| LobWedge |
Thu Mar 09, 2023 6:53 am |
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| Thank goodness I found this thread. I had my cluster out for some maintenance, and when I went to reinstall I saw this grey/white wire sitting there, and I'm thinking "I don't remember disconnecting this". Drove myself nuts for an hour trying to figure it out, including poring over wiring doagrams, until I ended up here. :lol: |
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| DigiMatrix |
Sat Mar 11, 2023 11:37 pm |
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djkeev wrote:
It turns out that the difference between an 87 ECU plug and an 88 ECU plug is the addition of connectors for terminals 20 and 23. (See the wiring diagram below, Digifant Control Unit, current tracks 18 & 23)
Why are these connectors here?
What do they affect in the daily operation of the fuel injection system?
Dave
Pin 20 at the ECU is a bidirectional (Input/Output) connection to the ECU micropocessor com port. The "D" version ECU has special circuitry that connects to the 2 pins of the com port of the microcontroller (input and output) - used to get the fault codes stored in eeprom. Blink code info from the Vanagon chip below:
2322 Air temp sensor or ATS circuit
2312 Coolant temp sensor or CTS circuit
2232 AFM sensor or AFM sensor circuit
1111 ECU defective (Internal ECU failure)
2341 Oxygen sensor control range exceeded (Inoperative)
2342 Oxygen sensor or OXS circuit
2121 Throttle switch
4444 OK - No faults found in the ECU
0000 End of fault code output
Pin 23 this is connected to the microprocessor and is an output that goes high when a hall signal is recieved by the processor and low when the Hall signal is lost.
I have never looked how this relates to the Vanagon wiring, but I have in the Corrado/Passat - it was connected to Digifant Control Unit relay (terminal 5/86A)
Note: the Output from the Processor is high, but the circuity in the ECU itself may change what happens at pin 23 - more research is required but I think it just converts the 5 volt microprocessor signal to 12 volts
Edit: I have simulated the circuit and the 5volt microprocessor signal is converted to 12 volts at pin 23
From 1990 Corrado - click to enlarge
Now, in the 1990 Corrado VW used Relay 30, which is the 5 pin relay as shown above
and in the 1992 Passat G60 (same engine and ECU) they used relay 32 which does not have the 86A pin
Both of these run Digifant1 but a more complicated (complete) version than the Vanagon "D" and they will run just fine with either relay. The code in the chip for each car sets pin 23 high, but if I remember correctly the Passat didn't have the wiring back to the relay. I think it was a safetly circuit to keep the relay powered as long as there were hall pulses but I am not sure. More investigation required.
Update: the built in circuitry in the "D" version ECU is not populated on the circuit board so the feature i described above is not available. Pin 23 does nothing without the 3 required resistors, 2 transistors and a diode
Hopefully this helps shed some light on your questions.
No affect in the daily operation of the fuel injection system |
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