P0120
High SeverityThrottle Position Sensor A Circuit
Fuel System
P0120 — Instant Answer
Throttle Position Sensor A Circuit
Severity: HIGH SEVERITY
Meaning: General fault in the TPS circuit. The TPS tells the ECM how far the throttle is open.
Safe to drive? NO if CEL is flashing. YES with caution if solid, but repair this week.
Estimated repair cost: $20 - $150
Most common causes:
- 1. Faulty TPS (35-45% of cases)
- 2. Corroded TPS connector (10-25% of cases)
- 3. Wiring issue (10-25% of cases)
- 4. Worn throttle body (10-25% of cases)
Symptoms
- ⚠️Erratic idle
- ⚠️Hesitation on acceleration
- ⚠️Surging
- ⚠️Reduced power mode
Common Causes
How to Diagnose P0120
- 1Check TPS connector for corrosion
- 2Sweep TPS with scan tool — look for dropouts
- 3Measure TPS voltage at closed and WOT
- 4Replace TPS if erratic
OEM Procedures for P0120
Throttle/Pedal Position Sensor/Switch A Circuit Found 9 OEM service manual procedures.
Remove/Install/Overhaul - Removal (Tracker)
Remove/Install/Overhaul - Removal (Tracker)
Remove/Install/Overhaul - Removal (Tracker)
Remove/Install/Overhaul - Removal (Tracker)
Remove/Install/Overhaul - Removal (Tracker)
Remove/Install/Overhaul - Removal (Tracker)
Replacement - Replace Throttle Position Sensor
Replacement - Replace Throttle Position Sensor
Showing 8 of 9 procedures
OEM Diagnostic Flowchart
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Parts & Tools for This Job
Common parts shoppers buy for P0120 Throttle Position Sensor A Circuit.
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OBD2 scanner
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Check SpecificationsBattery tester
Check cranking and charging health before replacing expensive parts.
A weak battery can mimic alternator or starter problems.
Check SpecificationsMultimeter kit
Confirm voltage, continuity, and sensor power with one simple kit.
A meter is the cheapest way to rule out a bad circuit fast.
Check SpecificationsRelated Resources
Repair guides, symptom pages, and wiring diagrams related to P0120.
OEM Manual Evidence
Browse →A L L Diagnostic Trouble Codes ( DTC ) — 2013 Cadillac CTS Coupe RWD V8-6.2L SC Service Manual ~ LEMON Manuals LEMON Manuals: Repair Knowle...
A L L Diagnostic Trouble Codes ( DTC ) — 2013 Cadillac CTS Sedan RWD V8-6.2L SC Service Manual ~ LEMON Manuals LEMON Manuals: Repair Knowle...
A L L Diagnostic Trouble Codes ( DTC ) — 2013 Cadillac CTS Wagon RWD V8-6.2L SC Service Manual ~ LEMON Manuals LEMON Manuals: Repair Knowle...
A L L Diagnostic Trouble Codes ( DTC ) — 2013 Cadillac Escalade AWD V8-6.2L Service Manual ~ LEMON Manuals LEMON Manuals: Repair Knowledge...
Exact Vehicle Hubs
Browse →Open the exact vehicle hub grounded by OEM manual evidence related to P0120.
Open the exact vehicle hub grounded by OEM manual evidence related to P0120.
Open the exact vehicle hub grounded by OEM manual evidence related to P0120.
Open the exact vehicle hub grounded by OEM manual evidence related to P0120.
Related Codes
The TPS reading does not match expected values based on MAP, RPM, and other inputs. Erratic readings indicate a worn TPS.
TPS voltage is below minimum threshold. The ECM cannot determine throttle position accurately.
TPS voltage is above maximum expected. ECM sees the throttle as more open than it actually is.
Frequently Asked Questions
- Can a dirty throttle body cause P0120?
- Yes — carbon buildup can prevent the throttle from closing fully, confusing the TPS. Clean the throttle body first.
- What is limp mode?
- When the ECM cannot trust the TPS, it limits power to protect the engine. This is called limp mode or reduced power mode.
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Author & Review
Published by AllOEMManuals, founded by Lyndon Bedford, an automotive technician with 20 years of experience. He owned and operated a mechanic shop in Hurst, Texas from 2014 to 2022 and continues hands-on repair work.
Content may combine manual references, general repair templates, and AI-assisted drafting. Confirm the source, vehicle configuration, and applicability before working. Report corrections through our contact page.
Last updated: 2026-10-29