Code 13: Open O2 Sensor Circuit

Code 13 indicates an open in the Oxygen (O2) sensor circuit with the following conditions:

• O2 sensor voltage is within a specified range.
• Above a specified TPS value.
• More than specified time after engine has warmed up.

The ECM supplies about .45 volt between terminals "9" and "14". Voltage may read as low as .32 volt when measured with a 10 megohm digital volt-ohm meter. The O2 sensor varies the voltage within a range of about 1 volt (rich exhaust) to about .1 volt (lean exhaust).

1. This test checks to see if problem still exists. Fixed dwell indicates fault.
2. By grounding the O2 sensor circuit to the ECM, a "low voltage (lean) signal" is sent to the ECM. This should result in a full rich (low dwell) command".
3. This test checks O2 sensor. With the rich command, the O2 sensor should read a high voltage, over .8 volt. If the O2 sensor functions, fault is in the connections to the sensor.
4. Checks for an open in the ECM-O2 sensor ground circuit. Normal voltage is below 1 volt if the circuit is complete. The worse the connection is, the higher the voltage will read.
5. This grounds the O2 signal wire at the ECM. Dwell should go to below 10°, since this is a "low voltage signal" indicating lean exhaust. No change indicates a problem at the ECM connections, or the ECM.