12-pin DTRL LED Flasher Modification (2012 Tacoma)

I recently bought some LED replacements for my DTRLs and rear turn signals, and managed to modify the flasher module to get them to not hyper-blink. I'll do my best to describe the process here with pictures, but if you have any questions (or tips) definitely feel free. IMPORTANT: Read the tips at the bottom of this guide! They'll help you figure out if you have too much or too little resistance.

Caveats:

• The value of the resistors you will need to use is based on how much current your LED bulbs draw. Any values mentioned here are for my LEDs and may not translate directly for you.
• It is definitely possible to make the modification in such a way that the bulb-out detection still functions (i.e. if a bulb is missing or goes out that side will hyper-flash), but my final result doesn't have that. I did have it working at one point, but got too lazy to fine-tune the resistance to make sure it stuck around.

1. Remove steering column cover. First, I removed the lower part of the plastic steering column cover. This can be done by removing the two Phillips screws that face the driver's seat. You'll need to rotate the steering wheel to get access to both of them. After the screws are out, you can gently pull the two halves apart, and carefully pull the bottom half out from the dash. The "proper" way to do this probably involves removing a lot more of the dashboard, but I managed without damaging anything. Tip: it may help to unlock the steering column so you can move it around a little bit to work things free. When you're done, you should have a decent view under the dash:
   
   
   
2. Unbolt flasher module bracket. The flasher module is a blue (or at least it was blue for me) box that's attached to a bracket right next to the fuse box and has a cable with several wires connected to it. You can't slide it off the bracket where it is because the fuse box is in the way, but you can remove the bracket. There are two bolts that hold the bracket in place. You should be able to get to the first from underneath the dashboard (i.e. by laying down by the pedals). You can see the lower bolt circled in red , and the wire connector off to the right:
   
   
   You should be able to get to the upper bolt through the hole you've opened up in the steering column. You'll need a small socket driver or wrench as the clearances are pretty tight, but once it's loose you can just use your fingers to get it the rest of the way out. Tip: At this point, if you haven't already, it's probably a good idea to pull out the little door in front of the fuse box so you can see what's going on better. You can see the hole where the upper bolt was circled in red:
   
   
   
3. Open up flasher module You should now be able to disconnect the wires from the module and free it from under the dashboard. There are two tabs holding the module to the metal bracket (circled in red) that you'll probably need to use a screwdriver on. There is a black plastic cover on the bottom of the module that is held on by two tabs on the sides (in green) that you'll also need to remove.
   
   
   You should then be able to just slide the circuit board out of the blue box:
   
   
   There are two shunt resistors (metal loops) on one corner labeled RS1 and RS2. RS1 is the resistor for the left circuit, and RS2 is for the right. I can't think of any situation where you'd be using different bulbs on one side or the other, but if you run into problems and need to troubleshoot, it'll be good to know. Here's another view of the resistors:
   
   
   
4. Replace resistors. So now the tricky part. I wasn't able to find any spec sheets for the IC on this board, so I don't have any exact equations for determining proper resistor values. There are specsheets for the Amtel IC used by non-DTRL flashers though, and I imagine the ciruit is similar. Basically, the stock shunt resistors will be something on the order of 30 milliOhms. The more current per circuit, the lower the resistance. So conversely because LEDs will be using a lot less current, we need to raise the resistance values.
   
   The DTRL LEDs I got draw about 200 mA (as determined using a multimeter and a 12v power supply) and the rear signal LEDs draw about 100 mA, for a total of 300 mA for one side. Like I said, I don't actually have an equation to determine the exact resistance required, but you'll probably be looking for something in the 100-500 milliOhm range.
   
   It might be easiest to start with a 470 milliOhm resistor (which was just barely too much for my 300 mA circuit), and solder on different valued resistors in parallel until you get the result you want. I used 1watt resistors to be overly safe, but 1/2watt should be fine too. Here's what the initial replacement looks like:
   
   
   And here's the final product after I brought the resistance down a little bit with some parallel resistors:
   
   
   When all was said and done, I'd used a .470 Ohm resistor first (which was a tiny bit too much; see below for how I could tell it was too much), and a 4.7 Ohm resistor in parallel to bring the total resistance to .427 Ohms. This is enough to prevent hyper-flashing, but still a little too much to allow the bulb-out detection to work (i.e. if I remove one of the bulbs, it still flashes at normal speed)
   
   
5. Test the modifications. To test, I slid the circuit back into the blue box (so nothing shorted on the metal dash parts), but left the cover and bracket off and just plugged the module back into the cable. Make sure you test with the headlights on, headlights off, DTRLs on and off, and the emergency flashers! The module expects different amounts of current for these different situations and your blinkers might work fine in some conditions but not others.
   
   
6. Re-assembly. Putting things back together should be pretty much a reverse of disassembling them. Personally, I would suggest that before you go through the trouble of re-attaching the bracket, that you plug in the module and drive for a couple days to make sure everything works correctly. Different situations affect the circuits differently, and you may need to still make modifications (after my first attempt, the right-side blinker would hyper-blink only when the headlights were on and I pressed the brake pedal, lol).

Important tips:

• If your blinkers flash only once and then stop, you have too much resistance for the bulbs you have installed. This will happen if the resistor is not connected (no resistor basically equals infinite resistance), the resistor value is too high (try a lower valued resistor or connecting a resistor in parallel), or the bulbs you have are drawing too much current (e.g. if you left the incandescent bulbs in-place of the LEDs).
• If your blinkers flash twice as fast as they should, you have too little resistance for the bulbs installed. This will happen if your resistor value is too low (try a higher valued resistor), or your bulbs are not drawing enough current (e.g. you put LED bulbs in without modifying the flash module)
• Test under all conditions! Headlights on or off, DTRLs on or off, hazards on or off, etc. If you're right on the borderline, even small fluctuations (like the brake lights turning on or off) might make the flashers stop working or hyper-blink. Also the longer bulbs and circuits run, the warmer they get, and their resistance increases slightly.
• You can connect resistors in parallel in different combinations to make adjustments without having to re-solder through the holes in the circuit board. The total resistance will always be less than the lowest-valued resistor, and you can find calculators online to help you with figuring out the values to use.
• If you want bulb-out detection to work correctly, you'll need to tune the resistance so that with one bulb out you get hyper-flashing, but with all the bulbs in things flash normally. The module appears to compensate for the headlights being on, so it may only be possible to get the detection to work while the headlights are on. As I said, I didn't have the patience to figure it out, but in theory with the correct resistance it's doable.

 

i was going to do this...but i got lazy and just bought the resistors with the leds and connected them on the outside right behind the lights

awesome write up

 

Ah, not entirely true. Electricity will travel through the lower value resistor as expected (i.e. I = V/R), but some of it will also travel through the higher valued resistor also following Ohm's law. The total resistance for resistors in parallel is found using the following equation:

1 / Rtotal = (1/R1) + (1/R2) + (1/R3) ...

Another way to think about it is to consider a circuit with two equally valued resistors. The current would travel through both of them, and since there's more available pathway to travel through, the total resistance would be less (half as much).

 

Correct you are haha. I'll use this once I get LEDs. Want to keep the DRLs but also have LEDs.

 

nice work man, if I decide I want to go back to DTRL I'll have to try this

I just pulled the DTRL and went with the LED flasher for now, but its all still under the dash.

 

Calculation example:
I want to calculate the correct replacement resistor value.

The current used to provide power to the front & rear signal light flows through the shunt resistor in the flasher's circuit. The current flowing through the resistor provides a voltage level that is measured by the flasher's circuit. The more current flow through the resistor, the larger the voltage measurement.

The flasher circuit measured voltage needs to be at least 0.049Volts. If it is less than that, the flasher does the hyper-flash output.

The spec for the LED bulbs I intend to use for the signal lights show 490mA for the front, and 340mA for the back = 830mA. If I want the hyper-flash to let me know when a bulb is not working, then I should calculate a resistor value to provide greater than 49mV at approx. 500mA (0.5Amp) The resistor value should be 0.049V / 0.5A =
0.098 Ohm. Best match would be 0.1 Ohm (100 milliOhm).

Next post will look at what power the resistor should be able to handle.

 

Calculation example: Power rating for the flasher's shunt resistor.

The one challenge from the example above is that I do use my truck for towing.
Adding a normal incandescent bulb to the flash circuit = 27W.
27Watts/12Volt = 2.25Amp . Add that to my LED load from the above post example = 3.08 Amp.

The 3 Amp load is passing through my new resistor value of 0.1 Ohm. The power, in the form of heat this produces = square of the Amps x Resistance value.
3A x 3A x 0.1 Ohm = 0.9W The 0.1 Ohm resistor needs to have a power rating of at least 1 Watt. I know from experience, that for long trouble free service life I should double this and use a 2 Watt resistor.

So now I know I need two, 0.1Ohm 2 Watt resistors for my flasher mod.
You can check out mail order supply houses such as mouser electronics or digikey.
example:
http://www.digikey.ca/product-detail/en/RSMF2JTR100/RSMF2JTR100CT-ND/2021752

 

That works, but I'm a bit nervous running resistors on DRLs.
That's a lot of heat. I'd almost rather just run a 2nd socket and parallel a lamp with the LEDs.

 

If we use the stock flasher setup with incandescent bulbs, the power dissipated inside the flasher is :
stock resistor is 0.03 Ohm (30milliOhm)
worst case scenario - towing = 3 bulbs flashing at 27Watts a piece
= (2.25A/bulb x 3 bulbs)^2 * 0.030 Ohm = 1.36Watt
This tells us the stock setup from the factory is designed to handle at least 1.36Watts dissipating as heat inside the flasher.

for DTRL, only the one bulb is lit, and I suspect the flasher circuit then may not run the current through the flasher's shunt resistor. In any case there is only one bulb on, so each resistor (Left & Right) is only seeing 1/3 of the above calculation = 0.5W for when the DTRL is on = no problem.

When the lights are in flash mode, technically they are at approx. 50% duty cycle, so the actual power dissipation by the resistors is only half of the above calculation.

The power rating of 2Watts for the replacement resistor specification to allow for long life, and does not represent the power it is actually dissipating as heat.

 

Get ready for a monkey wrench to be thrown into your calculations.

The OP wrote this thread for the 2012, and it apparently uses a different flasher than the '05-'11.

Your '05 only has a single shunt loop, likewise for the flasher relay that I purchased with my factory DRL retrofit harness.

 

Absolutely spot on. I should have posted this stuff at

http://www.tacomaworld.com/forum/2n...acement-stock-drl-flasher-no-resistors-5.html

for the 2005-2011 models. Thanks Rich.

That's true, and the very big assumption here is that the integrated circuit in use is based on the Atmel chips. The shunt resistor calculations are based specs such as the Atmel 6432 or similar, without even knowing this is the actual chip that Denso uses. I noticed the large# of leads on the IC in there does not match any spec sheet I was looking at. If anyone can read the part# on that black multi-leg spider on the circuit board that would be helpful.

 

Totally different from what the OP has.

I just opened up my DRL flasher (12-pin) and it has the two 3-led tabbed parts (HAF1001 A25 10Y (or TOY), four of the brown relays, three electrolytics, and a handful of small SMT parts.
The reverse side has a 10-leg SMT IC and a smattering of components.
Chip looks like 10N05 SE336

It is a 12-pin flasher. It's a 14-pin header with two missing at the keyway.

OP's looks to be an 18-pin header.

 

Rich, I did not have any luck with the part# for the 10 pin device. It looks like Denso has their own p/n on there. The automotive flasher ICS I've been able to find are either made by Motorola, or the majority are copies of the Atmel circuits, either single or dual outputs. I'd have to pull my own one out to trace the circuit out to confirm its operation.

 

Yeah, based on on the Amtel flasher's manual, I was expecting to be able to calculate the resistance required, but to my dismay, opened up the flasher box and found a completely different IC. There was a number on the chip that I Googled, but wasn't able to find any spec-sheets and ended up having to just figure it out through trial and error.

If anyone does find out what IC is on there though, I'd love to know.

 

Chances are the part# is specific to "made for Denso" so the challenge then is tracing the circuit out and comparing chip functions to existing datasheets. I would guess the 2012 model probably has CANBus communication architecture built-in to communicate with the chassis/body controller. Looking at a schematic for the 2012 could confirm this.

but we're all here for the resistor value. It is very probable that the same architecture of using a current monitor resistor, developing a voltage drop is still the method of choice, and the value is likely still to be 49mV. Engineers are always happy to re-use what already works!

Ultimately trial & error substitution, or
Measure the voltage drop while in use with the original parts and signal on, then remove one bulb and measure the result during a hyper flash.

(may need an analog voltmeter readout, or the Max function on a digital meter to capture the value while flashing, or an oscilliscope to view the result)
lots of fun!

 

And considering the drop across what is practically a zero-ohm resistor is not going to be measurable on standard meters... digital or analog....

 

Correct. Most general purpose Digital meters have a resolution of 100mV. The higher grade (read more expensive) meters will have a resolution down to 100uV, and that would work. An Oscilloscope is still the best bet, as you can visually sort out the noise, vs the change in voltage level you're interested in. Trial & error sounds much easier at this point. I have a scope, but wouldn't be working on this till maybe in Jan, and would be working on the 2005 model. I can post what I find out then. This doesn't help the 2012 model though.

 

for 2005-2011 DRL Flasher,

I removed the flasher and took off the case, then plugged it back into the harness (making sure it couldn't touch any metal under dash parts!)
I measured the VDrop across the shunt with a digital voltmeter, mV setting, and using small clips for the meter's test leads to attach to the base of the shunt, with engine running.
While the flasher was flashing, I set my meter to capture the max value.

signal light bulbs were stock.
Single side flashing, Vdrop max. was 75mV
Hazards flashing, Vdrop max. was 143mV

With the DRL (same bulbs, but not flashing) on, I did not measure any Vdrop. It looks like the power for DRL mode is delivered separately, but that's not how I remember the electrical schematic - will have to recheck this.

with two 3157 bulbs (@27Watts) operating at 13.8VDC = total current of 3.91Amps

.075V / 3.91A = .019Ohm = 19milliOhhm resistor stock.

 

I can confirm the current to operate the front signal lights as daytime running lights does not flow through these resistors. I suspect the extra relays accomplish this function. (2005 - 2011 flasher)

 

My comment was in reference to the traditional method of simply adding load resistors in parallel with the new LEDs to maintain stock current draw.
It stops "hyperflash", but it also eliminates your bulb-out warning.