DTC 13

Fig. 12 Oxygen sensor wiring circuit. 1984:

Fig. 13 Oxygen sensor wiring circuit. 1985:

If oxygen sensor boot becomes caked with dirt or mud, it may become inoperative. Sliding the boot back and cleaning it may restore the sensor to normal operation.
1. When the oxygen sensor temperature is above 200° F, its output voltage will vary between zero and one volt. Code 13 indicates that the oxygen sensor will not vary above or below its cold voltage output of .5 volts and that the system will not go to closed loop operation. Possible causes of this condition are as follows:
a. Defective oxygen sensor.
b. Defective wiring and/or electrical connectors.
c. ECM is not processing oxygen sensor signal.
2. Disconnect oxygen sensor electrical connector, then enter engine data display diagnostic mode.
3. If oxygen sensor voltage is less than .37 or greater than .57, check wiring harness for defects. If wiring is not at fault, check ECM and ECM connector.
4. If voltage is between .37 and .57 volts, connect suitable jumper between oxygen sensor harness pins, and note voltage reading.
5. If voltage reading is greater than .05 volts, then ECM is not able to recognize that a fault was artificially created. Therefore, either ECM is malfunctioning or an oxygen sensor circuit is open between connector and ECM.
6. If voltage reading is less than .05 volts, ECM is operating properly and wiring harness is satisfactory. Check oxygen sensor.