Code 13 - Oxygen Sensor Failure
Trouble Code 13 indicates that the exhaust stream oxygen content sensor (O2 sensor) is not responding as expected. When cold, the sensor is 'biased' by the ECM to about 450 millivolts. Before it warms to at least 600 deg F (315 deg C) it acts as an open circuit and when the ECM reads it, it reads the 450 mV bias. The ECM expects the sensor to warm in a short period of time and begin sending its own voltages.
The conditions for setting this code are:
engine running at least 40 seconds and
no code 21 or 22 (TPS errors) present, and
coolant temperature is at least 118 deg F (48 deg C), and
O2 sensor voltage not fluctuating (i.e. steady between 350 and 550mV), and
TPS signal indicates above idle (over 6%), and all the above conditions met for more than 8 seconds
If the conditions for a Code 13 exist, the system will not go "Closed Loop"
Typical causes for this code include:
Defective or degraded O2 sensor
Deposit contaminated O2 sensor (running leaded fuel, RTV silicone deposits etc.)
Corroded/defective O2 sensor connection
Defective sensor ground circuit
Defective connection at ECM
Defective ECM