get a good plug and play TCM, yes I know I have to give them the VIN…

I have found a couple places but am wondering where y’all recommend, or have had good luck with before…

Big thanks to Tester and db4690 for the technical (paperwork) help as well everyone else for the suggestions…

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If the signal at the input to the TCM looks ok on an o’scope, and the only symptom is the P-code, I wonder if you’ve already solved the problem with your ground connection rework, but the car’s computers haven’t yet figured out that it is already solved? Maybe all you have to do is wait and the P-code will go away, or maybe there’s a way to reset the computers so they start from scratch & don’t remember anything about the ISS problem. Just an alternate theory is all. The TCM could in fact be the remaining problem.

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Live data (from a $6K Snap-on scanner) shows the ISS dropping off (down to 0 mph) on multiple test drives as well as engine running in park and increasing/decreasing the engine rpms, it is in fact not dropping off (confirmed by test), the TCM is the issue and not able to read the small electrical signal produced by the ISS as already mentioned and not the ground wire, that had already been bypassed by a hack, but the ground issue for the need of the hack has been solved, but it is not the current issue… The ISS sensor ohms were almost dead middle of the specs and all wires were in spec, the TCM is just not recognizing the ISS signal…
But the ground wire could have been the cause of the TCM failure, plus we had already done a hard reset on both the ECM and TCM…

And no the only problem is not just the P code, the transmission is hunting gears as I had mentioned in the OP… But thanks for the suggestions…

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Given what you say, it definitely sounds like the next step is a TCM replacement. With any luck that will solve it.

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I’m always hesitant to recommend a place because in case something goes wrong I don’t want to be to blame, but I’ve had good luck with Flagship One out of New York.

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That is one that I was looking at using, so thanks, that makes me feel a little better, and I understand about not wanting to be blamed… lol…

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TCM ordered, now we play the waiting game some more… lol

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Update, I replaced the TCM with a reman unit using the VIN, with the new TCM, it now shifts fine even after multiple engine stop restarts on test drives, it would always turn on the CEL after the 2nd start up and start hunting for gears with the old TCM, now with the new TCM the CEL/MIL light still comes on setting the P0717 code but it no longer hunts for gears, again drives normal.
Now with the very limited use of a Pro scanner, the transmission live data still shows the same ISS drop out below around a 1,000 RPMS with both TCM’s, but when I use a DVOM to check the voltage output of the ISS straight off the jumper harness (I did this before and after TCM replacement), the voltage values go up smoothly and back down smoothly with the engine RPMs, but the scanner is still showing the same ISS dropping out. Is it possible to have a bad ECM that is not picking up the ISS reference voltage from the TCM and displaying it on the scanners live data and setting the code P0717?

I know I could have gotten a defective new TCM, but it is a different TCM (I kept the old one) with the same (only one) transmission code set, but with no symptoms with the new one, meaning if the light did not come on, you would not know anything was wrong.

So I beat my head on the wall and walked away for a while… lol
NOTE: I posted this on 2CarPros (May 30th), changing the wording a bit from here…