These are the diagnostic codes I'm getting after my 92 4runner check
engine light started up last night. Are there really 2 unrelated
things that happened to go at precisely the same instant, or does this
indicate a third, bigger problem? The vehicle is running fine. I'm
worried that my ECU is causing all of this, and I'm not bright enough
to do electrical diagnoses

21=
OXYGEN SENSOR SIGNAL/OXYGEN SENSOR HEATER SIGNAL

OPEN OR SHORT IN OXYGEN SENSOR OR OXYGEN SENSOR SIGNAL

43=
STARTER SIGNAL--NO "STA" SIGNAL TO ECU UNTIL ENGINE SPEED EXCEEDS
800RPM

--IGNITION SWITCH/CIRCUIT

--ECU

"Joe" <in2deep (AT) airpost (DOT) net> wrote

disturbed a wiring harness between those components and the ECU. ECU
failures are very rare. Since you happen to have a short or open in 2
different components, I'd check the O2 sensor before replacing it.
--
Ray O
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well today sometime after doing the diagnostics the check engine light
went off. Maybe it was all a bad dream.

"Joe" <in2deep (AT) airpost (DOT) net> wrote

good trips without the ECU sensing the fault, it turns the check engine
light off.
--
Ray O
correct the return address punctuation to reply