Code
P1157
PEUGEOT
P — Powertrain
Electric throttle signal malfunction
Views:
UK: 3
EN: 7
RU: 4
AI status
Completed
Completed
100%
Causes
- Faulty throttle body (throttle position sensor or throttle motor)
- Faulty accelerator pedal position sensor(s)
- Damaged wiring or poor electrical connection (open/short/poor ground)
- Corroded or loose connector at throttle body or pedal module
- ECU/software fault or corrupted throttle adaptation values
- Intermittent mechanical binding or carbon buildup in throttle plate
Symptoms
- Check Engine Light (MIL) illuminated
- Reduced engine power / Limp-home (reduced throttle response)
- Poor or unstable idle; stalling at idle or during deceleration
- Delayed or erratic throttle response
- Loss of cruise control function
What to check
- Read freeze-frame and full DTC list with an OEM-capable scan tool; note related codes
- Capture live data: accelerator pedal sensor 1 & 2, throttle position sensor, throttle actuator command and position
- Compare pedal position to commanded and actual throttle position for correlation and lag
- Inspect wiring harnesses and connectors for damage, corrosion, water ingress or loose pins at pedal, throttle body and ECU
- Check reference voltages (typically 5 V) and ground continuity at sensors
- Measure sensor output voltages at rest and during pedal movement and throttle actuation
Signal parameters
- Accelerator pedal sensor outputs: typically two signals that vary smoothly ~0.5–4.5 V across travel (one may be inverse or different slope depending on design)
- Throttle position sensor output: closed throttle ~0.5 V, wide open ~4.0–4.5 V (values vary by model—check OEM data)
- Reference supply: stable 5.0 V ±0.25 V to sensors
- Ground: low resistance to vehicle chassis; no intermittent voltage drop
- Throttle motor current: pulses up to a few amps during movement (check with scope or clamp ammeter if needed)
- Correlation: pedal inputs should correlate proportionally with commanded throttle position within system response time
Diagnostic algorithm
- Retrieve P1157 and any related codes. Record freeze-frame and live data.
- Visually inspect connectors and wiring for damage, corrosion or water intrusion. Repair any obvious faults.
- With ignition ON (engine off), measure reference 5 V and ground at pedal and throttle sensors. Replace wiring or repair grounding if out of range.
- Backprobing: monitor both accelerator pedal sensor signals while slowly pressing/releasing pedal. Confirm smooth, monotonic voltage change and proper sensor correlation.
- Start engine and monitor commanded throttle vs actual throttle position. Note any large discrepancies, lag, or error flags.
- If signals are out of specification or intermittent, disconnect sensors one at a time to observe code change and isolate the faulty module.
- Clean throttle body if carbon build-up is present, then perform throttle adaptation/learn procedure per manufacturer instructions.
- If wiring and sensors test good but fault persists, test/replace the throttle body assembly (including position sensors and motor).
- After repairs, clear codes and perform road test while monitoring live data to confirm proper operation and that P1157 does not return.
- If fault persists after component replacement, consider ECU diagnosis or reflash by a dealer-level tool.
Likely causes
- Wiring/connectors between pedal, throttle body and ECU (corrosion, pin damage, chafing)
- Throttle body sensor or motor failure (internal electronics)
- Accelerator pedal position sensor out of specification or inconsistent between sensor channels
- Throttle body requires cleaning or adaptation/reset
- ECU needs software update or has internal fault (less common)
Fault status
Status
Electric throttle signal malfunction — throttle/pedal position signals out of expected range or correlation. May cause limp mode and reduced engine performance.
Repair difficulty: Medium
Diagnostic time: 1.5-3.0 hours
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