Intermittent Operation- UTC

[Greenlight]

I have a M400 with a UTC and have had occasional problems not being able to communicate with the PC. Usually after a couple of tries it works. I'm currently running Windows 7, 32 bit, but have had the same problem running Windows Vista and Windows XP.

This past weekend at a race it connected fine once, but the next time I tried it would not connect. The engine was really rich at some RPMs and I was trying to make adjustments to the ECU file. I spent probably 15 hours this weekend trying to make it communicate with no luck.

I tried changing the USB cable, changing USB ports on the computer, replacing the pins on the CAN wiring harness at the ECU, running wires directly from the UTC pins to the ECU pins, removing and resoldering the wires on the round CAN connector, removing the cover from the UTC and checking the internal 3 wire connector, reloading the software, and finally changing computers.

I tired connecting and disconnecting at least 200 times over the course of 3 days. Each time I returned from a qualifying run I would try again and again and again and again.

After the last elimination run (I lost) I tried connecting and it worked flawlessly. I was able to download the stored data and upload a revised file to the ECU.

Has anyone experienced this type of intermittent operation? I sent my ECU to Motec (USA) a month or so ago and had them check it out. They did not find any problems.

The only thing left is the UTC ??????

Can I connect using the RS232 wires and not use the CAN/UTC or should I purchase a new UTC and pray that it works?

[MattW]

Hi Greenlight,

I noticed you didn't mention the terminating resistors on your CAN bus at all.
Do you have one at either end of your CAN bus?
Do you have any other devices running on CAN, if so, are they working okay?

[Greenlight]

I don't have any other devices running on CAN and I'm not sure about the resistor.

I have the #61022 CAN cable/harness and the #61059 UTC adapter with a USB cable running from the adapter to the PC.

Is the resistor contained in the #61022 cable?

Can I use an ohm meter to confirm the presence of the resistor? Which wire? What is the correct resistance?

[Holmz]

I don't have any other devices running on CAN and I'm not sure about the resistor.

I have the #61022 CAN cable/harness and the #61059 UTC adapter with a USB cable running from the adapter to the PC.

Is the resistor contained in the #61022 cable?

Can I use an ohm meter to confirm the presence of the resistor? Which wire? What is the correct resistance?

Between CAN-Hi and CAN-Lo (usually yellow and green).
50 ohms is good, if it is over a couple of hundred then you do not have resistors.
Are the CAN wires twisted as a pair?

[Greenlight]

I did not see a resistor anywhere in the CAN cable/harness.

I even removed the heat shrink protective cover near the connector.

I will check it with an ohm meter and install the resistor if needed.

The CAN wires are twisted and enclosed in a protective sheathing (this is how it came from Motec).

Thanks for the help.

[CPL Racing]

I am experiencing exactly the same problem, I wired and tuned a car approx 12months ago no problems the same cae then returned for a retune yesterday I connected straight to the ecu and spent several hours tuning I then took break and when I returned ecu connection has been lost and I have yet to find the problem.

I have checked:

Continuity on all wires
The resistor is in place between can hi and lo
Twisted pairs as per wiring diagram
Tried 3 USB cables
Another laptop

Any help would be greatly appreciated

[YuriK]

When you plugh the UTC into your PC ,can you see the USB to CAN devise in Devices and Printers on your computer?

[CPL Racing]

I can.