DTC 13

Code 13 Chart:

Code 13 Wiring Diagram:

CIRCUIT DESCRIPTION:


The ECM supplies a voltage of about 0.45 volt between terminals "YE14" and "YE15". (If measured with a 10 megohm digital voltmeter, this may read as low as 0.32 volt.) The 02 sensor 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 316~C (600~F). An open sensor circuit or cold sensor causes "Open Loop" operation.

TEST DESCRIPTION: Numbers below refer to circled numbers on the diagnostic chart.

1. Code 13 will set under the following conditions:

^ Engine running at least 30 seconds after start.
^ Engine temperature at least 50~C (122~F).
^ No Code 21 or 22.
^ 02 signal voltage steady between 0.34 and 0.55 volt.
^ Throttle position sensor signal above 4% (About 0.58 volt above closed throttle voltage).
^ All conditions must be met and held for at least 30 seconds.

If the conditions for a Code 13 exist, the system will not go into "Closed Loop".


2. This will determine if the sensor is at fault or the wiring or ECM is the cause of the Code 13.


3. Use only a high impedance digital volt ohmmeter for this test. This test checks the continuity of CKTs 412 and 413, because if CKT 413 is open, the ECM voltage on CKT 412 will be over 0.6 volt (600 mV).

DIAGNOSTIC AIDS:


^ Normal "Scan" voltage varies between 100 mV to 999 mV (0.1 volt to 1.0 volt) while in "Closed Loop". Code 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. - Intermittent Malfunctions