Toggle Side Panel

Shopping Cart

No products in the basket.

Shopping Cart

No products in the basket.

Close search
Home / DTC / P0121 — TPS(main) range

P0121 — TPS(main) range

Detailed page for trouble code P0121.

34,405codes
59brands
11,914generic
22,491specific
All codes P-codes (Powertrain) B-codes (Body) C-codes (Chassis) U-codes (Network/User) Tesla Alerts
Reset
Code

P0121

MITSUBISHI P — Powertrain

TPS(main) range

Brand: MITSUBISHI
Type: P — Powertrain
AI status
Completed
ready
Completed 100%
Page language: EN

Causes

  • Open, shorted or corroded wiring/connectors in TPS circuit
  • Failed or contaminated throttle position sensor
  • Incorrect sensor reference voltage or ground
  • Mechanically sticking throttle plate or worn throttle shaft
  • ECM input circuit fault
  • Aftermarket modifications or connectors

Symptoms

  • Check Engine Light (MIL) illuminated
  • Poor or erratic idle
  • Hesitation, stalling or lack of power under acceleration
  • Sudden changes in engine speed when throttle is moved
  • Vehicle may enter limp mode or reduced power

What to check

  • Read freeze frame and live data with a scan tool: monitor TPS voltage/angle vs throttle movement
  • Visual inspection of TPS connector and wiring for damage, corrosion, or loose pins
  • Back-probe TPS connector to measure reference voltage, signal voltage, and ground
  • Wiggle test wiring and connector while observing signal for intermittent changes
  • Inspect throttle body for carbon build-up or mechanical binding
  • Check for related codes (sensor correlation, short/opens, ECM faults)

Signal parameters

  • Reference voltage: ~5 V supply from ECM to TPS (verify specific vehicle spec)
  • Sensor ground: near 0 V (good continuity to chassis/ECM ground)
  • TPS output at closed throttle: typically ~0.2–1.0 V (varies by design)
  • TPS output at wide open throttle (WOT): typically ~4.0–4.8 V
  • TPS output should change smoothly and monotonically as throttle opens/closes (no jumps or dropouts)

Diagnostic algorithm

  1. Retrieve freeze frame and all stored codes; note engine conditions when code set.
  2. Clear code and perform a key-on engine-off (KOEO) and key-on engine-running (KOER) scan of TPS voltage while moving throttle manually; verify voltage changes smoothly.
  3. With a DVOM or oscilloscope, back-probe connector: verify reference ~5 V, ground near 0 V, and signal changes across expected range. Check for noise or intermittent loss.
  4. Perform wiggle test on harness and connector while observing live data to reveal intermittent wiring faults.
  5. Inspect connector pins for corrosion, bent pins, or poor contact; repair or replace as needed.
  6. Measure TPS resistance (if service manual specifies) or compare sensor output to factory chart; replace TPS if out of spec or non-linear.
  7. Inspect throttle body for binding or carbon deposits; clean throttle plate and retest.
  8. If wiring and sensor check good but fault persists, trace harness to ECU and check continuity to ECM pin and for shorts to battery/ground. Repair wiring as needed.
  9. As a last step, if all wiring and sensor are correct, consider ECU input circuit failure and consult manufacturer-level diagnostics before replacing ECM.
  10. After repair, clear codes and road test to confirm proper behavior and that code does not return.

Likely causes

  • Damaged TPS connector (bent pins, corrosion)
  • TPS internal wear or contamination
  • Broken/frayed wiring or short to 12V or ground
  • Loose or poor ground at engine harness
  • Throttle body carbon build-up preventing smooth movement
  • Faulty ECM (less common)

Fault status

⚠️ Status
Throttle Position Sensor (main) signal out of expected range or performance threshold. ECM detected TPS voltage or behavior inconsistent with throttle position.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 0.5-2.0 hours

Similar codes

P0120 P0122 P0123 P0220 P0221 P2135
406

Browse 406 MITSUBISHI manuals: repair procedures, diagnostics, wiring diagrams, component locations, service data and Labor Times by year, model and trim.

MITSUBISHI

Your experience will help others
+100 karma for a short comment :)
Keep it short and practical. Up to 500 characters.
Send to email

Report

Harassment or bullying behavior
Contains mature or sensitive content
Contains misleading or false information
Contains abusive or derogatory content
Contains spam, fake content or potential malware

Block Member?

Please confirm you want to block this member.

You will no longer be able to:

  • See blocked member's posts
  • Mention this member in posts
  • Invite this member to groups
  • Message this member
  • Add this member as a connection

Please note: This action will also remove this member from your connections and send a report to the site admin. Please allow a few minutes for this process to complete.

Report

You have already reported this .