P0122: How to Diagnose & Fix — Throttle/Pedal Position Sensor/Switch 'A' Circuit Low Input

The electronic throttle module (ETM) on S40/V50 models with the 2.4L non-turbo (B5244S) and early T5 engines fails due to internal solder joint cracking from thermal cycling. The ETM controls the throttle blade electronically, and when it fails, the engine enters limp mode with severely limited power or refuses to rev above idle. The issue primarily affects pre-2008 models, as Volvo updated the ETM design. Volvo issued an extended warranty program for the ETM on affected models. The ETM failure is distinct from the P2 platform (older S60/V70) ETM issue but has similar symptoms.

Many owners of 2000-2011 Rangers report intermittent high idle, unstable idle, or stalling when coming to a stop, often traced to a failing throttle position sensor, dirty or failing idle air control valve, or both. The problem is especially common on older cable-throttle trucks where carbon buildup and sensor wear accumulate with age. Symptoms can be inconsistent, which leads to repeated parts swapping before the root cause is isolated.

First-generation Terrains (2010-2017) are prone to a sudden 'Reduced Engine Power' warning caused by a failing electronic throttle body. Carbon and grime build up inside the bore and the internal throttle position sensor (TPS) fails or reads erratically, causing the ECM to enter a limp/reduced-power mode that limits the vehicle to very low speed. This is a widely reported failure on the naturally aspirated 2.4L four-cylinder and 3.6L V6 engines and frequently appears alongside a 'Service StabiliTrak' message. The most commonly cited trouble code is P2135 (throttle/pedal position sensor voltage correlation). No NHTSA recall covers the throttle body; it is addressed through non-recall repair.

Impalas frequently throw a cluster of warnings at once — 'Engine Power Reduced,' 'Service StabiliTrak,' and 'Service Traction Control' — that are usually one underlying drive-by-wire fault rather than three separate failures. The most common root cause is the electronic throttle body actuator (or the dual throttle-position sensors inside it) going out of range; the accelerator pedal position sensors can also disagree. Because the ECM cross-checks these dual sensors, any disagreement forces the car into limp-home mode with drastically reduced power. Carbon buildup on the throttle plate aggravates it, especially in cold weather.

The CD3 Edge uses a Ford electronic throttle body (ETB) with an integrated throttle position sensor. Non-conductive deposits build up on the internal sensor contacts, so the PCM sees an implausible or drifting throttle plate position and drops the vehicle into failsafe/limp mode - the amber wrench warning lights up and engine output is cut to idle-ish power, often at highway speed with no warning. Owners describe it as the truck 'just quitting on me' merging or passing, sometimes clearing after a key cycle and then recurring more frequently. Cleaning the throttle bore does not fix it because the fault is on the electronic contacts inside the sealed unit, not carbon on the plate. Ford acknowledged the family-wide ETB problem with extended coverage programs on several models, and the failure is heavily represented in NHTSA complaints for the Edge.