Without Speed Density Update

Chart - Code 45 Oxygen Sensor Circuit, Rich Exhaust Indication:

Wiring Diagram for Oxygen Sensor Circuit.:

CODE 45 OXYGEN SENSOR CIRCUIT (RICH EXHAUST INDICATED)


Circuit Description:
The ECM supplies a voltage of about .45 volt between terminals "A16" and "A22". (If measured with a 10 megohm digital voltmeter, this may read as low as .32 volt.) The O2 sensor varies the voltage within a range of about 1 volt if the exhaust is rich, down through about .10 volt if exhaust is lean. The sensor is like an open circuit and produces no voltage when it is below about 315 degrees C (600 degrees F). An open sensor circuit or cold sensor causes "Open Loop" operation.


Test Description:Numbers below refer to circled numbers on the diagnostic chart. Code 45 will set if
Voltage on CKT 412 remains above .7 volt for 30 seconds.
Engine time after start is 1 minute or more.
Throttle angle between 3% and 45%.
Operation is in "Closed Loop".


Diagnostic Aids:

Using the "Scan", observe the block learn values at different rpm and air flow conditions. The "Scan" also displays the block cells, so the block learn values can be checked in each of the cells to determine when the Code 45 may have been set. If the conditions for Code 45 exists, the block learn values will be around 115.
Fuel Pressure. System will go rich if pressure is too high. The ECM can compensate for some increase. However, if it gets too high, a Code 45 may be set. See fuel system diagnosis CHART A- 7.

Rich Injector. Perform injector balance test CHART C-2K.

Leaking Injector. See CHART A-7.
Check for fuel contaminated oil.

02 Sensor Contamination. Inspect oxygen sensor for silicone contamination from fuel, or use of improper RTV sealant. The sensor may have a white, powdery coating and result in a high but false signal voltage (rich exhaust indication). The ECM will then reduce the amount of fuel delivered to the engine, causing a severe surge driveability problem.


CODE 51 - MEM-CAL ERROR (FAULTY OR INCORRECT MEM-CAL)


CODE 51 MEM-CAL ERROR (FAULTY OR INCORRECT MEM-CAL)


CHECK THAT ALL PfNS ARE FULLY INSERTED IN THE SOCKET AND THAT MEM-CAL IS PROPERLY LATCHED. IF OK, REPLACE, MEM-CAL, CLEAR MEMORY, AND RECHECK. IF CODE 51 REAPPEARS, REPLACE ECM.