ECM Code EO13 - Oxygen Sensor Not Ready: Notes

If code EO13 is accompanied by current or history code EO45, diagnose code EO45 using chart. If code EO13 is accompanied by current or history code EO44, diagnose code EO44 using chart.

TEST CONDITIONS: Codes EO14, EO15, EO21, EO22, EO26 and EO27 are clear. Coolant temperature greater than or equal to 176°F (80°C). TPS value between 6 and 29 degrees. Throttle switch open. RPM greater than or equal to 800.

FAILURE CONDITIONS: Oxygen sensor voltage stays between .275 and .630 volts for more than 30 seconds (not toggling).

ACTION: ECM turns on "ENGINE CONTROL SYSTEM" light. ECM commands BCM to display "SERVICE SOON" message on CCDIC panel. ECM turns on canister purge and diverts AIR management air to air cleaner. Closed loop is disabled.

When warm, a properly operating oxygen sensor will drive the ECM's .45 volt reference signal lower (below .45 volts) to indicate a lean mixture, and higher (above .45 volts) to indicate a rich mixture. If under test conditions the oxygen sensor does not vary from the cold or not ready voltage, ECM assumes sensor can't respond to air/fuel mixture changes and sets a code EO13.

NOTE: Test numbers refer to test numbers on diagnostic chart.

With key on and oxygen sensor disconnected, the parameter for ED07 should read about .45 volts. Lower or higher voltage indicates problems within the circuit.
The ECM compares voltage on circuit No. 412 to the ground voltage on circuit No. 413. It is essential that oxygen sensor ground and ECM ground on pin "A1" indicate good continuity (no voltage difference) with engine running.
Fault is most likely at ECM connector or ECM. See CHART C1 - ECM REPLACEMENT CHECK before replacing ECM.