P0717 Trans input speed sensor no signal

Took the H3 into town earlier this week (don't drive it near as much as I used to now that I work from home and have another car I can drive) and right off the bat it started having hard shifts for 1-2. The rest were fine. Finally it threw a check engine light so I checked the code and got three, P0717 (No ISS signal), P0700 (General Trans error, apparently doesn't mean much more than the other code), and P0118 (Coolant temperature sensor signal issue) (or it was P0117? Something like that) if I recall correctly, but I get this one somewhat often and I think it's a wiring issue since it is intermittent. This is a potentially relevant issue to the transmission codes I think. More in a bit.

Stopped a few places and each time I started the truck back up it would immediately go back into the limp mode from the P0717 issue. So it wasn't intermittent. I cleared the codes a few times but gave up eventually as it immediately came back.

Even let it sit overnight and still the same issue. Hard 1-2 shifts and P0717.

The transmission is not very old, I ordered it in June 2018 and got it towards the end of the month and installed it. It is a reman. It has a 3 year warranty on it so it's still just inside the warranty period in case it really is something wrong inside the transmission, but I have my doubts.

Reason I doubt it is something in the transmission is that the typical cause for the input speed sensor to fail is the wiring inside the transmission rubbing through and shorting to ground. However looking at pictures of that part it seems they have addressed this issue by adding sheathing where it used to be exposed wires (which is why it could rub through and short, a few inches of the wires were unsheathed and could rub against the housing). I am betting that has been fixed like that for long enough that what is inside my transmission probably uses that same part. But I am also reeeeeeally hoping it's not the sensor since you have to pull the transmission out and crack it open in order to replace it. Moab is only a couple weeks away and it would suck to have to pull the transmission right now.


So today I finally got some time to start looking at it. Here's where the wiring harness is coming into mind for me as the source of this problem. I have had two separate but likely related issues with a couple sensors on the engine since my rebuild. The first was the crankshaft sensor. I would get a code every now and then complaining about losing the signal for the crankshaft sensor. Investigation resulted in me finding that the new sensor I put in when I did the rebuild had partially failed in a couple ways. First was the oring that sealed the sensor to the block had hardened and shrunk. I also discovered oil inside the connector which is a waterproof connector so it didn't get in from the outside, it had to have come in through the internals of the sensor itself. I replaced the sensor and that helped but I have still gotten that same code a few times since then. It's been mostly quiet but again, I don't drive the truck near as often as I used to.

Second issue is the coolant sensor. It too was replaced when I rebuilt the engine. I have been getting codes for this far more frequently. It tends to happen when first starting up the truck. I can watch the value for the coolant temperature read -40F for a while before the sensor finally starts registering. It doesn't always set a code but I monitor that with my Ultragauge so I can see it happen even if it doesn't set a code. I've checked the connector a few times but it seems fine.

I have also had another issue before that I have written about on here where I was getting some problems and ended up discovering that the conduit for the harness that the temperature sensor and transmission wiring all run through had disintegrated in the spot right where there is a metal clip that is supposed to hold the harness in place right at the back of the passenger head. The clip was starting to wear into one of the wires and seemed to be shorting it intermittently.

So there is a ongoing theme of wiring issues with this particular harness. This is what lead me to believe that there was probably yet another problem with it that was causing my transmission issue.

I disconnected the harness from the transfer case and transmission and pulled everything up so that I could inspect all of it. Of course I couldn't find anything obviously wrong, even the spot I had noticed was rubbing against the stud on one of the transmission bolts (that of course is supposed to be used to hold the wiring harness in place with a clip but for some reason it wasn't clipped on) didn't show any real problems (though it eventually would have rubbed through anyway). I put a meter on the wires that are for the input speed sensor and didn't detect any breaks or even conductivity issues. They both measured out at almost zero Ohms. I fed the harness back down and connected it to the transmission again and tested to see if there was a short to ground for the signal line but it came back fine. Same with the other side that is the ground for the sensor (the sensor has three wires, 12v from an ignition source, ground to the transmission control module, and the signal line to the transmission control module). So it doesn't appear to be anything in the sensor wiring causing an issue.

I turned the ignition on to verify power was getting to the sensor OK (it was) and to see what I got from the signal side. It came back with 12v which would be expected if the sensor had a tooth right next to it. And that is where I am now stuck. I have no idea if simply turning the engine/torque converter will cause the input shaft to rotate or not. If it does then I can't seem to get a low signal from the sensor (it should go high when a tooth is next to it and low in-between teeth). I have the transmission in park currently. I can't get it out of park because I don't have the gear selection switch connected at the transmission since it's kind of a pain to re-route the harness. I don't think having it in park locks the input shaft though either, but maybe it does?

I also can't try to turn the engine over right now, likely due to the same reason. Since the sensor appears to be OK so far (unless it failed with a high signal, which from what I have been able to find about these devices is unlikely) I am likely going to pull the harness back out, redo the conduit completely since quite a bit has gone missing from the section that is right next to the engine, and then put it all back together and see if I managed to fix it. At the least then I can probably get the engine started up and see if I can detect anything more than what I have determined so far.

Any thoughts or ideas or knowledge of the matter is appreciated.

I got a 2008 alpha as well and I am getting the same P0717 code. Since my Alpha had 250K miles on it, I figured it was time for a rebuild anyway, so I went ahead and got a rebuild done on it, but the thing is... this stupid check engine light literally turned back on after driving 0.5 mile after driving it home from the trans shop. I haven't had the chance to bring it back yet, because of work but I intend on doing it soon. My guess that the problem is wire related.

Looking at the parts diagram for the engine harness I think my next step is going to be pulling the harness to the trans back out, unmounting the coolant reservoir, unhooking the harness from the ECU and peeling that whole section open, double checking all the wires for any damage, and then replacing the damaged/missing conduit and re-installing the harness completely and then see if I still have the issue.

Really what I should have done before pulling this all apart was hook up my laptop with HPTuners and run some diagnostics, but I was really hoping to just find a wire that had the insulation rubbed through since that seemed the most likely cause. It still could be a failed sensor which will mean dropping the transmission and cracking it open to replace the sensor. Wouldn't be such a big deal for me if I didn't have less than two weeks to get this done before the Moab trip. There's always something...

Most likely the internal transmission harness is the problem. It might not of even been replaced when it was reconditioned.

jakesz28 said:

Most likely the internal transmission harness is the problem. It might not of even been replaced when it was reconditioned.

Click to expand...

Could be, but I didn't find any issues with the signal circuit when I tested it directly from the transmission (no short to ground) and when I plugged the harness back in and tested from the TCM connector everything checked out as far as I could tell. 12v on the ground connection (sensor gets 12v from switched power source in fuseblock so seeing 12v on the ground is expected) and 12v on the signal wire. It's hard to say if that's how it should be or not since the transmission input shaft is not rotating right now to generate the square wave signal one would see. If I could have it rotating and at least back probe the signal wire I can either hook up my oscilloscope to check for a signal pattern or if I instead get a lower voltage reading on a voltmeter I'd know that was working.

At this point I think it is one of two things. Either the sensor is bad and isn't generating a square wave signal and is instead somehow just putting out a constant high voltage, or there is something in the wiring harness (or even a connector pin) that is shorting or going open circuit.

If it would stop raining/snowing this weekend and dries out I could go back out and work on testing the engine/transmission harness and making sure it isn't that. Then all that would be left is the transmission itself. I think I am going to call the transmission shop that i bought it from to see what their thoughts are on it as well. If anyone should know I would hope it'd be them. I'd hope that they'd replace a $30 retail sensor that probably costs them $10 or less to buy in bulk and just replace it to avoid warranty issues. Having to pay out $1000 in warranty because of a $10 at cost sensor is a bad strategy I would think.

Never underestimate the ability of people to come up with bad business models.

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Got the harness refurbished today. Haven't finished hooking it all back up yet, I'll do that Monday.

The bad spots:







All done. Had to use some 1 inch red split loom to replace the 3/4" split loom that was disintegrating since that is all I had on hand that fit. Didn't feel like taking an hour plus to run into town to hope that whatever Lowes or Home Depot have on hand isn't garbage. Can't really see the red section anyway since most of it is in the tunnel.





I am really hoping that even though I didn't find anything obvious that the act of taking it out and cleaning it all up will have magically solved my problem. I'll get it hooked back up tomorrow and then plug in my laptop and run diagnostics on it.

Well, got it all hooked back up and hooked up HPTuners and took it for a drive.

$#!&

Still ended up throwing a code, and what I saw was at first I got zero reading for the input shaft speed but after a bit it started to register. Drove around a bit and kept seeing it register an input that seemed inline with that I should be expecting. So unless after a bit the computer starts making up that number it's not the sensor directly that is the issue.

I tried a few more times and what I noticed was that it didn't always register a speed at first, and sometimes it would seem to jump in and out, just as if the signal wire (or even power/ground wire) were having intermittent connectivity (or shorting out). But it only did it at idle or when first moving. Once I got moving it'd give me a constant readout.

So unless there is still something wrong with the engine/trans harness (seems unlikely unless one of those wires somehow has a bad terminal, which also seems unlikely) then it's something inside the transmission. Either it's the transmission harness or the ISS harness. Guess the first step is to drop the pan and try checking the main transmission harness first. If everything looks good there then I guess I get to pull the transmission itself out and crack it open. I already have a new ISS on the way from Amazon. I ordered it last night hoping if I did that I would end up not needing it. Guess I probably will after all.

Crud. Should have called the transmission shop sooner. They're send a whole transmission out for a replacement. But they have to get a core to build it with so it might not get here soon enough for Moab.

If I had known they'd just send me a whole new one I would have called last week.

Well, the warranty rep that is handling my case has tried reaching production a few times now and hasn't been getting a response. Even if it goes out Monday it's not likely to get here in time unless they expedite the shipping.

I watched a disassembly video for the 4l60e though and it looks like if I drop the pan I should be able to find the spot the wire is rubbing and be able to at least bandaid it to get me through the trip. I'll be dropping the pan tomorrow to see if I can find the issue. Sure hope I can find it and fix it.

The saga continues.

Dropped the pan, checked the wiring, still cannot find a smoking gun. Used a couple zip ties to pull the connector so that it should prevent the wires from touching the housing. Buttoned it all back up with a new gasket.

Went to put fluid in, I had a couple bottles from the installation so I figured I would use those first. First one was a partial bottle. Unfortunately it turned out to not be a partial bottle of ATF but instead old used motor oil that apparently made it through the purge of old fluids before we moved. :roll:

I only realized it when I got to the bottom of the bottle and something plopped out and into the funnel. Turned out to be some old paper towel and a bug...

Yes, I am an idiot for assuming a partially full ATF bottle was in fact fresh ATF. I spent an hour and a half dropping the pan again, draining it, cleaning out the motor oil, and putting it all back together again and this time putting actual ATF back in.

Of course this whole exercise was in vain. The code is still getting set and giving me hard 1-2 shifts. From what I can figure now the sensor itself must have failed and is no longer sending a square wave signal. I think what I am seeing in the logging is when there is no code set the output of the ISS signal shows zero RPM but after a while the TCM figures out it really is a problem and starts calculating the input shaft speed based off of other numbers and starts reporting that to the logger. I tried clearing the code without shutting the car off and it exhibited the same behavior as when I first start it up. Zero RPM for the input shaft, after the first 1-2 shift it starts reporting, sets the code and goes back to hard 1-2 shifts.

At this point I am going to say screw it. Unless they can get me the new transmission by Friday I will just drive it like it is for the trip. It's liveable and I don't want to put off going down just for this.

Transmission finally shipped, they're sending it via 2 day Fedex so it should be here Thursday. Time to start pulling the old one. From the looks of it I can remove it with the transfer case attached so that will make it a bit easier, it's kind of a pain to get the transfer case bolted up with the transmission in the truck.

So you cannot really pull the transmission with the transfer case attached. So thanks to help from a neighbor I was able to get the transfer case and transmission pulled and then the new transmission bolted up along with the transfer case Thursday night. Took about 6 hours total, which is a lot faster than if I had tried doing it by myself.

Got the rest of it all buttoned up tonight and once everything was filled back up and double checked I had everything hooked up I got my laptop back out and plugged in the HPtuners module and got the scanner logging.

Started up the engine and right away I was seeing the input shaft RPM's registering! It was definitely a failed sensor in the old transmission. Went through the gears and let it warm up a bit before backing it off the ramps and then took it for a drive. Shifts beautifully again. Now all that is left is cleaning up the mess I made and getting all my tools put away and then finish getting the truck ready for Moab, which mainly includes getting the UCP back on, hooking up my CB antenna, and then packing up the truck with all my recovery gear and tools and getting the fridge put back in. I also need to get the old transmission drained and boxed back up and get a pickup date scheduled for after my trip to Moab.

So good thing to know is that when in park or neutral you should see the ISS reading about the same RPMs as the engine speed, and once you shift into gear they will drop to zero until you start moving.