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2014 Cruze U0101 Lost Communication with TCM (only on startup)

1794 Views 17 Replies 5 Participants Last post by  Emstion
I have a 2014 Chevy Cruze LT RS 1.4L Turbo with ~135k miles on it. Recently I have been getting the following on the info upon initial start;
Service Traction Control
Service Stabilitrak
Service Power Steering

but they clear themselves after a few seconds of the car running (85% of the time) or after I shutdown and restart.
After restarting the MIL (CEL) is on with the code U0101 - Lost communication with TCM but it doesn't initially set that code. Only after shutting down and restarting. To be clear it starts, the STC SS SPS comes across the info screen, they clear themselves and the car will drive and shift normally with no problems. It seems to me that I'm not getting comms with the TCM on startup but soon after I am (maybe 5 seconds).
Has anyone had this problem before, or maybe have an idea where I should start to try and diagnose it?

Thanks,
Emstion

EDIT: I've just discovered that if I turn my key to the number 2 position (ON) the 3 service messages will appear everytime and stay there, then if I start it they will clear themselves like i described above and setting the U0101 - Lost Communication with TCM code.
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Discussion Starter · #3 ·
I guess I should have mentioned that I have checked the negative cable, I believe it has been replaced with the updated version, as it has the bolt on the side for the wire going to fusebox. I have also cleaned/retightened all the ground points (that I could see).
 

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When I had this exact issue, I looked everywhere, everyone said it had something to do with the electrical system in general, but eventually I found out that one of the ABS speed sensor cables was broken and not connected properly, I wired it back together and taped it, then everything went back to normal. I hope this helps!
 

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Wiring on the sensors seem fine. I would think that a broken wire would itself throw a code wouldn't it? Any other suggestions?
These are the codes I got along with the "service traction control" and "service stabilitrak" and "service power steering" Also U0100 code which I just noticed is different from yours. All these were caused by the ABS speed sensor cable! So your problem could be very simple.. check all the related connections and inspect the fuses.
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Discussion Starter · #8 ·
Yeah I'm not getting any codes other than the U0101 Comms to TCM. I edited the original post to include a new observation which reads;

"EDIT: I've just discovered that if I turn my key to the number 2 position (ON) the 3 service messages will appear everytime and stay there, then if I start it they will clear themselves like i described above and setting the U0101 - Lost Communication with TCM code."

I'm getting the impression it's somehow not receiving enough power from the battery while not running but is as soon as the car starts and the alternator starts charging. I tested voltage on the battery before startup and got a reading of 12.4V to 12.5V during startup it dropped as low as 11.6V to 11.8V then would climb to 15.1V while charging from the alternator.
 

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2015 Cruze 1.4L engine 6 speed AT
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Try cleaning all three wiring harness connectors and pins on the ECM. Corrosion there is pretty common on Gen 1s.

Also, your battery seems a bit weak. But may be good enough for the moment. Maybe.
 

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Discussion Starter · #10 ·
I removed them and looked but didn't clean them as I didn't see any corrosion but I will pull them again and clean them with some electronics cleaner. Might as well do the TCM plug as well while I'm at it. It's a PITA to get to.
 

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Has anyone found any new solutions? I'm having the exact same issues as originally described. I've found a few suspect wires but after repairing nothing has resolved. The car is dangerous to drive at this point, it will randomly start jerking and go into limp mode when driving. Multiple different electrical systems start going crazy like door locks and turn signals and I'll come to a stop and restart and drive away like nothing happened. I've changed battery cable and cleaned every ground I could find along with cleaning all connectors going to ecm.
 

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Discussion Starter · #12 ·
I have not had a chance to dig into this any further lately, It's been cold and rainy and my garage has been turned into a "workshop" so no room to bring it in. I do plan to tinker with it some tomorrow and try to narrow it down though. Will update with any progress I make.
 

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Discussion Starter · #13 ·
It's been awhile longer than I had planned but started tearing it apart today. Will post some pics with questions and observations of some things I've come across sometime tonight or tomorrow morning. I'll post this pic for now and ask if this is indeed a fusible link and what best way to test it would be.
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Discussion Starter · #14 ·
Ok, so I started tearing this thing apart yesterday. I removed and cleaned all the ECM connectors, didn't see anything there. I removed the battery box to get better access to the TCM connector. It's a PITA to get to, but doable with the battery box out of the way. I unplugged the connector and this is what I found:
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Automotive lighting Automotive tire Liquid Motor vehicle Water

Couldn't tell what the wetness was (water, ATF, oil etc..) too small of an amount. in any case it is definitely not supposed to be there.
Any clue as to what it could be or how it got it there?

I used some electronics cleaner and sprayed the crap out of both a couple times and finished them off with compressed air to remove the excess.
I removed the cover from the back of the connector to make sure there was no corrosion. None to be seen but I did notice this:
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Looks a little pinched but don't see any broken insulation. Not sure if this could be causing the intermittent comms issue. The white wires are the data lines. (According to the diagram I have)
If I try and repair this what would be the best/preferred way to do it?


I have a couple short videos, taken with my cheapo endoscope camera of the TCM pins before and after cleaning if needed.

Thanks,

Emstion

EDIT: Almost forgot. Does anyone know what connectors these are? They are located under the battery box.
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Discussion Starter · #15 ·
UPDDATE: I repaired the pinched wire at the TCM connector replaced the current sensor (the loop the negative cable runs through) and replaced the valve cover, Discovered it was sucking air through the vent at the "burst disc". Oddly enough it wasn't throwing any codes for that. Installed the old battery and started it up. U0101 returned, so I let it run for a few minuted to charge the battery. The info screen showed it charging as high as 15.2V but started coming down. I cleared the code and when it was reading at 14.6 volts I restarted and no code. I restarted a few more times and no code. I will let it sit overnight and see if it does the same. (Code on first start then no code after charging.) If so I will replace the battery as well and update again.
 

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UPDDATE: I repaired the pinched wire at the TCM connector replaced the current sensor (the loop the negative cable runs through) and replaced the valve cover, Discovered it was sucking air through the vent at the "burst disc". Oddly enough it wasn't throwing any codes for that. Installed the old battery and started it up. U0101 returned, so I let it run for a few minuted to charge the battery. The info screen showed it charging as high as 15.2V but started coming down. I cleared the code and when it was reading at 14.6 volts I restarted and no code. I restarted a few more times and no code. I will let it sit overnight and see if it does the same. (Code on first start then no code after charging.) If so I will replace
 

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Happy to see you've made some progress, I've worked on mine a bit with no luck still. Did you verify that the data wire that was pinched was in fact compromised? Or just repaired it based on visual inspection? Curious to see if that fixed it for you, might have to pull my battery box and check there. Is the current sensor in circuit with the tcm? I don't have a wiring diagram to check but if so were you able to test the sensor or just replaced it for good measure?
 

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Discussion Starter · #18 · (Edited)
I repaired the wire based on just visual inspection. It felt weak when massaging it so I took preventative action and just repaired it. I cut it at the pinch bared it about 3/8" on each side frayed the wires a little and pushed them together. Soldered it up nice using flux to get good solder flow. Then I applied some dielectric grease to the connection, added some heatshrink tubing and topped it off with a good coating of liquid electrical tape. Might have been overkill but didn't want to take any chances of moisture or corrosion. The current sensor is not in circuit with the TCM it connects to the BCM. I changed it just for good measure as I had never noticed my voltage ready going as high as it was.
It is still reading at 15.1V on cold start but slowly droppes down to mid 14's after a couple of minutes. I'm gonna replace the battery as well as its about 3yrs old now. Next thing will probably be the intake PCV upgrade kit from @XtremeRevolution . Just gotta get it ordered.
So far the code has not come back, but will update with any changes.


I've attached a diagram of the charging circuit in case you need it.
EDIT: I have a few other diagrams as well if you need any let me know.
 

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