Oxygen Sensor Relay: Testing and Inspection

Relay Terminal Identification:

OXYGEN SENSOR HEATER RELAY TERMINAL IDENTIFICATION
The following is a list of the terminal numbers, with circuit codes, and color codes, and their function:

Circuit No. Terminal No. Color Code Description

F22 4 OR/BK This circuit provides a switched voltage source to the fuel pump (bypassing the ballast resistor).

F86 2 GY/YL This circuit is the voltage source for the oxygen sensor heater relay, from the ECU.

F22 1 OR This circuit provides voltage to the fuel pump via the ballast resistor.

63 3 OR This circuit provides battery input voltage to the oxygen sensor heating element.

11 5 YL This circuit provides the ground path for the oxygen sensor heater relay to the ECU.


OXYGEN SENSOR HEATER RELAY TEST

NOTE: The oxygen sensor heater relay operation may be tested with the use of the DRB II scanner or equivalent. Scan Tool Testing and Procedures
If no scanner is available proceed with the following test.

NOTE: The fuel system wiring diagrams should be used in conjunction with the following test to correctly diagnose the problem.

1. Pull the oxygen sensor heater relay out of its connector and connect a voltmeter to the Orange F22 wire (terminal 1). With the engine running, or for 2 to 3 seconds while starting, battery voltage should be present at this terminal. If no voltage is present, refer to FUEL PUMP RELAY TEST. If voltage is present proceed to step 2.
2. Connect the voltmeter to the OR/BK F22 wire (terminal 4) at the oxygen sensor heater relay connector. Turn the ignition key to the START position and crank the engine. If output voltage is present during cranking, or wide open throttle, the oxygen sensor heater relay is functioning normally and no further testing of the oxygen sensor heater relay is necessary. If no voltage is present at the OR/BK F22 wire, proceed to step 3.
3. Connect the voltmeter to the GY/YL F86 wire (terminal 2) at the oxygen sensor heater relay connector. Turn the ignition key to the RUN position, wait for 5 seconds, and check for voltage. If voltage is present, go to step 4. If no voltage is present, pull the oxygen sensor heater relay out of its connector and connect an ohmmeter across the F86 and 11 terminals of the relay, and check for continuity. If continuity exists, repair the 11 circuit between the oxygen sensor heater relay and terminal B8 of the ECU. If no continuity exists, replace the oxygen sensor heater relay and retest its operation.
4. Disconnect the 24-Way and 32-Way ECU electrical connectors, and connect an ohmmeter between the F86 wire (terminal 2) of the oxygen sensor heater relay connector and terminal A7 at the ECU, and check for continuity. If continuity exists, the problem is computer related. Testing and Inspection
If no continuity exists, repair open in wire and retest the operation of the oxygen sensor heater relay.

NOTE: If the there is continuity between circuits 11 and F86, and voltage is not present at F86 (there is voltage at the oxygen sensor heater relay on circuit 11 with circuit 11 disconnected from oxygen sensor heater relay), then the ECU may be grounding the oxygen sensor heater relay continuously through circuit F86.