CAN bus connected?

Philip Educator California Posted   Latest  
Unsolved
Drivetrain
2011 Toyota Sienna 3.5L (2GRFE) 6-spd (U660E) — 5TDDK3DC6BS018925
U0101 — Lost Communication with TCM
C1201
C1280
MIL On

Friends,

The only complaint on this 2011 AWD Toyota Sienna is the MIL and AWD lights. The U code is in the ECM, complaining of failure to communicate with the AWD. However, the AWD will communicate fine with the scanner. In looking at the data bus wiring, I'm really puzzled how CAN L and CAN H (OBD2 CAN bus presumably) can be hardwired connected to CAN P and CAN N as shown the attached illustrations. The signals are different at the ECM pins 8 and 9 (CAN P and CAN N respectively) and pins 9 and 10 (CAN H and CAN L respectively.) So, why does the factory and Mitchell wiring diagrams both show them hardwired together in D127? How can they do that and have completely different waveforms?

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Interesting
Dmitriy Analyst
Ontario
Dmitriy
 

Philip, could you look up SYSTEM DIAGRAM in the SI?

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Philip Educator
California
Philip
 

Dmitri, What you see is what I've got and it is Toyota factory info. is spread out over 4 diagrams of which I posted just one, the one showing that the two networks are supposedly connected. Mitchell (Valley Forge redraws) shows it the same way (attached.) It's under “Computer Data Lines” and there doesn't appear to be any other diagrams showing the “schematic” i.e., the data bus layout that we…

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Dmitriy Analyst
Ontario
Dmitriy
 

I wonder how to find a page like this then: diag​.​net/file/fgcfpnupr… ​ May be text search for CAN COMMUNICATION SYSTEM? Anyway, it looks like on these diagrams pin markings do not really correspond to network category (unlike other wiring diagrams). For example, your first diagram has CANP, CANH, and CA3P connected together. So, CANH on one module does not have to be connected…

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Agree
Manuel Diagnostician
New Jersey
Manuel
 

Ask customer if car was in an accident or how long they owned it. Had one problem like this with newer Toyota mismatched used parts make the problem.

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Philip Educator
California
Philip
 

Manuel, The problem started when a used motor was installed. Grounds so far have checked good as that is what I figured, but which mismatched parts on the motor would I look for? Toyota had the vehicle for seven weeks. The ECM and AWD modules have both been replaced with new parts.

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Guy Educator
Illinois
Guy
 

I recently had a GTO with a similar CAN issue/waveform, and it ended up being a bad ground on a module.

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Rusty Owner/Technician
Massachusetts
Rusty
 

I’d be suspicious that the module communication isn’t what the ECM is expecting rather than a “no communication” issue. Does Techstream show the correct calibration?

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Philip Educator
California
Philip
 

I didn't check it Rusty with the TS, just the Snap On but that's worth looking at. The vehicle has already had the ECM and AWD modules replaced with new.

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John Mobile Technician
Illinois
John
 

Hi Phil, The wiring diagram is correct, but the notes are hard to see. I attached the same diagram with the notes within red lines. The A/C amp has only 1 set of CAN Bus wires. With Smart Key, the violet and white wires are used for CAN P and CAN N. Without Smart Key, the green and white wires are used for CAN H and CAN L. It is an “either or” setup. So, without Smart Key, there are no bus…

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Helpful
Philip Educator
California
Philip
 

Hello, John. That is helpful but this thing DOES have Smart key. Would you say the A/C AMP is on the CAN P and CAN N network with Smart Key? I do wish they wouldn't combine these diagrams for such radically different vehicle. All I can say for certain is that the ECM has pins 8,9,10, and 11 and those are two distinct waveforms so they cannot be wired together. I'm really bothered by the this…

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John Mobile Technician
Illinois
John
 

Phil, That is correct. With Smart Key, the A/C Amp is on the Power Management Bus. See attached. Getting back to your issue. U0101 means that the PCM can't com with the Trans Control Module; see attached. There is a dedicated CAN Bus between the PCM and TCM. I have attached 2 diagrams. I think you are chasing the wrong CAN Bus.

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Helpful
Thanks
Philip Educator
California
Philip
 

I think I am too. Thanks, John. I will redirect tomorrow and report back. Wouldn't be the first time a scan tool code description turned me sideways.

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Philip Educator
California
Philip
 

I connected to the dedicated CAN lines between TCM and ECM and they look perfect. However, the code is also gone. The tech reported he did see a -40 degrees trans temp in the FF data. I'm trying to tie the open or bad thermistor to the U0101 before recommending the huge job of replacing that sensor, deep inside the trans apparently. I have put stabalint 22 on the pins where the TCM plugs into…

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Philip Educator
California
Philip
 

I am waiting for feedback from the shop as it was closed until yesterday and as of yesterday, the customer had not reported back on the vehicle. Presumably that means that my Stabalint 22 on the pins of the TCM did something but as with most intermittences, only time will tell. I will update here as soon as I find out.

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Stephen Technician
Tennessee
Stephen
 

What if the engine harness is from the donor and has a different pinout than the original?

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Chad Diagnostician
Arizona
Chad
   

Good Evening Phil, How have you been? I just recently diagnosed one of these cars and the U0101 code is a loss of communication with the TCM according to service information. I am not sure why the scan tool says loss of comm with the transfer case module. The code sets when the TCM cannot communicate with the ECM. When I looked through the ECM data, it showed the transmission oil temperature…

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Philip Educator
California
Philip
 

Going to give it a look-see, Chad. Thank you very much.

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Robert Technician
Michigan
Robert
   

This thing runs , hey look at the bright side .. I cant make heads/tails of that scope shot except CAN H/L wrong but could be me ; or schematics except some wire colors.. I usually start Toyota from the DLC on out ..891011 junction more than likely a terminating resistor consult SI or i should say could be is on some .. C1280 could be a Yaw sensor C1201 is a vague code that dont mean much , the…

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