Code 27, Sub-O2 Sensor/Open Or Shorted CKT (CALIF. Only)
ECM supplies a voltage of .45 volt between terminals OX(2) and OX(1). If voltage is measured with a 10-megohm DVOM, reading may be as low as .32 volt. When the suBoxygen sensor reaches operating temperature, it produces a varying voltage of about .1-.9 volt. The suBoxygen sensor produces no voltage when it is less than 600°F 316°F). An open sensor circuit, or cold sensor, results in open loop operation.
NOTE:
Test numbers refer to test numbers on diagnostic chart.
- A Code 27 will set if the following conditions are present for about 60 seconds: engine is at normal operating temperature, at least 2 minutes have passed since engine start, and O2 sensor voltage does not vary.
- This determines whether problem is faulty suBO2 sensor, or faulty ECM and wiring.
- This checks continuity of White and Black wires from ECM. If Black wire is open, ECM voltage on White wire will be greater than .6 volt.