DRL (incandescent) on with ignition? 2020 Tacoma SR5

Pretty much.

Well essentially we're using the switch (which is also and input to the ECU) to ground the relay so the relay switches another input. I was thinking though of 2 potential issue with my design, 1 is possible backfeeding 12v to the ECU which may or may not affect it (a diode inline would solve this). The other would be unless your switched IG source goes open circuit when the key is off it will pull that side of the relay to ground (and thus the other leg of the relay and the wire it's attached to) and turn the tail lights on. I'm not exactly sure how to solve this other than a second relay.

Yea I started thinking about that (see above) but a diode inline should solve that issue.

Your confusing inputs with outputs, 1F Pin 28 is an output. There is no "pull up" or "pull down" on an output, an output switches either ground or power (in this case ground). An output has current available on it although on a computer controlled output you have to be careful, some are "protected" and others aren't as in if it's not "protected" you can fry the driver if you pass too much current.

https://www.youtube.com/watch?v=ZXhqGkNAFgI

 

- First, I've double-checked and holding DRL to ground when the ignition is off or acc will NOT activate the DRL lights. DRL only work if the engine is running, both with the factory wiring and by manually taking DRl 20 to ground. Parking/tails and headlights will work in those switch positions even with key out and engine off.

- I'm not sure why the Ignition source would need to be an open circuit when off? How would the tails (18 green) ground through the relay coil? I don't think 85 on the relay connects to any other pins of the relay. I just checked the 5pin relay I have (generic 30 or 40A from the autoparts store) for continuity with my meter and there is no continuity between pin 85 and any other pin. At rest 87a and 30 connect as expected, energized 30 to 87 as expected, but 85 remains alone always.

- Backfeeding the 12v into the combination meter is my concern, though again I don't know if it is a valid concern. That is an area of electric theory I do not know very well. Using a diode seems like it would work (again based on my rudamentary knowledge), even the lowest rated rectifier diode 1n4001 has a reverse votage of 50V (it will stop up to 50v in reverse direction well over the 14v max it might see here) and drops around 0.6 - 0.7v in the forward direction. Given I've measured 10 to 12.5vdc on the greeen 18 wire from the combination meter/switch to ground, I'm guessing theres enough tolerance in the system to handle the smaller voltage drop.

But, I'm confused by the diode in your drawing and I don't understand how it would work to protect the combination meter from seeing the 12v IGN source? As I read it, the diode you drew (black) will allow current to flow from the meter/switch to the relay but would prevent current flow from the relay to switch, and from there to ground when the switch closes and grounds 18 green (tail/parking). In that orientation (black diode) the relay coil would never energize (since the current path to ground is blocked by the diode) and DRL would remain grounded at all times. Wouldn't the diode need to be between the combination meter and the tap to the relay, oriented to allow current flow from meter to switch only? See below my addition in RED to your drawing. In that orientation (red diode) current cannot flow from relay to combination meter but can flow from relay to ground when the combination switch is closed in that position, additionally the combination meter circuit (tails, green) will be taken to ground like normal when the switch allows.

I'll play around with some spare diodes and relay shortly to see if I'm understanding this right.

That makes sense, thanks. So to be safe, stick with things in the expected load range of the output just in case it isnt protected. For example, you could probably add a circuit with lower curent to an existing power output, say to trigger a relay coil (160-200mA), but you wouldn't want to pull enough current to run lights unles syou knew for sure the pin could handle the much higher added current?

I'm still curious if a different type of relay would work better.

The micro relay shown below is very comonly used in many household devices like smart switches, thermostats, heat/AC controllers. etc. This particual one as a 12vdc relay coil and will safely switch up to 10A at 28vdc. Further, it has a coil current of only 30-40mA.
I have checked the current on the combination meter to switch to ground wires and they seem to pull 1.5mA when taken to ground. I don't know if the combination meter can supply the 40mA needed. I've ordered some, which will arrive tomorrow. Even if they don't work here I don't mind as I can find a use for them elsewhere (I dabble with home automation a lot also). If this style relay would work with the available current from the combination meter, then protection diodes would seem to be unnecessary.

It seems though that a diode in the tail/park line (green 18) between the combination meter and new relay would protect everything when using a standard automotive relay and an ignition ON 12v source (power outlet 1, cig lighter, fuse 3 of the MB-ECU fuse panel).... again providing I undersand all this correctly.

Thanks again for the help!

 

@Dm93 , are those your videos you linked? If so, well done! I've been checking them out and they are very helpful!

 

I knew that.

I'm not exactly sure how to explain it in a way you would understand but I'll try.

We are dealing with a pull down input to the Body ECU, the relay control is a coil of wire. So we have 12v coming from the Body ECU on Pin 22 waiting to be pulled to ground, so say we have that attached to Pin 85 of the relay and we have Pin 86 of the relay on a switched source that has other loads on it.

Forgive my crude drawings but we'll use a lightbulb as a representation of the loads, when we have the switch on that leg of the circuit is at battery voltage.





With the switch off however that leg of the circuit would be pulled to ground via the load in this case the bulb. Thus anything attached to it not capable of supplying enough current to overcome the load would be pulled to ground as well if that makes sense.



If we have no load on the other end of the circuit and it is only connected to a switch then when the switch is open there is nothing to pull it to ground.

The Combination Meter isn't even on the circuits in question here, the switch inputs are to the Body ECU.
In any case most switched inputs have a voltage threshold where a switch is considered on or off that is rarely at the lowest or highest expected voltage so I'm not 100% sure but I would suspect that at 0.5v it would still consider the switch to be on.

Yes you are correct, my placement is incorrect.

Correct you never really want to add any significant load to a computer output over the design load but we are typically safe using a 200mA test light to test it or using it to control a relay although unless it's a suppressed relay you do need to be cautious about the flyback voltage.

I don't think your gona be able to "power" a relay off a switch input because by design they have a very high value resistor as they only need to provide a voltage and no current.

Again we are dealing the the Body ECU here not the Combination Meter.
The only option I see that looks like it is isolated (providing nothing is plugged into the port) is the POUTLET No2/USB fuse, everything else would be at ground potential with the key off.

 

They are not, but I have learned a ton from him as well as the other guys I have linked in my sig and threads.

 

I have to ask, why are yous still using the #20? Since the OP has auto lights with sensor #20 is NOT DRL alone.
Use LOW filament on TURN Lamp.


P.S. Turn DRL OFF through Head Unit.

 

Sorry, I was really just restating that for myself.

Actually, you nailed it. Seeing your drawings it makes perfect sense now, and should have been obvious to me from the beginning. Thanks!

Thanks. Dumb luck on my part. I always need to double check diodes and other directional components because while the drawings do make logical sense (current flows with the arrow), I somehow still cannot remmber if its the logical way or the opposite. So many things in life are not logical.

Is it correct that at times when flyback voltage is a concern, a suitably rated reverse biased diode can be used across the relay coil for protection?

I believe you are right. I poked around a bit with a meter and there really isnt any current there, I believe i was measuring it wrong before. 0.6 to 1.6mA is all they seem to carry. Shame, casue that would be so easy. Well, easiest would be to swap out for a light stalk switch that doesnt have an off but those are like $200 to get here and will take some time. Plus, Rube Goldberging a complicated mousetrap is instructive. I realize it may be silly to spend so much time on this weird problem (that I probably don't need to solve) but I've learned so much about this truck and about 'modern' automotive electrical systems in the process. I plan to have this truck until one of us dies and is burned, and understanding how it works in important to me. I appreciate the instruction.

Can I ask where you get the real drawings from?
I am using a 2016 version of the Tacoma 3rd gen Service Manual (found as a pdf in the big maintainanace thread on this forum, I think I linked to it in my first post). I had found diagrams in that indicating the combination switch connected to the combination meter. Now looking around the documant more I also see dioagrams showing it connected directly to the MB-ECU. Obvioulsy what I have is older. I've seen several people using diagrams that look liek they come from the same source as yours, but I've yet to come across it.

I will double check this later, but today I probed the #3 fuse on the MB-ECU panel. Ignition off, no key the outside showed 12v to ground. The inner side had no connection to ground. Truck on, hot side 12, inner leg had continuity to ground. I checked the bottom left fuse (#17, reported as always on and without a fuse from factory), truck off no key, outside 12v, inner leg to ground. Regardless, I have POUTLET2 also available.

If it was you, and you wanted to do this, would you be comfortable using a standard relay, powed from POUTLET2, with a protection diode for the ECU?

Thanks again.[/quote][/quote]

 

If you switch to LED for TURN lamps and require a resistor for proper blinking, it can be part of the added harness.

 

Thanks for your reply!
A couple of reasons..... I think.

One, I do not believe I have auto lights. I have auto dimming of high beams. Maybe I'm wrong. I have a 2020 SR5 with factory fogs and incandescent/halogen all around. My stalk has OFF, DRL, Park, Headlights and on the inner ring Fog OFF and ON. On the dash to the left there is the auto dim highbeam push button. With the truck on or off, if the stalk is in OFF there are no lights on. In DRL position only the DRL come on, unless turned off in the headunit (my headunit looks slightly differetn than your image, with different graphics and no sensitivity option). If parking is selected on the stalk then front and rear parking and markers come on. DRL remains on (brite filament). If fogs on is selected also, DRL goes off and parking (dim) remains on, along with tails and markers. Headlights position no DRl and all other expected lights, if fogs on also, they go off with High beams.

My DRL/Turns and park are wired as you show, two filament incandescent, DRL/Trun to bright filament, park to dim. Wire color matches.

Second, I'm sure I'm just dense and confused here, but would using a double diode allow the bright filament to flash with the turns? Would it allow the DRL to be off with Fogs or Headlights? Since the fused ignition source would be on whenever the ignition is on, would not that make the DRL filament (bright) always be on regardless of what the turn signal says? Wouldn't dual diodes allow a circuit to be controlled by two sources, but one source cannot turn off the other?

To re-state my goals, I need the DRL filament (bright) to be on whenever the truck is running (my stalk allows them to be turned off, which i need to 'over-ride') but they must be off when either headlights or fogs are also on.

If a dual diode would work here, is the below a safe way to power the DRL filaments (screenshot of one of your posts from a while back)?

Where do you get the diagrams from, like the first attachment above with the front turn/DRL lights? I've seen those a bit searching around but never found the source. Thaks again!

 

The only behavior I have not witnessed is the Bright DRL switch DIM with fogs.
By removing the #20 wire from C11 the light stalk switch looses the ability for OFF/ON DRL.
Have you tested having#20 to ground bypassing the light stalk switch?
The drawing shows that a fused feed is supplied to the LED DRL's so they do not dim when LOW beams are selected.

P.S. Fogs only come on with parking circuit.

 

On my 2020 SR5 (in fully factory configuration), yes, fogs only come on if parking is seleted. On the stalk switch that happens if either park or headlight positions are selected. Fogs never come on in the OFF or DRL stalk positions.

Yes, that is what I observe.

Yes, If #20 wire (white) at C11 is removed from the stalk switch circuitry, then the DRL never come on, regardless of selected stalk position or headunit settings (as expected).

Yes, I have tested that several times to confirm.......
With DRL ON in the head unit, if I bypass the stalk switch for wire #20 (DRL) to ground, then the DRL come on with Ignition (as expected). They are off when the ignition is off or acc (as expected). If DRL OFF in head unit, they remain off with #20 grounded and ignition on. (as expected)

With the ignition ON and #20 held to ground (bypassing the stalk switch), then selecting Park or Headlight positions on the stalk DOES NOT WORK. The DRL and only the DRL stay on, no tails of any kind, no markers, no headlights, no fogs. Keeping #20 to ground seems to prevent the "computer" from controlling the other light circuits.

Turns DO work (as expected) if #20 is held to ground providing the ignition is on, even when park, tails, heads, etc are prevented from operating by the grounded #20.


On the stalk switch (factory config) in the OFF position all input signal wires are high, none are grounded (well, #16 is always grounded through the switch EXCEPT when High beams are selected by pusing the stalk forward). This test was done with C11 removed from the stalk switch, testing the pins of the switch only to the switch's two ground pins (8 and 15).
In DRL position, #20 is grounded through the switch.
In Park position, #20 is NOT grounded but #18 green is grounded through the switch. 18 green is grounded through the switch in either Park or Head positions on the stalk.
In Heads position, #20 is NOT grounded but 18 green and 19 yellow are both grounded through the switch.

And for posterity:
17 lite blue is grounded whenever teh stalk is pulled back and held (momentary highbeam ON)
16 is always grounded UNLESS stalk pushed forward to highbeam position.
15 white/blk stripe is ground
14 Beige grounded when stalk pushed forward or pulled back fo rhigh beams
13 Red grounded with either turn position seleced
12 Grey grounded ojly when Right turn selected
11 Violet grounded only when Left turn selected
8 white/blk stripe ground
9 Dark Blue grounded when fog ON position is selected

So, holding 20 to ground turns on the DRL and if held at ignition ON then DRL come on when the truck is started. But, without breaking the ground when moving to park or heads, all other lights are prevented from functioning properly (except turns).
This makes sense to me know, thanks to help from @Dm93. Since the stalk switch is an input for the ECU(s) it does not control any light circuits directly, it simply tells the 'computer' what I want to happen. Since 20 is not grounded in the park or head positions on the switch, holding 20 to ground artifically 'confuses the computer'


I have all incadescent bulbs on my SR5, no LED in fronts or tails.
I am making this truck pass a (one time) import inspection to bring it with me to British Colombia, Canada (moving from the US). Here, DRL must come on automatically when the truck is running and itm ust not be able to be turned off while the truck is running, except when "higher order lights" are active (my wording). Since DRL cannot legally be active here when Fog or low beams are active, their state supersedes the DRL state. If the DRL are also the turn (as mine are) then the DRL must flash to function as the turn.
Becasue my stalk has an OFF position, then the DRL can be manually turned off while the truck is running, and it will not pass the inspection.

The way I see it there are exactly three options for the inspection issue....
One, I can replace the stalk switch with one having only DRL, Park, Heads but NO off position. The cost and time needed to source the appropriote switch (assuming a 3 position stalk works and is wired identically to my 4 position) make it relatively unfeasable.
Two, I can completely replace the headlight assembly with LED (since the LED stolk assemblies separate DRL from Turn ), then add in the DRL wiring and relays, etc. Even more cost and time and even less feasable for me.\
Three, I can connect #20 white on C11 to ground with the Normally Closed posts of a 5 pin relay, relay coil powered from an Ignition ON source (and not having a path to ground when OFF, I believe one of the POUTLET or USB fuses on the MB-ECU fuse panel should work there) and grounded through #18 green wire (parking) on the C11 stalk switch connector. This will keep #20 always grounded UNLESS Parks or Heads are selected on the switch. When parks or heads are selected the coil pulls to the NO position and #20 is no longer grounded. This was Dm93's suggestion above, along with using a Diode to protect the ECU (or everything upstream of the tie in point to 18 green) form backfed 12v. Please see the image below. I've absolutely no problems wiring that up if it will work as expected. This was discussed more above in posts 21, 22, 24, and 27.
Does that look like a suitable and safe method, grounding through the stalk switch on 18, with a diode to protect upstram?

Thank you. This won't work for my application but that does show a safe method for adding fused ignition on power for other accessories. How much additional current would be safe to pull from there? I see a 10A fuse is suggested. Might be a useful place to someday add a light bar or other higher current accessory.

Thanks again for all the help!

 

I'll have to read through and reply to all this later tonight when I have time but I just thought of something that should solve all of this with only a relay T-Tap and a add a fuse.

 

Thank you, I appreciate it

 

Another easy solution:


Trio of diodes for Left, Right and Hazards switch (Posi-taps)
Fused IGN source in engine bay fuse/relay box.
Only on wire entering cab, Diodes in cab also.

IGN source illuminates TURNS/DRL's. When turns are selected or hazards the tie in activates added relay to cut off IGN source, allowing OEM turn flash.

@daveeasa
@Puppypunter
@memario1214

 

Thank you! I'm going to have to study that a bit to make sure I understand it. Where would I tie into the Turns and Hazard? Is that still at C11 wires or somewhere else? Wouldn't I also need to tie into the Heads and Fogs to make the DRL also go off when those lights are on? If I'm understanding this right, when the relay is pulled to ground the DRL are no longer powered by the fused ignition source (such as off of the 5 terminal of the bat charge relay?) and the computer then fully controls the lights, allowing them to be on, off, or flash controlled by the ECU?

I'm still curious if the below is a reasonable solution, but really I'm just curious if it is safe to ground that way through the combination switch with a diode (such as a standard 1N4004 or similar) to protect the upstream electronics like the ECU or combination meter?

 

Did you not mentioned that Canadian Regs say they shouldn't ever turn off when vehicle ON?

 

Another relay added to LOW beam fuse would cut off the IGN source.

 

C9 has all the wires to tap in one location. C9 is one of the connectors to the Combination Meter.
The stalk will continue to do its OEM job, except for the DRL's, which need to be turned OFF at head unit.


China sells the harness, or you could purchase the harness from HyperTech (speedometer corrector)

 

Sorry if I wasn't clear, they need to come n automatically with the truck but cannot be on with the headlights or fogs. They also cannot be manually turned off once the truck is on (aside from when they are superceded and turned off when headlights or fogs are on. Essentially, if my 4 position switch did not have the off position, it would be legal here. The switch would sit in DRL at the lowest setting, so would come on with the truck. Clicking up through the stalk switch to park and heads would work like normal. But the physical off position is the issue. I need to emulate DRL in OFF, easy to do by grounding C11 #20, but since holding 20 to ground permanently prevents the computer from controlling the other light systems properly.

 

Buy Canadian ACLB OffRoad MT, win.