What Does P2123 Mean?
The PCM has detected that the voltage signal from accelerator pedal position sensor 'D' is above the acceptable maximum threshold. This indicates an open circuit, short to voltage, or sensor failure causing abnormally high voltage reading.
Safety Warning
Vehicle will activate limp mode with severely restricted or no throttle response. Engine may idle only or refuse to rev. Unsafe to operate; immediate repair required.
Common Causes
35%
Open circuit in accelerator pedal position sensor 'D' signal or ground wire
30%
Failed accelerator pedal position sensor with internal open circuit
25%
Damaged connector with backed-out pins or poor terminal contact
10%
Short to voltage (reference voltage or battery voltage) in sensor circuit
Diagnostic Steps
1
Step 1: Disconnect accelerator pedal position sensor and measure sensor 'D' output voltage at sensor connector (sensor side); check for proper reference voltage
2
Step 2: Check for open circuits by measuring continuity between sensor connector and PCM connector on signal and ground wires (key off, disconnected)
3
Step 3: Inspect connector terminals for backed-out pins, corrosion, or spread female terminals preventing proper contact
4
Step 4: With sensor connected, backprobe signal wire and verify voltage does not exceed approximately 4.5-4.8V at full pedal depression
5
Step 5: Replace accelerator pedal position sensor if circuit integrity is confirmed but sensor output is out of range
Estimated Repair Cost
$120 - $650
Parts + labor, varies by vehicle and location
The PCM has detected that the voltage signal from accelerator pedal position sensor 'D' is above the acceptable maximum threshold. This indicates an open circuit, short to voltage, or sensor failure causing abnormally high voltage reading.
The most common cause of P2123 (Throttle/Pedal Position Sensor/Switch "D" Circuit High) is: Open circuit in accelerator pedal position sensor 'D' signal or ground wire
Typical repair costs for P2123 range from $120 to $650, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Vehicle will activate limp mode with severely restricted or no throttle response. Engine may idle only or refuse to rev. Unsafe to operate; immediate repair required.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P2123 to identify the root cause.
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Quick Info
Category
Powertrain
System
Electronic Throttle Control
Difficulty
Type
Generic (SAE)
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