I bought my Daughters 2015 Fit EX a few months ago and have been looking for the solution to the check charge system warning along with the VSA, TPMS, EPS Lights. She drove the car like this for 6 years and had several shops take a look without solving the issue for long. So I started by replacing the alternator with a unit from Rockauto for $200.00. Car ran for about 2 days before the check charge started again. Scanning the system showed several codes, but specifically the P16E2 shows PGM-FI-ACC LIN Communication Error. In looking at the wiring diagram, it shows a simple wiring with only a wire from the battery sensor connected to the alternator and the PCM. I check the resistances of these wire with a volt/ohm meter and the alternator/PCM and the battery sensor/PCM where 0.1 ohm or less. The alternator to battery wire measured the same. But I had read that several people had the problem solved by replacing the wiring harness. So, I thought the only wiring that could be an issue would be the battery to the alternator wire that could be faulty under load and cause too much voltage drop which would cause the PCM to think the alternator was not responding to the voltage changes requested. So I wired an 8 gauge wiring in parallel from the alternator to the battery connection. Since this the car has ran for the last could of weeks without any issues. I use a plug in USB with voltage readout in the plug on the dash to see what the voltage is from the alternator and have seen an increase of .1 to .3 volts since the wiring change.

Looks like a possible and inexpensive solution without having to replace the engine wiring harness.

 

Did you get a new battery? 2015 Fits should be due or close to getting a new battery right about this time.

 

Battery a year old, had it checked and it's OK.

 

I would go to your local Honda Dealer to fix your charging system problem.

I know it's more expensive. But they have the know how to get it fixed

 

That takes all the fun out of it. I've built numerous cars, 510 Datsun with Haltech ECU connected to a VG30 Turbo making 350 Wheel HP, a 67 C10 Chevy Truck and many others. Most older vehicles I have completely re-wired the vehicles to run larger alternators for electric fans, fuel pumps and the like.

Plus, I hate talking to service advisers. They are least knowledgeable car people I know. I'd rather find an independent expert on Honda's that I can talk to directly.

In any event, the issue is fixed and the car is running better than ever. I just wanted to share with others who might want to fix it themselves.

 

i think there is a "load sensor" literally on the battery that reduces alt output if no load....you have bypassed that,,,,so maybe that's faulty ...i think it did have some...... "issues"....this is good info....usually those codes are a injector problem...or possible carbon buildup ? good to know we have a knowledge detective on the case! please keep us updated!. you may be onto something,

 

If you looked at the wiring diagram posted, you will note that the battery sensor is located on the negative terminal of the battery. This device measure the current going to the body ground and outputs a voltage signal to the PCM and the alternator. This was done by Honda to save fuel by reducing the load on the engine when no additional current is needed. I did nothing to this circuit, it is intact and functioning. The cause of the Check Charge Error is when the ECU detects that the alternator is not responding correctly to the requested changes due to the current load on the system. I suspect that the wiring connection between the alternator and the battery positive connections (where I placed the wiring in parallel to the stock wiring) is either undersized or has a fault causing a voltage drop when the load increases. My daughter drove the car for about 2 years before this was an issue and started after the first battery failure. When the PCM detects the unexpected voltage drop it trighgers the check charge system error. By adding the additional current carrying capacity to the circuit, the voltage drop no longer occurs so the system is happy.

If you note the error code that is triggered, P16E2, PGM-FI-ACC LIN Communication Error, it looks like the PCM is signaling that the alternator is not responding to the requested change from the Battery Sensor. The battery sensor appears to be the active device in this system and the PCM is only monitoring the signal from the sensor and the voltage in the system. This is an analog signal only, it is not on the CAN Bus. Since others on the board have had the issue fixed by replacing the wiring harness I reasoned that it must be a wiring fault and installed the additional wire to carry more current to reduce any possible voltage drop. The only thing the PCM sees is the voltage coming from the battery sensor (low voltage signal) and the voltage on the bus. This is why a weak battery, faulty alternator, bad battery sensor will trip the code. As to why bad fuel injector caused the code I can only assume that the early injectors demanded more voltage than was available causing enough voltage drop in entire system to trigger the check charge code in the PCM. Anything in the system that causes the voltage to drop below the expected levels should trigger the check charge code on the system.

There is no downside to a parallel wiring since the fusing on the positive battery terminal are still in place and will work as intended. You have a better connection between the alternator and the battery so the battery should last longer and work better.

 

huh....sounds logical.....out of interest,do you think it would be easy to ELIMINATE the load sensor ?...like easy ?? one less device to go wrong?...or is it a can of worms.
geez...i dont understand that wiring diagram at all....the alt has only 2 wires coming out it ? ...usallly its a 3or 4 wire plug isnt it?...plus the giant + wire

 

I don’t think the sensor can be eliminated since the PCM is expecting a voltage signal from the sensor based on the current load.

 

tell it battery voltage.............

 

No need now, everything is working well after 2 weeks.

 

Hey, I am having the exact same issue with the exact same vehicle. I was wondering how exactly you wired it. Did you simply place another wire connection between battery and alternator while leaving the faulty wire intact? I would like to try this method.

 

Yes, I wired in parallel to the existing harness connection. I used a teflon coated 8 gauge mill spec wire. Don't use a cheap wire or speaker amp wire for this since it is under the hood and subjected to high heat. Use the terminal shown with the red heat shrink wire.

Alternator to Battery Wire

 

dumb ass question the other end goes to the big giant terminal on the alternator.
Thanks for the pic, really helps!!

 

That is correct. The Alternator has only one screw terminal. It''s hard to get to this terminal without moving the alternator.