Morning, does anyone know where the daytime running light relay is hiding away on a 2015 Nismo RS? Trying to find out why they're not working. Fuses are good, light units are both good, etc. Trying to prove as much as I can before I start to suspect the driver units behind the bumper.

It's internal to the IPDM and not replaceable separately, see EXL-34 here...
https://www.nicoclub.com/service-manual ... %2Fexl.pdf
....and PG-80 here:
https://www.nicoclub.com/service-manual ... 5%2Fpg.pdf

You can see in the wiring diagram that the fuse (#50) is downstream from the relay, so if the fuse has power with the DRL's on, it means the relay is good. If it doesn't have power then the relay is shot and you need to replace the IPDM. Don't be confused by the wiring diagram, the Nismo trades fogs for DRL's and the car has one or the other, not both. So only the paths marked <ND> exist on your Nismo, the paths marked <FG> don't.

I looked at the IPDM already, but couldn't find a relay associated with the DRL's so assumed it might be inside. I didn't realise the fuse comes AFTER the relay though, as I haven't studied the workshop manuals yet. Got them all downloaded ready for me to investigate further tomorrow, so I'll check for voltage while the Mrs holds the car on the brake with the handbrake off, since apparently the DRL's only come on when the handbrake is off?

Our current IPDM is labelled as S1, so I assume if there's no power I'd need to find another S1 version so it's coded correctly for the car? So not like other modern cars where you could just code it yourself. Speaking of coding, is it possible that the DRL's could be deactivated in the BCM? Or are they not able to be coded either?

StuartTheFish wrote: ↑

Sat Dec 10, 2022 3:00 pm

Our current IPDM is labelled as S1, so I assume if there's no power I'd need to find another S1 version so it's coded correctly for the car? So not like other modern cars where you could just code it yourself. Speaking of coding, is it possible that the DRL's could be deactivated in the BCM? Or are they not able to be coded either?

The outside markings can't be trusted except for the Nissan part number, which will be 284B7-something. I don't actually think you'll have an easy time finding one for a Nismo (they are different, plus there are three different Nismo variations). The IPDM and BCM are the two control units on the vehicle which are strictly not reprogrammable, due to security concerns.

That all said, if the DRL Relay is the only thing not working, it's pretty easy to rig a pair of parts store relays and two diodes to run them instead if the IPDM. The fuel pump fuse gets juice only when the engine is running, so one relay triggered off the pump and another "cut relay" diode-wired to both the low and high beams will give you DRL's only when running with the headlights off.

Just checked the fusebox while the Mrs sat in the car with the handbrake off, 14v passing through the 10a DRL fuse in the engine bay fusebox. So now to figure out what else could be causing neither of them to work. Unless both driver units are faulty, which would be fantastic considering Nissan would want £400+ for each side.

To rule out a bad IPDM circuit board, you should put a test lamp or voltmeter on pins 19 White and 20 Green of the IPDM connector (E12). If those have voltage then the IPDM is exonerated and the issue has to be in the lamps or wiring. To find out which, put a bulb-type test lamp across the connectors at the lamps. If those give you a bright light then both power and ground wiring are exonerated, meaning the DRL's are bad. If you get no light or a dim light then there's a problem in the wiring, so put the test lamp probe on the power sides of the DRL connectors (Red on the righthand, Green on the left) and the gator to a good chassis ground. If the light is bright then the problem is in the ground wiring, if it's still dim or out then it's in the power wiring. Don't make assumptions, I once saw an Altima with both front blinkers and both fog lamps out which turned out to be extensive rodent damage to the Front End Module Harness. Ya never know.

The DRL's themselves are brand new, since when we first bought the car the lenses were letting water into them, so hoped the new ones would just work. Got a brand new pair of them, but neither of them light up. Think I need to take the bumper off sometime to have a proper look.

Make sure the polarity on the new lamps matches the car. We've occasionally seen incorrect polarities even on genuine OE parts. Hook battery power direct to the lamp pins to see which is positive and which is negative. Then see if the +/- orientation matches the +/- coming out of the hookups on the car. If they're backward, simply un-pin the connectors and swap the pins. If you don't know how to un-pin, it's easy, you just need a sharp pick. See this post for how it works generically. Your connectors will be slightly different but the principle is identical:
led-headlight-delete-for-gen2-rogues-t628641.html

Yep, one of them came with the wrong plug on it so I've already swapped the plug over. The wire colours were in the same positions, just the rib was on the wrong side of the plug.

Just had a little bit of time to get the bumper off today to have a closer look. Doesn't appear to be any wiring damage whatsoever, but we're not getting 12v down the green wires to either DRL driver units. The earth to them is fine when testing from the black wire to a chassis earth, there's power going to and through the fuse in the engine bay fusebox, but nothing getting down to the DRL's. It's as if they've been turned off somehow. Any other ideas? Or do I have to see if I can borrow a spare IPDM?

I wonder if it's just got the wrong IPDM? If it has a non Nismo version, I wonder if it's just acting like I'm not turning the front foglights on since we obviously don't have the required switch on the stalk? I wonder if the wiring for the extra switch is still in the loom from the stalk to the IPDM?

If there's juice at pins 19~20 then the IPDM is doing its job and your problem is in the wiring.

If there's no power and somebody already messed with the IPDM, then yah, your problem could be a matter of unscrewing whatever they screwed up. IPDM's are strictly non-reprogrammable, so a dealer code scan can tell you whether the IPDM is the right or wrong part. Consult3+ uploads the firmware part number and prints it out along with the codes. Request a copy of the code sheet, then a trip to the Parts Dept can tell you if that part number matches your VIN.

Can't say I've tried checking for voltage at pins 19 and 20 yet, as I don't have enough slack on the wires to get the IPDM upside down. Unless I unwrap some of the loom to get into the wiring further up.

Nice to hear consult will be able to bring up part numbers though, I'm taking it to the local dealership anyway on Wednesday to get the free firmware update for the head unit, so could maybe ask them to check for any BCM or IPDM errors or mismatches.

Unless there's a way I can do more than just read engine error codes for myself, like me using datascan or conzult on my Z32.

The radio repros don't use the Consult, so they're only going to do a code read if you ask for it and they won't check if it's the right part number unless you ask for it.

The easy way to get a test light on the IPDM connectors is to pop the connector, back-probe it with an ordinary safety pin, then plug it back in and apply the test lamp. Until you check that, you're just flailing in the dark.