Art

Thanks for your help once again. My test results given below along with your latest note.

Thanks for the clarifications.

Let me try to help by explaining the heater test. A good oxygen sensor heater measures around 4 ohms cold and 13 hot - roundabout. If you begin with a cold engine, get your meter in place and ready to use quickly, start the motor and let it run for one minute.

Shut it off, and immediately disconnect the two-pin oxygen heater plug. Measure the resistance toward the two white wires and watch it over the next minute. You are expecting to see it somewhere above 10 ohms and gradually fall to a lower value as it cools.

The idea of this test is you are seeing that the voltage warmed it (not exhaust, because that would take much longer) and watching it cool tells you it is not opening up as it contracts. That verifies the sensor's heater and the supply from fuse 4 all in one test.

Sorry to declare your AMM had no pin 6. Yes it does, but inside nothing is connected, and of course, the harness has no pin 6. It responds, and that was the object of the test. Just means you still need to swap in a known good AMM to be absolutely sure yours is good. Nothing you've done so far proves it isn't.

When you re-measure the oxygen sensor's signal output, take into account whether the 113 code has already been set, which takes the system out of closed loop and runs the rpm-dependent limp home mixture adjustment, which should be on the rich side to be safe.

[Measuring the O2 sensor heater resistance cold yields 3.0 ohms. Running the engine for one minute and shutting down, quickly measuring resistance of the sensor heater yields 5.0 ohms. Watching the sensor resistance for several minutes as it cools down yields a steady reduction in resistance down to the cold value. It takes about 4 min to reach the cold value.]

[Reseting the ECU by pulling the fuse, checking the pulse code led output before starting the engine confirming 1-1-1 and then running the engine yields voltage from the green wire to ground (by ground I mean the exhaust pipe connected near the sensor or the negative of the battery) of initially 0.3 volts (quickly running around the car after starting) which rapidly goes to the level previously seen of 38 milllivolts (this happens in 1 minute). The check engine light does no show a 1-1-3 fault for about 10 min but the led pulse output does show a 2-3-2 code very quickly after engine startup.]

[One other thing I noticed was when measuring voltage from the O2 output (green wire connected to the sensor) to the low side of the heater (black wire) I read almost no voltage. I assume that this is attributable to voltage drop in the heater wire pair with 2 amps returning to ground through the black wire since my measurement is at the harness plug.]

Looking forward to receiving your view and suggestions.

Bob Platt