3-90 FUEL SYSTEM (DFI)
Oxygen Sensor Heater (Service Code 67)
Disconnect the oxygen sensor lead connector and con-
nect the measuring adapter [A] between these connec-
[B] Main Harness
[C] Oxygen Sensor
Special Tool - Measuring Adapter: 57001-1700
Connect a digital meter [D] to the measuring adapter lead.
Oxygen Sensor Power Source Voltage
Connections to Adapter:
Digital Meter (+) → Y (sensor P/BK) lead
Digital Meter (–) → Battery (–) terminal
Measure the power source voltage with the engine
stopped and with the connector joined.
Turn the ignition switch to ON.
Power Source Voltage
Standard: Battery Voltage
Turn the ignition switch to OFF.
If the reading is in specification, but the problem still ex-
ists, replace the ECU (see ECU Removal/Installation).
If the reading is out of the standard, check the following.
ECU Fuse 15 A (see Fuse Inspection in the Electrical
Power Source Wiring (see Oxygen Sensor Circuit)
If the fuse and wiring are good, remove the ECU and
check the wiring for continuity between main harness con-
Disconnect the ECU and sensor connectors.
ECU Connector [A] ←→
Oxygen Sensor Connector [B]
P/BK lead (ECU terminal 64) [C]
If the wiring is good, check the ECU for its ground and
power supply (see ECU Power Supply Inspection).
If the ground and power supply are good, replace the ECU
(see ECU Removal/Installation).