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Speed & Idle Control Trouble Codes: List & Fixes

P05xx codes cover vehicle speed signals, idle speed control and several auxiliary inputs, including system voltage, oil pressure sensor circuits and cruise control. Idle problems often come from a dirty throttle body or a vacuum leak rather than a failed idle control part. A vehicle speed sensor fault can also upset the speedometer, shift points and ABS on some vehicles.

57Codes
2.9Average severity
16%High or critical
26%DIY-friendly
Severity distributionSeverity distribution

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P0505 Powertrain The engine computer can't hold idle speed where it wants it – usually a dirty or sticking idle… Low P0507 Powertrain The engine idles faster than the computer's target – most often extra air is sneaking… Low P2111 Powertrain The throttle plate stayed more open than commanded – a real safety concern until you know why. High P2138 Powertrain The two sensors in the gas pedal report different pedal positions, so the PCM limits throttle… Moderate P0500 Powertrain The engine computer lost its vehicle speed signal – speedometer, shifting and cruise control… Moderate P0501 Powertrain A speed signal exists, but it doesn't match what engine rpm, gear and other sensors say the car… Low

All codes (38)

All Severity 3+ Severity 4+
P2121 Powertrain The main gas pedal signal stays within normal voltage but moves in a way a real pedal can't. Moderate P2122 Powertrain The main gas pedal sensor reads close to 0 volts, below anything a working pedal produces… Moderate P2123 Powertrain The main gas pedal sensor reads near its full 5-volt supply or higher, even with your foot off… Moderate P2125 Powertrain The PCM lost a valid signal from the second, cross-check sensor in the gas pedal. Moderate P2127 Powertrain The second gas pedal sensor dropped below its minimum voltage, so the PCM can't verify pedal… Moderate P2128 Powertrain The second gas pedal sensor reads above its allowed maximum, so the pedal position can't be… Moderate P2135 Powertrain The two position signals inside the throttle body disagree, so the PCM can no longer trust… Moderate P2138 Powertrain The two sensors in the gas pedal report different pedal positions, so the PCM limits throttle… Moderate

Subsystems

Fuel & Air Metering 193Emission Controls 97Ignition & Misfire 66Transmission 57ECU & Outputs 54Module Communication 43Brakes, ABS & Chassis 36Body Systems 31Hybrid / EV 14