Code
P1156
DS
P — Powertrain
Electric throttle signal malfunction
Views:
UK: 2
EN: 0
RU: 2
AI status
Completed
Completed
100%
Causes
- Damaged or corroded wiring or connectors between pedal sensors, throttle body, and ECU
- Failed throttle body (throttle position sensor or actuator motor)
- Faulty accelerator pedal position sensor(s)
- Low or intermittent battery/charging system voltage
- ECU/PCM internal fault or software issue
- Contamination or mechanical binding in the throttle plate
Symptoms
- Reduced engine power / limp-home mode
- Erratic idle or stalling
- Poor throttle response or unresponsive accelerator
- Check Engine Light / MIL illuminated
- Inability to reach higher RPMs or limited top speed
What to check
- Read and record all stored DTCs and freeze-frame data with a capable OBD-II scanner
- Visual inspection of wiring harnesses and connectors at the throttle body, accelerator pedal, and ECU for damage, corrosion, or water ingress
- Check battery voltage and charging system under load (should be ~12.6 V resting, 13.5–14.8 V when running)
- Monitor live data: accelerator pedal position(s) vs. throttle plate angle, 5V reference and ground voltages
- Check for related codes (pedal/TP sensor correlation, throttle actuator circuits) that provide context
- Perform basic wiggle tests while watching live data to detect intermittent connector/wire faults
Signal parameters
- Accelerator pedal sensor voltages: typically two channels that should correlate; idle ~0.5–1.0 V, wide open ~4.0–4.5 V (values vary by vehicle)
- Throttle position sensor/angle: 0–100% or 0–90° sweep; should follow pedal input after ECU processing
- 5 V reference supply present and stable at sensors (approx. 5.0 V)
- Sensor ground near 0 V (low millivolt level)
- No large voltage spikes, dropouts, or inverse signals during operation
Diagnostic algorithm
- Connect a professional scan tool and read all codes and freeze-frame data. Note ignition state and any historic occurrences.
- Monitor live data: compare accelerator pedal position sensors (both channels, if present) and throttle plate angle. Check for correlation and smooth response as pedal is pressed/released.
- Inspect wiring and connectors for physical damage, corrosion, or loose pins at the throttle body, pedal assembly, and ECU. Repair any faults.
- Measure 5 V reference and ground at pedal and throttle sensors with key ON. Verify stable supply and ground.
- Measure sensor output voltages at rest and during pedal travel. Look for open, short to ground, or short to voltage conditions.
- Perform wiggle tests on harnesses while monitoring live data to find intermittent faults.
- If wiring and connectors are good, bench-test or replace the throttle body / pedal assembly per manufacturer procedure. If replacing, perform throttle adaptation/learn if required.
- If faults persist after parts and wiring verified, check ECU power/ground circuits and consider ECU software update or ECU replacement as a last step.
- Clear codes and road-test to confirm repair. Re-check for reappearance and for other related codes.
Likely causes
- Wiring/connectors between throttle body and ECU (most common)
- Faulty throttle position sensor or throttle actuator
- Accelerator pedal position sensor fault or sensor correlation error
- Low battery voltage or intermittent supply to sensors/ECU
Fault status
Status
Electric throttle signal malfunction — reduced engine power. Inspect throttle/pedal sensors and wiring. Service required.
Repair difficulty: Medium
Diagnostic time: 1.0-2.5 hours
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