P2122 Code: Accelerator Pedal Position Sensor D Circuit Low
The main gas pedal sensor reads close to 0 volts, below anything a working pedal produces at rest.
At a glance
Severity: Moderate
- Meaning
- Accelerator Pedal Position Sensor D Circuit Low
- System
- Speed & Idle Control · Powertrain
- Safe to drive?
- With caution
- Typical repair cost
- $0–$450
- DIY difficulty
- Moderate
Pedal sensor D should never read zero: even with your foot off the pedal it normally sits somewhere between about 0.4 and 1.0 V. P2122 sets when the D signal drops below the PCM's lower limit, commonly around 0.2–0.3 V, for longer than a moment. A low reading means the sensor output is being pulled toward ground or has lost its supply. That can be the 5-volt reference to D being open, the D signal wire shorted to ground, the pedal connector not seated, or the sensor's electronics dead; many newer pedals use non-contact Hall or inductive sensors that fail electrically rather than by wear. Since sensor E still works, most cars keep driving in a restricted mode, but if E is also low at the same moment the fault is almost certainly a shared supply or connector.
Can I keep driving? Drive slowly and only as far as needed. The PCM relies on sensor E alone and limits power; if E also fails, the engine drops to idle.
How to read P2122
- P Powertrain
- 2 Generic (SAE)
- 1 Fuel & air metering
- 22 Specific fault
Symptoms
- Check engine light and reduced-power or limp mode
- Pedal D shows 0–0.2 V in live data while pedal E looks normal
- Gas pedal responds only slowly and the car won't accelerate hard
- Engine falls back to idle when the brake is pressed
- P2138 stored at the same time because D and E no longer agree
Possible causes
Ranked by how often each cause is behind this code (editorial estimate).
- Pedal sensor D failed internally (open track or dead Hall element)
- Open or loose 5-volt reference to sensor D at the pedal connector
- D signal wire rubbed through to ground near the pedal bracket or steering column
- Pedal connector not latched after dash, pedal or footwell work
- Reference pulled low by another sensor on the same 5-volt circuit
- PCM reference output or input fault
Diagnosis step by step
Compare D and E and look for other 5-volt codes
Key on, engine off, read both pedal sensors. D near zero with E normal points at D's own circuit or the pedal. If E is also low, or codes for throttle position, MAP or other 5-volt sensors are stored, suspect a shared reference before touching the pedal.
Tools: OBD-II scanner
Back-probe all three D pins at once
With the pedal plugged in and the key on, measure reference, ground and signal of sensor D. Reference around 5 V, ground near 0 V and signal near 0 V means the pedal isn't producing an output. Reference near 0 V means the supply never reaches the pedal.
Tools: Multimeter
Trace a missing reference
If D's reference is missing, unplug the pedal and measure again. Still zero means an open wire between the PCM and pedal or a supply pulled down elsewhere. Unplug the other sensors sharing that reference one at a time; if the voltage returns, the last one unplugged is shorting it.
Tools: Multimeter
Check the signal wire for a short to ground
Disconnect the battery, unplug the pedal and the PCM connector, then measure resistance from the D signal wire to chassis ground. It should be open; a reading of a few ohms means the insulation is damaged. Look where the harness passes the pedal bracket and column supports.
Tools: Multimeter, Flashlight
Replace the pedal and confirm the curve
If reference and ground are good and the signal stays at zero, replace the pedal module. Afterwards, D should read its rest value and rise smoothly as you press the pedal, with E following at its own ratio.
Tools: Screwdriver, OBD-II scanner
Where the parts are
- 1Ignition coil
- 2Spark plug
- 3Fuel injector
- 4Camshaft sensor
- 5Crankshaft sensor
- 6Engine computer (ECM)
- 7Intake manifold
Repair options & costs
| Repair | DIY? | Estimated cost |
|---|---|---|
| Seat and lock the pedal connector | Yes | $0–$60 |
| Replace accelerator pedal module | Yes | $150–$450 |
| Repair open reference or grounded signal wire | No | $120–$380 |
| Replace a shorted sensor that was loading the shared reference | Yes | $80–$350 |
Rough US estimates for parts and labor; shop rates vary by region. Not a quote.
Notes by brand
Field data
| Chevrolet | 15 | Impala, Malibu Eco, Avalanche | |
|---|---|---|---|
| Jeep | 4 | Cherokee, Renegade | |
| Dodge | 3 | Dart, Durango | |
| Ford | 2 | F-150 SUPERCAB, Freestyle |
Source: NHTSA Complaints API (US government open data), analyzed by DTC mention.
Emissions / smog test impact
Will fail
P2122 lights the check engine light, which means an OBD-II emissions test fails. If a shared 5-volt reference was the cause, make sure all related sensor codes are gone too.
Frequently asked questions
Why does my car still drive with a dead pedal sensor?
The pedal has a second sensor, E, that the PCM can fall back on. It lets you move, but with slow throttle response and limited power, because there's no longer a second opinion to confirm the pedal position.
Is P2122 the same as P0122?
No. P0122 is the throttle position sensor on the throttle body, P2122 is the gas pedal sensor under the dash. They can appear together when they share a 5-volt reference, which is a strong clue to check that supply.
Can I test the pedal with an ohmmeter?
Only older contact-type pedals, where the track resistance changes as you press. Many newer pedals use Hall or inductive sensors with electronics inside, so they can only be judged by their voltage output with the connector plugged in.
The code appeared after I replaced a floor mat. How?
Pulling mats and carpet in and out can tug on the pedal harness or knock the connector loose. Check that the connector is fully seated and locked before anything else.