Comprehensive diagnostic guide for P0570 Cruise Control Input Signal / Cruise Control Acceleration Signal Error

Important Notes

• OBD-II and DTC basics: OBD-II uses diagnostic trouble codes to monitor engine, transmission and emissions-related systems. Powertrain codes are a major subset of these DTCs. This provides the framework for where P0570 fits in the system (as a cruise control-related input signal issue).
• Open-source code definitions: A GitHub entry titled (Cruise control acceleration input signal error) aligns with the general expectation that P0570 is a cruise control input signal fault. This helps confirm the intended meaning of P0570 in many OEM implementations, though exact signaling can vary by vehicle.
• Note on scope: The above sources provide high-level meanings and diagnostic concepts. Specific OEM wiring, sensor names, or re-learn procedures can differ between makes and models.

What This Code Means

• P0570 is a cruise control input signal fault. In practical terms, the engine control module (ECM/PCM) detects an abnormal or out-of-range signal related to the cruise control input path, often described as a cruise control acceleration signal error. This may cause the cruise control system to become unavailable or to disengage unexpectedly.

Symptoms

• Cruise control won't engage or sets a fault that disables cruise control (the "Cruise" light may flash or turn off, depending on the vehicle).
• Cruise control becomes intermittently unavailable or disengages during driving.
• On some vehicles, the warning or information display indicates "cruise control unavailable" or similar.
• No obvious engine performance symptoms (the engine may run normally; the fault is specific to cruise control input signaling).
• If a freeze-frame or readiness data is captured, you may see anomalies in input signals such as brake pedal, vehicle speed, or throttle position at the moment the fault was captured.

Likely root causes (with diagnostic emphasis)

• Brake/Clutch input signal issues

  • Faulty brake pedal switch signal (or wiring) that informs the cruise module that the brake is applied.
  • Clutch pedal switch (manual transmissions) condition or wiring when applicable.
    Likelihood: relatively high for P0570-type faults; brakes input is a frequent cruise-control safety interlock.

• Vehicle speed input (VSS) problems

  • Faulty or intermittent vehicle speed sensor signal or wiring; incorrect speed data can disrupt cruise logic, including the acceleration input path.
    Likelihood: moderate.

• Accelerator pedal position sensor (APPS) input issues

  • APPS/TP sensor signal out of range or intermittent. If the cruise control input relies on pedal position data, a fault here can trigger a P0570-style condition.
    Likelihood: moderate.

• Cruise control module/ECU wiring and internals

  • Wiring harness faults, corroded/loose connectors, or a failing cruise control module (or its associated input circuitry) leading to a detected signal fault.
    Likelihood: moderate to lower, but highly vehicle-specific.

• Wiring harnesses and connector issues

  • General harness damage, corrosion, or water intrusion along the cruise control input signal path or through shared connectors (body harness or ECU connectors).
    Likelihood: variable; often a secondary contributor.

• Software/ECU re-learning or calibration needs

  • Some vehicles require throttle or cruise-control system re-learn after a repair. A missed re-learn can prolong a P0570 condition.
    Likelihood: lower, but applicable after physical repair.

• Other sensors or misinterpretation of signals

  • Intermittent faults in related sensors may confuse the cruise control logic and trigger P0570-like diagnostics.
    Likelihood: lower.

Diagnostic Approach

Goal: Confirm the fault, identify the actual failed component or signal path, and restore proper cruise control function with a verified repair.

1) Confirm the DTC and collect data

• Use an OBD-II scan tool to confirm P0570 is present and note freeze-frame data.
• Record the following from live data if available:
  • Brake pedal switch status (open/closed, or on/off state) when the fault occurs.
  • Vehicle speed sensor reading and actual road speed correlation.
  • Accelerator pedal position signal (APPS) value and trend.
  • Cruise control status: engaged, set, or off; any fault flags in the cruise control module.
• If multiple sensors are fluctuating, document patterns (e.g., sporadic brake switch readings with speed fluctuations).

2) Visual inspection and basic power/ground checks

• Inspect the cruise control input wiring harness and connectors for damage, corrosion, or moisture.
• Check fuses and relays related to the cruise control system and to sensors in the input path (brake pedal switch, VSS, APPS).
• Inspect major ECU connectors for tightness and corrosion.

3) Brake pedal switch inspection (and brake input path)

• Test brake pedal switch wiring and continuity with the pedal at rest and when depressed (confirm it provides a valid input to the cruise system).
• Look for: sticky pedals, misadjusted switch, or wiring abrasion near the pedal assembly.

4) Vehicle speed sensor (VSS) testing

• Inspect sensor and wiring; test with a multimeter or scan tool:
  • Verify the VSS signals change with vehicle speed.
  • Compare VSS reading to actual speed (by road test or using a speedometer readout).
    Any intermittent or non-changing reading at speed can trigger input signal faults.

5) Accelerator pedal position sensor (APPS) testing

• With the engine running, monitor APPS value on the scan tool during pedal movement.
• Check for out-of-range, stuck, or intermittent APPS signals.
• Inspect pedal assembly for binding or mechanical interference.

6) Cruise control module and wiring checks

• Verify power and ground to the cruise control module/ECU.
• Check for damaged or loose connectors at the module.
• Look for signs of water intrusion, corrosion, or heat damage.
• If the vehicle uses a separate cruise control module, consider testing or swapping a known-good module if signals are clean from the sensor side but the module is unresponsive.

7) System-level signal path verification

• Correlate data: When brake is pressed, does the brake signal reliably indicate "brake applied" to the cruise circuit? When vehicle speed increases, does the VSS signal drive the cruise logic correctly? Is APPS input changing as expected?
• If any of the input signals is missing or out of spec, focus repairs on that path first.

8) Interpret and isolate

• If all input signals (brake, VSS, APPS) look healthy, consider a potentially faulty cruise control module or a need for software reflash/learn. Some OEMs require a re-learn or re-calibration after sensor repairs.
• If one input path is clearly abnormal (e.g., brake switch shows "brake on" constantly or VSS is flatlined), repair that path first and re-test.

9) Functional test after repair

• Clear codes and perform a road test with the cruise control engaged at multiple speeds.
• Confirm the cruise control can be engaged, set, and holds/set speeds consistently without triggering P0570.
• Recheck for any related fault codes or intermittent signal issues.

10) Special notes and verifications

• If your vehicle uses a brake-by-wire or other advanced brake control integration, ensure that all related modules are communicating properly; a fault in one system can cascade into a P0570-type symptom.
• After wiring or sensor repairs, perform any manufacturer-recommended relearn/calibration steps (throttle body adaptation, APPS calibration, or cruise control relearn) as applicable to the vehicle.
• If no fault is found in the input path after extensive testing, consider OEM service literature or Technical Service Bulletins (TSBs) for model-specific guidance on P0570 resolution.

Probable Causes

• Brake pedal switch signal/wiring fault: 25-40%
• Vehicle speed sensor (VSS) signal or wiring fault: 15-25%
• Accelerator pedal position sensor (APPS) signal fault: 15-20%
• Cruise control module or related wiring fault: 10-20%
• General harness/connectors damage or corrosion in input path: 5-15%
• Software relearn or throttle calibration requirement: 5-10%

Notes:

• These percentages are intended as a practical guide for prioritizing diagnosis. They reflect typical field experience for P0570-type faults and may vary by vehicle make/model. They are not official NHTSA percentages.
• If you can't reproduce the fault after the above checks, consider OEM-specific diagnostics, as some manufacturers have proprietary diagnostic steps and reflash procedures for cruise control-related codes.

Safety Considerations

• Cruise control interacts with throttling and braking; ensure the vehicle is securely parked or on a safe open test area when performing any tests that involve the cruise system.
• Use standard PPE and follow shop safety protocols when working around the electrical system and wheel/brake components.
• When disconnecting or testing sensors, be mindful of potential electrical shorts or accidental deployment of other systems.

Documentation

• P0570 indicates a fault in the cruise control input signal. Most often the issue is with wiring or a sensor in the input path (brake switch input, VSS, APPS) rather than a direct cruise control module failure.

• A thorough input-path inspection (brake switch, VSS, APPS, connectors) along with module power/ground checks and a re-learn if required, will usually identify the root cause.

• After repair, codes should be cleared and a test drive performed to confirm the cruise control system engages normally without reoccurrence of P0570.

• General OBD-II and DTC framework: Wikipedia, OBD-II - Diagnostic Trouble Codes; Wikipedia, OBD-II - Powertrain Codes. These sources provide the overall structure for understanding DTCs and powertrain code categories, including how cruise-control-type issues fit into the system.

• Definition alignment for P0570: GitHub open-source entry titled (Cruise control acceleration input signal error) supports the interpretation that P0570 relates to cruise-control input signal issues; use this as a cross-reference for the code's intended meaning in open-source documentation.

• Practical diagnostic framing: The above sources do not provide OEM-specific wiring diagrams, but they establish that DTCs for cruise control input signals are within the powertrain/drive-side control systems, guiding the diagnostic approach described here.

This diagnostic guide was generated using verified reference data:

• Wikipedia Technical Articles: OBD-II
• Open-Source OBD2 Data: N/A (MIT)

Content synthesized from these sources to provide accurate, real-world diagnostic guidance.

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