Tranny slip? Electrical or mechanical? Please help asap

gmc
terrain

#21

By furnishing your own parts you have zero warranty on labor and the mechanic will charge you to remove it and it will be up to you to handle the part warranty if it is defective. This is not really a good way to save money in the long run.


#22

Who did the scan?
Who supplied the part?
Who did the labor?


#23

That’s an emissions related code, discovered by the TCM, and sent to the ECM, so the ECM will turn on the check engine light. The ECM only displays p0700, but the freeze frame data will display the actual transmission diagnostic codes. That’s the info you need to determine what’s wrong. This code doesn’t usually imply a problem w/the TCM. The p0716 indicates a problem with the transmission’s input speed sensor. It’s a gadget that monitors something going around in a circle to determine how fast it is rotating, using a stationary magnetic pickup and a rotating reluctor wheel. A reluctor wheel has a magnetic pattern on it that the pickup senses as it rotates by. That info is used by the TCM to decide what gear to use, what the hydraulic pressures should be, etc. So if it fails it probably affects the ability of the ECM to control the emissions. That’s probably what is causing the p0700 to appear, and is what to focus on. As mentioned above, check the harness and connectors for that sensor. If nothing found there, remove the sensor and check the reluctor wheel. Still nothing? Replace the sensor, you may get lucky.


#24

Hello and thanks for replying,
My regular shop did the scan, showed me the result, and he installed the part (I bought the OEM part from Auto Zone


#25

Good Lord George, do you teach mechanics at a university or what? I bet 99 in 100 working mechanics couldn’t break down the process, and I’m betting 1 in 4 would misdiagnose or go off the OBDII reading and just say “replace the TCM and Speed Sensor, $500 please!”
I will have to pay for the labor since I dont own ramps and I’ve never touched a Tranny (I think the speed sensor is in the bell-housing and beyond my skillset anyway). Do you suggest paying to install a new speed sensor and following up from that point? My place allows me to provide parts, do you know if mine has one or two? Thanks for taking me through the process and for chasing the least costly likely culprit. I can show you the actual scan if you like?
Tommy


#26

Thanks Mustang. George sees the same thing you do, he thinks the code is throwing fault codes and I should begin with the speed sensor and go from there. If it’s a ground or loose harness etc, I’ll have to trust the mechanic since I can’t access the bell-housing area to see if something is loose. I wonder what the boot is that plugs into the intake manifold cover that I found free-swinging? George thinks it’s also emissions related and that “boot” is an emissions line for sure.
Tommy


#27

George, I forgot to tell you, I found a loose hose that was originally plugged into the side of my intake manifold cover, the boot is shaped just like a spark plug wire boot, but half the size. It was laying on the block, no longer plugged in. My mechanic clearly didnt replace it properly when he changed out a bad sensor under the cover this week, charged me $100 labor to install it, didnt take him 15 min. It is clearly an emissions hose. I popped it back on, but I ran the codes before I noticed the disconnected hose


#28

Hey Volvo, I do realize there’s no warranty, but my mechanic is pretty honorable, if he does a repair that doesn’t solve an issue, he goes the extra mile to fix things. I do however, hope the sensor he replaced was actually bad, cost me over $150 and 3 days later my car is in limp mode…so it solved nothing, It did come up on his very high end OBD as faulty…then again, he said 3 of my O2 sensors are bad (I have 4) in my other car (Olds Aurora Northstar engine) and I just passed smog, how did I pass smog with 3 O2 sensors out? Also, my Aurora is running just fine, not flawless, but only bogs down a tiny bit when I really jump on the accelerator…


#29

You could save even more money if you took the vehicle to someone that could fix it right the first time using their parts.

Which module and which sensor were replaced?


#30

Just because your car passes the tailpipe test, doesn’t mean the oxygen sensors are 100% functional

At your car’s age . . . I mean the 1996 Aurora . . . I wouldn’t be surprised if some of the oxygen sensor heater circuits are dead, or maybe the sensors themselves are sluggish

When a car passes an emissions test . . . plug-in only, dyno run and tailpipe test, two-speed idle, etc. . . . it means the car passed the test

You shouldn’t read into much further than that

There are many problems which won’t prevent the car from passing the test, or portions of the test

You could have a car with low compression, and no fault codes, which nevertheless passes the tailpipe test

The “pass” means the car passed the required test and you can re-register it. Doesn’t mean everything is fine.


#31

It takes a pro-mechanic 4.3 hours to replace the input speed sensor. The transmission’s valve body must be removed to access the sensor apparently. Definitely not a diy’er job, at least for a diy’er who mainly just does their own oil changes. So it would probably be worth it to invest in some pro-diagnostic time to make sure the problem is the sensor or tone wheel vs the wiring harness that services the sensor. If I had that problem and nothing visually obvious was wrong, the way I’d address it is ask my regular shop who’s the best transmission specialty shop in town, and go there ask them to fix it. And I wouldn’t buy the replacement parts myself, I’d let the transmission shop choose the parts. That’s so if the replacement parts fail or is the wrong version, it is their problem, not yours.

You might find the following link interesting.

https://www.obd-codes.com/p0716


#32

Thank you for all this info, I just wanted to be sure I wasn’t following bad PCM readings and I start changing costly sensors that arenn’t in fact, faulty. I’ve learned the hard way not to just do an OBDII scan and replace parts without investigating…


#33

You couldn’t have been more right, but I think I chose the wrong shop George. My very trusted regular mechanic (also a friend) told me to start by replacing the tranny filter because it was acting like it was low on fluid (or fluid wasnt getting through). He found it was 1 quart low, but he didn’t have a tool needed to get to my filter. I took it to a popular tranny shop not half a mile away, the owner offered to swing by my mechanic and drive my car to his shop (for a filter change? Awfully nice of him right?).
I went to his shop at 8:30 am and his guy hadn’t popped my hood yet (they had just opened), he called me at 8:52 to tell me my tranny was shot, 22 minutes later! My mechanic spends that much running a complete OBDII scan and this guy dubbed my tranny as toast in 22 minutes or less? He said “your fluid is almost black” and that was the sole determining factor. My mechanic added a quart of fluid and it drove fine for him in drive, it only slipped in reverse… I plan on having my car towed elsewhere in the am. I meant to tell you he informed me the entire tranny had to be pulled to change my filter? The GMC dealer quoted me $199 to change my filter, but they charge $1,050 to replace the input speed sensor ($985 is labor for pulling the tranny), this means the tranny doesn’t have to be dropped to change my filter, so my new tranny shop pal lied to me.


#34

I meant to tell you I got codes 716 and 717. The car is at a tranny shop now, he had my Terrain for 22 minutes and called me to tell me my tranny was shot, $3000 rebuild. My regular mechanic will run extensive diagnostics that take about 30 min, and doesn’t include the time he spends on physical inspections. I think the tranny shop is the biggest snake oil salesman I’ve ever met. I should have been suspicious when the owner offered to go to my mechanic to pick up my car from my mechanic and drive it to his shop when I was only asking for a tranny filter replacement (not much profit in a filter replacement). My mechanic didnt have the tool to get to my tranny filter. The car drove fine for my mechanic in drive, it was only in reverse that it slipped. I cant say 100%, but this sounds like electrical issues, not a rebuild…I’d like to hear from you please before i take it elsewhere tomorrow. We need a reliable car asap as my wife has major surgery scheduled a week from tomorrow. Thanks once again


#35

Hey Nevada, would you take a look at my most recent posts as things have changed and we need our car back on the road soon. I think the tranny shop I brought it to has decided I’m an easy mark and desperate.
I asked for a tranny filter change and he has told me the tranny is shot, he had my car for 22 minutes.
I’m sorry if I’m being “needy” but my wife is going for major surgery next week and I have to have a reliable car to take care of my family while she recovers. We can’t just take this guy’s word for it and drop $3K with the hospital copay looming, we have to be sure the tranny is genuinely shot, pretty unlikely at 70k Miles. Thank you


#36

The website was helpful, thanks. I see the tranny has to be dropped to replace the input speed sensor, so now it’s left to find if it’s the sensor itself, a broken wire/ground or something else before dropping $1000 to replace that sensor. The tranny shop is saying rebuild, they had my car for 22 minutes before making that determination, as you can imagine I’m getting some bad info from someone. I hate not knowing anything about this and being left at the mercy of someone else’s ridiculously fast assessment. My very trustworthy mechanic ran a 30 minute diagnostic just to determine the 716/717 not including his physical inspection, I know, I was inside the bay when they worked.


#37

The fact the atf is black, along with slipping in reverse, makes me think the transmission has severe mechanical problems, not electrical

I see a rebuild in your future

That’s just my opinion, without even being there, without seeing anything, without being able to hook up my scanner, etc.

I don’t know anything about this tranny shop . . . but sometimes 22 minutes is all it takes to determine a component is in need of a complete overhaul


#38

Fair enough, I appreciate your honest appraisal. It’s hard to believe the tranny lasted only 70K “easy” miles (we rarely even leave the county and my wife works 3 miles away. It figures, we will have it paid off in just 6 months. Thank you


#39

Is this a CVT transmission . . . ?!

Anyways, how frequently has the fluid been serviced?


#40

Here is the code definition for code P0717:

Code: P0717 __ Make: GMC

Description:
CVT Input Shaft (Drive Pulley) Speed Sensor “A” Circuit No Signal

While it is possible that the sensor itself is faulty it is also possible that the trouble is with the wiring to the sensor. The code is indicating a “circuit problem”. Replacing the sensor before verifying that the wiring to it is okay first is like buying the cart before the horse, that could result in a needless and expensive repair bill.