Bench testing the 14cux

[Trevor Allen]

Has anyone fired up the 14cux on the bench? I've tried to get one communicating to rover gauge to check operation. I've made the power connections and the resistive sensor inputs but on applying power get connected but reads nothing. The FTDI serial cable is working according to a logic analyser. Am I missing something obvious.

[Colin Bourassa]

Just to clarify, is RoverGauge successfully connecting to the diagnostic port? In other words, does the "Communications" light turn green on the display? I'm trying to establish whether the ECU is not powered on, or if there's another problem. I believe the ECU should draw about 400 mA when running. I assume that you've connected both the +12VDC "battery" voltage (always on) and also the switched +12VDC "ignition-on" pin, as well as all the grounds. See the pinout table on the Wikipedia 14CUX article for reference: http://en.wikipedia.org/wiki/Lucas_14CUX

Note that there are a few ECU inputs that are not read if the ignition pulse interrupt is not received. The temperature sensors, fuel map data, and most other inputs should still work before the engine is started, however.

--Colin

[Trevor Allen]

HI Colin, the comms light stays red. I can see the TxD from the FTDI cable polling the ECU. I will check current drain. The connections I made were as per the wiki and the Land Rover manual so the battery and ignition inputs were both connected. I kept the sensor ground separate from the other ground connections. I'll meter everything directly at the pcb connections just to make certain I have continuity then try again. At least I now know that it should respond so thanks for the very quick reply. Trev

[Trevor Allen]

Success! It appears the signal ground must be tied to the ECM ground. if you connect the ground of the diagnostic cable to either signal ground or ECM ground nothing, however when the two are linked it all fires up and works as advertised. The temperatures were all showing the values according to the resistor values I wired across the connections so sensible data.

Once again Colin, many thanks.