'83 ur-q Brain

["Mike Hopton" <mike@genesis-microchip.on.ca>]

     Paul,
     Has the garage looking at your car confirmed what function on the ECU is 
     dead? Is it the signal to the frequency valve or the timing control unit? I 
     fixed two ECU's one for an '85 ur-q and one for an '83 ur-q, both of them 
     had open traces in the main PCB. Does the car run at all? It sounds from 
     your message that it just won't pass emission testing? If this is the case 
     you probably have a problem with the signal from the ECU to the frequency 
     valve, are you running 50% duty cycle - with no variation? Check continuity 
     from the O2 sensor to the ECU, is the O2 sensor voltage okay?
     
     The PCBs (particularly if you have the revision 0 MAC02 PCB) are prone to 
     burning out traces. Particularly the traces providing the signal to the 
     frequency valve, this is a high current circuit "many amps" and the PCB 
     traces are no thicker than for the other low current signals. I strongly 
     recommend you remove the ECU, take off the cover and carefully examine the 
     top of the ECU PCB for burn't or discoloured traces, you probably won't 
     find any. Now remove the screws that hold the PCB to the metal base, turn 
     over the PCB and examine the bottom side, look for opens and hair line 
     cracks in the PCB traces caused by too much current in the traces.
     
     Of course if could be one of the chips or discrete components on the board. 
     All except one of these are still available and can be repaced. If it's the 
     surface mount Hitachi ASIC on the daughter PCB your SOL but the chances are 
     the ECU can probably be fixed - given time.
     
     I may be able to lend you an ECU (more likely if you have the Rev02 board), 
     give me a call 905 470 2742 ext 244.
     
     Regards, Mike
     
     p.s. Make sure you you ground yourself and the ECU before you start working 
     on it.