DTC 13

Fig. 019 - Chart - Code 13 Open Oxygen Sensor Circuit.:

NOTE: Code 13--ECM detects open oxygen sensor circuit under the following conditions:

a. Oxygen sensor voltage is within a specified range.
b. TPS voltage is above a specified value.
c. More than a specified time after the engine has warmed up. The ECM supplies a voltage of about 0.45V between Terminals "9 and 14". (Voltage may read as low as 0.32V when measured with a 10 megohm DVOM.) The O2 sensor varies the voltage within a range from about 1 volt if the exhaust is rich down through about .1V if exhaust is lean.

1. This step is to determine if the problem is still present.
A normal dwell will vary indicating the fault is not present, while a fixed dwell indicates the fault is still present.
2. By grounding the O2 sensor circuit to the ECM, a "low voltage (lean) signal" is sent to the ECM.
If the ECM is not faulty and the circuit is complete a "low voltage signal" should result in a full rich command (low dwell) from the ECM.
3. This step determines if the O2 sensor is functioning. With the rich command, the O2 sensor should read a high voltage, over .8V if it is functional, since the exhaust is rich. If the O2 sensor functions, fault is in the connections to the sensor.
4. This step 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 step grounds the O2 signal wire at the ECM. If the ECM is functional, 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.