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· Registered
2005 FX45 120K miles
190 Posts
Discussion Starter · #1 · (Edited)
As the FX35/FX45 fleet ages, more and more people (like me) are reporting engine no-start symptoms, which come-and-go, until one day you need to call a tow truck.

I have experienced this problem first hand, and I have found that cleaning my fuses (in the block next to the emergency brake pedal) fixed this problem. (Just saying it’s sometimes the easy things you should do as part of your preventative maintenance plan.)

In my case, I have not had any no-start problems for the last 9 months, which was starting to occur often. And BTW, sometimes just cycling the key on-off-on did start the engine.

(Never mind that the Infiniti dealer tried to clip me for a new starter, but that obviously was not the problem so I’m glad I did my research first.)

Just today, I took a look at several circuit diagrams I found after visiting this website, which I highly recommend everyone put in their library:

And, I have posted many times on this subject, with the hope these posts will help people avoid costly repairs and tow bills. For example: "I strongly suggesting that everyone carry a Lithium Jump Pack so you can jump start your battery to prevent very a tow.

NOW... I want to know why using a Jump Pack on a perfectly good battery will seemingly will reset the BCM/ECM so you can start the car normally.

My efforts to understand this subject keeps showing that this "pesky" AC-Amplifier (AKA HVAC Air Conditioning Amplifier) is involved, because it interacts with the ECM and CAN bus.

Questions: How does this AC-Amp really function? ...Because the name seems misleading. And when it does malfunction it seems to be linked to both engine no-starts and even speed sensor problems (DTC-P0500).

Further, I have noticed a number of owners who live in cold climates fixed their no-start problem by replacing the AC-Amplifier, but I'm thinking that it would easier and cheaper to do a board level inspection to look for a cold/crack solder joint that can be easily reflowed -- assuming you can open this AC-Amplifier up?

Note: I have never removed the AC-Amplifier (located under the radio), because I found my intermittent no-start problem was solved by just cleaning my fuses as mentioned above. However, I still would like to know if anyone has removed and opened up their AC-Amp and repair it. If so, please share this effort with everyone.

I also need help understanding the following circuit diagrams -- and how the AC-Amp functions with the ECM and CAN Bus?

Replacing the AC-Amp in your car may prove difficult since there are different AC-Amp part numbers based on how your car came equipped from the factory. ...And who wants to get one from a junk yard if you can fix your own?

Rectangle Slope Line Font Schematic

* Can I assume the Unified Meter is inside the AC-Amplifier; and they share the same connector?
  • What functions represent the M45, M85, and M35 connector as shown above?
  • What is a Combination Meter? Is that your instrument cluster?

Is the Can-H and CAN-L talk to the security system and/or Infiniti Vehicle Immobilization System (IVIS)?
Rectangle Slope Parallel Font Schematic


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