g37 parking brake for drl

Hey Guys

Got DRLs running through the fog lights for a U.S g37 car. I would like to activate the DRL only when parking brake is off like the Canadian cars are done. I've done all the wiring through the IPDM, so how can I get parking brake signal. I don't want to touch BCM or ECM, I don't think IPDM gets this signal. Do I've to physically run it from the parking brake switch on the parking brake and run it through the firewall ? If so can anyone guide me through a similar job done.

thanks very much

What year is your G37?

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Sylvain Rochon
MECP security specialist
Tech support for remote starters
26 Years of experience counts
I'm here to help.

This is what I would do




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Sylvain Rochon
MECP security specialist
Tech support for remote starters
26 Years of experience counts
I'm here to help.

Parking brakes typically output a (-) signal when engaged - therefore with the above diagram the fogs would only come on with the parking brake set.

You're going to have to tap the parking brake inside the vehicle. I've never traced it out, but I would assume it runs to the BCM. What is your hesitation with messing with the BCM? It's really no different then the IPDM you've already messed with. They are both small electronic modules that control outputs based on both digital inputs and CAN bus data.

Assuming you grabbed switched 12vdc at the IPDM I would run the (-) side of the DRL relay coil in to the passenger compartment (should be an OEM grommet high on the passenger side behind the battery) and towards the BCM that is in the passenger kick panel. Connect a 2nd relay across the parking brake signal at the BCM (again, assuming it is there) and wire the (-) feed from the underhood relay through pin 87A to ground.

If you did not add a relay at the IPDM let me know how you hooked it up and I may be able to provide more detailed info.


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Kevin Pierson

"therefore with the above diagram the fogs would only come on with the parking brake set." No, the fog won't come "on" with the brake switch set because the relay breaks the circuit. When brake is set, it sends a "-" to 85 and with ignition "on" on 86, it breaks the contact when relay makes the connection between 87 and 30 thus keeping the fog lights off til the parking brake is un-set and the relay comes back to make the contact between 87a and 30 thus lighting up the fog lights... So I don't agree with Kevin's statement. Sorry Kevin...lol...

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Sylvain Rochon
MECP security specialist
Tech support for remote starters
26 Years of experience counts
I'm here to help.

Sorry about that, I misread the little numbers!

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Kevin Pierson

Thanks Guys. Hello Kevin, I guess I should be thanking you as I got some help from a Infiniti G35 forum and KP Technologies had great deal of input on a posting there. Anyways, I'm bit reserved in touching the BCM, first it was ECM/BCM were recently replaced at a dealership because of their screw ups and secondly it sits behind the glove compartment I think.

The parking brake 'SWITCH' on the parking brake outputs a (+)'ve upon parking brake release (OFF), so all I've to do is run it from inside through a firewall opening to the engine bay. Alternate easier route would be opening up BCM.

I'm trying to design my DRL with parking brake release AND Light/Auto/Park are OFF. I'm guessing no need to touch 'Auto' pin in IPDM, if lights come on through AUTO then the Light pin will have power going through. One thing I'm not sure about is if the Lights are ON, then DRL should be off as per the below diagram. Is there any other component I can combine this logic of parking brake ON and light OFF and would this still retain the Fog original functionality?

I'm using SmartDraw trial version, sorry about their logo.

There are 2 problems that I see with that diagram. First, make sure that the park brake wire does not rest at 12v when the ignition switch is off because if you have forgotten to put your park brake on, you'll have a current draw of 150mA because your relay #1 will be constantly on. Second, the way that I see your diagram, you'll be using the car's ignition to turn on your fog lights which I wouldn't do if I would be in your place. I would simply find the fog relay, find it's ground wire and simply use a relay to disconnect the ground when the park break is "on". That would simplify the project and you wouldn't play in the IPDM and BCM.

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Sylvain Rochon
MECP security specialist
Tech support for remote starters
26 Years of experience counts
I'm here to help.

The OEM foglight is integrated in to the IPDM. The IPDM is CAN based. There simply isn't an easy (non destructive)way of accessing the wiring to the fog light relay.

You should see what is required to just interface the OEM fog light switch (it is part of a matrix style multiplexed system that needs to be decoded). Fun cars for sure!



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Kevin Pierson

stclaus37 wrote:

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Thanks Guys. Hello Kevin, I guess I should be thanking you as I got some help from a Infiniti G35 forum and KP Technologies had great deal of input on a posting there. Anyways, I'm bit reserved in touching the BCM, first it was ECM/BCM were recently replaced at a dealership because of their screw ups and secondly it sits behind the glove compartment I think.

The parking brake 'SWITCH' on the parking brake outputs a (+)'ve upon parking brake release (OFF), so all I've to do is run it from inside through a firewall opening to the engine bay. Alternate easier route would be opening up BCM.

I'm trying to design my DRL with parking brake release AND Light/Auto/Park are OFF. I'm guessing no need to touch 'Auto' pin in IPDM, if lights come on through AUTO then the Light pin will have power going through. One thing I'm not sure about is if the Lights are ON, then DRL should be off as per the below diagram. Is there any other component I can combine this logic of parking brake ON and light OFF and would this still retain the Fog original functionality?

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You're more then welcome for the info I posted - I was kind of a pioneer in the fog light hacking and to this day I am still the only person that has came up with a reliable way to use the OEM fog light switch to turn the fog lights on and off independent of the the headlights.

Unfortunately, your diagram won't work. Do not confuse 12vdc at rest with actual 12vdc power. The 12vdc signal on the wire with the parking brake is not applied is simply a pull up voltage - there is no current behind it. You will NOT be able to power a relay off of that 12vdc signal. The current comes from the (-) side of the parking brake switch (that goes to the combination meter, not the BCM). So, you'll have to trigger your relay off of the (-) when on parking brake signal. Use igniton power for (+) voltage on the coil and for power through the relay to your fog lights (make sure you fuse it around 10A).

In order to get the system to work when the switch is only in the off position I would consider using the parking light bulb as a trigger. You could possible tie the (-) side of the underhood relay to a parking light (+) wire instead of directly to ground. When the parking lights are off they will rest at ground and should be able to provide enough current to switch the relay. As soon as you turn the parking lights on the ground will drop out and the underhood relay will no longer work! You would have to install a diode in the ignition feed towards the underhood relay.

So this is how I would do it:

Relay 1 (inside car):
Pin 85: Parking Brake (-) at combination meter
Pin 86: Ignition Power
Pin 30: Ignition Power
Pin 87A: Ignition Power to Relay 2 Pin 86 with diode stripe facing under hood relay

Relay 2 (under hood):
Pin 85: Parking light (+)
Pin 86: Ignition Power from Relay 1
Pin 30: Fog light output to both OEM fog light (Cut wires going to IPDM)
Pin 87: 10A fused supply from battery
Pin 87A: One of the cut fog light wires going to IPDM

If you don't cut the wire going to the IPDM you can backfeed voltage through the IPDM and create all sorts of problems. The two wires are common inside the IPDM so only one has to be hooked up - the other can be hooked up as well or just taped off. This should allow the fog light switch to still work as OEM, should disable the DRL if the switch is in any position other the "OFF" and should disable the DRL if the parking brake is pulled!

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Kevin Pierson

Thanks Kevin and Sylvain.

Kevin, here's the diagram based on your reply.

What kind of diode can I use on pin 87a of Relay 1? Is parking lights(IPDM 91) enough to switch off DRL or should I also include Headlights(IPDM 83) as shown in the diagram ? could you please confirm the cut on the fog wire in IPDM.

thanks very much

The wire coming from the IPDM labeled fog 86 needs to be cut. The IPDM side of that wire is not used, the fog light side of that wire connects to pin 30 of the relay.

The headlamp low 83 wire is not needed. The head lights can not be on without the parking lights, so the parking lights alone will monitor all conditions.

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Kevin Pierson

Fog pin 86 either connected as shown or capped off.

Hey Kevin

Need your help again. I have an issue right now, my fog fuses keep blowing up with or without any sort of relay.

As I mentioned before the bcm/ecm were replaced recently, I didn't have this issue before that. And the fogs were working fine when I picked it up from the dealership after the work was done. The fogs (or DRL) stopped working few days after I got it from the dealership.
i figured it must be fuse, but whenever I change the fuse in IPDM it blows up right away and that was with the relay. So I took the relay out and connect fog wiring in IPDM as from the factory, still same issue.

BTW, I do have some aftermarket lights connected to the fogs connection. But this has been the setup for more than a year.

Any suggestions. thanks

The very first thing I would do is remove the aftermarket lights from the circuit and see if anything changes. The lights, themselves, may be OK on the circuit, but that would be the most likely place for a short / damaged wire.

When you put the relay in the circuit the relay bypasses the OEM fuse and provides power directly from the battery.

If the fuse is blowing as soon as you put it in it, with all lights turned off, it would indicate a short to ground between the output side of the fuse (which should be in the IPDM) and the input side of the fog light relay (which should also be in the IPDM). You can check this by measuring resistance to ground between the output side of the fuse and ground.

I would also check the integrity of the OEM foglight relay - make sure that internal contacts are not shorted. If they are, that opens the door to much more wiring that could be damaged. If the aftermarket wiring for the added lights rubbed through and shorted to ground and then the OEM fog lights were turned on it is very possible that the internal contacts of the relay arced and stuck.

So, to sum it up:
1. Check output of fuse to ground to verify short (should be <1ohm)
2. Remove all aftermarket wiring connections to OEM fog lights
3. Check output of fuse to ground to see if short still exists (factory fog lights should read around 8-50 ohms I would guess).

If this fixes the problem you can then put a fuse back in and see if the fog lights stay on all the time (indicating a stuck internal contact on the fog light relay).

If this doesn't fix the problem then the next thing to investigate would be the IPDM....

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Kevin Pierson

Thanks Kevin.
Fog fuse blows up only when the fogs are switched on, i.e. when switched on as DRL using a relay, or when switched on just with Fog switch with no relay in connection.
Other lights function fine, Auto, headlights, parking even when fog fuse is blown.


"When you put the relay in the circuit the relay bypasses the OEM fuse and provides power directly from the battery. "


With regards to the above statement, in my initial setup I was supplying power to the relay using a 12v 'wiper motor' power supply from IPDM and this worked fine but this blew the wiper motor fuse as well after the fog lights fuse was gone.
I changed the setup to powering it from the battery using a 15A fuse, and when I made the connection this blew the 15A fuse. !!!

If the fuse only blows when you apply power to the circuit then the fault will have to lie in either the wiring between the IPDM and the lights or in a bulb itself. Sometimes when bulbs fail they short out. Throw your ohm meter on a fog light wire and see if you can determine where the short is (I would recommend starting with the bulbs then work backward through the wiring. As I told you already the OEM foglight relay has two outputs, although internally they are connected. It would be beneficial for troubleshooting to cut one of the fog light wires so you have two independent circuits - you can then ohm out both circuits and compare the results to each other.

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Kevin Pierson

thanks Kevin.

I had to replace one of the fog bulbs twice before. Maybe there's a different related problem to this. But if it is a fog bulb and is dead, why would this cause a short??

Can you please elaborate on the OEM foglight relay, where should I look for?

Bulbs typically fail in the "open" position but I have seen them fail in the "closed" position. When the element blows it is possible that either end of the elements could end up touching. When you apply electricity to the bulb it will arc and weld itself together, thus causing a permanent short.

The OEM foglight relay is in the IPDM. It sounds like the relay is working properly to me and that the problem is after the relay.

I would check for corrosion and a loose fit in the socket that you have replaced multiple bulbs in - if there is a poor contact with the bulb it can cause bulb issues.

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Kevin Pierson

Will keep you posted.

thanks very much, mucho appreciato.

Hey Kevin

So got my lights working again and without blowing a fuse. It was a blown fog light, I didn't have to open each one of them but took a look at them from the front of the headlight where its visible. Noticed that one of the lights looked burnt a bit, so got a replacement and it worked.

so that worked out fine as I tested with just factory fog connections. Relay connections are not, btw I haven't got the relay from parking brake yet.
pin 30 to fogs
pin 87 to fogs from IPDM
pin 85 to headlight Lo
pin 86 to ground
pin 87a to IGN source.

for some reason fogs come on all the time, and even if reverse 87 to 87a. If I take out the ground while they're on, the fogs turn off.

Have you verified that the relay is working properly? 87A should be to fogs from IPDM and pin 87 should be IGN source although that shouldn't make much of a difference with the problem you are having.

When you say the fogs are on ALL the time, do you mean even with the ignition off?

Have you verified that you can hear the relay "click" when you toggle the headlights on and off?

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Kevin Pierson

I tried two relays of same brand and same result. Right now my IGN source is from the car battery, fused at 15A. Later on I'll use the Wiper motor pin that outputs battery voltage on IGN from IPDM.

With IGN ON, the fogs are on all the time with the setup mentioned above. They only turn off if I remove the ground, so I guess this does show that the coil in the relay gets powered when running the Headlight Lo thru Pin 85.

And there is a click with headlights ON and OFF. I must be doing something wrong.

I'll try one thing at a time once I get home this evening.

If your "IGN" source is from the battery then it is NOT an "IGN" source it is a "battery" source. "IGN" implies only powered when the ignition is on.

With battery voltage applied to 87A your fog lights will ALWAYS be on, even with the car off. When you turn the head lights on the fogs would stay on IF you had the fog light switch in the "ON" position.



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Kevin Pierson

True that the fog lights will be always ON with battery source, except when Headlights are ON but Fogs are OFF, but they're ON.

I ruled out fog functionality from IPDM because they work with factory connections,

I ruled out relay because coil switching works. I'll check my connections for the fogs coming from the IPDM.

Hey Kevin

So I got everything working, it was probably loose connection somewhere with the relay.
pin 30 to fogs
pin 87 to fogs from IPDM
pin 85 to headlight Lo
pin 86 to ground
pin 87a to IGN source
as before
fogs are ON when IGN is ON
fogs remain ON when headlights are ON
fogs are OFF when parking are ON

fog switch has no function. Apparently this is the way it works as per this post https://myg37.com/forums/audio-video-and-electronics/188175-how-to-hook-up-daytime-running-lights.html
look at 'Mid-life crisis' last post on that page.

When I tested the light functions with US car factory setup, fogs retain the factory functionality i.e. ON/OFF with Headlight but I had left and right connected separately. I'm thinking something to do with the matrix logic, if left and right fogs are connected together they might lose that function !!
Not sure why the fogs remain ON .


Btw, what is the best source for IGN, right now I'm using wiper motor (pin 88) of IPDM and it was suggested somewhere not to use switched source of IPDM.