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Discussion Starter · #1 ·
Hello all. Hopefully someone can give me some advice. So i have been getting my ride fixed up. My 06 is a high mileage car, but the engine runs great and I'm thinking it's been rebuilt or a replacement. Last year I had the transmission serviced with a new filter and fluid and there was not one shred of metal in the pan and the fluid did not smell burnt at all. The trans shop said it was in good condition. So my problem is that I can drive the car around for awhile and it shifts up and down just fine. But after a while of driving, sometimes it will "lock" in whatever gear it is in at the time, usually 2nd or 3rd and won't down shift, or upshift even after turning off the car and restarting it. However, if I let it sit overnight it shifts normally again. It will shift normally for awhile too if I disconnect the battery for about 10 minutes. I am beginning to wonder if the PCM/ECM is going bad. I had some suspension work done on the left side a couple of weeks ago and the ESP/traction control light came on because the steering wheel is off center and needs to be realigned...but the shifting problems was happening well before then. I took the car down to O'reillys and hooked in a decent scanner and it said it could not communicate with the PCM/ECM. Any ideas?

This is the car
123666
 

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Sounds like a communications problem. You need to scan with an advanced scantool that can read U and C codes, not just P (Powertrain) codes. You might need a conductor plate, but I wouldn't start replacing parts without being sure I've read all the available codes.
 

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Discussion Starter · #3 ·
Sounds like a communications problem. You need to scan with an advanced scantool that can read U and C codes, not just P (Powertrain) codes. You might need a conductor plate, but I wouldn't start replacing parts without being sure I've read all the available codes.
Have you got any suggestions where to get it checked? The scanner O'reilly had was a good scanner, but I'm not sure how good.
 

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Have you got any suggestions where to get it checked? The scanner O'reilly had was a good scanner, but I'm not sure how good.
If you have an Android device, pick up AlfaOBD and a Bluetooth OBD adapter like this one. That will give you essentially dealer-level diagnostics and configuration tools. If you're fixing up the car, it'll come in handy down the road. Plus it can read every module and all your error codes.

Otherwise, you can take it to a dealer, or to any shop with an advanced scantool.
 

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Discussion Starter · #5 ·
If you have an Android device, pick up AlfaOBD and a Bluetooth OBD adapter like this one. That will give you essentially dealer-level diagnostics and configuration tools. If you're fixing up the car, it'll come in handy down the road. Plus it can read every module and all your error codes.

Otherwise, you can take it to a dealer, or to any shop with an advanced scantool.
Thanks for the info!
 

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Discussion Starter · #6 ·
If you have an Android device, pick up AlfaOBD and a Bluetooth OBD adapter like this one. That will give you essentially dealer-level diagnostics and configuration tools. If you're fixing up the car, it'll come in handy down the road. Plus it can read every module and all your error codes.

Otherwise, you can take it to a dealer, or to any shop with an advanced scantool.
I checked on the Google Play Store and the AlfaOBD appears to be a download file and they wanted $49.00 for it and it was called AlfaOBD soft . I checked the link to the adapter and it was the BAFX adapter. Is that the one you were referring to?
 

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I checked on the Google Play Store and the AlfaOBD appears to be a download file and they wanted $49.00 for it and it was called AlfaOBD soft . I checked the link to the adapter and it was the BAFX adapter. Is that the one you were referring to?
Yes.

You don't need the BAFX adapter specifically, any ELM327-compatible Bluetooth OBD adapter will do. I usually suggest the BAFX because it includes free USA-based support, and you can buy it on that big website named after a river in South America for $22.

They have similar no-name units starting around $10.
 

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Discussion Starter · #8 ·
I purchased the BAFX adapter since it had a lot of good reviews. Regarding the app though...BAFX seemed to recommend Torque Pro. What did you use?
 

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Torque is not a scantool. Try the free version if you want, but AlfaOBD is the one to have.
 

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OK...The only one I could find is the AlfaOBD light. Hope that's the right one. Thanks!
That's the free "demo" version. Again, try that if you want. Supposedly, it is fully-functional but time-limited, I was never able to do anything with it. The full version is $50 on either the Play Store or that other big website.
 

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Discussion Starter · #12 ·
I did try out the demo version. It worked for about 7 minutes when the PCM stopped communicating again. I have tried 4 different scanners and OBD2 readers and it has a real problem communicating. When it did actually connect today I was able to get readings of a P0700 code and recent freeze frame readings for a P2767 code. Yesterday when i was driving the car for awhile, it locked into 2nd or 3rd gear and there was a definite vacuum leak that you could hear at idle, but went away as it was given gas. I only hear the leak when it starts having shifting problems. When it shifts fine, there is no vacuum leak. I drove it a bit today and it shifted fine. It usually starts having problems after I start driving it for awhile. Today when I was getting the OBD2 to communicate, it should a vacuum reading of 20 at idle. I don't know if it's the PCM, but suspect there is a problem there because it has such a problem communicating and a problem with the transmission. It's driving me nuts. Should I pay the $50 for the full version if it's having such problems connecting and communicating?
 

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P0700 just means there's a DTC (diagnostic trouble code) stored in the TCM (transmission control module). P2767 is the TCM code and it's calling out the transmission input speed sensor circuit. The transmission turbine speed can not be measured directly so the TCM uses the input speed sensors to calculate transmission turbine speed. P2767 is logged if there's no signal from the Input Speed Sensors.

The NAG1 5-speed transmission is electromechanical (i.e. not vacuum operated). If your hearing a vacuum leak it's coming from something other than the transmission. Check for vacuum leaks in the engine bay. Also check the torque of the intake manifold bolts. They should be 9 ft. lbs. If they're loose tighten them in the sequence shown in the image below.

123694



As for input sped sensors ... they are mounted on the electric valve control unit that is mounted on the hydraulic control unit. The combined assembly is the electrohydraulic control unit (aka valve body). They reside inside the transmission. The electro control unit, and the speed sensors, communicate with the TCM via a 13-pin connector that connects to the car's wiring harness and to the TCM; see images below.

Electrohydraulic unit in the transmission
12 - ELECTRICHYDRAULIC CONTROL MODULE
13 - SHIFT PLATE
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Electrical control unit
Input speed sensors (1,12)
13-pin plug connection (2)
123696



123697

123698
 
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Discussion Starter · #14 ·
P0700 just means there's a DTC (diagnostic trouble code) stored in the TCM (transmission control module). P2767 is the TCM code and it's calling out the transmission input speed sensor circuit. The transmission turbine speed can not be measured directly so the TCM uses the input speed sensors to calculate transmission turbine speed. P2767 is logged if there's no signal from the Input Speed Sensors.

The NAG1 5-speed transmission is electromechanical (i.e. not vacuum operated). If your hearing a vacuum leak it's coming from something other than the transmission. Check for vacuum leaks in the engine bay. Also check the torque of the intake manifold bolts. They should be 9 ft. lbs. If they're loose tighten them in the sequence shown in the image below.

View attachment 123694


As for input sped sensors ... they are mounted on the electric valve control unit that is mounted on the hydraulic control unit. The combined assembly is the electrohydraulic control unit (aka valve body). They reside inside the transmission. The electro control unit, and the speed sensors, communicate with the TCM via a 13-pin connector that connects to the car's wiring harness and to the TCM; see images below.

Electrohydraulic unit in the transmission
12 - ELECTRICHYDRAULIC CONTROL MODULE
13 - SHIFT PLATE
View attachment 123695


Electrical control unit
Input speed sensors (1,12)
13-pin plug connection (2)
View attachment 123696


View attachment 123697
View attachment 123698
Thanks for the information and diagrams. I would assume a new valve body would have the speed sensors already installed? Is it possible to change the valve body without pulling the transmission?
 

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Discussion Starter · #15 ·
That's the free "demo" version. Again, try that if you want. Supposedly, it is fully-functional but time-limited, I was never able to do anything with it. The full version is $50 on either the Play Store or that other big website.
I think you are right about the demo version. I was able to get it to connect again today before I drove the car. It stayed connected for about 15 minutes then the connection failed and it would not connect. When it was connected and working, I tried to clear a fault code, but it didn't do anything. Maybe it takes the paid version to do that. Do you ever try and clear a DTC with the demo version?
 

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Do you ever try and clear a DTC with the demo version?
I was never able to do anything but read codes and settings with the demo version, and that's apparently the same experience some others have had.

Some say that the demo version works fine for them. For what it's worth, the publisher says that the demo is fully functional except for the time limit.
 

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Discussion Starter · #17 ·
I will just get the paid version. Like you said, it will be useful down the road. Do you know if I can use the the BAFX OBD2 reader and the full AlfaOBD app on another car? I have a 2005 Chrysler 300 as my daily driver and would like to use the reader I have and app on it too.
 
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