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I have a 1990 W150 with stock computer and wiring, 360, A518. My question is: what does the sensor return circuit do and can I run the truck without it?
The engine began surging, like it was moving between default mode and closed loop mode. I checked all my connectors for engine wiring and vacuum. They were OK.
I went to the oxygen sensor next. The sensor was getting current over the main power wire, but not the heater wire. The heater wire is connected to a circuit called "sensor return" in the FSM. The circuit goes to 7 sensors.
The splices go off the 18 gage BK/LB wire that comes off #4 terminal at the computer SBEC. I checked voltage across the splices. The protocol is to turn the ignition key to on and check voltage for 2 seconds before the ASD shuts it off. I watched and my wife turned the key.
Battery voltage is supposed to be present, but at this point .4V is the most I can get across the circuit. I tried running battery power directly to the circuit with the lead from the computer disconnected. The truck will not start.
Now, the wire to terminal 4 at SBEC is burnt up all the way to terminal #4, because I crossed it with battery voltage. I don't think I can run a new wire.
The engine began surging, like it was moving between default mode and closed loop mode. I checked all my connectors for engine wiring and vacuum. They were OK.
I went to the oxygen sensor next. The sensor was getting current over the main power wire, but not the heater wire. The heater wire is connected to a circuit called "sensor return" in the FSM. The circuit goes to 7 sensors.
The splices go off the 18 gage BK/LB wire that comes off #4 terminal at the computer SBEC. I checked voltage across the splices. The protocol is to turn the ignition key to on and check voltage for 2 seconds before the ASD shuts it off. I watched and my wife turned the key.
Battery voltage is supposed to be present, but at this point .4V is the most I can get across the circuit. I tried running battery power directly to the circuit with the lead from the computer disconnected. The truck will not start.
Now, the wire to terminal 4 at SBEC is burnt up all the way to terminal #4, because I crossed it with battery voltage. I don't think I can run a new wire.
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