Quick answer: The ECU sees an implausible signal-circuit problem at the Bank 1 Sensor 3 oxygen sensor, usually a rear-most catalyst-monitor sensor on systems that use one.
Drivers also search this fault as bank 1 sensor 3 circuit, rear-most O2 sensor circuit bank 1, downstream oxygen sensor circuit bank 1 sensor 3.
P0142 points to the signal side of Bank 1 Sensor 3. On vehicles that actually use a third oxygen sensor on Bank 1, this is usually a far-downstream sensor used to monitor catalyst behavior after an additional converter stage. The trap is treating it like an ordinary upstream fuel-control O2 code. In practice, P0142 is much more often about rear-sensor credibility, wiring integrity, and catalyst-monitor logic than about a direct drivability problem.
P0142 is often driveable short-term because it usually does not create strong drivability symptoms, but emissions readiness and catalyst-monitor logic stay unreliable until the rear-most Bank 1 sensor path is fixed.
Cause phrases often tied to this code: bank 1 sensor 3 wiring fault, rear-most O2 sensor failure, connector corrosion, exhaust heat damage, post-catalyst monitor issue.
Brand hubs help broaden internal linking now and can evolve into make-specific diagnostic notes later.
Useful when the driver knows the wording but not the exact DTC yet.
No. Many vehicles stop at Sensor 2. P0142 only applies on platforms that use a third oxygen-sensor location on Bank 1.
Usually not by itself. It is commonly a rear-sensor circuit and catalyst-monitor credibility problem.
Yes. Rear-sensor wiring and connectors are easy to disturb during catalyst or exhaust replacement.