Powertrain Controls - ECM/PCM

DTC 13 Oxygen Sensor (O2S) Circuit (Open Circuit):

Oxygen Sensor (O2S) Circuit:

CIRCUIT DESCRIPTION
The Powertrain Control Module (PCM) supplies a voltage of about 0.45 volt between terminals "A10" and "A12". (Using J 39200 digital voltmeter, this may read as low as 0.32 volt.) The Oxygen Sensor (O2S) 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 about 315°C (600°F). An open sensor circuit or cold sensor causes "Open Loop" operation.

DTC 13 WILL SET WHEN
^ Engine Coolant Temperature (ECT) greater than 79°C (175°F).
^ At least 2 minutes engine time after start.
^ Oxygen sensor signal voltage steady between 0.35 and 0.55 volt.
^ Throttle Position (TP) signal above idle (6%).
^ All conditions must be met for about 60 seconds.
^ If the conditions for a DTC 13 exist, the system will not go "Closed Loop."

ACTION TAKEN (PCM WILL DEFAULT TO)
The PCM will turn "ON" the MIL (Malfunction Indicator Lamp).

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 fuse #9 is removed for 10 seconds.

DTC CHART TEST DESCRIPTION
Number(s) below refer to circled number(s) on the diagnostic chart.
1. This step determines if DTC 13 is the result of a hard failure or an intermittent condition.
2. This will determine if the sensor is at fault or the wiring or PCM is the cause of DTC 13.
3. In doing this test, use only a high impedance digital volt ohmmeter J 39200. This test checks the continuity of CKTs 412 and 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 mV to 999 mV (0.1 and 1.0 volt) while in "Closed Loop." DTC 13 sets in one minute if voltage remains between 0.35 and 0.55 volt, but the system will go "Open Loop" in about 15 seconds. Verify a clean tight ground connection for CKT 413. Open CKT 412 or CKT 413 will result in a DTC 13.