Code
C1506
HYUNDAI
C — Chassis
Idle Switch | Closed Throttle Position Switch
Views:
UK: 9
EN: 16
RU: 25
AI status
Completed
Completed
100%
Causes
- Faulty idle/closed-throttle position switch
- Damaged, corroded or disconnected connector or wiring (open, short to voltage or ground)
- Contaminated or mechanically sticking throttle body / switch
- Incorrect switch adjustment or misaligned throttle stop
- Faulty PCM/ECM or poor ground at control module
- Intermittent wiring damage from chafing, heat or moisture
Symptoms
- Check Engine Light or warning lamp illuminated
- Engine idle unstable, rough idle or higher-than-normal idle speed
- Engine may stall at idle or on deceleration
- Reduced or delayed throttle response; possible limp-home mode on some vehicles
- Cruise control inoperative (on some models)
- DTC stored in freeze frame when condition observed
What to check
- Retrieve DTC and freeze-frame data with a scan tool; verify C1506 is current or historical
- Visually inspect throttle body, idle switch connector and wiring for damage, corrosion, or loose pins
- Check for related codes (powertrain/ECM throttle codes) that may give context
- Backprobe the idle switch connector and monitor signal while slowly closing/opening throttle (or using a scan tool)
- Measure reference power and ground at the switch connector (typically a 5V reference and ground)
- Check continuity between the switch connector and PCM pins; check for shorts to power/ground
Signal parameters
- Signal type: digital (ON/OFF) switch indicating throttle closed/idling
- Typical wiring: reference (5V) or ignition-switched supply, signal return to PCM, and ground (verify with factory data)
- Closed position: switch changes state (logical HIGH or LOW) when throttle reaches closed position — consult Hyundai service manual for exact polarity
- Switch transition should be consistent and instantaneous when throttle plate reaches closed position
Diagnostic algorithm
- Connect a scan tool, confirm C1506 and view live data while cycling the throttle to observe closed-throttle switch status.
- Visually inspect the throttle body, idle switch connector and harness for damage, corrosion, rips or pinched wiring.
- With ignition ON (engine off) or as directed by factory procedure, backprobe the switch connector: verify reference voltage, signal voltage and ground presence. Compare to specs.
- Slowly operate the throttle and observe the switch signal state change. If signal does not change at the expected throttle position, test switch continuity with a multimeter per service manual.
- If wiring or connector faults are found, repair/replace damaged wiring or connector and retest. If intermittent, perform wiggle test and secure harness.
- If wiring and connector are good but switch fails spec, replace the idle/closed-throttle position switch and retest.
- After repair, clear DTCs, perform a drive or idle test to ensure code does not return. If C1506 persists, consider throttle body assembly replacement or further ECM diagnosis with factory tools.
- If multiple unrelated throttle/TP sensor codes are present, follow manufacturer procedure for throttle/pedal position sensor relearn and ECM checks.
Likely causes
- Switch contacts worn or stuck from contamination
- Connector pins corroded or bent causing poor continuity
- Broken/shorted harness between throttle body and ECM
- Throttle body return spring weak or binding preventing full closure
- Aftermarket modifications or improper reassembly after service
Fault status
Status
Closed throttle position (idle) switch signal not as expected — closed-throttle switch circuit malfunction detected.
Repair difficulty: Medium
Diagnostic time: 0.5-2.0 hours
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