DTC 13

Code 13 Chart:

Oxygen Sensor Wiring Diagram:

CIRCUIT DESCRIPTION:

The ECM supplies a voltage of about of 0.45 volt between terminal Y19 and ground. (If measured with a 10 megohm digital voltmeter, this may read as low as 0.32 volts). The oxygen 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 360°C (600°F). An open sensor circuit, or cold sensor, causes "OPEN LOOP" operation.

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

1. Code 13 WILL SET:

A. Engine at normal operating temperature.
B. At least 2 minutes engine run time after start.
C. Oxygen sensor signal voltage steady between 0.35 and 0.55 volts.
D. All conditions must be met for about 30 seconds. If the conditions for a Code 13 exist, the system will not go into "CLOSED LOOP."

2. This test determines if the oxygen sensor is the problem, or if the ECM and wiring are at fault. In doing this test, use only a high impedance digital volt ohm meter. This test checks the continuity of circuit's 412 and 413. If circuit 413 is open, the ECM voltage on circuit 412 will measure over 0.5 volts (500 mV).

DIAGNOSTIC AIDS:

Normal voltage on circuit 412 varies between 100 mV and 999 mV (0.1 and 1.0 volt), while in "CLOSED LOOP." Verify a clean, tight ground connection for circuit 413. Open circuit(s), 412 or 413 will result in a Code 13. If Code 13 is intermittent, see DIAGNOSIS BY SYMPTOM - NO CODES.

NOTE:

1. Before diagnosing according to the Code 13 chart, check to make sure that the following system, and parts other than EFI system, are in good condition.

- Air cleaner (clogged)
- Vacuum leaks (air inhaling)
- Spark plugs (contamination, gap)
- High tension cords (crack, deterioration)
- Distributor rotor or cap (wear, crack)
- Ignition timing
- Engine compression
- Any other system and parts which might affect A/F mixture or combustion.

2. If Code 13 and another code are indicated together, the latter has priority. Therefore, check and correct what is represented by that code first and then proceed.

3. Before replacing ECM be sure to check for proper connections at ECM connector.