C1117 — RPM Input Circuit Failure #

Note: The wording of this Diagnostic Trouble Code (DTC) may vary depending on the vehicle manufacturer.

• RPM Input Circuit Malfunction (Nissan, Infiniti)
• Engine Speed Input Circuit Failure (Chrysler, Dodge, Jeep)
• Input Speed Sensor Circuit Error (Hyundai, Kia)
• Transmission Input RPM Signal Fault (Ford, Lincoln)

Summary of the C1117 Code #

The C1117 — RPM Input Circuit Failure code indicates that the vehicle’s control module has detected a fault within the circuit responsible for monitoring engine or transmission RPM (Revolutions Per Minute). The “input circuit” refers to the electrical pathway that delivers the RPM signal from a sensor—typically called the input speed sensor—to the relevant control module, such as the ABS (Anti-lock Braking System) or TCM (Transmission Control Module). When this circuit is interrupted, shorted, or receives an implausible signal, the module sets the C1117 code and may trigger a warning light. The input RPM signal is critical for proper shifting, speed calculation, and safety systems operation. Prompt diagnosis is essential to maintain optimal vehicle performance and avoid further complications.

Common Symptoms for Code C1117 #

If your vehicle has set the C1117 code, you might notice a range of symptoms. While some drivers report minimal changes, others experience clear performance issues. Here are the most frequently observed indicators:

• Illuminated warning lights (ABS, Check Engine, or transmission warning lamp)
• Erratic or harsh shifting (automatic transmissions)
• Speedometer inaccuracy or intermittent failure
• Loss of cruise control function
• ABS or traction control system deactivation
• Reduced engine power or limp mode activation

Most Likely Causes for Code C1117 #

The C1117 code is most often triggered by electrical issues or sensor failures in the RPM input circuit. Understanding the most common sources helps prioritize diagnostics:

1. Faulty input speed sensor (sensor itself is defective or producing erratic signals)
2. Damaged wiring or connectors (corrosion, chafing, open circuit, or short to ground)
3. Loose or corroded electrical connections (especially at the sensor or control module)
4. Failed control module (rare, but possible if all else checks out)
5. Sensor reluctor ring or tone wheel damage (physical damage or excessive debris)

Step-by-Step Diagnostic for Code C1117 #

Diagnosing a C1117 code requires a methodical approach to avoid unnecessary parts replacement. Here’s a structured checklist that both professionals and advanced DIYers can follow:

• Retrieve all stored DTCs and freeze frame data with a scan tool; clear codes and see if C1117 returns.
• Visually inspect the input speed sensor and its wiring harness for physical damage, corrosion, or loose connectors.
• Check for continuity and resistance in the sensor circuit using a digital multimeter—refer to OEM specifications for acceptable ranges.
• Test the input speed sensor signal output (if possible) while spinning the related wheel or shaft; compare readings to OEM values.
• Inspect the reluctor ring (if accessible) for missing teeth, cracks, or excessive debris buildup.
• Check the relevant control module’s connector for bent pins, corrosion, or water intrusion.
• If all previous steps pass, consider testing or substituting the control module as a last resort.

Possible Repairs for Code C1117 #

Resolving the C1117 code involves addressing the root cause identified during diagnostics. The most effective repairs, in order of likelihood, include:

• Replacing the faulty input speed sensor
• Repairing or replacing damaged wiring or connectors in the RPM input circuit
• Cleaning or replacing a damaged reluctor ring or tone wheel
• Securing or cleaning electrical connectors at the sensor and module
• Replacing the control module (only if proven defective after exhaustive testing)

Can You Drive with Code C1117? #

Driving with a C1117 code is generally not recommended. While some vehicles may continue to operate with limited symptoms, the loss of accurate RPM input can affect critical systems such as ABS, transmission control, and engine management. This may compromise vehicle safety, result in poor shifting, or cause limp mode activation. For your safety and to prevent further damage, address this code as soon as possible.

Vehicles Most Commonly Affected by Code C1117 #

The C1117 code is most frequently reported on certain vehicle lines, often due to similar sensor designs or wiring layouts. While it can appear on many makes, the following vehicles are most commonly associated with this fault:

• Nissan Altima, Maxima, Murano, Rogue
• Infiniti G35, QX60, FX35
• Chrysler 300, Town & Country
• Dodge Charger, Journey, Grand Caravan
• Hyundai Santa Fe, Sonata
• Kia Sorento, Optima
• Ford Fusion, Escape

Common Mistakes & Best Practices for Code C1117 #

Technicians and DIYers sometimes fall into predictable traps when working on a C1117 code. Avoiding these pitfalls saves time and money:

• Replacing the input speed sensor without verifying wiring or connector integrity
• Overlooking corrosion or water intrusion at connectors
• Skipping OEM-specific diagnostic procedures or using incorrect resistance specifications
• Neglecting to clear codes and confirm repair with a road test
• Failing to inspect the reluctor ring for physical damage

Best practice: Always follow the diagnostic steps in order, consult OEM wiring diagrams, and double-check repairs before reassembly.

Quick FAQ for Code C1117 #

Here are straightforward answers to the top questions about the C1117 code:

• Q: Can a simple battery disconnect clear the C1117 code?
  A: Temporarily, yes. However, if the underlying issue is not fixed, the code will return once the system runs its next check.
• Q: Is the input speed sensor the same as the vehicle speed sensor?
  A: Not always. The input speed sensor usually monitors RPM of the transmission input shaft, while the vehicle speed sensor tracks wheel or output shaft speed. Always verify your vehicle’s sensor layout before replacing parts.