Powertrain Control Module PCM

DTC 13 Chart (HO2S):

DTC 13 Circuit (HO2S):

Circuit Description:
The PCM applies a bias voltage of approximately 450 millivolts (350-550 mV is normal bias voltage) between terminals "A10" and "A12". The Heated Oxygen Sensor (HO2S) varies the voltage within a range of about 1 volt if the exhaust is rich, and down to about .010 volt if exhaust is lean. DTC 13 is set when the voltage does not vary on CKT 412 within a predetermined amount of time.
The sensor is like an open circuit and produces no voltage when it is below 315° C (600° F). An open sensor circuit, or a cold sensor causes "Open Loop" operation.

DTC 13 Will Set When:

^ Engine has been running longer than 2 minutes.

^ Engine Coolant Temperature (ECT) greater than 70° C (158° F).

^ Throttle Position (TP) signal has been above 5%.

^ HO2S signal voltage steady between .35 and .55 volt.

^ All conditions must be met for about 60 seconds.

Action Taken (PCM will default to): The Malfunction Indicator Lamp (MIL) will illuminate and system will go into "Open Loop."


DTC 13 Will Clear When: Conditions for fault are no longer present and Tech 1 "clear DTCs" function is used or 50 ignition switch keycycles have passed with no further faults or ignition switch is turned "OFF" and ECM B fuse is removed for 10 seconds.

DTC Chart Test Description: Number(s) below refer to circled number(s) on the diagnostic chart.

1. This test verifies operating temperature and "Closed Loop" conditions.

2. This test checks the oxygen sensor's heating element. The heating element resistance should be 3.5 ohms at 20° C (68° F) or 14 ohms at 350° C (662° F).

3. This will determine if the sensor is at fault.

4. For this test use J 39300. This test checks the continuity of CKT 412 and CKT 413. If CKT 413 is open, the voltage on CKT 412 will be over .6 volt (600 mV).

5. If the fuse was open, check the wiring diagram for complete wiring circuit.

Diagnostic Aids: If the oxygen sensor heaters are not operating properly, system may go into "Open Loop" after extended idle.

Normal Tech 1 scan tool voltage varies between 100 mV to 1000 mV (.1 and 1.0 volt), while in "Closed Loop." DTC 13 sets in one minute if voltage remains between .35 and .55 volt, however the system will go "Open Loop" in about 15 seconds.

Refer to DIAGNOSIS BY SYMPTOMS/ INTERMITTENTS - Intermittent Malfunctions.

An oxygen supply inside the HO2S is necessary for proper HO2S operation. This supply of oxygen is supplied through the HO2S wires. All H02S wires and connections should be inspected for breaks or contamination that could prevent reference signal from reaching the HO2S.