C1117 — RPM Input Circuit Failure

OBD2 code C1117 flags a problem with the sensor and actuator circuits (RPM input circuit failure). The car is usually drivable while you plan the repair. Common culprits: faulty sensor or actuator of the affected circuit, open or shorted wiring in the circuit, corroded, loose or damaged connector.

chassis (brakes/steering/suspension)

Is it safe to drive?

Short-term driving is OK In most cases the car remains drivable, possibly with reduced performance or a disabled auxiliary system. If symptoms include stalling, no-start or brake/steering warnings, treat it as urgent.

How to diagnose with an OBD scanner

Read the code and freeze frame Connect an OBD2 scanner, confirm C1117 is stored, and save the freeze frame data — it shows engine conditions when the fault was detected.
Check for companion codes and TSBs Related codes often reveal the real root cause. Also check manufacturer technical service bulletins (TSB) for your make and model — many C0xxx issues have factory fixes or software updates. Search by VIN on the manufacturer site or nhtsa.gov.
Inspect wiring and connectors Visually inspect the wiring harness and connectors related to the RPM input circuit for damage, corrosion, chafing or poor contact.
Subsystem check Measure reference voltage, ground and signal continuity at the component connector.
Subsystem check Wiggle-test the harness while watching the signal in live data — dropouts reveal broken wires.
Verify the repair Clear the code, complete a full drive cycle including the conditions from the freeze frame, and confirm C1117 does not return.

Approximate repair cost

Repair cost depends on which component actually failed. Typical scenarios for C1117 (parts and labor, USD, independent shop rates): Control module repair: $300–$1,000; Repair wiring or connectors: $80–$250; Replace the faulty sensor or actuator: $150–$500. Overall, fixing C1117 usually costs between $80 and $1,000. An accurate diagnosis before buying parts saves money — the most expensive scenario is rarely the first one to check.

Common questions

Will C1117 clear itself?

Sometimes C1117 clears after a few drive cycles if the fault was intermittent — for example a loose connector or a tank of bad fuel. The underlying cause usually remains, so the code tends to return. Clear it once; if it comes back, diagnose rather than erase it repeatedly.

How do I diagnose C1117 myself?

Start with a scan: confirm C1117, save the freeze frame and note any companion codes. Then inspect the wiring and connectors related to the RPM input circuit, and verify the suspect component against live data before buying parts.

What is the most common cause of C1117?

The most common causes are: faulty sensor or actuator of the affected circuit, open or shorted wiring in the circuit, corroded, loose or damaged connector.

How much does it cost to fix C1117?

Control module repair — $300–$1,000; Repair wiring or connectors — $80–$250; Replace the faulty sensor or actuator — $150–$500. Exact cost depends on the root cause, your vehicle and local labor rates — a proper diagnosis is the cheapest first step.

What does OBD2 code C1117 mean?

When your scan tool displays C1117, the vehicle's control module is reporting that a signal in the RPM input circuit has fallen outside its expected range. Technicians classify this as a chassis-system fault, meaning the issue lives somewhere in the network of sensors and actuators that report rotational data to various controllers — often the ABS, traction control, or stability system. The module does not flag this code after a single bad reading; it waits until the anomaly shows up repeatedly under specific conditions before lighting the check engine or ABS warning lamp.

To understand why C1117 triggers, it helps to know how modern vehicles process RPM data. Wheel-speed sensors, engine-speed sensors, and output-shaft speed sensors all feed information to different control units. Those units compare the incoming data against calibrated values. When the signal voltage, frequency, or pattern drifts outside the acceptable window — due to a bad sensor, damaged wiring, or a poor ground — the module logs C1117 and captures a freeze frame snapshot. That snapshot records engine load, RPM, coolant temperature, and vehicle speed at the moment the fault occurred, and that information is your most valuable clue when you start diagnosing the problem.

Common Symptoms of C1117

The check engine or ABS warning lamp stays illuminated on the dashboard
The vehicle may enter a reduced-power limp mode, depending on which component lost reliable RPM data
The system that relies on the affected sensor operates intermittently or stops working entirely
Some vehicles show a noticeable jump in fuel consumption because the engine management system is receiving unreliable speed or RPM signals
Traction control or stability systems may become unavailable, since they depend on accurate wheel-speed data
In rare cases, the speedometer or tachometer behaves erratically or drops to zero

What Causes C1117?

A failed or dying sensor or actuator that feeds the RPM input circuit — this is the most frequent culprit
A weak or interrupted ground connection at the affected component or control module
Corrosion, looseness, or physical damage at the electrical connector, preventing clean signal delivery
A break or abrasion in the wiring harness that causes intermittent signal loss
An internal driver fault inside the control module itself, where the circuitry that processes the sensor signal has degraded

How to Diagnose C1117

Plug in a quality OBD2 scanner and confirm C1117 is present in the stored codes. Save the associated freeze frame data before clearing anything — those recorded conditions are exactly what you need to replicate during your road test.
Look for any other trouble codes stored alongside C1117. Related codes often point directly to the failing component. Check for technical service bulletins specific to your make and model; manufacturers sometimes publish known issues with software updates or repair procedures for chassis network codes.
Perform a close visual inspection of the wiring harness and connectors tied to the RPM input circuit. Look for chafed insulation, bent pins, moisture intrusion, or greenish corrosion that could interrupt the signal.
With the connector unplugged, check reference voltage, ground integrity, and signal wire continuity at the component using a multimeter. Compare your readings against the manufacturer's specifications.
Reconnect the sensor and use live data on your scanner while gently wiggling the harness and connectors. Any signal dropout or erratic reading while moving the wires confirms an intermittent wiring fault.
Clear the code and drive the vehicle through a complete drive cycle — especially the conditions recorded in the freeze frame — to see whether C1117 returns.

Repair Options and Costs

The right fix depends entirely on what your diagnosis reveals. Sensor or actuator replacement is usually the least expensive route, while control module work sits at the higher end of the scale.

Replace the faulty sensor or actuator — parts and labor typically run $150–$500
Repair wiring or connectors — expect to pay $80–$250 for the labor and any necessary parts such as terminals or weather seals
Repair or replace the control module — this is the most costly scenario, ranging from $300–$1,000 depending on whether the module can be reprogrammed or needs physical replacement

How Much Does It Cost to Fix C1117?

The total bill for C1117 depends almost entirely on which part of the circuit has failed. Based on typical independent shop labor rates in the United States, most repair scenarios fall between $80 and $1,000. Wiring and connector repairs cluster at the lower end of that range and are the most common cause. Control module replacement or repair sits at the upper end but is relatively uncommon as a root cause. The smartest move is to invest in a thorough diagnosis before purchasing any parts — an expensive control module is rarely the first thing to blame, and many C1117 issues turn out to be nothing more than a corroded connector.

Can You Drive with C1117?

For most vehicles, C1117 does not immediately leave you stranded. The car will typically continue to run, though you may notice reduced performance or certain auxiliary systems going offline. However, if the fault causes stalling, a no-start condition, or triggers warnings related to the brakes or steering, stop driving and address it right away. Do not ignore a fault that affects safety-critical systems, even if the engine seems to run fine.