2017 Infiniti no crank mystery

Ryan Owner/Technician New Jersey Posted   Latest  
Case Study
Driveability
Electrical
2017 Infiniti Q50 2.0L (C) 7-spd (RE7R01A) — JN1CV7AR7HM681138
U0104 — Lost Communication With Cruise Control Module
U0103 — Lost Communication With Gear Shift Control Module "A"
U0164 — Lost Communication With HVAC Control Module
U0212 — Lost Communication With Steering Column Control Module
U0101 — Lost Communication with TCM
Crank / No Start

Good evening all

this vehicle came from a local body shop who replaced the front Bumper For minor cosmetic reasons. After the repair the vehicle did not start and chassis malfunction and key malfunction lights came on dashboard. all Lights on dash board turn on however no start. The vehicle did recognize the brake pedal was depressed to start.

Found several communication Codes in ecm however could not communicate with multiple other modules including abs and transmission. Easiest place to tap in was abs module. I back probed the communication lines at the module to find a fantastic waveform. Checked for power and found ignition power to module was at 2.2v. Consult with wiring diagram to find module is fed from fuse block in trunk. upon checking fuses in trunk all fuses found to have 2.2 volts. Power feed to relay in rear fuse block to power fuse block at 2.2 volts. Following the wiring diagram brought me to some fusible links at the battery. All checked good. Decided to trace wires from battery To rear block. Wire had 12 volts right before fuse block where I could access. Pulled some more panels off to find that harness actually continued down to a auxiliary battery that is faulty and holding 2.2 volts. Apparently feeding this fuse block. Unfortunately for me Mitchell diagrams did not show this . So after much wasted time and a new aux battery in trunk the vehicle is repaired .

Hope this helps someone!

good night all 

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Helpful
Thanks
Missing Info
Tommy Technician
Georgia
Tommy Default
 

Was there no codes or messages for the auxiliary battery being low.

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Ryan Owner/Technician
New Jersey
Ryan Default
 

i don’t know if there was any messages when the car was running because when it got to me the car would not start. However there were absolutely no low voltage codes or battery related codes in the modules. Only had communication codes.

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Stephen Educator
Ohio
Stephen Default
 

Here's where multiple sources of service information can come in handy. There is a chance something could be left out of one source and found in another. That having been said,we should always check the basics out first before doing further diagnosis. You would be surprised how many time the root cause of a problem is found here. Don't feel bad I have done the same thing. At the end of the day…

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Agree
Geoff Diagnostician
Hawaii
Geoff Default
 

An extra battery, interesting! I was curious what it looked like, and when I put the MMY into NAPA ProLink I got no batteries for it at all.

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Ryan Owner/Technician
New Jersey
Ryan Default
 

I will take a picture of the battery and it’s location tomorrow and post up for you.

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Geoff Diagnostician
Hawaii
Geoff Default
 

Cool! thanks bro. p.s. I was born in Morristown, GO YANKEES

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Michael Mobile Technician
Utah
Michael Default
 

Hopefully this saves us all the hassle for when we see this. Maybe you should send a bill to Mitchell.

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Funny
Geoff Diagnostician
Hawaii
Geoff Default
 

The only thing I (almost) trust those made-up color diagrams for is the location hints. Any diagram that omits all the inline connectors as policy really shouldn't be considered "professional level".

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Justin Mobile Technician
Utah
Justin Default
 

Did you check any other service information providers. I’m sure you could find it in factory info but I would be more interested in knowing if any of the other aftermarket providers had it in their information. My bet would be no.

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Ryan Owner/Technician
New Jersey
Ryan Default
 

I only use Mitchell. so I cant answer that but I would be curious as well.

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Mohammad Owner/Technician
Illinois
Mohammad Default
 

Motologic clearly shows a Main and a Sub battery.

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Helpful
Ryan Owner/Technician
New Jersey
Ryan Default
 

Interesting. However still does not show that battery feeding the rear fuse block on the blue wire.

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Mohammad Owner/Technician
Illinois
Mohammad Default
 

I only showed a partial part of the schematic. If you go further in the schematic it would show it. Maybe Mitchell needs to be informed! Happy New Year

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Ryan Owner/Technician
New Jersey
Ryan Default
 

it actually does show that sub battery. my mistake. I must have got frazzled during diagnosing it. again as I had no indication of a low battery. also had issues locating that "fuse block" as I could not find a component location on that. its very interesting to me that they would run those modules off of the fuse block powered solely from the sub battery.

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