93 O2 sensor woes
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93 O2 sensor woes
I recenty bought a new (for me) 93 4x4. 209k but the previous owner rebuilt the motor <5000k ago. the check engine lamp was burned out when I got it, I put a new one in and found a code 21 and 25. I checked underneath, found the wiring for the o2 sensor a little funky, so I spliced in a new section from a wrecker. also replaced the sensor with a new bosch unit. it's the 4-wire warmed version. I'm positive I wired everything correctly. now the code 25 is gone but the 21 is persistent. I measured the voltage from E1 to Vf1 and didn't get anything, no matter what I did. the FSM troubleshooting flowchart says to replace the ECM under that condition. I've never encountered a bad ECM before, so I'm wary of that. anyone have any ideas where to look next? is there a way to test the ECM, other than trying a different one? thanks...
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code 21 is : open or short in : main heater circuit of oxygen sensor or main circuit of oxygen sensor, or failure of heater circuit or oxygen sensor. or ECM.
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