Code
P1191
MAZDA
P — Powertrain
TP Controlled Circuit
AI status
Completed
Completed
100%
Causes
- Damaged, corroded or disconnected TP sensor connector or wiring (open/short/ground fault)
- Faulty throttle position sensor (TPS) or electronic throttle body assembly
- Poor 5V reference or ground from the PCM/ECM
- Intermittent wiring damage due to heat, chafing or pinched harness
- Faulty accelerator pedal position sensor (if circuit correlation used)
- PCM/ECM internal fault or software issue
Symptoms
- Check Engine Light (MIL) illuminated and DTC stored
- Unstable or high/low idle, surging or stalling
- Poor throttle response, hesitation or reduced engine power
- Engine may enter limp/reduced-power mode (electronic throttle systems)
- Irregular throttle position reading in live data (stuck, jumping or out-of-range values)
What to check
- Read and record freeze frame and all stored DTCs; note related codes (APP, throttle actuator)
- Visual inspection of throttle body, TPS connector and harness for corrosion, damage or pinching
- Scan tool: monitor TP sensor voltage (or percentage) and accelerator pedal sensors while moving throttle slowly — check for smooth, linear change
- Backprobe and measure reference voltage (typically ~5.0 V) and ground at the TPS connector with ignition ON
- Measure TPS signal voltage at closed throttle and at wide-open; look for noisy or intermittent signal
- Perform wiggle test on harness and connector while observing live data for intermittent faults
Signal parameters
- Typical TPS reference voltage: ~5.0 V (check vehicle spec)
- Typical TPS signal voltage at closed throttle: ~0.2–1.0 V (commonly ~0.4–0.6 V)
- Typical TPS signal voltage at wide open: ~4.0–4.5 V (check vehicle-specific values)
- Signal should change smoothly and monotonically with throttle movement; no sudden jumps or dropouts
Diagnostic algorithm
- Retrieve all codes and freeze frame data; note whether P1191 is current or historical. Clear codes and perform a road/test cycle to verify repeatability.
- Perform a visual inspection of throttle body, TPS connector and wiring for damage, corrosion, compression or oil contamination.
- With ignition ON (engine OFF), backprobe the TPS connector: verify 5V reference, good ground, and signal voltage at rest. Values out of range = wiring or PCM issue.
- With engine running (or key on per service manual), operate throttle slowly and monitor signal voltage in live data or with meter/oscilloscope. Look for smooth linear change; identify jumps, noise or dropouts.
- Wiggle harness and connector while observing live data to locate intermittent open/short. Repair any damaged wiring, repair connector pins or replace harness sections as needed.
- If wiring and connectors test good, replace or bench-test the TPS or throttle body assembly per manufacturer instructions. For drive-by-wire systems, inspect accelerator pedal sensors and perform sensor correlation tests.
- After replacement or repair, perform any required throttle/idle relearn or PCM adaptation procedures, clear codes and road test to confirm repair. Re-scan to ensure P1191 does not return.
- If fault persists despite known-good sensors and wiring, consider PCM/ECM fault and verify by substitution or authorized repair diagnostic flow.
Likely causes
- Wiring harness connector corrosion at throttle body
- TPS signal wire shorted to 12V or ground
- Failed throttle position sensor (voltage not changing smoothly across throttle travel)
- Faulty 5V reference from PCM
- Intermittent open circuit caused by vibration or harness damage
Fault status
Status
PCM detected an abnormal or out-of-range signal in the throttle position/controlled circuit (missing, intermittent, shorted or inconsistent voltage) and stored DTC P1191.
Repair difficulty: Medium
Diagnostic time: 0.5-3.0 hours
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