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Low voltage Keyless Entry Receiver

  #1  
Old 12-17-2018, 10:25 PM
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Low voltage Keyless Entry Receiver

My remote for keyless entry is not working. I tried to program it and when i press the unlock or lock key it does not sense it. I checked the connector to the keyless entry receiver and it was only getting 1.4 volts instead of 4.5 volts. I then checked the pwr terminal 55 on the bcm connector and its supposed to always have voltage and should be the batteries voltage. I checked the voltage and it was only 1.4 volts. It was a red wire and was on the very end of the BCM connector. Its weird i was looking at the service manual and it says that the terminal 55 power wire is supposed to be R/W which im guessing is red and white or does that mean read or white? The only colors on the ends that had a voltage reading were red and there was one on the opposite side that was yellow and it was getting 9 volts but i dont think its the yellow one because the manual says r/w and the red makes sense cause its 1.4 like the keyless entry receiver. Can anyone help with this, if its only getting 1.4 volts at the connector the only place it goes to is another connector then the 50 amp fuse. could there be a part of the wire that is touching a ground somewhere so its taking all the voltage or what could be making it lose 10 or so volts. I noticed that whoever had the car before did something some work to the electrical because all the wires are bundled with electrical tape so maybe the wire is touching or has a slit in it? Just wanted some advice before I try to follow possibly the wrong wire cause its red and im not sure what r/w is. The 50 amp fuse looks fine and im assuming if that was out then the windows and locks wouldnt work either but they work fine. I think the keyless entry receiver which is located on the passenger side is not getting enough volts to receive a signal. Any advice would be greatly appreciated.
 
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Old 12-21-2018, 11:56 AM
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So i tested the pin out to the keyless entry receiver and it is reading 1.5 volts and it should be 4.5. I also tested both pwr supplys to the bcm that have to do with the keyless entry and both are 10.5 volts and the battery is 12.6 volts and the service manual says the two power supplies should be the battery's voltage. So its narrowed down to either the bcm is doing it or the combination of bother power supply voltage drops. If its the pwr supply then the receiver pin out must use power from both pwr supplies cause theres a 4 volt drop from batter to bcm m1 connector and the pin outs supposed to be 4.5 and is only 1.5 so thats 3 volts. Wouldnt be just one pwr supply cause thats only 2 volts and thats not enough to get from 4.5 to 1.5. If its not that then its the bcm itself. I looked at the circuit board and noticed there was some yellow stuff on some of the contacts and on a (i think it was a resistor) and the yellow stuff looked like it was corroding the the contacts so maybe thats the problem? Does anyone know anything about the circuit board or where i can find schematics of it and if u think its the dropped pwr supply voltages or the bcm itself. Thank you for your help and I hope there is someone who has experience with the wiring of this car.
 
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Old 12-22-2018, 08:57 PM
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So my multimeter was faulty, i was using an old one and it wasnt working right. I checked the continuity of the body control module connector to the keyless entry receiver and had continuity on the power supply and 2 signal wires. I checked the body control terminal 55 and 42 for power and was getting 12v so that was good. I then checked the output pin for the body control module and it was 1.5v. So the answer is the voltage drop is in the body control module because the pin should be sending 4.5v to the receiver and with only 1.5v thats why my keyless entry doesnt work. Figured i would just say what i did in case someone elses keyless entry stops working. Ill replace the bcm and let you guys know if that fixed it.
 
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Old 12-23-2018, 11:55 AM
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What year, sedan or coupe?
 
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Old 12-23-2018, 11:56 AM
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Also, are you talking about the Intelligent Key system or the normal fob?
 
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Old 12-23-2018, 12:12 PM
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Pins 18, 19, 20 on the BCM are the ones that specifically need to be checked. You should have continuity to ground on pin 18 (black), 5 volts on pin 19 (yellow) if so then the problem is likely the key fob itself isn't recognized by the BCM.

You need an oscilloscope or Consult-II to read pin 20 since it's just a change in power frequency as a signal back to the BCM.




 
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Old 12-24-2018, 01:02 AM
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Its a 2006 g35 coupe and i checked the yellow and its only getting 1.5volts and the two power supply terminals or pins which are 55 and 42 from the battery to the bcm are both getting 12v so the bcm is losing 3 volts cause i checked the pin on the bcm that the yellow connects to and the output is 1.5 instead of 4.5 so the receiver is not getting enough volts for it to recognise the remote. Dont you think
 
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Old 12-24-2018, 01:07 PM
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Yep that's what it sounds like. One final thing to verify is that your DMM is set to test DC voltage, if it's set to AC voltage it doesn't accurately measure. Unfortunately it's looking like you're in the market for a new BCM and either a trip to the dealership for reprogramming or you can use an online BCM decoder and the NDS2 software to do it yourself.
 
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Old 12-24-2018, 06:33 PM
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Great i didnt know you had to reprogram it. How do i do it online?
 
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Old 12-25-2018, 01:05 PM
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Check out a BCM decoder, you will need the pin number for it and I think there's still a free one on the internet.

Next check out Nissan Datascan II. You'll need the software and an OBD2 interface cable for a laptop, that will allow you to match the ECM and new BCM together as well as program your keys to the new BCM.

Alternatively you can tow the vehicle to Nissan and pay them for the service, since a BCM swap is so quick and easy it might be better to just drive there and swap it in the parking lot, be sure to talk to the service manager about this all ahead of time because they might just have one of their techs swap it for no cost if you remove the panels and unbolt it, that way they can do the programming in a service bay.
 
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Old 12-26-2018, 08:28 AM
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Boy, i was thinking it was a quick swap. Yeah ill probably just take it to the dealership and have them program it. Hopefully they wont charge much. Thankyou for your help
 
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Old 01-24-2019, 08:51 PM
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So i put in a used bcm i bought from ebay and i wanted to test to see if the keyless entry receiver was getting the right amount of voltage with this bcm and its getting the same as the one i replaced. It is also 1.5v instead of 4.5v like the manual says. Im really confused, could i have gotten another bcm that isnt putting out the right voltage to the receiver? Could it be a programming issue and drivers that control how much voltage goes to the receiver and if not programmed right that it will give less voltage to keep the keyless from working, like in case you lost your keyless. I thought it would just be a signal not lowering the voltage. Could be just my luck though and the used one i bought also is bad when it comes to the keyless entry. I cant think of any other reason why both would be only giving the receiver 1.5 instead of 4.5.
 
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Old 01-28-2019, 12:18 PM
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Darn i was hoping someone would have some idea of whats going on with the bcm to have both show 1.5v when it should be 4.5v. I really dont want to have to take it to the dealership. Just makes no sense to me.
 
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