Hi guys,
I have a 2016 MX-5 1.5 SE-L Nav. The nearside front and side indicators are not functioning.
They don’t work with the hazards or indicator stalks. The rear indicator works but sometimes the bulb stays partially illuminated when the indicators/hazards aren’t on. All offside indicators work as they should. The left headheadlight also works fine, other than the indicator.
I’ve replaced both bulbs, checked the wiring for damage and the connectors for corrosion (all appears to be fine). All the fuses are okay as well.
I’ve come to the conclusion that the bcm is probably the issue. Unfortunately on a right hand drive car you have to remove the entire dash to access it which I have done. I purchased a used bcm from a car of the same year and spec. When fitted the car does not start, all the warning lights show up on the dash and none of the lights work other than the nearside rear indicator staying constantly illuminated.
I’ve been trying to find a company who can do bcm cloning but I’ve had no luck so far. I was wondering if anyone knows of company that can do it?
Also, does anyone have any suggestions as to what it could be other than the bcm as I’m still not convinced this is the problem.
The left front indicator and side indicator share a ground in the left front bumper chamber, see the red dot on the diagram below, other systems share that ground point too, but have you checked it? Was anything done to the car prior to the fault happening or did it just happen?
One thing to be mindful of when replacing the BCM, there are 2 plugs that are interchangeable near the BCM one for the BCM the other is a wiring harness plug, you haven’t got those mixed up have you?
To be honest though, I think that you’re entering a world of pain by putting a second hand BCM on. I know that it’s easier said than done but I’d put the original BCM back on and try and do some proper diagnosis for the cause of the concern.
@Roadster_Robbie suggestion of the front earth point is 99% going to be the problem. The clue is in the rear indicator glowing. Current flow from whatever other circuits use the earth point is feeding back through the front indicator earth wire.
The issue was indeed caused by a faulty ground. Thank you very much for pointing me in that direction @Roadster_Robbie . The connectors were quite corroded so we sanded them down and dipped them in vinegar overnight. After putting it back together the indicators all work as they should. I have also put the original bcm back in the car.
Unfortunately I think installing the non original bcm in the car has caused an electrical problem. Pressing the engine start/stop button doesn’t work unless you hold it or double press and then every warning light on the cluster illuminates. You then have to press and hold the start/stop button for the car to turn off. Any ideas what might be the problem?
