Code
P0121
Generic
P — Powertrain
Throttle/Pedal Position Sensor/Switch A Circuit Range/Performance
Views:
UK: 30
EN: 185
RU: 88
AI status
Completed
Completed
100%
Causes
- Faulty throttle position sensor (TPS) / pedal position sensor (sensor A)
- Damaged wiring harness (open, short to voltage, short to ground) or poor connector connection
- Corroded or bent pins at sensor or ECM connector
- Intermittent contact (moisture, dirt, pin deformation)
- Incorrect sensor installation or throttle plate misalignment
- Contaminated or sticking throttle body (mechanical binding)
Symptoms
- Check Engine MIL illuminated (P0121 stored)
- Erratic or high/low idle, idle surging
- Throttle hesitation, stumble or reduced throttle response
- Reduced engine power or limp‑in mode in some vehicles
- Poor drivability, hesitation on acceleration
- Possible increased fuel consumption
What to check
- Retrieve freeze frame and stored data with an OBD‑II scan tool; note conditions when code set (rpm, temp, pedal position).
- Inspect wiring and connectors at TPS and ECM for damage, corrosion, bent pins, or moisture. Check connector seated correctly.
- With ignition ON (engine off) use a scan tool to monitor TPS (sensor A) voltage/percentage while slowly moving throttle/pedal; watch for smooth monotonic change without dropouts or jumps.
- Measure reference voltage at sensor connector (should be ~5.0 V) and ground continuity to chassis/ECM.
- Backprobe TPS signal wire and measure voltage with multimeter: compare closed throttle and wide‑open readings to expected range.
- Perform wiggle test on harness while monitoring live data to reproduce fault.
Signal parameters
- Type: analog voltage (potentiometer) or Hall effect depending on vehicle; ECM expects a smooth ramp
- Reference voltage: typically ~5.0 V (key ON) supplied by ECM
- Ground: near 0 V (sensor ground/return)
- Closed throttle (typical): ~0.1–1.0 V (manufacturer specific)
- Wide open throttle (typical): ~3.5–4.5 V (manufacturer specific)
- Signal behavior: smooth, monotonic increase (or paired sensors should correlate); no sudden drops, spikes, or dead zones
Diagnostic algorithm
- Confirm P0121 is current—read codes and freeze frame. Note operating conditions when set.
- Visually inspect TPS and wiring harness for damage, corrosion, oil/contaminants, and secure mounting. Repair any obvious problems.
- With ignition ON (engine OFF) monitor live TPS A voltage with a scan tool while slowly opening and closing throttle/pedal. Look for smooth linear change. If erratic, suspect sensor or wiring.
- Measure reference (≈5 V) and ground at sensor harness using a DMM. If reference absent or unstable, trace wiring to ECM and check ECM fuse/grounds.
- Backprobe signal wire and measure signal voltage at closed and wide open throttle; compare to expected values in vehicle manual. If out of range, check wiring continuity to ECM.
- Perform a wiggle test on harness/connectors while monitoring signal to find intermittent faults. Repair splices or damaged wire.
- Inspect/clean throttle body if movement is sticky; verify mechanical throttle stop and return springs function correctly.
- If wiring and mechanical checks pass, substitute known good TPS or replace TPS. After replacement, clear codes and perform throttle adaptation/learn per service procedure.
- If problem persists after wiring and sensor replacement, test/replace ECM or consult OEM technical service information for module diagnostics.
Likely causes
- Wiring open/short between TPS and ECM
- Loose/corroded connector at TPS or ECM
- Failed TPS potentiometer or Hall effect sensor (A)
- Throttle body binding or carbon buildup causing non‑linear movement
- Faulty ground or 5 V reference feed from ECM
Fault status
Status
P0121 stored when the throttle/pedal position sensor A circuit reports a signal that is out of expected range or shows poor performance (non‑linear, erratic, or inconsistent with throttle movement). The fault may be caused by sensor failure, wiring/connectors, reference/ground issues, or mechanical throttle problems.
Repair difficulty: Medium
Diagnostic time: 0.5-2.5 hours
Similar codes
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Workshop ManualAudi A3 (1997) – 1.6L 4-cylinder (2‑valve) Engine Mechanical Components Service Manual (AEH, AKL, APF) – Edition 07.2002
Workshop ManualAUDI A3 (2004) Workshop Manual — 2.0L FSI Turbo (4‑cyl, 4‑valve) Engine, Mechanics — Edition 03.2017
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Workshop ManualAudi A4 / A4 Cabriolet – 4.2 l V8 (5‑valve, timing chains) – Workshop Manual (Mechanics) – Edition 04.2007
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Workshop ManualLand Rover Defender Workshop Manual Supplement & Body Repair Manual (1999 & 2002 MY)
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Workshop ManualYour experience will help others
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Code
P0121
GWM
P — Powertrain
- Invalid indicator / Throttle position sensor / A switch not adjusted
Views:
UK: 5
EN: 29
RU: 15
AI status
Completed
Completed
100%
Causes
- Faulty throttle position sensor (TPS) / pedal position sensor (sensor A)
- Damaged wiring harness (open, short to voltage, short to ground) or poor connector connection
- Corroded or bent pins at sensor or ECM connector
- Intermittent contact (moisture, dirt, pin deformation)
- Incorrect sensor installation or throttle plate misalignment
- Contaminated or sticking throttle body (mechanical binding)
Symptoms
- Check Engine MIL illuminated (P0121 stored)
- Erratic or high/low idle, idle surging
- Throttle hesitation, stumble or reduced throttle response
- Reduced engine power or limp‑in mode in some vehicles
- Poor drivability, hesitation on acceleration
- Possible increased fuel consumption
What to check
- Retrieve freeze frame and stored data with an OBD‑II scan tool; note conditions when code set (rpm, temp, pedal position).
- Inspect wiring and connectors at TPS and ECM for damage, corrosion, bent pins, or moisture. Check connector seated correctly.
- With ignition ON (engine off) use a scan tool to monitor TPS (sensor A) voltage/percentage while slowly moving throttle/pedal; watch for smooth monotonic change without dropouts or jumps.
- Measure reference voltage at sensor connector (should be ~5.0 V) and ground continuity to chassis/ECM.
- Backprobe TPS signal wire and measure voltage with multimeter: compare closed throttle and wide‑open readings to expected range.
- Perform wiggle test on harness while monitoring live data to reproduce fault.
Signal parameters
- Type: analog voltage (potentiometer) or Hall effect depending on vehicle; ECM expects a smooth ramp
- Reference voltage: typically ~5.0 V (key ON) supplied by ECM
- Ground: near 0 V (sensor ground/return)
- Closed throttle (typical): ~0.1–1.0 V (manufacturer specific)
- Wide open throttle (typical): ~3.5–4.5 V (manufacturer specific)
- Signal behavior: smooth, monotonic increase (or paired sensors should correlate); no sudden drops, spikes, or dead zones
Diagnostic algorithm
- Confirm P0121 is current—read codes and freeze frame. Note operating conditions when set.
- Visually inspect TPS and wiring harness for damage, corrosion, oil/contaminants, and secure mounting. Repair any obvious problems.
- With ignition ON (engine OFF) monitor live TPS A voltage with a scan tool while slowly opening and closing throttle/pedal. Look for smooth linear change. If erratic, suspect sensor or wiring.
- Measure reference (≈5 V) and ground at sensor harness using a DMM. If reference absent or unstable, trace wiring to ECM and check ECM fuse/grounds.
- Backprobe signal wire and measure signal voltage at closed and wide open throttle; compare to expected values in vehicle manual. If out of range, check wiring continuity to ECM.
- Perform a wiggle test on harness/connectors while monitoring signal to find intermittent faults. Repair splices or damaged wire.
- Inspect/clean throttle body if movement is sticky; verify mechanical throttle stop and return springs function correctly.
- If wiring and mechanical checks pass, substitute known good TPS or replace TPS. After replacement, clear codes and perform throttle adaptation/learn per service procedure.
- If problem persists after wiring and sensor replacement, test/replace ECM or consult OEM technical service information for module diagnostics.
Likely causes
- Wiring open/short between TPS and ECM
- Loose/corroded connector at TPS or ECM
- Failed TPS potentiometer or Hall effect sensor (A)
- Throttle body binding or carbon buildup causing non‑linear movement
- Faulty ground or 5 V reference feed from ECM
Fault status
Status
P0121 stored when the throttle/pedal position sensor A circuit reports a signal that is out of expected range or shows poor performance (non‑linear, erratic, or inconsistent with throttle movement). The fault may be caused by sensor failure, wiring/connectors, reference/ground issues, or mechanical throttle problems.
Repair difficulty: Medium
Diagnostic time: 0.5-2.5 hours
Similar codes
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Code
P0121
HUMMER
P — Powertrain
TP Sensor Circuit Insufficient Activity
Views:
UK: 9
EN: 81
RU: 49
AI status
Completed
Completed
100%
Causes
- Faulty throttle position sensor (TPS) / pedal position sensor (sensor A)
- Damaged wiring harness (open, short to voltage, short to ground) or poor connector connection
- Corroded or bent pins at sensor or ECM connector
- Intermittent contact (moisture, dirt, pin deformation)
- Incorrect sensor installation or throttle plate misalignment
- Contaminated or sticking throttle body (mechanical binding)
Symptoms
- Check Engine MIL illuminated (P0121 stored)
- Erratic or high/low idle, idle surging
- Throttle hesitation, stumble or reduced throttle response
- Reduced engine power or limp‑in mode in some vehicles
- Poor drivability, hesitation on acceleration
- Possible increased fuel consumption
What to check
- Retrieve freeze frame and stored data with an OBD‑II scan tool; note conditions when code set (rpm, temp, pedal position).
- Inspect wiring and connectors at TPS and ECM for damage, corrosion, bent pins, or moisture. Check connector seated correctly.
- With ignition ON (engine off) use a scan tool to monitor TPS (sensor A) voltage/percentage while slowly moving throttle/pedal; watch for smooth monotonic change without dropouts or jumps.
- Measure reference voltage at sensor connector (should be ~5.0 V) and ground continuity to chassis/ECM.
- Backprobe TPS signal wire and measure voltage with multimeter: compare closed throttle and wide‑open readings to expected range.
- Perform wiggle test on harness while monitoring live data to reproduce fault.
Signal parameters
- Type: analog voltage (potentiometer) or Hall effect depending on vehicle; ECM expects a smooth ramp
- Reference voltage: typically ~5.0 V (key ON) supplied by ECM
- Ground: near 0 V (sensor ground/return)
- Closed throttle (typical): ~0.1–1.0 V (manufacturer specific)
- Wide open throttle (typical): ~3.5–4.5 V (manufacturer specific)
- Signal behavior: smooth, monotonic increase (or paired sensors should correlate); no sudden drops, spikes, or dead zones
Diagnostic algorithm
- Confirm P0121 is current—read codes and freeze frame. Note operating conditions when set.
- Visually inspect TPS and wiring harness for damage, corrosion, oil/contaminants, and secure mounting. Repair any obvious problems.
- With ignition ON (engine OFF) monitor live TPS A voltage with a scan tool while slowly opening and closing throttle/pedal. Look for smooth linear change. If erratic, suspect sensor or wiring.
- Measure reference (≈5 V) and ground at sensor harness using a DMM. If reference absent or unstable, trace wiring to ECM and check ECM fuse/grounds.
- Backprobe signal wire and measure signal voltage at closed and wide open throttle; compare to expected values in vehicle manual. If out of range, check wiring continuity to ECM.
- Perform a wiggle test on harness/connectors while monitoring signal to find intermittent faults. Repair splices or damaged wire.
- Inspect/clean throttle body if movement is sticky; verify mechanical throttle stop and return springs function correctly.
- If wiring and mechanical checks pass, substitute known good TPS or replace TPS. After replacement, clear codes and perform throttle adaptation/learn per service procedure.
- If problem persists after wiring and sensor replacement, test/replace ECM or consult OEM technical service information for module diagnostics.
Likely causes
- Wiring open/short between TPS and ECM
- Loose/corroded connector at TPS or ECM
- Failed TPS potentiometer or Hall effect sensor (A)
- Throttle body binding or carbon buildup causing non‑linear movement
- Faulty ground or 5 V reference feed from ECM
Fault status
Status
P0121 stored when the throttle/pedal position sensor A circuit reports a signal that is out of expected range or shows poor performance (non‑linear, erratic, or inconsistent with throttle movement). The fault may be caused by sensor failure, wiring/connectors, reference/ground issues, or mechanical throttle problems.
Repair difficulty: Medium
Diagnostic time: 0.5-2.5 hours
Similar codes
Your experience will help others
+100 karma for a short comment :)
Was this AI description helpful?
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Code
P0121
LAND ROVER
P — Powertrain
Throttle Position Sensor A Range/Performance Problem
Views:
UK: 5
EN: 71
RU: 38
AI status
Completed
Completed
100%
Causes
- Faulty throttle position sensor (TPS) / pedal position sensor (sensor A)
- Damaged wiring harness (open, short to voltage, short to ground) or poor connector connection
- Corroded or bent pins at sensor or ECM connector
- Intermittent contact (moisture, dirt, pin deformation)
- Incorrect sensor installation or throttle plate misalignment
- Contaminated or sticking throttle body (mechanical binding)
Symptoms
- Check Engine MIL illuminated (P0121 stored)
- Erratic or high/low idle, idle surging
- Throttle hesitation, stumble or reduced throttle response
- Reduced engine power or limp‑in mode in some vehicles
- Poor drivability, hesitation on acceleration
- Possible increased fuel consumption
What to check
- Retrieve freeze frame and stored data with an OBD‑II scan tool; note conditions when code set (rpm, temp, pedal position).
- Inspect wiring and connectors at TPS and ECM for damage, corrosion, bent pins, or moisture. Check connector seated correctly.
- With ignition ON (engine off) use a scan tool to monitor TPS (sensor A) voltage/percentage while slowly moving throttle/pedal; watch for smooth monotonic change without dropouts or jumps.
- Measure reference voltage at sensor connector (should be ~5.0 V) and ground continuity to chassis/ECM.
- Backprobe TPS signal wire and measure voltage with multimeter: compare closed throttle and wide‑open readings to expected range.
- Perform wiggle test on harness while monitoring live data to reproduce fault.
Signal parameters
- Type: analog voltage (potentiometer) or Hall effect depending on vehicle; ECM expects a smooth ramp
- Reference voltage: typically ~5.0 V (key ON) supplied by ECM
- Ground: near 0 V (sensor ground/return)
- Closed throttle (typical): ~0.1–1.0 V (manufacturer specific)
- Wide open throttle (typical): ~3.5–4.5 V (manufacturer specific)
- Signal behavior: smooth, monotonic increase (or paired sensors should correlate); no sudden drops, spikes, or dead zones
Diagnostic algorithm
- Confirm P0121 is current—read codes and freeze frame. Note operating conditions when set.
- Visually inspect TPS and wiring harness for damage, corrosion, oil/contaminants, and secure mounting. Repair any obvious problems.
- With ignition ON (engine OFF) monitor live TPS A voltage with a scan tool while slowly opening and closing throttle/pedal. Look for smooth linear change. If erratic, suspect sensor or wiring.
- Measure reference (≈5 V) and ground at sensor harness using a DMM. If reference absent or unstable, trace wiring to ECM and check ECM fuse/grounds.
- Backprobe signal wire and measure signal voltage at closed and wide open throttle; compare to expected values in vehicle manual. If out of range, check wiring continuity to ECM.
- Perform a wiggle test on harness/connectors while monitoring signal to find intermittent faults. Repair splices or damaged wire.
- Inspect/clean throttle body if movement is sticky; verify mechanical throttle stop and return springs function correctly.
- If wiring and mechanical checks pass, substitute known good TPS or replace TPS. After replacement, clear codes and perform throttle adaptation/learn per service procedure.
- If problem persists after wiring and sensor replacement, test/replace ECM or consult OEM technical service information for module diagnostics.
Likely causes
- Wiring open/short between TPS and ECM
- Loose/corroded connector at TPS or ECM
- Failed TPS potentiometer or Hall effect sensor (A)
- Throttle body binding or carbon buildup causing non‑linear movement
- Faulty ground or 5 V reference feed from ECM
Fault status
Status
P0121 stored when the throttle/pedal position sensor A circuit reports a signal that is out of expected range or shows poor performance (non‑linear, erratic, or inconsistent with throttle movement). The fault may be caused by sensor failure, wiring/connectors, reference/ground issues, or mechanical throttle problems.
Repair difficulty: Medium
Diagnostic time: 0.5-2.5 hours
Similar codes
Workshop Manuals
Repair manuals for LAND ROVER
3
Land Rover Defender 300Tdi — Workshop Manual (1996 model year)
Workshop ManualLand Rover Defender Workshop Manual Supplement & Body Repair Manual (1999 & 2002 MY)
Workshop ManualLand Rover Range Rover — Electrical Library (LRL 0453ENG, 2002)
Workshop ManualYour experience will help others
+100 karma for a short comment :)
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Code
P0121
MITSUBISHI
P — Powertrain
TPS(main) range
Views:
UK: 9
EN: 84
RU: 48
AI status
Completed
Completed
100%
Causes
- Faulty throttle position sensor (TPS) / pedal position sensor (sensor A)
- Damaged wiring harness (open, short to voltage, short to ground) or poor connector connection
- Corroded or bent pins at sensor or ECM connector
- Intermittent contact (moisture, dirt, pin deformation)
- Incorrect sensor installation or throttle plate misalignment
- Contaminated or sticking throttle body (mechanical binding)
Symptoms
- Check Engine MIL illuminated (P0121 stored)
- Erratic or high/low idle, idle surging
- Throttle hesitation, stumble or reduced throttle response
- Reduced engine power or limp‑in mode in some vehicles
- Poor drivability, hesitation on acceleration
- Possible increased fuel consumption
What to check
- Retrieve freeze frame and stored data with an OBD‑II scan tool; note conditions when code set (rpm, temp, pedal position).
- Inspect wiring and connectors at TPS and ECM for damage, corrosion, bent pins, or moisture. Check connector seated correctly.
- With ignition ON (engine off) use a scan tool to monitor TPS (sensor A) voltage/percentage while slowly moving throttle/pedal; watch for smooth monotonic change without dropouts or jumps.
- Measure reference voltage at sensor connector (should be ~5.0 V) and ground continuity to chassis/ECM.
- Backprobe TPS signal wire and measure voltage with multimeter: compare closed throttle and wide‑open readings to expected range.
- Perform wiggle test on harness while monitoring live data to reproduce fault.
Signal parameters
- Type: analog voltage (potentiometer) or Hall effect depending on vehicle; ECM expects a smooth ramp
- Reference voltage: typically ~5.0 V (key ON) supplied by ECM
- Ground: near 0 V (sensor ground/return)
- Closed throttle (typical): ~0.1–1.0 V (manufacturer specific)
- Wide open throttle (typical): ~3.5–4.5 V (manufacturer specific)
- Signal behavior: smooth, monotonic increase (or paired sensors should correlate); no sudden drops, spikes, or dead zones
Diagnostic algorithm
- Confirm P0121 is current—read codes and freeze frame. Note operating conditions when set.
- Visually inspect TPS and wiring harness for damage, corrosion, oil/contaminants, and secure mounting. Repair any obvious problems.
- With ignition ON (engine OFF) monitor live TPS A voltage with a scan tool while slowly opening and closing throttle/pedal. Look for smooth linear change. If erratic, suspect sensor or wiring.
- Measure reference (≈5 V) and ground at sensor harness using a DMM. If reference absent or unstable, trace wiring to ECM and check ECM fuse/grounds.
- Backprobe signal wire and measure signal voltage at closed and wide open throttle; compare to expected values in vehicle manual. If out of range, check wiring continuity to ECM.
- Perform a wiggle test on harness/connectors while monitoring signal to find intermittent faults. Repair splices or damaged wire.
- Inspect/clean throttle body if movement is sticky; verify mechanical throttle stop and return springs function correctly.
- If wiring and mechanical checks pass, substitute known good TPS or replace TPS. After replacement, clear codes and perform throttle adaptation/learn per service procedure.
- If problem persists after wiring and sensor replacement, test/replace ECM or consult OEM technical service information for module diagnostics.
Likely causes
- Wiring open/short between TPS and ECM
- Loose/corroded connector at TPS or ECM
- Failed TPS potentiometer or Hall effect sensor (A)
- Throttle body binding or carbon buildup causing non‑linear movement
- Faulty ground or 5 V reference feed from ECM
Fault status
Status
P0121 stored when the throttle/pedal position sensor A circuit reports a signal that is out of expected range or shows poor performance (non‑linear, erratic, or inconsistent with throttle movement). The fault may be caused by sensor failure, wiring/connectors, reference/ground issues, or mechanical throttle problems.
Repair difficulty: Medium
Diagnostic time: 0.5-2.5 hours
Similar codes
Your experience will help others
+100 karma for a short comment :)
Was this AI description helpful?
Your feedback helps improve AI descriptions.
👍 Like
0
👎 Dislike
0
Send to email