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my 2015 started acting like it had a failing battery last year. Dealer checked it about 7 or 8 times 10 minutes apart, and it was fine. The test equipment today is capable of even determining if the plates are failing. A week later it did the weird thing again so I took it straight to the dealer again. The first test revealed one cell was failed so Acura replaced it for free. The behavior and test would imply a strap between cells was loose or cracked. - sometimes when it made a good connection the battery was fine and other times it was not. FWIW we also had another brand battery made about the same time in another car fail the same way when it was only 6 months old - and it was made in 2017. I suspect based on threads here, my own experiences and another forum that one of the battery manufacturing firms had trouble in 2017 with some of their batteries. I wouldn't hold it against Costco if that is whom you buy batteries from. There are only four or five companies in the world that make auto batteries whether in their name or they put another label on them.
 

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Seem to be going in circles on this and getting nowhere! You have exhausted the battery or alternator being the issue as you have changed it out and the test show that they are fine and are not the issue. So move on to what the other obvious problems would be such as fuel. It is obvious that the vehicle is getting fuel as it does run intermittently after getting a charge! This tells us that more than likely there is still an intermittent electrical fault with the the fuel system. To cut to the chase you had an error code P2101 that you just dismissed as being wrong?? I understand that you erased it and has not come back as of yet? HDMI cable you had removed previously and you still had the problem so it is not the issue. If you looked at it you would see that it points you in the direction that you are having issues!! The car does not start or starts and then stops. It points to the "Throttle Actuator Controller" which if you read up on will further explain the symptoms that you are experiencing and get you closer to your diagnosis. It may be the sensor is faulty which would explain the intermittence of the problem or that the harness has loosened or has a fault?



locate the Throttle Actuator A (TA-A) on your particular vehicle. This actuator is usually found mounted to the front of the engine, on top of the engine, inside the wheel wells or against the bulkhead. Once located, visually inspect the connector and wiring. Look for scraping, rubbing, bare wires, burn spots or melted plastic. Pull the connector apart and carefully inspect the terminals (the metal parts) inside the connector. See if they look burned or have a green tint indicating corrosion. Use electrical contact cleaner and a plastic bristle brush if cleaning of the terminals is needed. Let dry and apply electrical grease where the terminals contact. If you have a scan tool, clear the diagnostic trouble codes from memory, and see if P2100 code returns. If it does not, then the connections were most likely your problem. For this particular code, this is the most common area of concern, as are the relays / connections to the relays, with an actuator failure a close second. If the code does return, we will need to test the actuator and the associated circuits. Typically, there are 2 wires at each Throttle Actuator. First, disconnect the harness going to the Throttle Actuator. With a Digital Volt Ohm Meter (DVOM), connect one lead of the meter to one terminal of the actuator. Connect the remaining meter lead to the other actuator terminal. It should not be open or shorted. Verify the resistance specifications for your particular vehicle. If the actuator motor is either open or shorted (infinite resistance or no resistance/0 ohms), replace the Throttle Actuator. If that test passes, with a DVOM, check to make sure you have 12V to the Throttle Actuator power supply circuit (Red lead to the actuator power supply circuit, black lead to a good ground). With a scan tool that can activate the Throttle Actuator, turn on the Throttle Actuator. If there is no 12 volts to the actuator, repair the wiring from the PCM or relay to the actuator, or possibly a bad PCM. If that’s OK, check to make sure you have a good ground at the Throttle Actuator. Connect a test light to 12V battery positive (red terminal) and touch the other end of the test light to the ground circuit going to the Throttle Actuator circuit ground. Using the scan tool to actuate the Throttle Actuator, see if the test light comes on each time the scan tool actuates the actuator. If the test light does not light up, this would indicate the problem circuit. If it does light up, wiggle the wiring harness going to the actuator to see if the test light flickers, indicating an intermittent connection.
 

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Discussion Starter #23
Seem to be going in circles on this and getting nowhere! You have exhausted the battery or alternator being the issue as you have changed it out and the test show that they are fine and are not the issue. So move on to what the other obvious problems would be such as fuel. It is obvious that the vehicle is getting fuel as it does run intermittently after getting a charge! This tells us that more than likely there is still an intermittent electrical fault with the the fuel system. To cut to the chase you had an error code P2101 that you just dismissed as being wrong?? I understand that you erased it and has not come back as of yet? HDMI cable you had removed previously and you still had the problem so it is not the issue. If you looked at it you would see that it points you in the direction that you are having issues!! The car does not start or starts and then stops. It points to the "Throttle Actuator Controller" which if you read up on will further explain the symptoms that you are experiencing and get you closer to your diagnosis. It may be the sensor is faulty which would explain the intermittence of the problem or that the harness has loosened or has a fault?



locate the Throttle Actuator A (TA-A) on your particular vehicle. This actuator is usually found mounted to the front of the engine, on top of the engine, inside the wheel wells or against the bulkhead. Once located, visually inspect the connector and wiring. Look for scraping, rubbing, bare wires, burn spots or melted plastic. Pull the connector apart and carefully inspect the terminals (the metal parts) inside the connector. See if they look burned or have a green tint indicating corrosion. Use electrical contact cleaner and a plastic bristle brush if cleaning of the terminals is needed. Let dry and apply electrical grease where the terminals contact. If you have a scan tool, clear the diagnostic trouble codes from memory, and see if P2100 code returns. If it does not, then the connections were most likely your problem. For this particular code, this is the most common area of concern, as are the relays / connections to the relays, with an actuator failure a close second. If the code does return, we will need to test the actuator and the associated circuits. Typically, there are 2 wires at each Throttle Actuator. First, disconnect the harness going to the Throttle Actuator. With a Digital Volt Ohm Meter (DVOM), connect one lead of the meter to one terminal of the actuator. Connect the remaining meter lead to the other actuator terminal. It should not be open or shorted. Verify the resistance specifications for your particular vehicle. If the actuator motor is either open or shorted (infinite resistance or no resistance/0 ohms), replace the Throttle Actuator. If that test passes, with a DVOM, check to make sure you have 12V to the Throttle Actuator power supply circuit (Red lead to the actuator power supply circuit, black lead to a good ground). With a scan tool that can activate the Throttle Actuator, turn on the Throttle Actuator. If there is no 12 volts to the actuator, repair the wiring from the PCM or relay to the actuator, or possibly a bad PCM. If that’s OK, check to make sure you have a good ground at the Throttle Actuator. Connect a test light to 12V battery positive (red terminal) and touch the other end of the test light to the ground circuit going to the Throttle Actuator circuit ground. Using the scan tool to actuate the Throttle Actuator, see if the test light comes on each time the scan tool actuates the actuator. If the test light does not light up, this would indicate the problem circuit. If it does light up, wiggle the wiring harness going to the actuator to see if the test light flickers, indicating an intermittent connection.
This time no code was thrown. It just acted like a dead battery. And it jumped and started immediately when I connected it to another car via jumper cables. It’s very odd indeed.

I checked all the sensors the last time and nothing was apparent.

The HDMI Converter was back in play. The kids kept trying to get it to work and tried plugging it and unplugging it in different combinations. Maybe there’s something that the hdmi converter did that didn’t allow the car to fully go to sleep?

What throws off this theory is it did start again after stopping and we took a very short trip less than a min and then stopped and then no start.

If it were electrical or fuel why would it jump to start? That’s what throws me off too.
 

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FWIW: Here's what I found on my 2014. With a small electrical load (daytime with no lights, heater or A/C) the charging voltage often stays around 12.2 volts. This leaves the battery constantly undercharged, which in turn allows parasitic draw to pull it down to useless in about a week of being parked. I just use a battery maintainer now anytime I am parked at home, so I know I always have a fully charged battery. Takes 5 seconds to attach/detach, so no biggie.

Suggestion: Try watching the system voltage as you drive the car under the conditions I described above. If yours does the same thing, you may want to consider a maintainer also.
 

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Discussion Starter #26
Has the dealer put test equipment on this car?
I haven’t brought a car to a dealer for non-warranty repair/service in over a decade. It’s well out of warranty. I do have a trusted independent mechanic that I am considering going to but I generally have an absolute idea of what the issue is.

This time I have no idea so I get nervous.
 

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Discussion Starter #27
FWIW: Here's what I found on my 2014. With a small electrical load (daytime with no lights, heater or A/C) the charging voltage often stays around 12.2 volts. This leaves the battery constantly undercharged, which in turn allows parasitic draw to pull it down to useless in about a week of being parked. I just use a battery maintainer now anytime I am parked at home, so I know I always have a fully charged battery. Takes 5 seconds to attach/detach, so no biggie.

Suggestion: Try watching the system voltage as you drive the car under the conditions I described above. If yours does the same thing, you may want to consider a maintainer also.
I can’t see my wife opening the hood and connecting / disconnecting it and we park outside which makes that difficult.

what are you grounding to - I found the latch is not a good spot?

What makes this more strange is we just came home from a 150 mile trip which should have kept the battery fully charged but we did have several phones charging, the entertainment system on (dvd) heated steering wheel, seats, heat, wipers, basically everything was on.

And it started up again but we only drove it a few hundred feet so a cold crank could have depleted it?

Or it’s some random electrical issue with a failing sensor though I would expect a code and for it not to be jumpable.

This is well past my skill set and I am hoping it’s the HDMI converter since the two times I used it this is what happened shortly after. Silly strategy hope is
 

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Get methodical with your voltmeter and check the battery voltage at intervals throughout the day - ex: before starting up in the morning, before putting it to bed at night, and a couple of times during the day when it's just sitting there. Write down the timestamps and voltages. Check the voltage both when not running as well as when running (charging).
Do this for a few days. After the few days (or earlier) see if there's any issue or pattern to the voltage readings. Ideally they should all be about the same. If you see a significant drop it may be due to an unusually large parasitic draw or it could be due to a poorly charged battery or an excessively resistive starting circuit.

I can't remember if you indicated this already or not but make sure you check the cables quite well and not just where they mount to the battery but also where they mount to the starter and the frame/engine ground. I recall pics from the underside of your MDX and it looks like you're in a harsh environment that could easily corrode cables and make for less than ideal connections. It only takes a poor connection at any one point in the circuit to either keep the battery from charging fully or to inhibit the amount of current that can be drawn from the battery. Sometimes people check the cables at the battery terminals for corrosion but don't check where the cable gets grounded to the frame or gets connected to the starter.

You keep bringing up the HDMI converter. Can you simply not use that for a couple of weeks so you can eliminate it from the equation?

When it fails to start do you get any action at all, like a very slow attempt to turn the engine, such as with a weak battery, or is there nothing at all, such as with a completely dead battery? When it doesn't start, what's the voltage of the battery?

These kinds of things usually end up to be something fairly simple and straightforward, such as a bad battery, inadequate/corroded cable connection, or sometimes a bad alternator (but the latter isn't typical and most get replaced when they don't need to be). Sometimes it can even be due to a rodent chewing on wires.

fwiw - my 2014 has been left for a couple of weeks before with no starting issues and it's only had its battery replaced one - somewhere around the 4-4.5 year point and at that time the battery completely failed (Christmas tree'd and relay clicked the vehicle). One difference - I live in a mild climate.
 

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Discussion Starter #30
Get methodical with your voltmeter and check the battery voltage at intervals throughout the day - ex: before starting up in the morning, before putting it to bed at night, and a couple of times during the day when it's just sitting there. Write down the timestamps and voltages. Check the voltage both when not running as well as when running (charging).
Do this for a few days. After the few days (or earlier) see if there's any issue or pattern to the voltage readings. Ideally they should all be about the same. If you see a significant drop it may be due to an unusually large parasitic draw or it could be due to a poorly charged battery or an excessively resistive starting circuit.

I can't remember if you indicated this already or not but make sure you check the cables quite well and not just where they mount to the battery but also where they mount to the starter and the frame/engine ground. I recall pics from the underside of your MDX and it looks like you're in a harsh environment that could easily corrode cables and make for less than ideal connections. It only takes a poor connection at any one point in the circuit to either keep the battery from charging fully or to inhibit the amount of current that can be drawn from the battery. Sometimes people check the cables at the battery terminals for corrosion but don't check where the cable gets grounded to the frame or gets connected to the starter.

You keep bringing up the HDMI converter. Can you simply not use that for a couple of weeks so you can eliminate it from the equation?

When it fails to start do you get any action at all, like a very slow attempt to turn the engine, such as with a weak battery, or is there nothing at all, such as with a completely dead battery? When it doesn't start, what's the voltage of the battery?

These kinds of things usually end up to be something fairly simple and straightforward, such as a bad battery, inadequate/corroded cable connection, or sometimes a bad alternator (but the latter isn't typical and most get replaced when they don't need to be). Sometimes it can even be due to a rodent chewing on wires.

fwiw - my 2014 has been left for a couple of weeks before with no starting issues and it's only had its battery replaced one - somewhere around the 4-4.5 year point and at that time the battery completely failed (Christmas tree'd and relay clicked the vehicle). One difference - I live in a mild climate.
I am done with the HDMI converter (sniff sniff) unless I find it’s a something else.

I did a spot check at the the points and it looked fine but I’ll inspect it in detail over the weekend. I didn’t think about the the northeast rust buckets and it could be a loose connection.

The battery tested at 12.4v when it wouldn’t start which is exactly at what it tested at before I installed it. Which seems low now that I am reading 100% is 12.7.

What happens is it’s acted like it’s going to start, sounds very strong, gets to about 2.5k RPMs and then just dies and cuts out. I didn’t think to test it when it was attempted to start it.

I like the idea of a log and I just tested which was an hour after a short drive.

12.4 - again
10.5 when starting
14.5 when running it dipped to 13.6 when the fan came on but back up to 14.5 with the fan running after starting.

I am starting to think it’s not a battery issue but then why would it start when it was jumped. I tested for parasitic draw just before I installed the new battery and everything was in line showing no parasitic draw - UNLESS that darn HDMI converter did something to the entertainment console where the car wouldn’t fully go to sleep.

I’ll get it load tested at autozone and if it happens again (with no hdmi converter in the mix) I guess I’ll bite the bullet and take it in to my mechanic.

I like the idea of a log so I’ll start logging the readings and situations

Now my washing machine is busted - it will not agitate or spin, it will fill and drain. Belt is fine and the motor moves when I manually turn the drum. Gotta love multimeters.
 

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You are 100% correct it is not a battery Issue or an alternator issue! It is an electrical short which you need to find. Yes take that HDMI out of there for now. No i doubt it damaged anything (Hdmi converter) Check and test your ignition relay as they are problematic and no you can not tell by just looking at them, so fully test. They will work intermittently when damaged as they heat up and cycle they weaken and do not pass the proper current.


They will also cause a battery drain. The A/c relay is also prone to the exact same thing which baffled many! Regardless your problem is electrical related whether it be a chaffed wire, a faulty harness connection, or a Throttle actuator (also electrical) that is faulty and incapable of passing the correct current through it until the battery is fully charged and then it may may but it will weaken over time until it will not. Most certainly you can jump your vehicle until the connection finally fails and no you will not necessarily get a Error code just like the a/c relay and ignition relay troubles individuals have experienced again no codes there and the same for the HFL drain thousands experienced, no codes there either!



I agree run a log if still unsure? Test the battery voltage before you start it in the morning. Once started test the voltage at battery to confirm alternator is charging properly. Once at destination leave vehicle running and test voltage that still charging. Shut down and test battery voltage. I would check the voltage again at lunch to see if it has dropped and again before i start the car to drive home and then when i get home test with engine still running to confirm alternator charging and then test with engine off. If you have time check it again in a couple hours. This will further confirm if battery and charging system is doing its job or if you have a short/fault in your electrical. However based on the numbers and taking batteries back the battery and alternator are really not your problem and you can look elswhere.
 

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Discussion Starter #32
What’s the best way to test if a relay is bad? Is there a list of resistance bench marks for each one.

When I first had this problem I didn’t think it was the battery because it was less than a year old and it was showing signs of being strong - at the time I couldn’t find my multimeter so I went to the fuel pump relay and swapped it out from my buddies same Acura. It didn’t start. I then swapped out the main relay and it didn’t start.

I then scratched my head and said “well let me try to jump it” and it started.

Again the kids were playing with the HDMI converter before the car stopped which is why I keep pointing to that. Each time they connected it on a drive this is what happened at the next start up.

Right now it’s fine again but we haven’t taken a long trip (over 100 miles) since.

Now that it’s starting I don’t know what swapping out a relay can help me pinpoint. Maybe I can test his with a multimeter and then mine to see if mine tests different but id imagine both our cars would have to endore the same driving to get cold and hot readings - is that the right path?

Hopefully he’s willing to do. It’s a lot to ask of someone.

Could it be the coils going bad. It has 95k miles on it? I just never had a Honda coils go bad under 200k miles.
 

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If it is working fine now then swapping relay with friend is pointless. If it was coil related you would get an error code and the engine would start but be rough sounding. The chances of all your coils going out is highly unlikely. I had number 5 coil only go bad at 50000 mi but had error code, rough idle ,warning lights. If things happen when your kids play with HDMI then obviously you want to remove it totally to rule it out from the equation. If things are running fine afterwards you have your answer!



This may sound familiar .https://www.yourmechanic.com/article/symptoms-of-a-bad-or-failing-ignition-relay


Lots of videos on ignition relay testing on internet.
here is one of many.
 

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Discussion Starter #34
I called my trusted mechanic shop and he told me to remove the HDMI converter and see if it happens again. He said it sounds like a short and the hdmi converter could be creating a temporary short that confuses the computer before it sleeps or doesn’t sleep.

He gave me a scenario where when I got home from the long trip I didn’t let the car sleep and restarted before it did so it was still in that mode but when I went to my neighbors house I was there for a while that allowed the car to sleep and then when I went to restart it it tripped some error.

The only way to know is if it happens or doesn’t happen again. Hopefully it doesn’t happen at all but if it does it happens while at home like the last two times.

Thanks for everyone’s help.
 

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Not the same exact thing but in my fx35 it started to stall immediately after starting up after warm and also had occasional rough idle after cold start. Ended up needing to have the throttle body cleaned and the ecu reset, that fixed the issue.

Sent from my SM-G955U using Tapatalk
 

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I have the exact same issue, car cranks strong, fires, dies.

Interestingly, when the tow-truck driver rolled it down my driveway, took the car out of neutral, put his foot on the brake and put it into park the car started up as if nothing was ever wrong ! He didn't press the start button

We took it to the shop anyway and they couldn't find anything. Cleared 92 codes (bogus) out of the computer and gave it back to me.

Seems weird that moving from neutral to park would make the car start up which makes me think that maybe there is some credibility to the poster who claimed that an Acura dealer found a loose connector near the shifter and that fixed his issue.

Really frustrating as I'm just waiting for this to happen again. No doubt it'll be with my wife in the car and a long way from home.....
 

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Discussion Starter #37
What year do you have?

Did you see my video of the issue at the top of this post - is that what you experienced.

Super odd that the car started by being rolled in neutral and bumped to park.

Have you added or modified anything recently?
 

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Yes, exact same symptoms as your video. Mine is a 2014. No changes at all to the vehicle.

The exact same thing happened a year ago, Acura Dealer recommended changing the Throttle Body (had a code stored). They also mentioned that it could be a harness ($1800) or PCM issue.

I didn't replace the TB as most people on here were telling me that it's a waste of time.
 

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Discussion Starter #39
So odd!

I am assuming my issues was caused by the HDMI converter I was using because each time the kids used it is when it happened.

I got some random stored code too and I cleaned out the throttle body - complete waste of time as that didn’t do anything.

The only thing that worked was me Jumping the battery with the clips directly connected to positive and negative - using a ground didn’t work. I have to directly connect it to the negative terminal.


Mine is well out of warranty so I don’t think l’ll start switching out parts unless I know what it is and only if it returns. It hasn’t yet but that’s what I said the last time.

I would have think if it was the harness or pcm - wouldn’t it be a constant issue?

I think my next car will be a Toyota. I love(ed) Honda but between this and my accord VCM crap I think I am done with Honda after these guys.
 

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Is the MDX still doing the same thing as your video? On one of your updates you said you retrieved a P2101 dtc. Are you still getting that code?

Next time it doesn't start can you check if the throttle body blade is opening and closing?

Remove the air cleaner lid and shine a light down the air tube to the throttle body blade.

Key on engine off then have someone press down and release the throttle pedal as you verify the operation of the blade.

Does it operate normally?
 
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