I am trouble shooting my ABS as it is not working as it should. I have a couple of ECUs and they all perform the same. I have been working through various tests as the test function does not reveal anything to me. I have checked the resistances on all the circuits I can , wheel sensors, Valve earth, Main valve , delivery valves, retrun valves and all are within limits. I have carried out checks on the main control valve no probs. There are a few other checks to carry out electrically but these all need two people so I will do them later. I have looked at supplies in the 35 pin connector and this is where my question lies. In the book it hints if there light remains on all the time maybe there is a supply fault There are 35 pins in this connector Pin 1 is body shell earth , pin 2 is 12v from ignition , pin 3 12 volts from main relay , Pin 8 is 12v to main relay. Now there is power at pin 2 only. Pin 8 should send power to the relay to activate it so that the relay supplies power to pin 3. AT the moment the only supply I have is pin 2. I tried a bypass and if i supply power to pin 8 then the ABS works ok on start up ie light falshes on then goes out.. Test function still does not work though. I am getting stuck and I am not sure if anyone is electrically minded can help, or if there is somethng else i can try. Thanks Image Unavailable, Please Login Image Unavailable, Please Login Image Unavailable, Please Login
I will be interested in any results you may learn. I also have the early ATE Teves system in my 355. Same failure mode. Light on. No codes when in test mode. Have changed the ECU, all relays, tested servos etc. Found no errors. The test I still need to perform is the high and low pressure switch at the ABS pump. Need a high pressure gauge set to read the resultant pressure range. Next on my list. Good luck!
I tackled the maintance diagnostics today in detail. First I took out the union part number 131873 at the brake pump and drilled the head of the union and then brazed a coupling onto this point. I connected this to a pressure gauge. Total cost about £ 30.00 I now have a way of checking the pressures without a ferrari specialist tool! All hydaulic pressures were good , but ABS lights were not illuminating when they should . Accumalator fine, switches fine, everything except the lights. I then took the cover off the 35 pin connector and worked through the electric ohm tests everything was going fine and within limits. I came to diode test and it just wasnt going the wayit should and it wasnt failing as it should either. I did a bit more investigation to find that the relays at the ABS ECU were in the wrong order.! After checking the wiring diagram and ensuring the correct relays were in their correct position I could carry out the diode check as required and it failed. I opened up the diode and sure enough a cracked diode inside. I had had problems before as I was pulling the wrong fuse for the test as the relays were in the wrong place. I replaced it and tried agan and the lights now work with the hydraulic tests and I get fault codes which was not working before. Next to road test it to clear the memory and see if all is ok or not . At least now if there is a fault the ecu will tell me. The tests work !
