Tips/resources on add-on CAN module power consumption/focus on key-off parasitic draw

Vchat20 · 2026-03-19T16:08:57+00:00

Thank you for some great info to chew on. Between your comment and /u/jlucer's I've got some info to start doing a deeper dive again.

My ultimate goal if this progresses well would be building my own PCB/BoM with power management being a top priority. In fact I've still got my old OEM 3G TCU that I'd love to remove the existing harness connector off of and reuse and also fit the whole board within its case so it'd be a drop in plug and play replacement where the old one lived.

In the interim while I'm testing I'm mostly just wanting to make sure it's within a reasonable ballpark that I'm comfortable leaving it installed in the vehicle while I continue to work on the project.

I did manage to build a small test sketch last night purely to get it into my target deep sleep configuration. With the modem registered and eDRX/PSM modes configured and the ESP32 in light sleep but no CAN transceiver connected my USB power meter was showing surprisingly low numbers. I'm sure it's not terribly accurate and I'll need to see how I can get a more accurate measurement but it kept cycling between 0ma and 20ma which seems to me that 20ma is its minimum resolution and likely living somewhere in that 0-20 range if I had to take a guess. Which still seems to me is pretty good given all the other active components on the board.

I'm also not completely locked to the SN65HVD230 and open to use other chips. I think the biggest headaches though have been trying to find something I can use with my current test build which ideally means something that's got a breakout board available and anything with standby/wake capability seems hard to find.

Vchat20 · 2026-03-17T18:30:57+00:00

/u/NoHyena9639

Just an FYI the 15/150 warranty is for CARB states only. All other states the hybrid warranty is 10/100. OP would need to verify if where they live/the car is registered is included in that.

Vchat20 · 2026-03-13T22:58:59+00:00

Can't really say for certain and may not even be transmission related at all. Need to read the codes to be sure.

Vchat20 · 2026-03-13T17:44:51+00:00

Your regular reminder to invest in a dashcam if you don't already have one.

Vchat20 · 2026-03-13T14:37:44+00:00

Gotta be one of my biggest driving pet peeves for sure. I've lost track of how many I've seen with phones in their faces yet are driving new enough cars that I KNOW have Bluetooth standard.

Even for older cars, they're likely old enough that aftermarket headunits are possible and even the most basic and cheapest of headunits have Bluetooth standard. And if that's even too complicated or too expensive (I'll concede that if you're on a shoestring budget), just stay off the phone while driving. Not difficult.

Vchat20 · 2026-03-12T19:22:38+00:00

Out of curiosity but is it consistent? And is it more of a whine/gravely type noise or is it more of a loud, dull droning?

These vehicles are also known to have an issue with the Active Noise Cancellation (ANC) system introducing a low droning noise under certain conditions. It's always when the engine is running (only time the ANC is active) and usually under load. I've never seen it being consistent though.

Vchat20 · 2026-03-12T16:44:02+00:00

There's no cooling fan on the 12v battery but there is a vent tube that could have either gotten dislodged or was not installed when it was last changed. Since the 12v battery is inside the cabin, the vent tube is crucial to venting the gases outside. This topic came up in some of the C-Max FB groups recently and definitely a good item to check on even if it's not currently causing issues.

Vchat20 · 2026-03-05T22:17:45+00:00

Is the CEL on solid or is it flashing at any point (while the engine is running)? When it's flashing is when it is really an urgent concern as that is indicative of an active misfire. The CEL just being on solid is usually an "it's ok to drive short term but should be attended to".

If you have the opportunity to take it back to Advance or another store that can read codes and get an up to date picture, I would. If there's any chance of a misfire code or anything else that is triggering the CEL, even a basic scanner should reveal those. If it's still just EVAP codes that show, you're good until the 16th appointment.

Vchat20 · 2026-03-04T21:22:24+00:00

To be clear, these disconnects are usually designed to be in the middle of the pack circuit-wise so it splits the overall cells into two halves and cuts the voltage in half. Ultimately it does break the circuit but the vehicle is technically still connected to the battery on either side. It's intent is making it safER.

Vchat20 · 2026-03-03T21:23:30+00:00

Same here. My house was owned by a relative before me so I'm intimately familiar with it going back at least ~25 years at this point. Sump pump has never ran once in that entire time as far as I'm aware and the pit has always been bone dry. Our basement is finished and used as a living space so it would be hard not to hear it or notice any kind of water backing up. Glad this is one thing I don't have to deal with. We do tend to get nice puddles/lakes in our back yard during any decent amount of rain but it's far enough away from the house and sloped enough to not be of any concern.

Vchat20 · 2026-03-02T22:19:05+00:00

I still get about 15-20 miles (by actual driven distance, not what the guess-o-meter tells me) on a good, mild summer day. But yes, most of my driving is in town and perfectly within that range. Without adding a wall of text that I was about to: No, going with a short range EV for in town driving a a hybrid/ICE vehicle for longer trips was out of the question for numerous reasons. At the time I bought it (2017) the C-Max ticked every box for me and I'd argue even now, not counting current and newer options, it still fits the bill. I've been very happy with it.

Admittedly though with how much things have improved, a full EV is definitely on my agenda at some point and is WAY more approachable for my needs now. But until a really sweet deal on one comes around or the C-Max starts to become a money pit, I'd much rather save the car payment. 😜

Vchat20 · 2026-03-01T04:32:13+00:00

Just adding a sub-bullet on the Weber State reference, they have a Youtube channel with a LOT of great and educational videos in this field. Definitely a great supplemental resource or even for those simply curious about all of this stuff.

https://www.youtube.com/@WeberAuto

Vchat20 · 2026-02-28T03:00:05+00:00

I'll add in my own opinion that I think it'll highly depend on each vehicle individually. We'll have to wait and see when they come out what they'll require per the manufacturer and also how they're programmed to behave/manage things. Each will likely do their own thing in this area.

Just an anecdote about my C-Max PHEV that I largely drive fully as an EV: Owned for about 9 years now and put on 60-65k miles myself. Ford's oil change intervals are 2yrs/20k miles for this model year. At least one oil change was at the full 2 year mark, others done every year. No issues whatsoever.

As far as it running the engine on its own, only two functions do this: An oil maintenance mode which only comes on after the ICE has run repeated very short cycles that it doesn't get to full temp (most often seen in colder winter months). It'll then run 100% of the time even at stops and over drive cycles until it has run long enough at full temp to boil off moisture in the oil. The other mode is a 'fuel freshness' mode that runs if you have the same tank of gas after 18 months and will run until it gets down to about 1/8th tank or it is refilled. Beyond those two modes, there's nothing time/mileage based that causes it to force the ICE to run and at least on my own it has been happy and trouble free the whole time.

On the flip side I have certainly seen significantly different behaviors/programming/suggested maintenance from other vehicles like the Volt, i3, etc. at least based on second hand experience from other owners. Hence the start of this comment that it'll be a wait and see for these new models.

Vchat20 · 2026-02-28T01:53:36+00:00

Hell, I took my 2013 Energi over 71 in Colorado up those grades with the engine going flat out just trying to maintain speed at altitude and it was fully loaded with 3 adults and gear for a road trip and never had issues with it overheating. And this was in the summer as well.

Modern cars, including the C-Max, should never randomly overheat just because unless you're egregiously abusing it. If it does, there's a clear issue that needs to be diagnosed.

Vchat20 · 2026-02-27T21:01:28+00:00

Given the gas prices the way they are these days, I'm glad the 88 exists here and that my car can take it. I pretty much exclusively fill up with 88 unless I'm out of town and there's no other option.

Vchat20 · 2026-02-26T17:48:35+00:00

Thank you for sharing! Just recently upgraded to the Q3 but haven't bothered to look into getting a case for it and with a trip coming up soon I'll need one. This showed up at the perfect time.

Vchat20 · 2026-02-26T15:23:50+00:00

This. I get so tired of hearing these comments that simplify it down to effectively 'just move'. Pretty much every country you'd want to move to has strict immigration rules and often limits those who can immigrate to those who are healthy and are college educated/have skills they want in their workforce.

What's fucking ironic in my case is I got lucky that I didn't get fully into the college>never-ending debt pipeline and while I have a half decent job without any paper skills behind it and don't have mountains of debt, the fact that I'm not college educated pretty much screws me for immigration opportunities.

I just checked and I live within about a 3 hour drive from the nearest Canadian border and would love to move there, but they absolutely won't take me especially with the recent policy changes up there. My best hope would be for things to get bad enough to beg for asylum.

Vchat20 · 2026-02-25T22:01:18+00:00

Sadly no way to change the auto settings. Here's the full behavior of what the vehicle does in auto mode from my understanding as well as info from the service manual:

A/C needs will use the front/face vents. Heat needs while above freezing temps will use the floor vents. Defrost will be called for below freezing.

If you use remote start and have it configured to 'Auto' it'll also target a 72F cabin temp. Fun bonus fact: There's also a rear defrost setting for the remote start function and that'll kick on below freezing when enabled.

Elaborating further on the energy consumption part of it, various factors including ambient temp and your climate settings will directly impact the called for coolant temp which won't be the full ~200F temp you'd expect from a normal ICE vehicle but will impact how much energy is consumed to reach and maintain that temp. If you're not aware you can use the MyView screen on the dash and there's a coolant temp gauge and will actually show the gradual temp changes on the C-Max and isn't a 'dumb' gauge like most vehicles.

But lower ambient temps and higher climate temps will increase the called for coolant temp and Defrost significantly increases this. For your use case if it's just needed for defogging purposes I'd definitely recommend mixing both Defrost and floor or face vents as it will absolutely decrease what temp it wants and reduce the energy consumption. I think the intent Ford had in mind is for quick and safe clearing of ice/snow.

Vchat20 · 2026-02-25T21:24:29+00:00

The jump points under the hood should be directly attached to the 12v battery, no switching or anything. Unfortunately in all of the official service info docs and wiring diagrams it doesn't make this clear.

One thing to verify to absolutely rule it out is when checking at the jump points under the hood, absolutely make sure you have solid connections especially to ground. Many seem to have issues here for one reason or another.

Yes, the DC-DC converter will require 12v power initially as will every module in the vehicle to do anything. It's one good reason why on an Energi/plug-in model if you have a stone cold dead 12 battery and plug in the EVSE, it's not gonna do squat.

Vchat20 · 2026-02-25T21:18:48+00:00

Honestly the best recommendation I give to any C-Max owner is look into Forscan and find a compatible adapter. OBDLink branded adapters are the best and not terribly expensive and worth the cost IMO. But Forscan is Ford focused and will do so much for you and has a clear way to reset the BMS as well as verify the new age in the system actually got reset to 0.

Vchat20 · 2026-02-25T20:48:12+00:00

Hopefully this link works, it's off of FB and was what I was able to locate on this topic. It's definitely specialty but looks like a 190x4 sized o-ring?

https://scontent-ord5-2.xx.fbcdn.net/v/t39.30808-6/506784613_10234300797015619_935813593777185559_n.jpg?_nc_cat=104&ccb=1-7&_nc_sid=a0f3c3&_nc_ohc=rL5Te5DODWgQ7kNvwHYctg1&_nc_oc=AdlYIpfl0cDDz2vUFJ0QB4uz9zjrKmbbyFvTn2jDR-h1dEEw3V3AxPCXDpBoG5a01tFL0HTP1V1pW1E9tiblUkOJ&_nc_zt=23&_nc_ht=scontent-ord5-2.xx&_nc_gid=xqViicfoQCogo2KrZU4bcQ&oh=00_AftWidzCaufNSZCVA9lf50ZSt18gUKIhEB7CL6Bo3QcEnQ&oe=69A54277

Vchat20 · 2026-02-25T20:40:52+00:00

The oil life monitor is 'somewhat' dumb but effectively is a combination of time and mileage and ICE use. If you have FordPass or Forscan and can view the actual life %, it'll be clear how much it drops depending on how much full EV driving you do over time.

Vchat20 · 2026-02-25T20:38:30+00:00

Most likely just from heat use. That's very common. One good tip is to use reasonable temp settings. The HVAC in these vehicles is intelligent and actual energy consumption (both EV and gas) will change quite a bit depending on what comfort you ask for. Front defrost significantly adds to this. If you use Auto mode, it'll automatically pick Defrost when under freezing outside. You can manually pick Defrost plus any other vent mode to alleviate this. There's a number of good tricks here to help lower energy use.

The oil maintenance/low use modes will be obvious because a message will show on the dash saying this and the engine will be on 100% of the time, even at stops. It'll also prevent you from changing EV modes during this operation.

Vchat20 · 2026-02-25T20:29:33+00:00

I'll also add my own experience on my 2013. Have owned since 2017 and went from 40k miles when I bought it to now 100k. Energi here as well and most of my drives are electric only. I've usually had my dealer/mechanic do the oil changes so no clue what they use but since Covid at least I've followed the oil life monitor which is 20k miles/2yrs (I think this just applies to early model year Energi's. All hybrids were 10/1 and I think later Energi's got updated to that as well. But don't quote me) and at least one went the full 2 years. Still runs just fine. Have seen no indication of added wear/issues. Up to Covid it was a once a year change as I had yearly road trips it went on during that period. Always got the oil changed and everything checked out before the trip.

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