Diagnosis & Repair

WARNING: This page is about a different car, the 2003 Lexus RX 300. However, it is still accessible from the selected car via links, so may be relevant.

Remove the glove compartment. Turn the ignition switch ON. Measure the voltage between terminal HTS of the ECM connector and body ground. See Fig 1. If voltage is 9-14 volts, check and replace ECM. If not, go to next step.

Fig 1: Checking Voltage At ECM HTS Circuit
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Check resistance of heated oxygen sensor heater. See SENSOR OPERATING RANGE CHARTS article. Replace sensor as necessary. If sensor is okay, check and repair harness or connector between EFI relay and heated oxygen sensor, and heated oxygen sensor and ECM.