Throttle/Pedal Position Sensor Maximum Stop Performance (P2163–P2168)

What these codes mean

This family is the mirror image of the minimum stop codes, and the difference between the two is worth understanding before any money is spent, because it changes which repairs make sense.

A drive-by-wire system has two mechanical references, not one. There is a hard stop that defines the throttle plate fully open and the accelerator pedal fully depressed, and another that defines fully closed and fully released. The module learns the sensor reading at each so it can turn a raw voltage into a meaningful percentage of available travel. The minimum stop codes say the closed reference is wrong. These codes say the open one is.

The first consequence is that these faults are latent, and that is the single most useful thing to know about them. The closed reference is verified constantly — at every key-on, every time the engine returns to idle, dozens of times per journey. The open reference is only verified when something actually travels to the stop, which means a driver pressing the accelerator to the floor or the module commanding the plate fully open. A car driven gently around town may not visit that end of the range for weeks. So the fault does not begin when the warning light appears; it was already there, and the first hard merge or overtake is simply when the module got around to looking.

That also explains the complaint these codes generate. A closed-position fault upsets idle and gets noticed within a mile. A maximum-stop fault takes the top off the range and leaves everything below it feeling entirely normal, so owners describe a car that is fine in traffic but refuses to pull past roughly two-thirds throttle, or that suddenly runs out of power exactly when they ask for it. Most vehicles respond by restricting power rather than by guessing at driver demand they cannot verify, so a reduced-power warning usually arrives with it.

The second consequence is that the causes are not the same as the minimum stop family's, and one substitution in particular wastes money. Carbon in the throttle bore is the headline cause of the closed-position codes because deposits physically prevent the plate returning to its stop. Deposits do not prevent a plate from opening. Cleaning a throttle body is worthwhile maintenance on its own terms and a poor bet as the repair for one of these codes, and it is fair to ask a shop what evidence points at it before agreeing.

What does cause them falls into three groups. Something physically limiting travel — a floor mat bunched under the accelerator, a failed mat retaining clip, a stray object, a damaged or displaced pedal stop, a plate obstructed at the open end. This deserves to be checked first on every one of these codes: it costs nothing, it is the cheapest possible fix, and an obstructed pedal is a safety problem regardless of what the scan tool says.

Second, a signal path that is sound at rest and fails only at full travel. These sensors output a voltage that rises with travel, so the signal is at its highest at the maximum stop, and the voltage drop across a resistive joint is proportionally largest exactly there. A corroded terminal, a spread connector contact or a partly broken conductor can pass every measurement taken with the pedal released and still cap the reading at the top of the range. Testing one of these circuits statically proves very little; the measurement that matters is a voltage drop taken with the channel held at full travel.

Third, a stored reference that no longer matches the hardware. A sensor, pedal assembly or throttle body replaced without the relearn procedure, a module reflashed, a battery disconnected, or a part fitted with a different output slope than the original all leave the module comparing live readings against a learned value that no longer applies. If one of these codes appeared immediately after service work or a battery change, run the relearn before buying anything at all.

The letter is the part people over-interpret. A through F identifies which position channel failed the check, and it is a slot index the manufacturer assigned rather than a description of a location. There is no cross-industry table mapping letters to physical sensors, and the wiring diagram for your exact year, make, model and engine is the only authority. What the letters do reveal collectively is how much position sensing your vehicle carries: four channels — two redundant tracks on the pedal and two on the throttle body — is the mainstream arrangement, so a code naming a fifth or sixth channel means either an unusually well-equipped vehicle, a second throttle assembly, or a module carrying a calibration for a variant your car is not. Because F is the last slot the enumeration provides, a vehicle that genuinely uses it has every available channel in service, and counting the position parameters the module publishes in live data is the quickest way to find out whether yours does.

There is a fast way to work out which assembly a channel belongs to without opening a diagram. Watch which channels move during the key-on self-test sweep, with nobody touching the pedal. Those are throttle body channels. The ones that only move when the pedal moves are pedal channels. On a four-channel system that identifies the side in seconds, and on these codes the side is most of the repair decision.

Treat these as urgent rather than as an emergency. The vehicle will normally still drive, steer and brake, so it is not a roadside situation — but the power that has gone is specifically the power you would reach for merging into fast traffic or pulling out to overtake, and discovering the shortfall in the middle of the manoeuvre is the genuine hazard. Drive gently and directly to a workshop, skip the slip roads and the overtakes, and check under the pedal for a trapped mat before setting off.