P2122 code: Pedal Position Sensor/Switch D Circuit Low
P2122 means pedal Position Sensor/Switch D Circuit Low. The code says where to look, not what failed — the fix depends on which cause your car actually has.
What P2122 means
Drive-by-wire cars have no throttle cable — the accelerator pedal contains two (sometimes three) position sensors, and the computer compares them constantly. P2122 means the signal from pedal sensor D is stuck below its valid range, essentially reading 'less than zero throttle.' That points to an electrical problem: an open signal wire, a lost 5-volt reference, a dirty or corroded connector at the pedal, or a failed sensor inside the pedal assembly. Because the redundant sensor no longer agrees, most cars respond with reduced-power mode, and some will ignore the pedal entirely and idle only. The pedal sensors are almost always built into the pedal assembly, which is usually a simple unbolt-and-plug replacement — but check the connector first, since that's the cheap and common fix.
P2122 symptoms
- Reduced-power or 'limp' mode
- Pedal that feels dead or unresponsive
- Car may only idle regardless of pedal input
- Intermittent hesitation or power loss
- Check-engine light
What it costs to fix P2122
Typical range: $40–$450 · about ~0.3–1 hrs of labor
| If the cause is… | Part | Labor |
|---|---|---|
| Connector cleaning / minor wiring repair | $5–$80 | ~0.3–1 hrs |
| Accelerator pedal assembly | $80–$300 | ~0.3–1 hrs |
The pedal assembly is one of the easier drive-by-wire parts to replace — typically a few bolts and one connector under the dash — so labor stays low. The spread is mostly in the part price, and a connector cleaning sometimes fixes it for nearly nothing.
The price swings on which cause it turns out to be — so confirm the cause before paying. Diagnose P2122 for my exact vehicle →
How to fix P2122
Easy — basic tools, most owners can do this
- See whether P2127 or other pedal codes set too
Pedal sensor D failing alone points to its own signal, reference, or ground circuit. If the companion sensor E code or other pedal faults appear at the same time, the shared connector, harness, or a reference supply is far more likely than two sensors dying together.
- Inspect the pedal connector for wet carpet and corrosion
The pedal connector sits low in the footwell, so check the carpet for dampness from wet shoes or a cowl or windshield leak. Unplug the connector and look for green corrosion, moisture, or a loose latch; cleaning and reseating it fixes a good number of these codes.
- Back-probe sensor D's reference and ground
With the key on, check sensor D's reference pin for roughly 5 volts and its ground pin for near zero to battery negative. If the reference is missing, unplug the pedal and measure again at the harness: still missing means the wiring or computer supply, and a short elsewhere on that reference can be pulling it down.
- Watch sensor D as the pedal leaves its rest position
Graph sensor D on a scan tool and press the pedal slowly from rest. The wiper inside the pedal spends most of its life at the rest position, so that's often where the track wears first; a dropout toward zero volts at or just off rest, with good wiring, confirms the sensor inside the pedal.
- Swap the accelerator pedal assembly
With wiring and reference proven good, replace the pedal assembly — the sensors are built in. It usually mounts with a few nuts or bolts under the dash. Clear codes, cycle the key, and follow any pedal or throttle learn in the service manual before confirming full power is back.
DIY or shop? P2122 is very approachable at home: the connector sits under the dash, the voltage checks need only a multimeter, and replacing the pedal is a short job with hand tools. Make sure the wiring tests good first, because a new pedal won't fix a missing reference. A shop earns its fee when the reference is being pulled low by another component or a hidden harness fault, or when the car won't leave reduced-power mode without a dealer-level relearn. If the car will only idle, tow it.
Tools for the DIY steps: Digital multimeter with back-probe pins · Scan tool that graphs pedal sensors · Electrical contact cleaner · Basic socket set · Flashlight for under-dash work
Not sure which step applies to your car? Get the likely cause for your exact vehicle before buying anything for P2122.
Start a case with P2122 and your car. Redline weighs these causes against what your car shows, and names the check that would settle it before you buy parts.
Can I drive with P2122?
Redline can’t determine from a symptom or code alone whether your car is safe to drive.
P2122: common questions
Why does my gas pedal feel dead with P2122?
The computer only opens the throttle when both pedal sensors agree on what your foot is doing. With sensor D reading below its valid range, the computer stops trusting the pedal and limits or ignores it — that's the dead-pedal feeling.
Is P2122 the pedal or the wiring?
Both are common. A corroded or loose connector at the pedal produces exactly this code and costs almost nothing to fix, so inspect and clean it first. If the connector and wiring check out, the sensor inside the pedal assembly has likely failed.
Can I replace just the sensor instead of the whole pedal?
On nearly all vehicles, no — the sensors are sealed inside the pedal assembly and it's replaced as one unit. Fortunately it's usually an inexpensive, quick job compared to most drive-by-wire repairs.
What's the difference between P2122 and P2127?
Same fault, different sensor: P2122 is pedal sensor D reading too low, P2127 is pedal sensor E reading too low. D and E are the two redundant sensors in the same pedal assembly, so the diagnosis and repair are essentially identical.
Related trouble codes
Don’t have a scanner yet? A ~$25 Bluetooth adapter reads codes like P2122 from your phone. See our guide to the best OBD2 Bluetooth adapters. Run a repair shop? See Redline for shops.
Generic OBD-II reference. Manufacturer-specific behavior varies. Confirm with a scan tool and, for safety-related codes, a professional inspection. Cost ranges are reference ranges, not quotes.
Seeing P2122 on your car?
Every problem becomes a Case. Tell Redline what the car is doing: it shows what the evidence supports, what’s still missing, and what to check next, before you approve a repair.
“Inner pad ~1 mm. Outer pad 3 mm.”
Next: check the slide pins move freely before buying parts.