Code 13 (DOHC) - O2 Sensor (Heated Sensor) Open/Shorted Circuit: Notes

The ECM supplies a .45 volt signal between terminals D6 and D7. When O2 sensor reaches operating temperature, it varies this voltage from approximately .1-.9 volt (lean to rich exhaust). O2 sensor does not produce voltage when temperature is less than 600°F (316°C) or when engine operates in open loop.

1. Code 13 will set if all the following conditions are met for 4 seconds:
   • Engine temperature is greater than 157°F (69.5°C).
   • Engine has been running for at least 2 minutes after start.
   • O2 signal voltage steady between .420 and .547 volt.
   • Throttle angle greater than 10 percent.

   If conditions for Code 13 exist, system will not go into closed loop.

2. This determines if sensor, wiring or ECM is the cause of Code 13.
3. Use only a high impedance (10-megohm) digital volt-ohmmeter. This tests continuity of circuits from terminals D6 and D7. If circuit from terminal D6 is open, ECM voltage on circuit from terminal D7 will be greater than .6 volt.