What is the 'maximum stop'?

It is the mechanical limit at the far end of travel — the throttle plate's fully open position, or the accelerator pedal's fully depressed position. The module learns what the position sensor reads there so it can turn raw voltage into a percentage of available travel, and it rechecks that learned value whenever something actually goes to the stop. This code means the 'A' channel is not reporting the expected value at that limit. It is the mirror of the minimum stop codes, which check the closed or released end instead.

Why does my car drive fine most of the time?

Because the fault only affects the top of the range and only gets checked when something goes there. Idle, light throttle and normal traffic driving never approach the maximum stop, so everything below about two-thirds throttle behaves exactly as it always did. That is also why the light often comes on during a hard merge or an overtake rather than at start-up — the fault was already present and that was simply the first time the vehicle looked. A car that feels fine is not evidence that the code is spurious.

Will cleaning the throttle body fix P2163?

Probably not, and this is the most common wrong turn on this code. Carbon deposits collect around the plate edge and shaft and physically stop the plate returning to its closed position, which is exactly why cleaning works so well on the minimum-stop codes. Nothing about deposits prevents a plate from opening. Cleaning a dirty throttle body is worthwhile maintenance on its own terms, but if it is being sold to you as the repair for a maximum-stop code, ask what evidence points at it before agreeing.

Can I keep driving with P2163?

The car will usually still drive and steer and brake normally, so it is not a leave-it-at-the-roadside situation — but treat it as urgent rather than as something to live with. The power you have lost is specifically the power you would reach for when merging onto fast traffic or pulling out to overtake, and discovering that at the wrong moment is the real hazard. Drive it gently and directly to a workshop, avoid motorway slip roads and overtaking manoeuvres, and check the pedal area for a trapped floor mat before you set off, since that is both a possible cause and a danger in its own right.

OBD-II trouble code

P2163: Throttle/Pedal Position Sensor 'A' Maximum Stop Performance

The module checked what the 'A' channel reports at the far end of its travel — the wide-open stop — and got a value it does not accept. Idle is untouched, so the car feels perfectly normal until someone actually asks for full power, which is why this fault can sit undetected for weeks.

High severityPowertrainThrottle / IdleDrivable short-term

Quick facts

System: Powertrain
Category: Throttle / Idle
Severity: High severity
Drivable: Usually safe to drive short-term
Repair cost range: $0 – $900
DIY difficulty: Intermediate DIY

Part of a 6-code family

P2163 is one of 6 codes covering throttle/pedal position sensor maximum stop performance. The letter is the slot number your manufacturer assigned — it is not a physical difference, and the same letter means different things on different makes. The diagnosis is the same for every code in the family.

P2163 P2164 P2165 P2166 P2167 P2168

Read the full guide for this family →

Browse every code in P2100–P2199, or start from the full code library.

What does P2163 mean?

A drive-by-wire system has two mechanical references, not one. There is a hard stop that defines fully closed and another that defines fully open, and the module learns the sensor reading at each so it can convert raw voltage into a meaningful percentage of available travel. P2163 sets when the 'A' channel's reading at the maximum stop falls outside the window the module will accept.

The single most useful thing to understand about this code is that it is latent by nature. The closed-position reference is verified constantly — every key-on, every return to idle, dozens of times per journey. The wide-open reference is only verified when something actually travels to the stop, which on a pedal channel means the driver pressing the accelerator to the floor and on a throttle channel means the module commanding the plate fully open. A car driven gently around town may not exercise that end of the range for weeks. So the fault does not develop at the moment the light comes on; it was already there, waiting for the first hard merge or overtake to be discovered.

That changes what the reported symptom looks like. Where a closed-position fault upsets idle and is noticed immediately, a maximum-stop fault takes the top off the range and leaves everything below it feeling ordinary. Owners describe a car that is fine in traffic but will not pull past roughly two-thirds throttle, or that suddenly loses its last portion of power when they ask for it. Because the module has lost confidence in its reading of full driver demand, most vehicles respond by restricting power rather than by guessing, so a reduced-power warning frequently arrives alongside.

It also changes which causes are plausible, and this is where the code most often gets misdiagnosed. 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 in response to a maximum-stop code is a reasonable thing to do for other reasons and a poor bet for this one, and it is worth saying so before a shop sells it as the fix.

What does cause it divides into three groups. First, something physically limiting travel: a floor mat bunched under the accelerator pedal, a failed mat retaining clip, a stray object under the pedal, a damaged or displaced pedal stop, or a throttle plate obstructed at the open end. An obstructed pedal is also a safety matter in its own right and is worth checking before anything else because it costs nothing to look.

Second, a signal path that is fine at rest and fails at full travel. Most of these sensors output a voltage that rises with travel, so the signal is at its highest at the maximum stop, and a resistive joint's voltage drop is proportionally largest exactly there. A corroded terminal, a stretched connector contact or a partly broken conductor can pass every measurement taken with the pedal released and cap the reading at the top. That is why testing this circuit statically proves very little.

Third, a reference the module is holding that no longer matches the hardware. A sensor or throttle body replaced without the relearn procedure, a module reflashed or reprogrammed, a battery disconnection that cleared adaptations, 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 the code appeared immediately after service work or a battery change, run the relearn before buying anything.

One point specific to the 'A' channel. It is the lowest-numbered position channel and is present on effectively every drive-by-wire vehicle, so unlike the higher letters it tells you nothing unusual about how your vehicle is equipped. What it does not tell you is which physical sensor it is: the letter is a slot index the manufacturer assigned, and on some platforms 'A' is the throttle body's own position sensor while on others it is the first track of the accelerator pedal assembly. Confirm which from the wiring diagram for your exact vehicle before ordering a part, because the two repairs have little in common.

Common causes

Floor mat, failed mat clip, or an object under the accelerator pedal limiting its travel
Damaged, displaced or incorrect pedal stop preventing the pedal reaching full travel
Throttle plate obstructed or mechanically limited at the open end of its travel
High resistance in the signal circuit capping the voltage at the top of the range while passing tests at rest
Corroded, spread or backed-out connector terminal at the pedal or throttle body
Sensor track worn or drifted at the upper end of its range
Relearn procedure not performed after a sensor, pedal or throttle body replacement
Adaptations cleared by a battery disconnection or module reflash without a relearn afterwards
Replacement part with a different output slope or range than the original specification
Module holding a calibration for a different pedal or throttle assembly variant
Damaged throttle actuator unable to drive the plate fully open
Low system voltage from a weak battery or failing alternator limiting actuator travel

Symptoms

Reduced engine power warning and a restricted upper throttle range
Car feels normal in traffic but will not pull past roughly two-thirds throttle
Acceleration that falls away at the top rather than being poor from the start
Check engine light that appeared during a hard merge or an overtake
Idle completely normal, which misleads people into looking elsewhere
Hesitation or a flat spot only at or near full pedal travel
Limp mode that clears on a restart and returns the next time full power is asked for
Fault that appeared immediately after a battery replacement or module reprogramming
Another throttle or pedal position code stored alongside it
Cruise control unavailable

Diagnostic steps

1.Check the accelerator pedal area first for a bunched floor mat, a failed mat clip or an object limiting travel. It costs nothing, it is the cheapest possible fix, and an obstructed pedal is a safety issue regardless of the code.
2.Establish from the wiring diagram which physical sensor your manufacturer designates 'A' on this vehicle. It is a slot index, not a location, and on some platforms it is the throttle body sensor while on others it is a pedal track.
3.Ask what happened before the light came on. A recent sensor, pedal or throttle body replacement, a battery disconnection or a module reflash makes a missing relearn the most likely cause and the cheapest to try.
4.Test the battery and charging system. Low system voltage limits actuator travel and produces the same failed full-travel check as a mechanical fault.
5.With the key on and the engine off, read the 'A' channel value while slowly pressing the pedal to the floor and watch for the reading to stop rising before the pedal stops moving.
6.Compare the value at full travel against the specification in service data rather than assuming what a correct number looks like.
7.Perform a voltage drop test on the signal and ground paths with the pedal held at full travel, not at rest. A resistive joint's effect is proportionally largest at the top of the range and is invisible at the bottom.
8.Inspect the connector at the pedal assembly and at the throttle body for corrosion, spread terminals and partly backed-out pins.
9.With the engine off and the connector unplugged, move the throttle plate by hand to the open stop and confirm it reaches it freely without binding or catching.
10.Do not treat a throttle body cleaning as the fix. Deposits stop a plate closing, not opening, so cleaning addresses the closed-position codes rather than this one.
11.Run the manufacturer's relearn procedure and retest before condemning any part.
12.If the reading still caps short of specification after a correct relearn and the wiring is sound, replace the assembly that carries the 'A' channel and relearn again.

Repair cost

$0 – $900

The zero end is genuine and more common than people expect: freeing a bunched floor mat or running the relearn procedure after recent service work resolves a real share of these with no parts at all. Diagnosis is $110 to $220. An accelerator pedal position sensor or complete pedal assembly is $80 to $350 for the part and $160 to $500 fitted. A throttle body assembly is $150 to $600 for the part and $280 to $900 fitted, with European and luxury platforms at the top. Connector or wiring repair is $100 to $400. Budget for a relearn on top of whatever else is done, and be sceptical of a throttle body cleaning quoted as the repair for this particular code.

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DIY vs shop

This is an intermediate DIY job. It usually involves diagnostic steps, specialty parts, and some careful work in tight spaces. If you have the tools and a service manual or trustworthy video for your specific vehicle, it is achievable in a weekend. Otherwise, a competent independent shop will be faster.