P0132

P0132 is the inverse of P0131 — bank 1 upstream sensor signal is pinned HIGH (over ~0.95V on a narrow-band, or above the AFR sensor's rich threshold on a wideband). The ECU sees a permanently-rich exhaust and will start subtracting fuel via negative fuel trim. Cheapest-first ladder: scan fuel trims first. If STFT + LTFT are pegged at -15 to -25%, the engine really IS running rich (leaking injector, stuck-open EVAP purge solenoid, failing fuel pressure regulator dumping fuel through the vacuum line, or saturated charcoal canister flooding the intake on a hot soak). If fuel trims look reasonable, the sensor signal is being driven high by something electrical: most commonly a short between the signal wire and the sensor heater B+ feed, especially where the wires share a connector body that's been heat-cycled. Backprobe the signal at the ECU — key-on engine-off it should sit at ~0.45V bias; if you see anything above 1.0V (impossible from a zirconia element), the harness is shorted to power upstream.

Vehicle-specific patterns: 2004-2011 Dodge Ram / Durango with the 4.7L magnum throws P0132 from fuel-soaked spark plugs after a leaking injector pintle floods cylinder 1 or 3 on hot restart — Mopar TSB covered injector replacement. 2007-2012 Nissan Altima / Sentra with the QR25DE throws P0132 from a saturated EVAP canister (gas station overfill is the trigger) venting raw fuel vapor into the intake. 2005-2010 Toyota Tacoma / 4Runner with the 1GR-FE occasionally sets P0132 when the fuel pressure regulator diaphragm tears and dumps fuel through the vacuum reference line — easy check is to pull the FPR vacuum hose and look for liquid fuel. 2006-2013 Chevy Impala / Malibu 3.5L/3.9L V6 throws P0132 after a coolant-intrusion event on the upstream sensor (intake manifold gasket failing). Cost band: $180-$400 for the sensor itself; $400-$1,200 if a leaking injector or FPR is the actual cause.