Code
P1156
PEUGEOT
P — Powertrain
Electric throttle signal malfunction
AI status
Completed
Completed
100%
Causes
- Faulty electronic throttle body (throttle position sensor inside throttle body)
- Faulty accelerator pedal position (APP) sensor(s)
- Open/short or poor connection in wiring harness or connector
- Corroded or contaminated connector / water ingress
- Low battery voltage or poor ground
- Carbon build-up or mechanical obstruction of throttle plate
Symptoms
- MIL/Check Engine lamp on
- Limp-home / reduced engine power mode
- Poor or unsteady idle
- Reduced or delayed throttle response, hesitation
- Engine may stall at low revs or not respond to accelerator
- Intermittent faults that may clear after restart
What to check
- Read freeze frame and full DTC list with a scan tool; record live APP and throttle position data
- Check battery voltage (engine off and cranking) and main engine grounds
- Visual inspection of throttle body and pedal connectors for corrosion, bent pins or water
- Inspect wiring harness for chafe, connector damage, repairs or heat damage
- Check for heavy carbon build-up on throttle plate or binding mechanism
- Verify there are no other related codes (ABS, CAN comms) that could affect throttle control
Signal parameters
- Typical throttle position sensor (TPS) closed valve voltage: ~0.4–1.0 V (varies by model)
- Typical TPS wide-open voltage: ~3.5–4.5 V (varies by model)
- Accelerator pedal sensors usually provide two channels — values should correlate and change smoothly together; one may be inverse to the other
- APP closed/rest voltages commonly around 0.4–1.0 V (channel A) and ~3.5–4.5 V (channel B) — check factory data
- Throttle control motor commanded via PWM/duty cycle — duty-cycle or duty % will vary by model; use factory values
- Expect smooth, monotonic change in voltages as pedal is pressed; abrupt jumps, flat-line or out-of-range values indicate fault
Diagnostic algorithm
- Connect a capable scan tool and read all stored codes and freeze-frame data. Note related codes and stored conditions.
- With ignition on, monitor live data: APP1, APP2, Throttle Position (TP) sensor, commanded throttle, motor duty cycle and battery voltage. Look for correlation and smooth response.
- Perform a battery/ground check: confirm >12.4 V at key on and good engine/chassis grounds.
- Visually inspect connectors at throttle body and accelerator pedal; unplug and inspect pins for corrosion, bent pins or water. Back-probe and measure voltages while operating pedal/throttle.
- Check harness continuity and for shorts to chassis voltage using a multimeter; wiggle harness to reproduce intermittent faults.
- Inspect and clean throttle body if heavy carbon restricts plate movement; ensure throttle plate moves freely by hand (with ignition off, follow safe procedures).
- If wiring and connectors OK, perform resistance/voltage checks per manufacturer data on TPS and APP sensors; compare both channels for expected correlation.
- Perform throttle body relearn/adaptation using scan tool where required, then clear codes and perform a controlled test drive to confirm repair.
- If fault persists and signal/wiring good, consider replacing throttle body assembly or accelerator pedal sensor(s) per factory procedure.
- After repair, clear codes and verify no reoccurrence over several drive cycles.
Likely causes
- Contaminated/thick carbon on throttle plate causing position feedback mismatch (common on European petrol/diesel engines)
- Damaged or corroded connector at throttle body (engine bay moisture exposure)
- Two-channel APP sensor mismatch due to internal APP fault
- Damaged wiring between pedal/throttle and ECM (chafing at bulkhead or near pedal)
- Failed throttle body electronics (motor or internal TPS)
Fault status
Status
P1156 — Electric throttle signal malfunction: ECM detected inconsistent or invalid signal from the electronic throttle control system (throttle body or pedal sensors).
Repair difficulty: Medium
Diagnostic time: 1–3 hours
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