Hi everyone, I'm from Brazil and I own a 2018 Honda Fit LX CVT. I'm trying to activate cruise control via the ECU. I’ve already installed all the necessary hardware (steering wheel buttons, correct clock spring, etc.), but I believe I still need to enable something through software.

Could anyone help me out? What tools can I use for this? Is HDS the only option, or is there a cheaper alternative that allows ECU function activation?

I have a good understanding of electronics, but I’m a beginner when it comes to this topic.

ECU: 38705-5v5-M630
VIN: 93HGK5840JZ122945

Thanks in advance!

 

Are you trying to install regular cruise control, or adaptive cruise control (much more complex)?

It would not surprise me if firmware changes were needed. Gauge cluster pin 14 (cruise switch input) should show 5V+ (from a pull-up resistor) with the cruise switch disconnected. If so, that at least suggests the pin is electrically configured to have a function, and could be recognized as a cruise switch by the appropriate gauge cluster firmware. Flashing the firmware via the diagnostic connector sounds very Honda-proprietary, so a relatively modern version of HDS is going to be needed there. No idea where to find the firmware.

 

I'm trying to install a conventional cruise control system.
I'll check the voltage at the pin you mentioned. Just one more question: is that pin located on the harness going to the gauge cluster, or on the one coming from the clock spring?

If I'm unable to enable it on my ECU due to firmware limitations, I'm considering getting a used ECU from an EXL model of the same year. I found one for sale with the same MPN, and it was used in an EXL model that comes with factory-installed cruise control.

 

It's a wire between the clock spring (which is just fancy wires, rolled up) and the gauge cluster. On US models, the gauge cluster converts the cruise switch button presses (voltage changes on the wire in question) into CAN messages that the ECU listens for.

The gauge cluster needs the wire from the cruise switch connected to it. The gauge cluster hardware needs the ability to measure the voltage on the cruise switch wire. The gauge cluster firmware needs to include programming that looks at the voltage, decodes it into button presses, and formats that information for transmission on the CAN bus. The ECU firmware needs to include programming that listens for that gauge cluster CAN packet, along with cruise control routine that watches vehicle speed and varies the throttle plate opening accordingly.

I suggest you work through troubleshooting in that order. Yes, the ECU may need a firmware update or replacement, but that may create compatibility problems with other major modules (gauge cluster, body control module, ABS/VSA unit, missing "Honda Sensing" hardware if the EX-L was so equipped). Rather than throwing parts at it, find someone with HDS or put together your own HDS setup, and figure out if there's cruise control firmware that's compatible with your existing hardware.

 

Thank you very much for the tips.
Based on your information, I believe the gauge cluster might be my main issue. It doesn't even have cruise control indicator lights (LX model), so it's probably not receiving or relaying the necessary signals from the clock spring to the ECU.
Therefore, I think replacing the gauge cluster might be the only way for me to enable cruise control.
Can you recommend a budget-friendly scanner compatible with Honda HDS?

Thanks again for all the helpful advice.

 

Looks like it would be center bottom on the panel just under the speedometer. From the 2020 owners manual:


You probably want to stay with the above style of gauge cluster, not the one with the digital tachometer.

Unfortunately, no. I've never had need for the HDS system. As I understand it, HDS is a software package that runs on a Windows laptop, with an adapter to connect the laptop to the car.

 

Yes, HDS is Honda's software used to access all vehicle functions.
However, not all scanners are compatible with it. The ones that are usually aren't sold in Brazil and become impractical due to import taxes.
My gauge cluster isn't the one shown — that's from the EX and EXL versions here in Brazil.
The LX version uses the one shown in the photo below (without cruise control lights):


As you saw, the gauge cluster is responsible for converting the cruize control signals, and it probably isn't doing that. So my problem can be the gauge cluster. Because the ECU, clock spring and steering wheel are the same that exl version (factory-equipped cruise control).

 

They are expensive in the US as well, as I understand it. I doubt it was due to taxes. Find a used unit maybe?

Interesting. We never got that style cluster. The style I posted seems to be standard for all US GKs, unless it has the Honda Sensing package. Then the right panel is a pixel-array color LCD which shows adaptive cruise status among other things, the left panel is a segmented LCD as far as I can tell:

THAT style is sure to give you trouble.

Ah, you checked the part numbers? Good, that narrows down the possible trouble spots greatly. That leaves the gauge cluster and firmware.

 

Yes, I checked all things. The hardware is compatible with exception the gauge cluster.
Yeah, here in Brazil, any technical difference ends up making a big impact on the final price of a car. Because of that, manufacturers tend to simplify everything in the base versions. A basic car here can cost the equivalent of 60 minimum wages.
What we spend on a popular car here, you guys could use to buy a high-end model if we keep the proportions.