DTC 13

DTC 13 Chart:

Wiring Diagram:

CIRCUIT DESCRIPTION:

The ECM supplies a voltage of about 0.45 volt (450 mV) between terminals "D7" and "D6". (If measured with a 10 megohm digital voltmeter, this may read as low as 0.32 volt). The O2S or HO2S varies the voltage within a range of about 1 volt if the exhaust is rich, down through about 10 mV if the exhaust is lean.

The sensor is like an open circuit and produces no voltage when it is below 315°C (600°F). An open sensor circuit or cold sensor causes "Open Loop" operation.


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

1. DTC 13 will set:

^ Engine at normal operating temperature 70°C (158°F).
^ At least 2 minutes engine time after start.
^ O2S/HO2S signal voltage steady between 0.35 and 0.55 volt.
^ Throttle Position (TP) sensor signal above 5% (about 0.3 volt above closed throttle voltage).
^ All conditions must be met for about 60 seconds.

2. This test checks the heated 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 only a high impedance Digital Volt Ohmmeter (J 39200). This test checks the continuity of CKT 412 and CKT 413. If CKT 413 is open. the ECM voltage on CKT 412 will be over 0.6 volt (600 mV).

5. If the #13 fuse was open, check the #13 fuse circuits for shorts.


DIAGNOSTIC AIDS:

If the heated oxygen sensor heater on the 4.3L engine is not operating properly, system may go into "Open Loop" after extended idle.

Normal scan tool voltage varies between 10 mV to 1000 mV (0.01 and 1.0 volt), while in "Closed Loop." DTC 13 sets in one minute if voltage remains between 0.35 and 0.55 volt, however the system will go "Open Loop" in about 15 seconds.

- Intermittent Malfunctions

An O2S/H02S supply inside the O2S/HO2S is necessary for proper O2S/HO2S operation. This supply of oxygen is supplied through the O2S/H025 wires. All O2S/HO2S wires and connections should be inspected for breaks or contamination that could prevent reference oxygen from reaching the O2S/HO2S.