DTC 44

Fig. 12 Oxygen sensor wiring circuit. 1984:

Fig. 13 Oxygen sensor wiring circuit. 1985:

When the oxygen sensor temperature is below 200° F, its output voltage will be .5 volts and the ECM will operate in the open loop mode. When the oxygen sensor temperature is above 200° F, the output voltage will vary between zero and one volt. When oxygen sensor output voltage begins to vary, the ECM will operate the system in the closed loop mode. Code 44 indicates that the oxygen sensor reference signal is less than .5 volts and constant. If voltage remains at this low range, code 44 will be displayed and the system will operate in the open loop mode. This condition may be caused by the following:
a. Defective oxygen sensor.
b. Defective electrical connectors or wiring.
c. ECM unable to process signal.
d. Modulated displacement malfunction which causes oxygen sensor to read lean fuel mixture.

To diagnose a Code 44, proceed as follows:
1. Turn ignition on, enter diagnostics and display parameter .0.7.
2. Disconnect oxygen sensor and note parameter value.
3. If value of parameter .0.7 is greater than .37 volts, proceed to step 4. If value is less than .37 volts, check circuit 412 for short to ground or short to circuit 413. If circuit is satisfactory, fault is in ECM or ECM connector. Repair or replace as necessary.
4. Connect jumper wire between oxygen sensor pins on ECM side and note parameter value.
5. If reading is greater than .05 volts, check circuits 412 and 413 for an open. If circuits are satisfactory, fault is in ECM or ECM connector. If reading is less than .05 volts, reconnect oxygen sensor and check operation of the following by referring to appropriate sections of this chapter: fuel delivery system, EGR system, air management system and oxygen sensor.