E013

TEST CONDITIONS:
1. Codes EO14, EO15, EO21, EO22, EO26, and EO27 not set;
2. Coolant temperature equal to or greater than 58°C;
3. Throttle angle between 6 and 30 degrees;
4. Throttle switch open;
5. RPM equal to or greater than 800.

FAILURE CONDITIONS:
Oxygen sensor voltage stays between 0.307 volts and 0.609 volts for more than 64 seconds (oxygen sensor voltage not toggling).

ACTION TAKEN:
1. ECM turns on the "Engine Control System Fault" telltale;
2. ECM commands the BCM to display "Service Soon" message on Driver Information Center (DIC);
3. ECM uses the left oxygen sensor signal to control the amount of fuel delivered unless Code EO17, EO42, or EO43 is set. If any of these codes are set, closed loop operation will be disabled.

DESCRIPTION
The ECM provides a 0.45 volt reference to the oxygen sensor on CKT 412. When the oxygen sensor warms up, it will cause the 0.45 volt reference to vary based on oxygen content in the exhaust gases. A lean mixture will cause the reference voltage to decrease and a rich mixture will drive the voltage above 0.45 volts. If during the test conditions described above, the oxygen sensor voltage does not vary, the ECM assumes that the oxygen sensor can't respond and will set a code EO13. Possible causes of Code EO13 are:
1. Open in CKT 412 or 413;
2. Short to voltage on CKT 412 or 413;
3. Oxygen sensor that cannot respond.

Notes on Fault Tree
1. At key on with oxygen sensor disconnected, parameter ED33 should read 0.38-0.57 volts. Significantly lower or higher voltages indicate circuit problems.
2. The ECM compares voltage on CKT 412 to the ground on CKT 413. It is essential that the oxygen sensor ground and ECM ground on pin E15 are at the same voltage potential with the engine running.

Notes on Intermittents
If Code EO13 is a history code; start engine and enter diagnostics. Operate engine at fast idle until "AUTO" closed loop status light is turned on. Observe parameter ED33 while manipulating CKT 412 and 413 wiring. If parameter ED33 stops fluctuating and stays fixed at 0.45 volts, repair intermittent open circuit. Check CKT 413 ground to engine for proper installation (clean, tight, star washer installed). Ground for CKT 413 is attached to the front of the engine at the power steering bracket. Check oxygen sensor connector terminals for corrosion or foreign material. Clean if signs of corrosion are evident (white film).