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Discussion Starter #1 (Edited)
Traverse is almost 2 weeks old, has 350 miles on it (I bought it with 12). Started car today and check engine light was on. Didn't notice it driving any different. Contacted ON-STAR and asked them to run a diagnostic and here's what showed up. I have a appt at the Chevy dealer for Thursday.


Through your recent On-Demand Diagnostic, OnStar detected an issue with your 2019 Chevrolet Traverse .

The code(s) and explanation(s) associated with this issue is/are:

p07bf The Engine and Transmission System is not performing as expected. An issue has been detected in the Transmission System that transfers power from the engine to the drive wheels. You may experience reduced power or shifting issues.If the vehicle is continually driven with the check engine light on, the emission controls might not work as well, the vehicle fuel economy might not be as good, and the engine might not run as smoothly. This could lead to future repairs.

p0700 The Engine and Transmission System is not performing as expected. An issue has been detected in the Transmission System that transfers power from the engine to the drive wheels. You may experience reduced power or shifting issues.If the vehicle is continually driven with the check engine light on, the emission controls might not work as well, the vehicle fuel economy might not be as good, and the engine might not run as smoothly. This could lead to future repairs.


Based on the results, you should service your Chevrolet within 7 days.
 

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I, my wife actually, had failure 300 miles from home 10 days ago. BLUF, Transmission Speed Sensor failed, had to be replaced. Transmission wouldn’t shift, 30 MPH @3,000 RPM. Couldn’t be determined until 2nd trip to dealership WHILE actively failing, check engine light on and associated history wasn’t enough info.
Ignition cycle can “reset” failing part, don’t turn engine off when failing, take it to dealer so they can connect computer and diagnose.

The code(s) and explanation(s) associated with this issue is/are:

P176C,P0700 Diagnostics Information
VIU - OnStar System
No Error Code Found
TCM - Transmission System
P176CNo action neededIGNORE UNKNOWN DTC
BOI - Bulb Outage Indicators
No Error Code Found
SDM - Airbag System
No Error Code Found
ECM - Engine System
P0700Service within 7 daysThe Engine and Transmission System is not performing as expected. An issue has been detected in the Transmission System that transfers power from the engine to the drive wheels. You may experience reduced power or shifting issues.If the vehicle is continually driven with the check engine light on, the emission controls might not work as well, the vehicle fuel economy might not be as good, and the engine might not run as smoothly. This could lead to future repairs.
Maintenance Information
Odometer Reading
Odometer Reading: 2,970 miles / 4779.265625 KM
Remaining Oil Life
Estimated Oil Life Reading: 59.9 %


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Discussion Starter #3
CEL went off Sunday morning, came back Sunday afternoon while my wife was driving. She actually said it felt unsafe to drive (she was with my 2 young sons) and she pulled over into a parking lot and shut the car down for a few minutes--described the car as slowing down by itself and when driving would rev real high. Took the car to work tonight (I work nights) and of course no CEL, I was hoping there would be one so I can take it right to the dealer in the morning after work. I know things go wrong, but feeling pretty pissed right now after spending 40k on this car.
 

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Sounds like the same symptoms my wife experienced. I advised her if it were to happen again, drop the transmission into “L” and shift manually. I suspect it is the Transmission Speed Sensor (hard to find part, took 3 days to get 1 of 12 listed in the “system”). Again, don’t believe the dealer can detect from error codes, have to get to the dealership while it is actively failing.


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Discussion Starter #5
Hope this isn't a sign for whats to come. We owned a 2011 Traverse LS and had no problems, sold it around 40k (should've kept it), replaced it with a mini-van, but my wife never liked the van which we sold and bought this Traverse. We were super impressed with the redesign. Now I'm worried about it.
 

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At least with the gen1 the transmission was with a direct linkage connection and not by fly by wire connection.
 

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Sounds more like a sensor problem common on many trannys.....I had the same problem on Chryslers. Half the mechanical guts used to govern speed control and shift points were stripped from the later model electronic controlled trannys and their duties taken over by an electronic control unit. Mechanical governors were replaced by speed sensors on the input and output shafts of the tranny which tell the tranny the speed of the motor and the speed/distance traveled by the wheels.


If one of these speed sensors fail (usually the output sensor) the control unit can't determine the optimal shift points for economy, emissions control, etc.. Usually if you restart the vehicle it will regain usage of all gears substituting a default algorithm for shifting (usually with lugging or over revving with the default shift points) but once it determines using the sensors are not responding it will set a code and turn on the engine light.....sometimes even locking into second gear limp-in mode for crawling to the service station. Hopefully it is a defective sensor...externally serviceable, quick and easy without opening the tranny case.


Even if the engine light goes out the dealer should be able to recover the pending code. Even those cheapo OBDll -CAN can read which codes have been erased and which ones are pending,
 

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Discussion Starter #8 (Edited)
UPDATE: Got Traverse back today, had dropped it off Monday but service was closed Monday and Tuesday. They said the Transmission Control Module wasn't current and Reprogrammed with SPS and cleared codes.

Have a message in this morning for the GM to call me, either he's off OR just didn't want to return my call.
 

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Discussion Starter #10
UPDATE: CEL again on 1/3 (aprox. 510 miles on it). Wife was driving again, good thing close to home as the transmission wouldn't switch gears, stayed in 1st. She said when the CEL came on it got jerky then rev'ed real high --I'm assuming automatically went to 1st gear. I immediately took it to the dealership. Dealership called the next day and said the transmission input sensor is on national backorder and they have no idea when it will arrive. I have a call into Chevrolet and am supposed to receive a call back within 2 business days, which would be Tuesday (Jan 8th) sometime. My traverse turns a month old on the 11th.

They did give me a Tahoe as a loaner, we'll see how long that lasts.

We'll see what happens.
 

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Sounds like from your and my experience, there’s going to be a lot more folks with issues on this Transmission Speed Sensor (TSS). Also, for the folks (who I will admit are much more knowledgeable on vehicle matters than me) who say the problem can be detected from stored diagnostics, in both our cases it was demonstrated that codes did NO GOOD! I described that there were only 12 TSS in “the system”. That leads me to thought that my replacement TSS is probably the same as used on the assembly line.... mmmm... I may not be out of the woods yet.


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At least with the Tahoe you should be in good hand. If i replace my Traverse for something else the Tahoe is my vehicle of choice.
 

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UPDATE: CEL again on 1/3 (aprox. 510 miles on it). Wife was driving again, good thing close to home as the transmission wouldn't switch gears, stayed in 1st. She said when the CEL came on it got jerky then rev'ed real high --I'm assuming automatically went to 1st gear. I immediately took it to the dealership. Dealership called the next day and said the transmission input sensor is on national backorder and they have no idea when it will arrive. I have a call into Chevrolet and am supposed to receive a call back within 2 business days, which would be Tuesday (Jan 8th) sometime. My traverse turns a month old on the 11th.

They did give me a Tahoe as a loaner, we'll see how long that lasts.

We'll see what happens.

Here's another .02 opinion on this mess. Programming/module change?...........original modules and software programming continue to work fine in older vehicles since /8/17 introduction. Fluid change? What is so magical about that?......it is either burned and contaminated or it is not, and if it is burnt or contains metal particles the torque convertor which shares the fluid needs replacement also!


Had my share of fun screwing with tranny sensors, carried two spares for my 3.5l Chrysler, either one would routinely crap out every 20K or so. Assuming GM functions the same way: the input sensor is the engine rpm sensor and the output sensor the speed of the tranny output shaft, i.e. proportional to and used for the road speed mph/kph of the vehicle. It was easy to determine which sensor went bad without codes........input sensor and you lose the tach signal, output sensor and you lose the speedometer signal.......tranny cannot function absent the output sensor because it cannot determine speed of vehicle and optimum shift points so it goes into 2nd gear limp-in mode. Usually with a bad output sensor, if you stop the car for a few minutes and restart the tranny will go through a closed loop and cycle through all gears for at least one (maybe more) upshift through the gears, then CEL lights and it goes again into limp in mode. No so with a bad input sensor you'd lose the tach signal and get a CEL but apparently the Chrysler's ECU used the engine's cam position/speed sensor as a backup for the tranny, but not the tach, in the interim.


And reflashing the software is a joke because it puts the tranny back into break-in mode and it is using a set algorithm for shifting and measuring, not using, stored driver feedback so will appear to function for a short while until it fully relies on all the sensors. With all these visits to the dealer it might be safe to say that their diagnostic and repair methods leave room for improvement.



Exactly what is their plan for more wasting time and screwing around if the input sensor doesn't correct the problem? Then try the output sensor and wait another few months? Maybe they should have an output sensor in stock in case their current guess proves wrong.



If it was me, first I'd call around to Chevy, Buick and Caddy dealers to confirm that there are no sensors available........they all use the identical HD version of the 9 speed.........in the meantime I'd be using their Tahoe as a "private limo" and picking up fares at the nearest airport as compensation for all the grief and making enough cash for a even trade against a new one.
 

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At least with the Tahoe you should be in good hand. If i replace my Traverse for something else the Tahoe is my vehicle of choice.

An equivalent 18+ Tahoe is another $15K+ USD. than an '18+ Traverse. The Tahoe being a shorter vehicle with less legroom.
 
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Discussion Starter #15 (Edited)
At least with the Tahoe you should be in good hand. If i replace my Traverse for something else the Tahoe is my vehicle of choice.
Tahoe is a great truck, I also own a 2002 Tahoe with 139k miles on it with a 6" lift and 35" tires. Truck has been great. Super easy to work on and parts are cheap.

What I meant is if the part doesn't come in for a month are they really going to let me have this brand new Tahoe for a month or more...?
 

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Discussion Starter #16
Also, for the folks (who I will admit are much more knowledgeable on vehicle matters than me) who say the problem can be detected from stored diagnostics, in both our cases it was demonstrated that codes did NO GOOD!
When I originally brought the Traverse in the CEL wasn't on (after being off an on for 2 days). There were codes stored, the same codes that ONSTAR emailed me, which I provided a copy for them the first time I dropped it off. The second time this happened my wife didn't stop the car, I left it running and brought it right over to the dealership.

The problem is based on their service bulletin is to flash and reprogram first, if it happens again then change the sensor. They're proving to be cheap and waste peoples time. I was supposed to get a copy of the service bulletin, but left without it in my haste of trying to stay calm.

I'm curious to see how my conversation will go with Chevrolet when they supposedly call me on Tuesday.
 

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Tahoe is a great truck, I also own a 2002 Tahoe with 139k miles on it with a 6" lift and 35" tires. Truck has been great. Super easy to work on and parts are cheap.

What I meant is if the part doesn't come in for a month are they really going to let me have this brand new Tahoe for a month or more...?

Why not? They should have provided signed papers to be kept as a temporary registration (may have an exp. date) with the loaner. Absent any further contact by the dealer, I wouldn't return it until the temp. reg. expires or they notify you to return it because your vehicle has been repaired.....whichever occurs first. Hope they repair yours correctly this time.



As far as Tahoes like my '11, long rides for 2nd row passengers not as comfortable as the longer 3 row '18 Traverse or my 2 row Avalanches, both with 2nd row seat spacing more like a Suburban.
 

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In 1972 when I had serious differential problems on a brand new Vauxhall Firenza I was able to keep a new loaner for over 2 months because of parts shortages coming from England. Instead of replacing the whole differential they kept trying to fix it but never succeded. There was always a whine when I was coasting and releasing the gas pedal a bit. Ended up replacing it myself after from a almost new differential from a scrapward on a car that cought Fire. In those years the warranty was only 12 months or 12K.
 

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Discussion Starter #19
Why not? They should have provided signed papers to be kept as a temporary registration (may have an exp. date) with the loaner. Absent any further contact by the dealer, I wouldn't return it until the temp. reg. expires or they notify you to return it because your vehicle has been repaired.....whichever occurs first. Hope they repair yours correctly this time.
My papers say 3 days for the loaner. The service person called Friday and said they were going to try to extend it for us. I haven't heard back, so I won't be returning it unless I hear otherwise.
 

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Discussion Starter #20
No call from Chevrolet today. I'm not surprised. I called around 3:30 Arizona time, and the Customer Service Rep who answered said the GM/Chevy Service Desk closes at 5 EST.
 
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