DTC 13

DIAGNOSTIC CHART





WIRING DIAGRAM

INSPECTION PROCEDURE

Circuit Description:
The Engine Control Module (ECM) supplies a voltage of about .45 volt between terminals "D7" and "D6". (If measured with a 10 megohm digital voltmeter, this may read as low as .32 volt). The O2S varies the voltage within a range of about 1 volt if the exhaust is rich, down through about .10 volt if 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. Code 13will set:
- At least 2 minutes engine time after start.
- Oxygen signal voltage steady between .35 and .55 volt.
- Engine coolant temperature about 70°C (158°F).
- Throttle position sensor signal above 5% (about .3 volt above closed throttle voltage).
- All conditions must be met for about 60 seconds.
If the conditions for a DTC 13 exist, the system will not go "Closed Loop".
2. This will determine if the sensor is at fault or the wiring or ECM is the cause of the DTC 13.
3. In doing this test, use only a high impedance digital volt ohmmeter. This test checks the continuity of CKT(s) D7 and D6. If CKT D6 is open, the ECM voltage on CKT D7 will be over .6 volt (600 mV).

Diagnostic Aids:
Normal "Scan" voltage varies between 100 mV to 999 mV (.1 and 1.0 volt), while in "Closed Loop". DTC 13 sets in one minute, if voltage remains between .35 and .55 volt, but the system will go "Open Loop" in about 15 seconds.
Refer to "Intermittents" in "Symptoms".