P1132

P1132 is the inverse of P1131 — Bank 1 Sensor 1 (upstream, passenger side on most Ford V8s) reads persistently rich without enough switching activity, meaning the PCM is pulling fuel out (negative trim) but the O2 sensor still sees a rich mixture. It is far less common than P1131 because Ford's fuel system rarely over-delivers without a hard fault. Cheapest-first ladder: confirm LTFT Bank 1 — a real rich condition shows LTFT at negative-10 percent or worse (Ford spec is plus or minus 8 percent at idle). Pull the upstream O2 connector and check for engine oil or coolant wicking up the wire from a leaking valve cover gasket or intake — contaminated sensors read falsely rich. Next, check fuel pressure: 4.6L/5.4L 2V Tritons spec 35 to 45 psi key-on engine-off and should hold above 30 psi for five minutes after shutdown; a leaky injector or stuck regulator pushes pressure to 55-plus psi and floods Bank 1 first because the front rail sees pressure first on cross-flow rails. The expensive misdiagnosis is replacing the O2 sensor when the real fault is a leaking fuel pressure regulator dumping fuel into the vacuum line (pull the regulator vacuum hose — if it is wet with gasoline, the regulator is done).

Vehicle-specific patterns: 1996-2003 Ford F-150/Expedition 4.6L/5.4L 2V trucks suffer fuel pressure regulator diaphragm failure that dumps fuel into the intake manifold via the vacuum reference line — pull the line, smell for gas, swap the $35 regulator. 1999-2004 Ford Mustang GT 4.6L 2V cars set P1132 when a stuck-open injector floods cylinder 1 or 5 (Bank 1 front pair); a flow-test at a shop runs $80 to $120 for all eight. 2005-2010 Ford Mustang GT 4.6L 3V engines log P1132 when the variable cam timing (VCT) phaser on Bank 1 fails advanced, altering valve overlap and the resulting exhaust signature — Ford TSB 14-0194 covers the phaser replacement kit. 2001-2007 Ford Escape 3.0L Duratec sets P1132 when a leaking lower intake manifold gasket pulls oil into a cylinder. Estimated repair: $35 to $1,400.