Powertrain Controls - ECM/PCM

DTC 13 Chart:

Oxygen Sensor (O2S) Schematic:

CIRCUIT DESCRIPTION
The Oxygen Sensor (O2S) sensor which is located in the exhaust stream near the engine monitors oxygen content of the engine's exhaust gases and produces a voltage. This voltage ranges from 100 mV (high O2 in exhaust-lean mixture) to 1.0 volt (low O2 in exhaust rich mixture).

The PCM always supplies a steady 450 mV bias voltage to the O2 sensor. When the sensor is cold, it either produces a very low voltage or a slow cycling unusable voltage. As the O2 sensor heats up, the voltage will begin cycling more rapidly above and below the 450 mV bias voltage which tells the PCM the voltage is ready to be used and then go into "Closed Loop." O2S voltage can read zero volts in a fuel cutoff mode.

DIAGNOSTIC TROUBLE CODE (DTC) 13 WILL SET WHEN
^ Engine run time is greater than 40 seconds.
^ Engine coolant temperature is greater than 42.5°C (108°F).
^ DTC 21 or 22 is not set.
^ O2S signal voltage is steady between 0.35 and 0.55 volt.
^ The Throttle Position (TP) sensor angle is above 6%. (About .3 volt above closed throttle voltage.)
^ All conditions are met for 20 seconds.

ACTION TAKEN (PCM WILL DEFAULT TO)
The Malfunction Indicator Lamp (MIL) will illuminate, the O2S system will go into "Open Loop," and the cooling fan will enable.

DTC CHART TEST DESCRIPTION
Number(s) below refer to circled number(s) on the diagnostic chart.

1. During engine warm up, the O2S should warm up and its voltage should vary between 100 mV to 999 mV. When O2S voltage varies the engine will go into "Closed Loop."
2. This will determine if the sensor, wiring, or PCM is the cause of the DTC 13.
3. Use only a high impedance digital volt ohmmeter for this test. This test checks the continuity of CKT 412 and CKT 413; because if CKT 413 is open, the PCM voltage on CKT 412 will be over 0.6 volt (600 mV).

DIAGNOSTIC AIDS
^ Normal Tech 1 scan tool voltage varies between 100 mVs to 999 mVs (0.1 volt to 1.0 volt) while in "Closed Loop." Always use at least a 10 megohm input impedance voltmeter when monitoring O2 voltage.
^ Check condition of pigtail wire from O2 sensor for any opens or shorts. Also check positioning of pigtail make sure it is clear of exhaust manifold.
^ Check condition of O2 sensor louvered end for contamination. A whitish appearance may be caused by silica or anti-freeze entering into the exhaust system.
^ Carbon deposits on the O2 sensor can be burned off by running the engine part throttle for two minutes.
^ Refer to Intermittents, in Diagnosis by Symptom. - Intermittent Malfunctions