P2104 on Ford

This is one of the best-documented electronic throttle faults in the industry, because NHTSA investigated it and Ford paid for it. Preliminary Evaluation PE13-003, opened February 2013, covered model year 2009-2013 Escape, Mariner, Fusion and Milan vehicles with the 2.5L and 3.0L engines. Ford's analysis, quoted in the closing resume, is that the electronic throttle body's internal motor contacts develop a high-resistance material buildup on the commutator, producing intermittent electrical connectivity to the throttle actuator motor. The motor then fails to drive the plate where the PCM asked it to go. The PCM sets P2111 (Throttle Body Stuck Open) or P2112 (Throttle Body Stuck Closed) as the root cause - about half of the 59,807 warranty ETB replacement claims Ford identified carried one of those two codes - and then commands Failure Mode Effects Management, Ford's name for limp home. The forced-idle branch of FMEM is what logs P2104: engine speed is pinned near 900 RPM, the pedal is ignored, and steering, brakes, lights and climate control keep working so the driver can pull over. Drivers describe it as suddenly losing all power at speed or refusing to accelerate from a stop, usually with the wrench light on, and the fault is often intermittent for weeks before it sticks. Note that on the Escape this is a motor-contact defect, not simply a dirty throttle bore, so cleaning is not the answer here.

Later 4th-generation Explorers with the 4.6L 3-valve V8 commonly suffer electronic throttle body problems. Owners report the wrench light illuminating, the vehicle abruptly entering fail-safe mode, and the engine losing throttle response or dropping to idle while driving. This issue is well documented across Ford products using similar electronic throttle bodies and is frequently associated with internal motor or throttle position sensor faults.

On 2004-2008 F-150s with the 4.6L 2V and 5.4L 3V Triton V8s, P2104 is rarely a standalone fault - it is the failure-management code the PCM sets after it has already decided the electronic throttle body (ETB) cannot be trusted. The F-150 ETB is an integrated unit: throttle plate, DC throttle actuator motor, dual-track throttle position sensor and return spring all live in one housing bolted to the intake. Two things go wrong with it. Carbon and crankcase oil mist from the PCV system coat the bore and the edge of the throttle plate so the plate hangs up and cannot reach the commanded position; and on higher-mileage trucks the brushes and commutator inside the small throttle actuator motor build up resistive deposits, so the motor stalls or moves erratically under command. Either way throttle-position feedback disagrees with the commanded position, the PCM sets P2111 (Throttle Body Stuck Open) or P2112 (Throttle Body Stuck Closed) as the root-cause code, then sets P2104 to record that it has entered Failure Mode Effects Management and forced the engine to idle. F-150 owners report the P2104 + P2111 and P2104 + P2112 pairings consistently on this platform. It is often intermittent at first - the wrench light flashes on a cold start or when merging, then clears on the next key cycle - before it latches. When it latches the plate is held near its default position and the truck will only crawl, which is genuinely dangerous pulling into traffic or towing.

The 2005-2007 Five Hundred, and its Freestyle and Mercury Montego siblings, use a coolant-heated electronic throttle body on the 3.0L Duratec V6 that is unusually prone to internal sludging and actuator failure. Crankcase vapour routed through the intake tract deposits an oily varnish in the throttle bore and around the plate edges, and because the unit is water-jacketed it runs at a temperature that bakes those deposits into a hard film. Ford acknowledged the sludge condition in TSB 09-24-12 for 2005-2007 Freestyle, Five Hundred and Montego vehicles with the 3.0L engine, where the symptom is a low idle with P0505 or P0506 set, and the service procedure is to clean sludge from the edges of the throttle plate and the mating surface of the bore. Left alone the condition escalates: the plate binds hard enough that the actuator motor can no longer position it against the return spring, or the motor itself gives up. At that point the PCM's commanded-versus-actual throttle comparison fails, it forces the engine to idle and logs P2104. Owner complaints collected on CarComplaints from NHTSA describe exactly this - a 2005 Five Hundred owner lost power, pulled P2104 along with a partner throttle code, and had the dealer replace the throttle body at roughly $690 in parts plus labor. Because the same platform is also known for surging, hesitation and no-start complaints traced to the same throttle body, a Five Hundred that idles poorly or surges is giving warning well before it strands you.