1. Inspect Air-Fuel Ratio Compensation System

HINT:

The system can be also checked by choosing "DATA MONITOR/O₂ SENSOR OUTPUT VOLTAGE" on the hand-held tester monitor.

Connect the hand-held tester to terminals 23 (OXL1) and 7 (E1) and to terminals 21 (OXL2) and 7 (E1) of the ECM.
CAUTION: Connect test leads from the back side of the connector with the ECU connected.

Fig 1: Identifying ECM Connector Terminals
Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
Warm up the heated oxygen sensor at 2,500 RPM of the engine speed for approximately 2 minutes.
Confirm that the voltage varies between 0V and 1V at 2,500 RPM of the engine speed.
OK: The voltage varies more than 8 times in 10 seconds.

CAUTION:

Perform the check immediately after warming up.
If the voltage variation could not be verified, warm up the heated oxygen sensor again.