Tip#23: Obd1 code 13 oxygen sensor for a 1993 Chevy S10 truck

If you get a check engine light code 13 for an obd1 system on 93 S10 truck, it means a failure in the oxygen sensor circuit. Assuming a vehicle owner has a voltmeter, the oxygen sensor has 3 wire connections and one of them (purple in color) can be tested for voltage signal to the ecm (computer). So how do you proceed to repair this problem besides replacing the oxygen sensor itself?

Symptoms:

Code 13 oxygen sensor after retrieving code from diagnostic connector.
Voltage reading at purple wire stuck at 0.400 to 0.475 volt all the time.

Basic Concept:

As discussed earlier in previous blogs, when you get a check engine light with oxygen sensor failure, the signal voltage should oscillates between 0.1 volt to 0.9 volt if it is working normally. In this case, our reading is stuck at 0.4-0.47 volt when tested. To eliminate the possibility that the oxygen sensor itself is the problem, you can inject a carb cleaner spray to the TB (throttle body) and the voltage reading should go up. If not or the reading is still stuck, 2 things are possible:

The oxygen sensor itself is bad
The purple wire connection to the ecm is no good.

The first can be easily fixed by replacing the oxygen sensor and the code reset. If the obd1 code 13 remains, it means the wiring connection from the oxygen sensor to the ecm terminal is buggered up. A long jumper wire can be substituted between the sensor and ecm and the reading verified. This should solve the problem otherwise; the ecm itself must be checked.