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· Registered
7 Posts
Discussion Starter · #1 ·
My car, 93 3vz-fe, is reading a check engine code of 28. This code is not in my Haynes manual and my local Toyota dealership will not tell me. They said I should bring it to them for a ~$60 USD diagnostic.

I did a Search but found nothing on this problem.

Does anyone know what this code means? Thanks.

· Grenaded piston
6,617 Posts
Not sure what 28 is.

27 is sub-oxygen sensor signal.

When sub oxygen sensor is warmed up and full acceleration continued for 2 seconds, output of main oxygen sensor is 0.45 V or more (rich) and output of sub-oxygen sensor is 0.45 V or less (lean).

1. Short or open in sub-oxygen sensor circuit.

2. Sub-oxygen sensor

3. ECM

My guess is that you have a bad O2 sensor.
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