P1157 — Electric throttle signal malfunction

Diagnostic algorithm

1. Read and record all DTCs and freeze-frame data. Note battery voltage when code set.
2. Verify vehicle symptoms and attempt to reproduce while monitoring live TPS, pedal position and throttle commanded/actual values.
3. Visually inspect throttle body connector, pins and wiring for corrosion, bent pins, water ingress or physical damage.
4. With ignition ON (engine off), measure reference voltage and ground at the throttle body connector. Confirm ~5 V reference and good ground continuity to ECU.
5. Measure TPS signal voltages at closed and open throttle positions; compare to expected ranges and to pedal sensor(s). Look for inconsistent or out‑of‑range readings.
6. Perform wiggle test on wiring and connector while watching live data for intermittent changes. Backprobe carefully or use breakout adapter to avoid connector damage.
7. If available, use an oscilloscope to check for noise, dropouts or incorrect waveform shape on sensor outputs.
8. Use diagnostic tool to command throttle actuator and observe reported actual position. Perform adaptation/calibration procedure if supported and required after repairs.
9. If wiring, connectors and power/ground are good but signal remains faulty, consider replacement or bench test of the throttle body assembly.
10. After repair or replacement, clear codes and road test to confirm fault does not return. Re‑check live data and perform final adaptation if needed.
11. If fault persists with good throttle body and wiring, investigate ECU input circuits or consult manufacturer technical service for module testing/recoding.