Action Taken
- ECM turns on "ENGINE CONTROL SYSTEM FAULT" light.
- ECM commands BCM to display "SERVICE SOON" message on DIC.
- ECM will use right oxygen sensor signal to control fuel delivery unless Code EO13, EO44 or EO45 is set. If any of these codes are set, closed loop operation will be disabled.
The ECM provides a .45-volt reference to the oxygen sensor on circuit No. 412. When the sensor warms up, it will cause the .45-volt reference to vary based on oxygen content in the exhaust gasses. A lean mixture will cause the voltage to decrease. A rich mixture will drive the voltage above .45 volts. If during the test conditions described, the oxygen sensor voltage does not vary, the ECM assumes that the oxygen sensor can not respond and will set Code EO17. Possible cause for EO17 is an open circuit No. 412 or 413, short to voltage on circuit No. 412 or 413 or oxygen sensor is unable to respond.
NOTE:
The following step numbers refer to circled numbers on diagnostic chart. See Fig 1
. For circuit identification, see Figure
.
- With key on and oxygen sensor disconnected, parameter ED34 should read .38-.57 volts. Significantly higher or lower readings indicate a problem.
- The ECM compares voltage on circuit No. 412 the ground on circuit No. 413. It is essential that the oxygen sensor ground and ECM ground on pin "B6" are at the same voltage potential with the engine running.