1JZ-GTE Check Engine Light - Understanding Single O2 Sensor Configuration

Electricalbeginner✓ OP Confirmed

Problem

Owner of a JDM JZA70 with 1JZ-GTE had a check engine light on and discovered a cut downstream oxygen sensor with wires to the ECU missing. The ECU pinout only showed one O2 sensor pin, causing confusion about whether it served both upstream and downstream sensors.

Check engine light onCut downstream O2 sensor wires found after catalytic converterMissing wires from downstream O2 sensor to ECUOnly one O2 sensor pin on ECU pinout diagram

Root Cause

The previous owner had installed an exhaust system from a different (likely OBD2) vehicle that included a second O2 sensor bung after the catalytic converter. The 1JZ-GTE is not an OBD2 vehicle and only uses a single narrowband O2 sensor located in the Y-pipe between the turbos. The cut downstream sensor was irrelevant to the car's system and was causing diagnostic confusion.

Confidence

Low confidence — Original poster confirmed this resolved the issue

View Original Thread →Posted September 2019 on SupraForums.com