codes 43 and 21

Dec 07, 2005 3 Replies
J

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



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R

I don't think the two codes are related unless someone or something has 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.

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J

well today sometime after doing the diagnostics the check engine light went off. Maybe it was all a bad dream.

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R

I believe both of those codes have a 2 trip detection logic. If you take 2 good trips without the ECU sensing the fault, it turns the check engine light off.

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