[Kyliecb7]

Respectfully,
Look closer at your results for IGN pin 13 to Ground pin 18.
Address (fix) Acc pin 15 to Ground pin 18.

Then change your tactic.

First, do a conventional PARASITIC DRAIN test series. You need to get a FAST SNAPSHOT of ALL the under-hood fuse box circuits. The test sequence and fill-in forms I use are in my help files. Keep it simple. Don't get fancy. Do the basic investigation and write down observations for each.

IF YOU CANNOT IDENTIFY PARASITIC DRAIN WITH KEY OFF AND REMOVED, AND ALSO WITH KEY ON, THEN YOU ARE GUESSING AND ASSUMING AND HOPING TO STUMBLE INTO A MASSIVE FIX. NOT GONNA HAPPEN.

Get some structure pointed toward the obvious trouble that is masking: power is draining the battery right before your eyes.

Fix the probably two parasitic drains, and fix the probably one key-on power drain, and your battery will stabilize.

When battery voltage is proper and stable, the SENSOR ARRAY (12v and 5v circuits) gets adequate power to support all sensors and devices and modules. Of interest: the 5v array is converted from 12v so the lower the 12v falls below 12v the lower the converted 5v array falls below 5v. RIGHT NOW YOUR ELECTRICAL SYSTEM IS UNDER-VOLTAGE. THAT MEANS ITS OVER-AMPERAGE. THAT IS DANGEROUS AND IT CREATES PHANTOM READINGS AND CONFUSES MODULES.

Chase the power drains, both key-off parasitic and key-on.

My help files:
II
V

Thanks! Yeah I had not had any issue with parasitic drain until yesterday. The car actually sat for over two weeks in early July, I came back and was able to start it right up. The drain occurred was evident to me yesterday after messing with the harness that runs over the transmission. I plan to head out and today and test which circuit is causing parasitic drain.

Could you please elaborate on your point of: "Look closer at your results for IGN pin 13 to Ground pin 18." Are you saying the 0.1V drop is indicating an issue on that circuit as well?

Also I'm not sure if you linked the help files but I couldn't click on them.

 

[GrizChev]

Scroll to bottom of Post #3 and tap the desired attachments themselves. There is also a fuse box layout sheet tobuse to check-off each fuse as it's pulled for inspection.

I listed the attachments at top of post for table of contents, but that's not active link.

 

[29 Chev]

The pin 15 test is what I would expect to see since the ACC line is actually serial data communication from what I have read - I think if you check your wiring diagram you will find that line connects to the BCM, ECM, CCM (chassis Module) and the TCM and transmits serial data between them using a series of highs (around 11.2 volts) and lows (0 volts) and if you looked at the signal with a scope it would be a non symmetrical square waveform. It is probably a very low current digital signal and using your load tester is dropping the voltage as the tester pulls it a bit closer to ground. Don't think that is your problem.
A voltage drop of 0.1 volts that you got when you tested pin 13 to ground is a problem - should not be that much as it is .03 volts higher than you got on the B+ test using the same ground (terminal 18). I would suggest checking the circuit from the battery positive terminal to that connection using your wiring diagram at easy access points where there is a connection point (fuse, terminal relay, switch, etc.) to see where the voltage is dropping. Use the power distribution wiring information to see how the current flows from the battery positive to get to pin 13 of the connector. Given the results of your B+ to the same ground point test (terminal 18) I would say the voltage drop is occurring in the positive portion of the ignition feed circuit somewhere - just my opinion. Note: this drop may actually be greater when the vehicle is running and in motion since the TCM is communicating with other modules and drawing more current than it would be using your tester.
You can also connect a jumper wire from the battery negative post (or terminal) to one terminal on your tester and connect the other terminal to your ground wire terminal 18 and use your voltmeter to determine how much voltage drop is occurring on the negative side of your circuit - just a suggestion.

If you check the bottom left of member GrizChev post he has a link to his help files. Hope this helps you.

 

[Kyliecb7]

The pin 15 test is what I would expect to see since the ACC line is actually serial data communication from what I have read - I think if you check your wiring diagram you will find that line connects to the BCM, ECM, CCM (chassis Module) and the TCM and transmits serial data between them using a series of highs (around 11.2 volts) and lows (0 volts) and if you looked at the signal with a scope it would be a non symmetrical square waveform. It is probably a very low current digital signal and using your load tester is dropping the voltage as the tester pulls it a bit closer to ground. Don't think that is your problem.
A voltage drop of 0.1 volts that you got when you tested pin 13 to ground is a problem - should not be that much as it is .03 volts higher than you got on the B+ test using the same ground (terminal 18). I would suggest checking the circuit from the battery positive terminal to that connection using your wiring diagram at easy access points where there is a connection point (fuse, terminal relay, switch, etc.) to see where the voltage is dropping. Use the power distribution wiring information to see how the current flows from the battery positive to get to pin 13 of the connector. Given the results of your B+ to the same ground point test (terminal 18) I would say the voltage drop is occurring in the positive portion of the ignition feed circuit somewhere - just my opinion. Note: this drop may actually be greater when the vehicle is running and in motion since the TCM is communicating with other modules and drawing more current than it would be using your tester.
You can also connect a jumper wire from the battery negative post (or terminal) to one terminal on your tester and connect the other terminal to your ground wire terminal 18 and use your voltmeter to determine how much voltage drop is occurring on the negative side of your circuit - just a suggestion.

If you check the bottom left of member GrizChev post he has a link to his help files. Hope this helps you.

Thanks again for the guidance. I will plan to test further in a bit.

 

[GrizChev]

Was IGN pin 13 to Ground pin 18 done after waiting for modules to sleep?

 

[Kyliecb7]

Results after today's testing.

Issue regarding the parasitic draw. Turns out that when I connected my voltmeter to the (-) Battery post and (-) Battery terminal there is a short 30sec window of amperage draw (I assume certain systems wake up and then shut back off) During my test yesterday I didn't have the Voltmeter connected long enough and i assumed the 3A draw was a short. Below is video of Amps dropping to 10mA after the 30 second window. See video for reference. So this is not an issue.
Video of Amp draw for first 30 sec

I had started testing before @29 Chev said that the ACC Wakeup Circuit reading is not the culprit. So I traced the ACC wire to the Harness connector between the engine and the Instrument Panel Harness (I/P) the connector is listed as X111 in the Service Manual. I tested with the voltage drop test at the I/P connector to test the circuit beyond the engine/trans harness to see if the same Voltage drop reading occurred.

Before testing I had the battery hooked to a charger which is why I assume the voltages are reading higher

For reference yesterday when testing, the Voltage drop for the ACC wire at the TCM was 0.39V shown by yellow line above.

Testing from Pin H (TCM ACC Wakeup) on I/P Connector to Ground. Shown by Blue line in diagram above
-Acc pin H to Ground: (Before Load Test) 12.26V
-Acc pin H to Ground: (Load Applied) 11.92V
Voltage drop of 0.34V

I then crossed checked with the other ACC Wakeup signal that goes to the ECM Pin D. Shown by Orange line in diagram above
-Acc pin D to Ground: (Before Load Test) 12.33V
-Acc pin D to Ground: (Load Applied) 11.98V
Voltage drop of 0.35V

Knowing that @29 Chev confirmed this was not an issue I can move on from that circuit.


Next is the IGN circuit that was a .1V Drop in yesterdays testing.

So the Voltage drop at Pin 13 to ground was 0.1V. tested at female end of TCM connector.

I tested the voltage drop at both side of the trans fuse (Shown by two pink arrows)
Both readings were the same at
-Trans Fuse to Ground: (Before Load Test) 12.72V
-Trans Fuse to Ground: (Load Applied) 12.61V
Voltage drop of 0.11V

My next steps will be to check Voltage at Relay Hot leads for that circuit.

 

[GrizChev]

Ref cool suggestion by @29 Chev

"You can also connect a jumper wire from the battery negative post (or terminal) to one terminal on your tester and connect the other terminal to your ground wire terminal 18 and use your voltmeter to determine how much voltage drop is occurring on the negative side of your circuit - just a suggestion."

Note that B- voltage drop up to 0.3v is acceptable in this sort of circuit. Anything connected thru a module needs time to sleep. Defined as all modules asleep.

I didn't see evidence in these circuits that simply metering would wake-up modules but the module circuits are black, and connections convoluted, and the 'master' module governing sleep is the last one to sleep. That can take ~20 minutes. So when possible test as B- voltage drop because that module would not likely raise beyond 0.3v after a 15~30 second momentary rise.

 

[GrizChev]

Keeping this reminder separate:

Test results are effected by battery voltage. As pressure drops, amperage rises.

Remember to occasionally run engine (alternator) or attach TRICKLE charger and allow time to reach static battery POS to NEG of 12.4v or more.

Disconnect any external charger or power source and allow time for modules to sleep before metering.

If you open a door or bump a remote button then the 'master' module will wake-up related other modules. It's a pita but it us what it is. Those related modules usually go back to sleep quickly. The 'master' takes time. The diagrams give likely hints - but much is black.

If your alarm senses a bump or contact with vehicle, then don't touch the body or door handles and put a thick blanket over fender as cushion. Or pull alarm fuse (most systems will not care).

 

[29 Chev]

Thought this might help you and others who read this thread understand the data signal voltage reading you are getting on pin 15 - found a youtube video that shows the type of signal that I would expect to see on the ACC wire terminal 15 if it was viewed using a scope. As you can see the waveform is going from just under 12 volts to 0 volts for very brief portions of time when data is being sent or received and in between the waveform remains high at just under 12 volts. Since a multimeter sampling rate is not fast enough to accurately catch and display such rapid changes of voltage levels and most of the time the voltage level is just under 12 volts the multimeter sampling rate averages the voltage level samples it sees and decides the voltage level in this circuit is just under 12 volts and that is what it displays (the 11.41 volts you obtained during yesterdays tests). The voltage level on this circuit is constantly swinging from 0 volts to just under 12 volts as the modules it is connected to communicate (jibber jabber as Eric O calls it) back and forth whenever the vehicle is in an awake state - the current level of these types of circuits is usually in the milliamps to keep power consumption on the "electrical grid of the vehicle" to a minimum to reduce load on the battery and alternator. As such if any external load (such as your tester) is connected to the circuit the voltage level will usually drop noticeably such as you observed. Hope this makes sense to you.

 

[GrizChev]

I remember the days of analog meters. Infinite definition. Some guys with oscilloscopes could dig deep fast. Elegant wave forms. No choppers. When digital came out most of us were unimpressed.

Today, circuit board manufacturing is in nano scale. Transistors and even relay coils and switches don't physically look like they did. They are 4 angstroms thick and built in a diffusion or epitaxy process in a wafer lab. A 2 angstrom gateway is by nature pressure sensitive, so if electrons flow thru the gateway their simple pressure pushes thru 2 angtroms thickness of atoms, and so flows down another circuit path. Boom. A relay your eyes cannot see. And it lives in the low milliamp range. It's astounding stuff.

I was fortunate to have an opportunity to run production machines in a custom wafer lab for Motorola and ON Semiconductor. Three years of math-heavy custom diffusion. Some were new development and circuit integrations (some very smart engineers made my work look good God bless them). Most were actual production sent to market including separate processing for gov stuff. Those were exciting days. When my 3 year stint was over (2016) I had an emotional crash from realizing I would likely never again work with people that smart and dedicated. But it was time for me to get back outside, I thrived in mines and powerhouses and factories. And that wafer experience gave me tools I still use every day EVEN RETIRED! And plus I have awesome memories.

 

[Kyliecb7]

Thanks for the info on communication networks. I figured the high speed data wires would do that but I didn't know that the wake up signal would do that as well. I assumed it was just power on to wake up the module Pins 2, 5, 12, 14 on diagram.

I went out again and tested what was recommended.

I first checked the Volt drop as recommended by @29 Chev by connecting leads to battery ground and pin 18. I had a reading of 0V across those.

For the fun of it I check Volt drop across the ECM/TCM fuse in the fuse box which supplies the power to the B+ Circuit.
-ECM/TCM Fuse to Ground: (Before Load Test) 12.68V
-ECM/TCM Fuse to Ground: (Load Applied) 12.64V
Voltage drop of 0.04V

I then turned the key to the ON position to activate the IGN relay and circuit.

Tested the IGN pin 13 from the TCM connector again to verify voltage drop
-TCM IGN Pin 13 to Ground: (Before Load Test) 12.38V
-TCM IGN Pin 13 to Ground: (Load Applied) 12.14V
Voltage drop of 0.24V

Then moved to the Trans Fuse in the fuse box which is the next point up on the circuit and tested volt drop
-Trans Fuse to Ground (Before Load Test) 12.34V
-Trans to Ground: (Load Applied) 11.98V
Voltage drop of 0.36V
Video of test Trans Fuse Voltage Drop Test

The only next point up on the circuit is the battery main that feeds the fuse box so i tested the red lead that comes from the battery to the fuse box.
-Fuse Box Main to Ground (Before Load Test) 12.34V
-Fuse Box Main to Ground: (Load Applied) 12.06V
Voltage drop of 0.28V
Volt Drop Video Fuse Box Main

Again stumped and now I'm not sure if my test methods are correct. I added videos you yall can verify.

At this point I'm wondering if its possible for the battery itself to be the culprit? The battery's date tag shows its around 3 years old. Anyone have any experiences with these electrical issues due to an older battery? I did bring the battery to an auto store and have them test it and they said it came back as good so i figured that wasn't the issue early on.

 

[29 Chev]

I would say you are getting close to finding the area of excessive resistance - a voltage drop of 0.28 volts using your tester is too much in my opinion. Can you post a picture of the battery positive terminal (where the cable connects to the positive post to the Fuse Box Main feed as there is probably another connection or two in between that is a problem or it may even be corrosion in the main feed wire.

 

[GrizChev]

Re video. Touch the stud post at fuse box and then compare to video where touched terminal. This may explain voltage drop, it's a joint, possibly micro-corroded. Or possibly the threaded post or the connecting terminal-eye is unexpectedly aluminum (does not conduct as well as some other materials).

 

[Kyliecb7]

Went back out, Here are the pictures.

I also retested the Voltage drop with the key OFF and the the car sitting for 30 min or so. I started with testing the voltage drop from negative battery cable to positive cable.

Ground lead on negative battery cable and positive lead on positive battery cable.
Before load 12.63
After Load 12.59
Drop 0.04V

Ground lead on negative battery cable and positive lead on Fuse Box Hot Lead cable.
Before load 12.63
After Load 12.59
Drop 0.04V

Video of Test

So it seems like the voltage drop testing while the key is off is quite different than when the key is ON. Not sure if this help solve anything though.

 

[29 Chev]

Just so I understand things - the video that shows where you had a voltage drop of 0.28 volts - was the ignition switch in the on or off position and if it was in the on position what all was working - radio, blower motor, etc.?
If you tested with the load pro connected to the battery positive cable terminal and the negative battery terminal with everything turned off and got the results above (0.04 volt drop) that could be very possible - did some research and the load pro adds approximately 0.5 amps of load to a 12 volt circuit which is about the same as lighting two 194 bulbs (used in side marker or dash light applications on vehicles made in the 70's to 90's.
If the test you did in the video was done with the key on then all the modules would be consuming a bit of power (current) as well as any components such as blower motor or radio as examples. Adding the load of two 194 light bulbs to a battery that is already being loaded by the modules and other components should not create a large voltage drop that you have observed (0.28 volts) in my opinion.
I would suggest redoing your test that you did in the video of the battery feed cable terminal with the key in the on position (both at the terminal and also the stud as suggested by GrizChev) and see what voltage drop you get and then connect the probe to the positive battery cable terminal at the battery post and to the positive post itself and see what drop you get there - leave your ground connected the same during all four tests. I am suspecting that the feed wire from the battery cable positive terminal to the fuse box main terminal has excessive resistance in it and the more the circuit is being loaded the more the excessive resistance is becoming a problem - this may be even more true if the alternator output trying to charge the battery may have to go through that portion of the wire to try and recharge the battery once the engine is running. Not sure why the TCM is the only module that appears to be having an issue but it may be the weak link in the chain and most susceptible to lower voltage. Just my opinion.

 

[Kyliecb7]

Just so I understand things - the video that shows where you had a voltage drop of 0.28 volts - was the ignition switch in the on or off position and if it was in the on position what all was working - radio, blower motor, etc.?
If you tested with the load pro connected to the battery positive cable terminal and the negative battery terminal with everything turned off and got the results above (0.04 volt drop) that could be very possible - did some research and the load pro adds approximately 0.5 amps of load to a 12 volt circuit which is about the same as lighting two 194 bulbs (used in side marker or dash light applications on vehicles made in the 70's to 90's.
If the test you did in the video was done with the key on then all the modules would be consuming a bit of power (current) as well as any components such as blower motor or radio as examples. Adding the load of two 194 light bulbs to a battery that is already being loaded by the modules and other components should not create a large voltage drop that you have observed (0.28 volts) in my opinion.
I would suggest redoing your test that you did in the video of the battery feed cable terminal with the key in the on position (both at the terminal and also the stud as suggested by GrizChev) and see what voltage drop you get and then connect the probe to the positive battery cable terminal at the battery post and to the positive post itself and see what drop you get there - leave your ground connected the same during all four tests. I am suspecting that the feed wire from the battery cable positive terminal to the fuse box main terminal has excessive resistance in it and the more the circuit is being loaded the more the excessive resistance is becoming a problem - this may be even more true if the alternator output trying to charge the battery may have to go through that portion of the wire to try and recharge the battery once the engine is running. Not sure why the TCM is the only module that appears to be having an issue but it may be the weak link in the chain and most susceptible to lower voltage. Just my opinion.

In that video of the 0.28 drop the ignition switch was in the ON position. Blower motor was off, radio was turned all the way down, Door was likely open so interior lights could have been on.

In the more recent video with voltage drop of 0.04v, the key was removed from the ignition all together and the car was sitting for 30+ mins. Here are the results of the test.

Here is the test with key in ON position and volt drop testing across fuse box stud, Positive battery cable & Positive battery post. and video for test process.
Volt drop from Fuse stud: 0.07
Volt drop from Positive Battery Cable: 0.04
Volt drop from positive post on Battery: 0.04

Video of Testing

Now I even more confused being that the car is in the ON position and the drop in the circuit is different that what was measured before...

 

[Kyliecb7]

Re video. Touch the stud post at fuse box and then compare to video where touched terminal. This may explain voltage drop, it's a joint, possibly micro-corroded. Or possibly the threaded post or the connecting terminal-eye is unexpectedly aluminum (does not conduct as well as some other materials).

I had gone through an used a wire brush to clean all positive leads and grounds across the car earlier this month.

 

[Kyliecb7]

Just took the car out for a 4 minute drive and no signs of faults. I know there is still an underlying problem. But I am losing my mind on what it could be!

My thoughts so far as to issue at hand:
1. Weird behavior going on with the battery being that it is 3 years old.
2. Resistance in positive battery cables causing intermittent low voltage.
3. The TCM itself is somehow failing intermittently.
4. Somewhere in the wiring there is an issue but its not always present (Which doesn't make sense to me either)

The only thing I can reason with is that the TCM likely wouldn't have intermittent issues. I presume if it was to fail there would be other fault codes or it would have died once and not been intermittent. However I could be wrong on this.

The battery seems fine and hasn't had any issues prior to this fault code coming up. So I would believe thats good. (The auto parts store tested it as well)

The Positive battery cables don't seem to result to any other issues / trouble codes which I feel a low voltage condition on the whole cars circuit would have tiggered something else.

That only leaves an issue with wiring, but when completing a voltage drop there is no smoking gun...

Going to share this diag strategy from the service manual, I highlighted a section in yellow which i thought was interesting. The way I read it is that any other module in the system that is connected to this module is looking for that SOH message. So perhaps the issue lies in the wiring / connectors that lead to the other modules from the TCM. Which in reading the Data / Comm Wiring diagram, the next modules that the TCM connects to would be the ABS Module and the ECM. See diagram at bottom.

 

[GrizChev]

@Kyliecb7

I believe your post #34 (repeated in #36) is accurate and the test method is valid. Part of my belief comes from the results mirroring my own tests over time. Another part comes from the uniformity for the test set, and the wait time so all modules were asleep.

Most of the frustrating oddities you reported are actually just phantom side effects. You're getting different numbers on different days.

So re: my earlier post #19 change your focus. Do those uniform tests. I expect it will lead you to the wiring outside the transmission but before going there you need to prove voltage drop in uniform manner but most importantly you need to identify parasitic drain. Otherwise you'll just keep chasing your tail.

 

[29 Chev]

I understand your frustration since nothing is jumping right out and screaming "I am the problem" - patience and the desire to not give up are two things that one sometimes needs in these situations.

My thoughts are that if it was a data communication issue only then when the ECM sets the code that it lost communication with the TCM then it should also loose communication with the ABS module since it is on the other side of the TCM and log a code about that (or at the ABS module) - this is why I believe it is a power / ground supply issue to the TCM where the voltage to the TCM is low enough that it can no longer do its job properly.

A 0.04 voltage drop using just your load pro is still significant voltage drop to me since it is only drawing 500 milliamps of current (as I stated about the same amount of current that is needed to light two 194 bulbs). A few suggestions you could try to verify or disprove there is excessive resistance in the cable running from the positive battery cable to the main fuse panel stud that you were testing at. Connect a small battery charger to the battery so the voltage remains constant at the battery. Then turn on the parking lights (leave the ignition off) and then do a test with your load pro and see what sort of voltage drop you get at the stud at the main fuse panel when the load pro button is pushed - I would expect to see only a drop of 0.01 to 0.02 volts if the cable running from the battery positive to the stud on the main fuse panel does not have excessive resistance. You can also then try this test with the headlights on and observe the results. As a last test you could connect a 14 gauge jumper wire between the positive battery cable terminal and the terminal at the stud at the fuse panel and then see if there is any difference between having the jumper wire connected or not connected when you test the voltage at the stud using the load pro - there should not be.

Just my thoughts and opinions.