Diagnostic Aids

NOTE: The following procedure is designed to account for intermittent codes. If no malfunction is uncovered using this procedure, it will indicate that the DFI system is OK at this time. Refer to NOTE ON INTERMITTENTS.

When the oxygen sensor is warm (above 200°C), the output voltage will swing between 0 and 1.0 volts. Code 13 indicates that the oxygen sensor will not swing above or below its cold voltage of approximately 0.5 volts and that the system will not go to closed loop operation. Possible causes are:

A. The oxygen sensor not functioning properly.
B. Defective wires, terminals, etc.
C. The ECM not processing the signal properly.

To check the operation of the oxygen sensor, observe engine data parameter .0.7 with the oxygen sensor disconnected. If the oxygen sensor voltage is less than .37 or greater than .57, the wiring harness must be investigated for defects. If the wiring is OK, then the ECM connector and ECM must be checked because the system is not functioning properly.
If the voltage is between .37 and .57 volts, then jumper the oxygen sensor harness pins together (ECM side) and note the voltage reading. If the voltage reading is greater than .05 volts, then the ECM is not able to recognize that a fault was artificially created. Therefore, either the ECM is not functioning properly or an oxygen sensor circuit is open between the connector and the ECM.
If the voltage reading is less than .05 volts, then the ECM is functioning properly and the harness is OK. The oxygen sensor should be checked using the procedure in CHART 14 - O2 SENSOR TEST .