Throttle/Pedal Position Sensor A Circuit Low Input
TPS circuit voltage is below expected range.
SeverityCritical
CategoryEngine
Est. Repair Cost$100–$400
Code TypePowertrain
DIY RepairYes
DifficultyIntermediate
⚡ Common Causes
›Short to ground in TPS wiring
›Faulty TPS
›Corroded connector
›Throttle body damage
⚠️ Symptoms
›Engine may go into limp mode
›Reduced power
›Rough idle
›Check engine light
✅ How to Fix — Step by Step
Step 1:Check TPS connector for corrosion
Step 2:Test TPS reference voltage (5V)
Step 3:Check wiring for short to ground
Step 4:Replace TPS
🔧 Diagnostic Tools Required
✔OBD-II Diagnostic Scanner
✔Digital Multimeter
✔Fuel Pressure Gauge
✔Compression Tester
✔Spark Tester
Using the correct diagnostic tools helps identify the root cause of P0122 before replacing parts unnecessarily. Always confirm the fault using live data and manufacturer-recommended diagnostic procedures.
🚗 Vehicles Commonly Reporting P0122
Chevrolet MalibuFord FocusToyota CamryHonda AccordNissan AltimaJeep Cherokee
❌ Common Mistakes to Avoid
✘Replacing the throttle body assembly on a drive-by-wire vehicle when the fault is actually at the accelerator pedal sensor
✘Not checking for a corroded ground connection before replacing the sensor itself
✘Continuing to drive extensively in limp mode, which limits power for safety but shouldn't be treated as a permanent state
✘Overlooking a simple wiring connector issue in favor of assuming the full sensor has failed
📋 Technical Service Bulletins
Several manufacturers have TSBs for updated accelerator pedal sensor assemblies after reports of intermittent low-input faults on drive-by-wire systems.
🏭 Manufacturer-Specific Notes
Chevrolet P0122
On GM vehicles with electronic throttle control, this code usually points to the accelerator pedal position sensor rather than a separate throttle body sensor.
Ford P0122
Ford models with cable-actuated throttle bodies (older platforms) have a separate physical TPS that can wear and set this code independently of the pedal.
Jeep P0122
Jeep SUVs occasionally develop this code from connector corrosion at the throttle body in wet or humid climates — inspect the connector before replacing the sensor.
🎓 Expert Tip: Determine whether your vehicle uses a traditional throttle-body-mounted TPS or a drive-by-wire accelerator pedal sensor before ordering parts — they are different components on different circuits, and replacing the wrong one won't fix the fault.
💡 Pro Tip: Limp mode (limited to low RPM) often indicates a TPS fault — the ECM defaults to safe operation.
Repair Cost Estimate
Full Repair Estimate
$100–$400
DIY Possible?
YES
Severity
Critical
Diagnosis Time
25–40 minutes
Repair Time
30 minutes–1.5 hours
Frequently Asked Questions
What does OBD2 code P0122 mean?+
P0122 stands for Throttle/Pedal Position Sensor A Circuit Low Input. TPS circuit voltage is below expected range.
What causes code P0122?+
Short to ground in TPS wiring; Faulty TPS; Corroded connector; Throttle body damage
How do I fix code P0122?+
Check TPS connector for corrosion; Test TPS reference voltage (5V); Check wiring for short to ground; Replace TPS
How much does it cost to fix P0122?+
Estimated repair cost for P0122 is $100–$400.
Is P0122 DIY-friendly?+
Yes — P0122 is generally DIY-friendly with basic tools.
References
SAE J1979 — E/E Diagnostic Test Modes (OBD-II communication standard)
ISO 15031 — Road vehicles: communication between vehicle and external equipment for emissions-related diagnostics
Vehicle manufacturer service manual (consult your specific make and model)
