Hey guys, about to do a smog check soon. No engine light just wanted to do checkup scan myself and got these 2 codes.
U1281 : Loss of communication with MICU. I had U1281 for a while. Last scan was in March 2024. I'm wondering if it started after I installed the new 51R battery. But I can't remember if I did the scan before or after the change ...
According to the Blue Driver app this code very common on this car?

P154A : Battery sensor internal failure. This code got me a bit worried. A bad battery sensor sounds like it's could lead to other electrical problems. And the app says the code is rare.

Anyone else have experience dealing with these 2 codes? Not sure if this is related. But is the negative terminal of my 51R too close to the cooling fins? Should I readjust it?
Any advice would be appreciated. Thanks







Bluedriver OBD2 scan

 

Wiper all that goop off the negative terminal, make sure the wiring and pins in the battery management sensor are ok, and make sure that the negative terminal is FULLY seated as far down as it can go on the terminal.

If all is good and the DTC returns, check for battery voltage at the battery sensor's connector on pin 1 with the red wire. If power is present and is similar to the battery's source voltage, you need a battery sensor.

If no power, go to your under hood fuse box and check the 15 amp fuse in slot B15 first. If good, check the 70 amp fuse in slot A2. Those are the only two fuses that protect the circuit and sending to the battery sensor.

If you're finding some oddball voltage number or you're finding that the code intermittent comes back then you may have a wiring ordeal going on. As a note, it is not uncommon to see internal breaks in the wiring with a voltmeter thanks to the wiring insulation HIDING the breaks internally. So using a small pin to backprobe the connection or even a pin fit tool (to ensure a proper connection) would be wise.

 

Thanks for the advice. I guess in short. Step 1 clean the terminals, check the wiring, retighten the bolts.
If code still occurs. Step 2 whip out the multimeter and start checking connections and fuses around the battery sensor.

Is the U1281 MICU code also related to the battery sensor error?

 

Not necessarily.

The U1281 is a tricky code to troubleshoot if it returns as it correlates with multiple control units. Those units include but may not be limited to the Gauge Control, Module, Immobilizer, Keyless Access Control Unit, and Automatic Lighting Control Unit. It can also set false codes, not want to clear if a control unit has a fault, and/or stop other units from communicating with others.

 

I'm pretty sure I had U1281 for a while. The only electrical work I've done was hot-swapping the original battery to the 51R. Successfully kept all the radio and Bluetooth settings. Now I'm just hoping I didn't mess something up. Thank you so much Hootie!

 

for the battery sensor, since you already changed the battery, and wire is really rare unless you snap it in the batterie change. i would change the batterie sensor. you can follow this dtc troubleshooting too if u have any kind of knowledge and multimeter




then for U1280 its way more tricky, if u have a scan tool you can maybe figure out what module is having this trouble. but first, clear the code : well use the next photo and if code dont come back, the system is ok at this time and its will be hard to diagnose.





i know its 1281 , gauge. but when u have confirmed u have this problem all the time you need to run diag on 1280. my question is, do you have the flikering problem on the right side of dash (like Fuel guage and stuff ) if so, maybe its your problem.

 

I've seen the wonky alien text in the fuel gauge before. The car was parked in snow during a ski trip. That was the only time I had to jump start my Fit. I remember reading about other people having this issue during colder weather. So I neglected the problem and it rarely appears. This happened before getting the larger battery. I know about the soldering fix. But just too worried I might break something in the process.

I rarely drive the Fit. I try to drive it once a week on the highway. I honestly haven't experience any issues. Starts smooth, never used econ mode. Passing traffic hitting 80 mph with ease. Average around 35 MPG. No engine light. Other people I asked said a bad battery sensor should trigger a check engine light.

I haven't used the multimeter yet. Since the car already passed the SMOG check, I plan on waiting for better weather before testing. Thanks @Lucky_luke for the detailed trouble shooting sheet. I'll be sure to follow it step by step. Changing the battery sensor seems to be easy. Just not sure it really has an issue.