Is 'C' the pedal sensor or the throttle body sensor?

It depends entirely on the vehicle, and this is the one code in the family where that ambiguity really costs money. A typical system has four channels — two redundant tracks on the pedal and two on the throttle body — and the third letter is where the numbering often crosses from one assembly to the other. Which way round it goes is the manufacturer's choice, and there is no industry table to consult. Find it in the wiring diagram for your exact vehicle, or identify it by watching which channels move during the key-on throttle sweep with the pedal untouched.

Why does the car feel fine until I floor it?

Because the fault only affects the far end of the travel, and the far end is only verified when something actually goes there. Idle, town driving and light throttle never approach the maximum stop, so everything below roughly two-thirds throttle behaves normally. The code usually appears during a hard merge or an overtake, which is not when the problem began — it is the first time the module checked that end of the range and did not like the answer.

Will cleaning the throttle body help?

It is unlikely to fix this code, whatever it may do for general maintenance. Carbon deposits build up around the throttle plate edge and shaft and physically prevent the plate from returning to its closed position, which is why cleaning is so effective on the minimum-stop codes. Deposits do not prevent a plate from opening. If a cleaning is being quoted as the repair for a maximum-stop code, it is fair to ask what evidence points at it before agreeing to pay for it.

Can I keep driving with P2165?

The car will usually still drive, steer and brake normally, so this is not a roadside emergency, but do not treat it as something to live with. The power that has gone is exactly the power you would reach for merging into fast traffic or pulling out to overtake, and discovering the shortfall mid-manoeuvre is the genuine risk. Drive gently and directly to a workshop, avoid slip roads and overtakes, and look under the pedal for a trapped mat before setting off, since that is both a possible cause and a hazard by itself.

OBD-II trouble code

P2165: Throttle/Pedal Position Sensor 'C' Maximum Stop Performance

The full-travel check failed on the 'C' channel. 'C' is the letter where the numbering most often crosses from one assembly to the other — the point at which the pedal side ends and the throttle body side begins, or the reverse — so working out which unit you are actually in matters more here than anywhere else in the family.

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

P2165 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 P2165 mean?

P2165 sets when the 'C' position channel reports a value at the wide-open mechanical stop that the module will not accept.

Every drive-by-wire system references two mechanical limits. One hard stop defines fully closed, another defines fully open, and the module learns the sensor reading at each so it can express live position as a percentage of available travel. This code concerns the open limit.

As with every maximum-stop code, the fault is latent rather than sudden. The closed reference gets checked at every key-on and every return to idle; the open reference is only checked when something actually travels there. That is why these codes so often appear during a hard merge or an overtake in a car that had been behaving perfectly — the fault was present the whole time and that was simply the first occasion the module looked.

Where 'C' differs is in how much uncertainty the letter carries, and this is the point worth taking seriously before anything is ordered. A modern system commonly has four position channels: two redundant tracks on the accelerator pedal assembly and two on the electronic throttle body. The manufacturer assigns letters to those four slots, and the third letter is where the numbering most often crosses the boundary between one assembly and the other. On a vehicle that lettered the pedal tracks 'A' and 'B', 'C' is likely the first throttle body channel. On a vehicle that started at the throttle body, 'C' is likely the first pedal track. On platforms with three tracks on a single assembly, 'C' is simply the third track of that unit and no boundary is crossed at all.

The practical consequence is that the two most plausible repairs for this code — an accelerator pedal assembly and an electronic throttle body — are entirely different parts in different places at different prices, and the code number does not distinguish them. There is no cross-industry table mapping letters to physical sensors. The wiring diagram for your exact year, make, model and engine is the only authority, and reading it first is not thoroughness for its own sake here; it is the difference between a correct repair and an expensive wrong one.

There is a diagnostic shortcut worth trying before the paperwork. Work out which side the channel is on by what moves it. A pedal channel changes only when the pedal is pressed. A throttle body channel changes when the module commands the plate, which on most vehicles happens at key-on during the self-test sweep with nobody touching the pedal at all. Watching which channel moves during that sweep, with the pedal untouched, identifies the assembly in a few seconds.

Beyond the identification question, the causes follow the rest of the family. Something physically limiting travel: a bunched floor mat, a failed mat retaining clip, an object under the pedal, a damaged pedal stop, or a throttle plate obstructed at the open end. A signal path that is sound at rest and fails at the top of the range, because these sensors output a rising voltage and a resistive joint's voltage drop is proportionally largest exactly where the signal is highest — which is why a circuit that passes every test with the pedal released can still cap the reading at full travel. And a stored reference that no longer matches the hardware after a replacement, a reflash, a battery disconnection, or a part fitted with a different output slope.

Carbon in the throttle bore is not on that list, and the omission is deliberate. Deposits stop a plate returning to its closed position, which is why cleaning resolves so many minimum-stop codes. Nothing about deposits prevents a plate from opening, so a cleaning offered as the repair for this code deserves a question about what evidence points at it.

Common causes

Worn or drifted 'C' sensor track at the upper end of its range
High resistance in the 'C' signal circuit capping its voltage at full travel but not at rest
Corroded, spread or backed-out terminal on the 'C' pin at the pedal or throttle body connector
Floor mat, failed mat clip or an object under the accelerator pedal limiting travel
Damaged or displaced pedal stop preventing the pedal reaching full travel
Throttle plate obstructed or mechanically limited at the open end
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
Wrong pedal or throttle assembly variant fitted, so the module's expected range does not match the hardware
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 with a capped upper throttle range
Normal behaviour in traffic, with nothing available past roughly two-thirds throttle
Check engine light that appeared during a hard merge or an overtake
Idle and light-throttle driveability completely unaffected
Hesitation or a flat spot confined to the last part of pedal travel
Limp mode that clears on a restart and returns the next time full power is requested
Other throttle or pedal position codes stored at the same time
Fault that followed a pedal assembly, throttle body, battery or module replacement
Cruise control unavailable
Throttle response that feels capped rather than slow

Diagnostic steps

1.Identify which assembly the 'C' channel lives on before anything else. On a four-channel system the third letter is where the numbering commonly crosses from the pedal to the throttle body or the reverse, and the two repairs have nothing in common.
2.Use the key-on self-test to identify it quickly: watch which channels move while the module sweeps the throttle plate with nobody touching the pedal. Those are throttle body channels; the ones that only move when the pedal moves are pedal channels.
3.Confirm that finding against the wiring diagram for your exact year, make, model and engine. There is no industry-standard mapping of letters to sensors.
4.Check the accelerator pedal area for a bunched floor mat, a failed mat clip or an object limiting travel. It is free to look and it is a safety issue in its own right.
5.Ask what preceded the fault. A recent replacement, reflash or battery disconnection makes a missing relearn the cheapest and most likely explanation.
6.Test the battery and charging system, since low system voltage limits actuator travel and produces the same failed check as a mechanical fault.
7.With the key on and the engine off, graph every available position channel together while pressing the pedal slowly to the floor, and watch for the 'C' trace to stop rising before the others do.
8.Compare the 'C' value at full travel against the specification in service data rather than against what looks plausible.
9.Perform a voltage drop test on the 'C' signal and its ground with the channel held at full travel, not at rest.
10.Inspect the connector at whichever assembly the channel belongs to, with attention to the specific pin rather than a general look.
11.Run the manufacturer's relearn procedure and retest before condemning a part.
12.If the reading still caps short of specification after a correct relearn with sound wiring, replace the assembly carrying the 'C' channel and relearn again.

Repair cost

$0 – $900

The spread here is mostly about which assembly the channel turns out to be on, which is exactly why identification comes before ordering. Diagnosis is $110 to $220. A trapped floor mat or a missing relearn costs nothing in parts. Connector or wiring repair is $100 to $400. An accelerator pedal position sensor or complete pedal assembly is $80 to $350 for the part and $160 to $500 fitted. An electronic throttle body is $150 to $600 for the part and $280 to $900 fitted, with European and luxury platforms at the top of that. Getting the assembly wrong is the characteristic expensive mistake on this specific code, so the wiring diagram is the cheapest tool in the job.

Estimate your repair

Run the numbers for your vehicle

Open the Repair Cost Estimator with throttle body replacement preselected. Adjust labor rate and vehicle category to fit your situation.

Estimate your repair cost

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.