Powertrain Controls - ECM/PCM

Code Chart 13:

Heated Oxygen Sensor Circuit:

CIRCUIT DESCRIPTION:

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:

^ Engine operating temperature greater than 70°C (158°F).
^ At least 2 minutes engine run time after start.
^ Engine speed greater than or equal to 2600 rpm.
^ Oxygen sensor signal voltage steady between 0.35 and 0.45 volts.
^ MAP greater than or equal to 350 mm (Hg).
^ 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.

DIAGNOSTIC AIDS:

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

NOTE: 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.

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