Code
P1503
DAEWOO
P — Powertrain
ACCEL. SWITCH
Views:
UK: 7
EN: 6
RU: 7
AI status
Completed
Completed
100%
Causes
- Faulty accelerator pedal position switch or built‑in accel switch assembly
- Open, shorted or corroded wiring or connector between the switch and ECM
- Poor ground or weak reference voltage to the switch
- Contamination, water ingress or mechanical binding of the pedal/switch
- Failed or intermittent engine control module (rare)
Symptoms
- Malfunction Indicator Lamp (MIL) or Check Engine Light illuminated
- Hard starting, reduced engine power or limp mode
- Poor or delayed throttle response, hesitation or surging
- Inability to accelerate normally or sudden loss of throttle
- Unusual pedal feel or pedal not returning smoothly
What to check
- Read and record freeze frame/scan tool data and note related codes
- Visually inspect accelerator pedal, switch and harness for damage or corrosion
- Backprobe connector at pedal while operating pedal and observe live data (switch state or voltage)
- Check for proper 5V reference and good ground at the switch connector
- Perform wiggle test on harness while monitoring signal for intermittent changes
- Measure continuity and resistance between pedal connector and ECM pins with ignition off
Signal parameters
- Reference voltage: typically ~5.0 V (check vehicle spec)
- Signal voltage: expected within 0–5 V depending on switch/sensor design
- Digital switch style: closed/open states — closed ≈ 0 V (or continuity), open ≈ reference voltage (≈5 V)
- Analog sensor style: smooth change in voltage as pedal moves; no sudden jumps or dropouts
- Expected response: consistent, repeatable change when pedal is pressed and released
Diagnostic algorithm
- Verify the code(s) with an OBD-II scanner and record freeze frame and related codes (e.g., throttle/PPS codes).
- Visually inspect pedal assembly, connector, and wiring for damage, water entry, or corrosion; repair obvious issues.
- With ignition ON (engine off), backprobe the pedal connector: verify the presence of reference voltage and a good ground.
- Operate the pedal while monitoring the switch signal or APP values on a scan tool: confirm correct state changes and look for dropouts or erratic readings.
- Check continuity and resistance between the pedal connector and ECM connector (ignition off) to identify opens/shorts.
- Perform a wiggle test on the harness and connectors while watching live data to reproduce intermittent faults.
- If wiring and switch fail testing, replace the accelerator switch/pedal assembly and retest.
- Clear codes and test drive; if the fault returns, consider ECM input circuit inspection or professional bench testing of the ECM.
Likely causes
- Broken/frayed wire or pinched harness at pedal or firewall
- Corroded connector terminals at pedal or ECM
- Accelerator switch electrical contacts worn or stuck
- Aftermarket modifications near pedal harness (alarms, stereo) damaging wires
- Intermittent ground at chassis/ECM
Fault status
Status
P1503 — Accelerator switch circuit malfunction: open, short, or intermittent signal detected between accelerator pedal switch and ECM.
Repair difficulty: Medium
Diagnostic time: 0.5-2.0 hours
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