Powertrain Controls - ECM/PCM

Code 13 Diagnostic Chart:

Oxygen Sensor Wiring Schematic:

CIRCUIT DESCRIPTION
The Powertrain Control Module (PCM) supplies a voltage of about 0.45 volt between terminals "PA12" and "PB6". (If measured with a 10 megohm digital voltmeter, this may read as low as 0.32 volt.) The Oxygen Sensor (02S) varies the voltage within a range of about 1 volt if the exhaust is rich, down through about 0.10 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.

DTC 13 WILL SET WHEN
^ Engine running at least 40 seconds after start.
^ Coolant temperature at least 42.5°C (108°F).
^ No DTC 21 or 22.
^ 02S signal voltage steady between approximately .35 and .55 volt.
^ Throttle Position (TP) sensor signal above 6% for more time than TP sensor was below 6%. (About 0.3 volt above closed throttle voltage.)

All conditions must be met and held for at least 30 seconds.

ACTION TAKEN (PCM WILL DEFAULT TO)
The system remains in "Open Loop," Malfunction Indicator Lamp (MIL) illuminates.

DTC 13 WILL CLEAR WHEN
02S voltage starts varying.

TEST DESCRIPTION
Number(s) below refer to circled number(s) on the diagnostic chart.
1. During engine warm up, the 02S should warm up and its voltage should vary between 100 mV to 999 mV (0.1volt - 0.9volt). When 02S voltage varies the engine will go into "Closed Loop." This step determines if the 02S is operating properly.
2. This will determine if the sensor is at fault or the 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; 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 mV to 999 mV (0.1 volt to 1.0 volt) while in "Closed Loop." DTC 13 sets in 30 seconds if voltage remains between 0.35 volt and 0.55 volt, but the system will go "Open Loop" in about 15 seconds. Refer to "DIAGNOSIS BY SYMPTOM/INTERMITTENTS." Testing and Inspection