ELD pin D10 Wideband Input ECU Board Modification
This ECU board modification will allow your OBD1 ECU to use the ECU pin D10 (ELD) for your wideband signal input. The advantage to using pin D10 instead of the stock O2 sensor pin D14 is that the ELD input is capable of processing a full 0-5 volt signal, while the D14 pin can only process 0-3.73 volts which will limit your air/fuel ratio datalogging ability of the wideband signal. UPDATE: With all newer wideband systems that use the Bosch LSU 4.9 sensor, 0-3.73 volts reading through the stock D14 O2 sensor input is more than sufficient for reading air/fuel ratio, so using the D10 ELD input is no longer beneficial. If your wideband uses the Bosch LSU 4.9 sensor, we recommend using the D14 input now, this way you can leave the ELD circuit functional.
To use the pin D10 ELD input, simply locate the bank of resistors near the ECU grey plugs labeled R136, R137, and R138. R137 (the middle resistor) should remain intact and unchanged, while R136 and R138 should be removed or cut. Not all circuit boards have a resistor in both locations (as pictured). Just be sure both R136 and R138 are empty or cut and you are good to go.
In the above picture, you can simply cut one "leg" of the resistor in location R136 to break the circuit. Your ECU is then ready to use D10 for your 0-5v wideband input. Be sure to configure your tuning software to use the D10 input now for your wideband instead of the standard D14 O2 sensor input.