P0121

High Severity

Throttle Position Sensor A Range/Performance

Fuel System

What Does P0121 Mean?

The TPS reading does not match expected values based on MAP, RPM, and other inputs. Erratic readings indicate a worn TPS.

Common Fix

Replace TPS

Estimated Cost (DIY)

$20 - $100

Symptoms

  • ⚠️Intermittent power loss
  • ⚠️Rough acceleration
  • ⚠️Surging at cruise speed
  • ⚠️Reduced power mode

Common Causes

Worn TPS with dead spotslikely
Throttle body carbon builduppossible
Loose TPS connectorpossible
Damaged throttle linkageunlikely

How to Diagnose P0121

  1. 1Watch TPS voltage on scan tool while slowly opening throttle — look for jumps or dropouts
  2. 2Clean throttle body
  3. 3Check TPS mounting and connector
  4. 4Replace TPS if readings are erratic

OEM Diagnostic Flowchart

Scroll to load technician if/then branches.

Read live data and freeze frame for P0121 to pinpoint the cause before buying parts.

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Related Resources

Repair guides, symptom pages, and wiring diagrams related to P0121.

OEM Manual Evidence

Browse →
2013 GMC Truck Yukon XL Denali AWD V8-6.2L A L L Diagnostic Trouble Codes ( DTC )OEM Manual

A L L Diagnostic Trouble Codes ( DTC ) — 2013 GMC Truck Yukon XL Denali AWD V8-6.2L Service Manual | Operation CHARM Operation CHARM : Car...

2013 GMC Truck Yukon XL Denali 2WD V8-6.2L A L L Diagnostic Trouble Codes ( DTC )OEM Manual

A L L Diagnostic Trouble Codes ( DTC ) — 2013 GMC Truck Yukon XL Denali 2WD V8-6.2L Service Manual | Operation CHARM Operation CHARM : Car...

2013 GMC Truck Yukon XL 4WD V8-6.0L A L L Diagnostic Trouble Codes ( DTC )OEM Manual

A L L Diagnostic Trouble Codes ( DTC ) — 2013 GMC Truck Yukon XL 4WD V8-6.0L Service Manual | Operation CHARM Operation CHARM : Car repair...

2013 GMC Truck Yukon XL 4WD V8-5.3L A L L Diagnostic Trouble Codes ( DTC )OEM Manual

A L L Diagnostic Trouble Codes ( DTC ) — 2013 GMC Truck Yukon XL 4WD V8-5.3L Service Manual | Operation CHARM Operation CHARM : Car repair...

Exact Vehicle Hubs

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2013 Gmc Truck Yukon Xl 4wd V8 5.3l Repair HubManual

Open the exact vehicle hub grounded by OEM manual evidence related to P0121.

2013 Gmc Truck Yukon Xl 4wd V8 6.0l Repair HubManual

Open the exact vehicle hub grounded by OEM manual evidence related to P0121.

2013 Gmc Truck Yukon Xl Denali 2wd V8 6.2l Repair HubManual

Open the exact vehicle hub grounded by OEM manual evidence related to P0121.

2013 Gmc Truck Yukon Xl Denali Awd V8 6.2l Repair HubManual

Open the exact vehicle hub grounded by OEM manual evidence related to P0121.

Related Codes

P0120: Throttle Position Sensor A CircuitRelated

General fault in the TPS circuit. The TPS tells the ECM how far the throttle is open.

P0122: Throttle Position Sensor A Circuit LowRelated

TPS voltage is below minimum threshold. The ECM cannot determine throttle position accurately.

P0123: Throttle Position Sensor A Circuit HighRelated

TPS voltage is above maximum expected. ECM sees the throttle as more open than it actually is.

Frequently Asked Questions

How do I test a TPS?
Using a scan tool, slowly open the throttle from closed to wide open. Voltage should rise smoothly from ~0.5V to ~4.5V with no jumps or drops.
Can I just clean the throttle body?
Sometimes cleaning fixes P0121 if carbon is preventing smooth throttle movement. Try cleaning first before replacing the TPS.

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