Member Avatar for grimaccce

hey guys a mate has a laptop with a 25pin to 9pin converter plugged in to it which he plugs a ecu managment for a drag car into the problem is the ecu software doesnt even reconise it being plugged in is their anything i can do make it scan the port its plugged into? like is their any way to find out what a ports number is i can manually enter it... please help

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Dani AI

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Practical checklist for a 25‑pin ↔ 9‑pin adapter that an ECU tool cannot see.

Start by identifying the connectors and signal type. A DB25 plug can be either an RS‑232 serial connector or a parallel (printer) connector — check the laptop port label or the ECU/cable documentation. Confirm the ECU’s interface voltage (RS‑232 +/-12V vs TTL 0‑5V/3.3V); connecting the wrong voltage can damage the ECU.

Locate the COM number in Windows Device Manager (Computer/This PC → Manage → Device Manager → Ports (COM & LPT)). If the adapter is a serial COM device it will appear there (for USB→serial look under USB devices if not). Note the COMx shown and enter that into the ECU software. If the software expects COM1–COM9 and Windows gave COM10+, change the port number in Device Manager → Properties → Port Settings → Advanced → COM Port Number.

Hardware checks and quick tests:

  • Verify cable wiring (null‑modem vs straight‑through). Many ECU tools need the Tx/Rx pair crossed; a null‑modem adapter fixes this.
  • Do a loopback test on the DB9: short TX and RX (DB9 pins 2 and 3) and open a terminal emulator (PuTTY/RealTerm/Tera Term) on the COMx with the expected baud/settings; characters typed should echo.
  • Check flow control: set to None or the hardware flow (RTS/CTS/XON) the ECU expects.
  • Use a multimeter to confirm continuity if the adapter is passive, or replace the cable with a known good RS‑232/FTDI USB→serial adapter for troubleshooting.

As asked, identification is the first step. As hinted, adapter/wiring issues are common — the above steps provide concrete checks: confirm COMx in Device Manager, verify physical wiring and voltage levels, test with a terminal and loopback, and change the COM number if needed.

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Member Avatar for TheNNS

can you be a little more specific? a 25pin to 9 pin what? what are you talking about?

Member Avatar for Prometheus12345

I have often had problems with serial-to-parallel adapters in the past. Try having your friend use a laptop that has a real serial port on it, and the problem should be solved. Runniing serial throught he parallel has never really worked out well for me, I suspect you are having the same luck.

Failing the above, disco the ECU for at least 5 minutes from any power supply, and as you are waiting, reinstall the software fresh, just to be safe. Don't foprget to wipe all registry keys and any other traces of the management program before reinstalling.....

Basically, try to start over from scratch as thoroughly as possible. Be sure not to strain the cable itself unnecessarily as well...

Aside from that, I dunno without more information...

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