Code
P1122
MAZDA
P — Powertrain
Throttle Position Stuck Closed
Views:
UK: 26
EN: 44
RU: 28
AI status
Completed
Completed
100%
Causes
- Faulty throttle position sensor (TPS)
- Short to ground or open in TPS signal/ground wiring
- Loss of reference voltage to TPS (5V) or poor ground
- Carbon buildup or mechanical sticking of throttle plate/throttle body
- Poor connector contact/corrosion at TPS connector
- Faulty engine control module (ECM) or intermittent ECU input
Symptoms
- Check Engine Light (MIL) illuminated
- Poor idle, stalling, or hesitant acceleration
- Loss of throttle response or limp-home mode
- High or unstable idle if ECU uses default strategy
- Inability to reach expected RPMs or throttle opening indicated by scan tool
What to check
- Retrieve freeze frame and live data with scan tool — observe TPS voltage/percentage at key ON and idle conditions
- Visual inspection of TPS connector and wiring for damage, corrosion, or pin pushed out
- Measure TPS 5V reference and ground at the connector with key ON; verify 5V reference present and good ground
- Backprobe TPS signal wire and monitor voltage while slowly opening the throttle — voltage should increase smoothly from closed (~0.1–0.6 V) to open (~4.0–4.8 V)
- Check for continuity and shorts between signal wire and ground/power/other circuits
- Inspect and operate throttle body by hand (engine off) to check for binding/carbon
Signal parameters
- TPS signal voltage at closed throttle: about 0.1–0.6 V (varies by model; near 0 V indicates stuck-closed)
- TPS signal voltage at wide-open throttle (WOT): about 4.0–4.8 V
- Reference voltage to TPS: ~5.0 V ± 0.25 V
- TPS internal resistance: typically a few kiloohms between reference and ground (specific value depends on sensor design)
- Signal should change smoothly and monotonically with throttle movement (no jumps or dropouts)
Diagnostic algorithm
- Connect an OBD-II scan tool. Read freeze frame/live data and confirm P1122 active or historic. Note TPS voltage/percent at rest and with throttle movement.
- Perform a visual inspection of TPS connector and wiring. Repair any obvious damage, corrosion, or loose pins before further testing.
- With ignition ON (engine off), backprobe the TPS connector: verify ~5 V reference on reference pin and a good ground on ground pin. If reference missing, trace to ECU and check power/ignition circuits.
- Backprobe the signal pin. Slowly open and close throttle manually or with scan tool command while watching signal voltage. Look for smooth increase from ~0.1–0.6 V to ~4.0–4.8 V. If signal stays low or stuck, suspect TPS or wiring.
- Check continuity of signal wire to ECU and for shorts to ground or battery positive. Repair wiring faults as needed.
- Inspect throttle body for carbon or mechanical binding. Clean throttle plate and bore if sticking is found and retest.
- If wiring and throttle body are good but signal remains stuck-low, replace the TPS/sensor. After replacement, clear codes and test drive to confirm fault does not return.
- If new TPS still shows stuck-closed signal, perform ECU input diagnostics and consider ECM repair/reprogramming as a last resort.
Likely causes
- TPS potentiometer failed internally and outputs a low (closed) voltage
- Signal wire shorted to ground or low-resistance path pulling voltage down
- Disconnected or weak 5V reference or TPS ground
- Throttle plate physically stuck closed due to deposits or linkage binding
- Corroded/loose connector pins at the TPS harness
Fault status
Status
P1122 - Throttle Position Sensor / Circuit Stuck Closed (MAZDA) — TPS signal indicates closed/throttle-not-open when a varying signal is expected.
Repair difficulty: Medium
Diagnostic time: 0.5-2.0 hours
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