[GrizChev]

I agree.

By nature I touch:
B+ POST to B- POST,
and then B+ TERMINAL to B- TERMINAL,
and then B- TERMINAL to FB+ TERMINAL (where FB = Fuse Box).

All should read exactly the same because the distances are very small, plus I use battery post protectors, plus I've been lucky enough so far to do regular preventive maintenance.

Another neat thing is when helping family and friends and neighbors, I often used some type of basic fill-in form as a way of helping them to understand and learn how-to. Plus it makes comparison possible. Warm fuzzies.

Anyway, I only mention it here because we're talking about consistency and comparing readings toward a fix, gotta be apples-apples.

 

[29 Chev]

I usually do the B+ and B- battery posts to verify battery voltage after turning something on (like the park lights or use a test light) to load the circuit I want to check out. Then I switch gears a bit and set the voltmeter to millivolts and go B+ post to B+ cable terminal. Then B+ cable terminal to FB + terminal, etc. That way using the voltmeter on the millivolts scale I can get a better idea of whether the drop is 0.01, 0.02, 0.03, 0.04 etc, volts - my meter will round if I use the 0 to 20 volt scale and all would show as say 12.5 volts on it until the voltage drop gets close to 0.1 volt level. I will then check out the ground portions of the circuit similarly.
Your method may be better plus you also keep a record so you can reference back to it in the future - good ideas. Here in Southwestern Ontario where salt and chemical ice melting spray is used during the winter time I use a product called Fluid Film to coat connections, terminals, etc. to prevent and slow down corrosion - it has capillary action (creeps / migrates) into things and does not conduct electricity according to the manufacturer.

 

[Kyliecb7]

Thanks for the suggestions. I took a break for the weekend to avoid losing my mind over it.

I'll plan to test voltage drop in both ways that @29 Chev & @GrizChev recommend. I will systematically check with the same conditions and report my findings Monday.

I agree. I think if it was a communications issue in the data wiring inside the TCM there would probably be more issues at hand. However, to be certain, I purchased a breakout box to plug into the OBD2 port so I can read for any open circuits or resistance in the data wiring. There was a good YouTube video on how to test across the entire canbus system to verify.
Some simple enough tests and a good tool to have regardless
CanBus Testing with Meter

As for the parasitic draw that @GrizChev mentioned. Following my previous tests after letting the car sit for 30 seconds, there was no parasitic draw. The amps read about 10mA which is well below any concern for parasitic draw.

If the ignition power wire seems to be the concerns I was starting to think that I might just run a jumper wire directly from the fuse box to the TCM female harness to verify that it would address the issue. Then if it does move through the harness inspecting for faulty wiring.

 

[GrizChev]

@29 Chev

Some of the guys use Fluid Film even on their watercraft with great success. And not just on the battery. I need to try it.

I've sorta standardized on stuff in-stock locally. I'm nearly a mile high elevation in the Sierra Nevada and lots of salt brine every winter so I know what you mean. I used certain brands in industry so always had some handy. Just sorta stayed with it. The brine means the number of under-body car washes is crazy. The moment winter temperature rises enough, zap. Gotta keep that brine at bay. So I like preventive steps.

I use NOCO Cleaner and Protector (2 part kit) for battery posts that display any level of corrosion. But its expensive so I first dip terminals into a cup of water with baking soda to bubble clean a few minutes and brush some onto the posts - and then I also pour part of a cup completely over the battery and surrounds. Then hose lightly and let dry a bit. Then NOCO Part 1 on the battery posts and loose terminals. Then hose again and let completely dry (usually while doing other things). That all takes maybe 10 minutes. Then after battery terminals are reinstalled (with pads) I coat the terminals lightly with NOCO Part 2 (*). I almost never have battery terminal corrosion the next year, meaning I consume more Part 2 than Part 1.

I also use two CRC products. One just for vehicle battery post quick-shots (*) when messing around. It gets used more on other vehicles like when someone asks for help figuring something out.

The other is a form of dielectruc grease I use for assembled but de-energized connections, home and auto, any electronics and fuse boxes and electrical devices and connectors. It's non-wicking so coats without danger of reducing circuit bandwidth.

I'm out of these two so did a screen shot.
The NOCO 2 and CRC Protector (*) get used most.

These two get used least, mostly because things stay clean longer. If I don't disassemble then I don't need them. But gotta have 'em handy!

I'm in a spot where I'm doing fewer and fewer repairs and projects. Getting older means looking for new things to do haha. I feel like I could go several years doing only the usual minor maintenance. I still hope to swap all 4 of the struts and coils this summer (but it's looking unlikely) meaning I might not put a jack under my car again until next summer. That will be weird!

 

[GrizChev]

@Kyliecb7

If you want that exact breakout box then get the type 2 that has the matching jumpers. Then, if you don't have one already, get a decent mid-to-top grade auto ranging multimeter.

Also, we all need to force ourselves to not make assumptions. The CAN buss is a unique animal.

That particular tool appears to be the type that reads circuit as a whole, but doesn't have capability to identify precisely where a trouble is along the selected CAN circuit. Also it looks to be voltage only (but I could be wrong).

I hope you'll do an after-action report for us!!

 

[Kyliecb7]

Hello All Hope you had a good weekend! I sure did having some time to step away from this issue for a few days.

I jumped back in today and took @29 Chev & @GrizChev advice and completed the sheet that GrizChev provided. Results are below.

Note: At time of testing I have no trouble codes and the vehicle shows no faults or issues with the TCM. The issue is still intermittent and today must have been a good day. I attempted to force the issue by moving and wiggling wiring harness / connectors but could not force the fault. At this point I will consider this my baseline for good working condition of the vehicle.

@GrizChev Voltage Drop Sheet

I also typed out @29 Chev recommended tests and completed those as well. When completing the voltage drop tests, I took 3 readings and averaged them out which is the Bold readings. See completed tests below. I also completed some additional tests again seen below. Similar to above tests, there were no faults / TCM errors at time of testing. For this testing, the car battery was hooked up to a battery charger to maintain voltage as best as possible.

Let me know if you guys feel any of these readings would be considered out of the ordinary. The only outlier is the IGN Pin 13 Wire in TCM harness connector but when looking into the connector specifics for the TCM connector the IGN wire is a smaller wire size (0.05) vs the B+ Pin 10 wire (0.75) so perhaps the smaller wire is why I am seeing a larger voltage drop due to more resistance. Food for thought.

I plan to drive the car around to force the TCM Fault code to appear so I can retest and compare to this baseline.

Additionally I plugged in the OBD2 breaker box and use a small portable Oscilloscope to read the Can Bus Network signals. The activity looks clear and communication is active. I Will check this again when I can force the fault to see if there are any shorts or open wires in the Can Bus Network. Here is a quick video of the Can Bus communication at baseline.
Scope of Can-Bus Network Baseline

 

[29 Chev]

Hard to fix a vehicle when it isn't broken which happens sometimes when problems are intermittent. Looking at your test results a few of the numbers are on what I would consider borderline to where there could be a problem but not going to say there is - just my thoughts. At least now you have some good data to work with if the problem reoccurs.
My thoughts on the CAN Bus video is something does not look right. It looks like you have the positive probe connected to CAN bus high and the negative lead connected to CAN bus low but cannot tell for sure. CAN Bus high should start off at the 2.5 volts scale and swing high to 3.5 volts - the positive probe of the scope should be connected to it and the negative to a good ground. CAN Bus low should start off at 2.5 volts scale and swing low to 1.5 volts again the positive probe of the scope should be connected to it and the negative lead to a good ground. If the two signals were displayed on the same screen the CAN bus high and low signals should be a mirror image of each other. I am assuming that your scope is only a single channel so what you could do is connect it to the CAN bus hi signal and then pause the waveform and take a picture or video. Then do the same with the CAN bus low waveform - that way you will have known good waveforms to compare to if the problem reoccurs. Will look to see if I can find some more info to show you what the waveforms should look like.

 

[29 Chev]

Here is some information regarding the CAN Bus high and low signals

 

[Kyliecb7]

Thanks for the breakdown of the CanBus voltage requirements. This is a single channel cheapo scope so I will follow your guidance and probe each Can high and can low separately with a good ground attached and take pictures. Now i need the car to fail so I can go through and measure again and see where the difference is. Probably going to take the car out today and see if I can generate the fault by road testing it.

Thinking back to when I first encountered the problem I remember blowing compressed air into that TCM connector and it seemed to address the issue. Along with @29 Chev first mentioning that some of the female pins look to be dirty. I bought some of the female terminals for that connector and pin removal tools to replace a few pins that may be dirty/corroded and problematic. The terminals themselves were only $7 for 25 terminals on mouser so it seems like a cheap & easy enough item to swap out. This at least will verify that those are not the issue and I can rule that out.

Terminals Specified in Service Manual:

Terminals purchased:

Specifically pins 5 & 10 look to have residue/tarnish which are respectively the GMLAN High speed + and the Battery + Circuits. I will probably replace all of the top tow pins as those seem to have more residue than the bottom row.

 

[GrizChev]

Mouser is great. All have high electrical life expectancy. Hard to beat.

 

[Kyliecb7]

Todays update. I retested the CanBus as described by @29 Chev and did se the correct signals for the low and high signals. Videos linked below.
Canbus High Video
Canbus Low Video

While reading the Canbus network I had the key in the ON position (Engine not running) and in a matter of 2 minutes all the lights in the car went out and the battery was dead! I hooked up my DVOM to the battery to check voltage and it was at 6V. I thought that was odd because I had it on the battery charger for around 30-40 mins the day before.
So I decided to take out the 3 year old battery and go pickup a new one. Perhaps this weak old battery along with some slight corrosion on the TCM connector pins had been causing my intermittent electrical issues. Not certain.
I still have the Female pins coming in this week but I might go out and drive around to see if the problem arises again before I move to the next item. More to come!

New Battery installed

 

[GrizChev]

I'm rooting for the fix! I hope the new battery does the trick. But I'm also worried why the battery failed. 6v is often unrecoverable and only occurs due to lack of consistent charge. Or a decade old battery (sulfation is managed for longer battery life).

I recall that you did clean all ends of both battery cables prior, and checked voltage drop, so that is all stable.

The two other suggestions (from my #17 and #18) again seem valid worries based on this development.

You performed an overall parasitic drain (#17) test - which at that moment passed - but you did not do the hard work of a full fusebox fuse-by-fuse test set, which nearly always finds a trouble if exists. I admit I lean toward your at-that-moment findings at-that-time, but zero-parasitic is not proven valid yet.

As likely right now is #18 the pesky Voltage/Current Sensor. I see tons of people ignore this. Including many here. I was one. And except me, none others have later admitted they should have gotten into it, they just do it and get on with life (very human so no worries).

That sensor and its separate plug are very inexpensive but a pita to install. IT'S WORK IS TO MONITOR BATTERY LEVEL ON THE FLY AND TO TRIGGER ON THE FLY THE ALTERNATOR (VIA MODULE) TO DELIVER A MEASURED AMOUNT OF CHARGE TO THE BATTERY.

You can do battery tests all you want, but if this system is not doing its job to the right levels at the right times then battery and alternator tests will likely not find it. You simply have to know the sensor needs to be tested, and have to actually test it (or replace it) INCLUDING it's lead wires and plug. That is the only way to prove it's SYSTEM is valid. Tests and docs are in that help file.


I hope the new battery solves everything. If not then I hope this sensor is all it is.
And I hope you look into it before . . .

Trust me I'm not being a smart arse. I'm worried that overlooking this will once again be the root of bad stuff and weird readings.

If none if these aspects solve the huge electrical troubles (which seem to morph and not really lead anyplace helpful), then it seems likely that no amount of tools are going to help, it's possible only a schooled oem electrical tech is going to dig deep enough and that is going to be bad news.


The thing is, in this case, I feel like this phantom menace is based on simple stuff. It almost always is. Heck there are pretty much no error codes in circuits that are powering many sensors, and modules having talk-back expectations, it just doesn't feel solid. It's gotta be something simple. I hope 🙂

.

 

[Kyliecb7]

I'm rooting for the fix! I hope the new battery does the trick. But I'm also worried why the battery failed. 6v is often unrecoverable and only occurs due to lack of consistent charge. Or a decade old battery (sulfation is managed for longer battery life).

I recall that you did clean all ends of both battery cables prior, and checked voltage drop, so that is all stable.

The two other suggestions (from my #17 and #18) again seem valid worries based on this development.

You performed an overall parasitic drain (#17) test - which at that moment passed - but you did not do the hard work of a full fusebox fuse-by-fuse test set, which nearly always finds a trouble if exists. I admit I lean toward your at-that-moment findings at-that-time, but zero-parasitic is not proven valid yet.

As likely right now is #18 the pesky Voltage/Current Sensor. I see tons of people ignore this. Including many here. I was one. And except me, none others have later admitted they should have gotten into it, they just do it and get on with life (very human so no worries).

That sensor and its separate plug are very inexpensive but a pita to install. IT'S WORK IS TO MONITOR BATTERY LEVEL ON THE FLY AND TO TRIGGER ON THE FLY THE ALTERNATOR (VIA MODULE) TO DELIVER A MEASURED AMOUNT OF CHARGE TO THE BATTERY.

You can do battery tests all you want, but if this system is not doing its job to the right levels at the right times then battery and alternator tests will likely not find it. You simply have to know the sensor needs to be tested, and have to actually test it (or replace it) INCLUDING it's lead wires and plug. That is the only way to prove it's SYSTEM is valid. Tests and docs are in that help file.


I hope the new battery solves everything. If not then I hope this sensor is all it is.
And I hope you look into it before . . .

Trust me I'm not being a smart arse. I'm worried that overlooking this will once again be the root of bad stuff and weird readings.

If none if these aspects solve the huge electrical troubles (which seem to morph and not really lead anyplace helpful), then it seems likely that no amount of tools are going to help, it's possible only a schooled oem electrical tech is going to dig deep enough and that is going to be bad news.


The thing is, in this case, I feel like this phantom menace is based on simple stuff. It almost always is. Heck there are pretty much no error codes in circuits that are powering many sensors, and modules having talk-back expectations, it just doesn't feel solid. It's gotta be something simple. I hope 🙂

.

Thanks for the insight on the Battery current monitoring sensor. I will look into the help files.
I completed another parasitic draw test yesterday with the new battery and was pulling only 15mA after around 30 seconds. Similar to the results of my first complete test.
I believe it has to be something simple as well. Most problems usually are. I will see if the battery makes any difference and then move to the next culprit if it doesn't.

 

[29 Chev]

Hope that the battery replacement fixes your problem. It is possible that the battery was allowed to become badly discharged at some point before you purchased the vehicle and it that was the case it may have had an intermittent connection at one the plates. I have seen batteries that will work ok for several days or longer under those circumstances but the right combination of a rough road and other factors can result in an unstable 12 volt supply. Having said that do not be surprised if the problem reoccurs as it would seem strange that just the TCM was being a problem - however it could also be that the wiring going to the TCM is very close to the alternator output and a bad battery as the main load for the alternator can produce some strange "hash" and "noise" in a 12 volt charging system which could create some strange signals on the CAN bus wires. Just speculation on my part.

 

[GrizChev]

See, we both revisit all these posts and still circle back to one trouble being someplace between the TCM following every wire to its other end. Maybe broken strands inhibiting adequate go-juice flow. Maybe TCM connector pin(s) corroded. Maybe a momentary contact break (vibration). But the other trouble really seems to be adequate battery power levels across load conditions.

 

[Kyliecb7]

Well today was my first drive with the new battery. I buttoned everything back up in the engine bay and reinstalled the airbox then went out for a drive. I took it across some rough bumpy roads, took it through a car wash, drove it over speedbumps, sat in a parking lot with it idle and hit some high speeds. All attempting to trigger the fault to come back. After about 52 minutes of city / stop & go driving I could not force the fault to come back. I stopped the car, let it sit, came back started it again and still all good!

As happy as I should be I feel this underlying issue could still be present and just isn't showing itself for the time being. I will continue to drive the car around and update this thread periodically to see if there was any faults that re occur. If not I will be amazed that all this troubleshooting lead down to replacing the battery. (Sometimes its always the simple stuff )

If the problem does reoccur I will be planning to replace the female pins on the TCM harness connector. I hope that this thread helps someone in the future as well, I think it is full of great electrical troubleshooting technique that can be applied.

I would like to say a to BIG Thank you @29 Chev & @GrizChev all of your discussion and knowledge that you shared during these painstaking weeks of troubleshooting. Appreciate you!

 

[Rick Stievenart]

Followed the entire forum post chain. My 2014 is having the EXACT same issue. I also replaced my battery ( 5 years old) which seemed like it had resolved the issue but after three weeks, it's back. How is yours holding up? Are you going to replace those pins in the connector?

 

[Rick Stievenart]

BTW, mine has been in the shop at my local dealership here in Sanford,NC on three s occasions, they cannot find the cause! If a dealership can't how is a DIY guy supposed to?

 

[Kyliecb7]

BTW, mine has been in the shop at my local dealership here in Sanford,NC on three s occasions, they cannot find the cause! If a dealership can't how is a DIY guy supposed to?

At this point I've abandoned all hope in Dealership Troubleshooting. I will only go there for warranty work or recalls. They never seem to be completely helpful and they always cost the most.

The car is still running as of today. I will post a milage update later today.

The only other thing I did notice during my troubleshooting was when I used the test probe pins to verify the circuit at the female connector, I saw that the test pins started to change color and have a residue on them. Almost like whatever debris/tarnish was on the inside of the female pin was being scrapped away by the test pin. I am not sure if this had removed any residue that was causing increased resistance or contact issues. Perhaps when doing this I helped clean the female pins of the connector to have a better contact. (Not sure just speculation)

The other thing i did was used some sound deadener and placed patches on the ribs of the transmission casing to help protect the wiring harness from the sharp edges of the casing. I also used some high heat wiring protection where the harness sits near the catalytic converter.

I'll post some pics for reference later today.

 

[Rick Stievenart]

I took the fuse block out yesterday and cleaned it with contact cleaner, no difference. Got a better scan tool from Launch, shows no communication with the tcm from the ecm, bcm, and IP. Same with each one U0101.