C1124 — Input Shaft Speed Signal Missing/Faulted #

Please note: The description for this code may vary depending on the vehicle manufacturer (OEM). Below is a list of known label variations for C1124.

• Input Shaft Speed Sensor Signal Fault (Nissan, Infiniti)
• Input/Turbine Shaft Speed Sensor Circuit Malfunction (Hyundai, Kia)
• Transmission Input Speed Sensor Signal Missing (Chrysler, Dodge, Jeep)

Summary of C1124 Code #

The C1124 code indicates that the vehicle’s onboard diagnostics (OBD-II/EOBD) system has detected a problem with the input shaft speed sensor signal. The input shaft speed sensor, also called the input or turbine sensor, measures the rotational speed of the transmission’s input shaft and sends this data to the transmission control module (TCM). This information is crucial for shift timing and overall transmission operation. When the sensor signal is missing, erratic, or out of expected range, the system sets the C1124 code. This may trigger a warning light and can lead to drivability problems if left unresolved.

Common Symptoms for Code C1124 #

A malfunction with the input shaft speed sensor can cause a range of symptoms—some subtle, others more obvious. Typically, you might notice changes in how your vehicle shifts or reacts during normal driving. Here’s what to watch for:

• Check Engine Light or Transmission Warning Light illuminated
• Harsh or delayed shifting
• Transmission stuck in limp mode (vehicle only operates in a single gear)
• Erratic speedometer readings (in some cases)
• Poor acceleration or reduced power
• Unusual noises from the transmission area

Most Likely Causes for C1124 #

The C1124 code is most often triggered by issues related to the input shaft speed sensor or its wiring. However, other factors can contribute as well. Here are the most common causes, listed in order of likelihood:

1. Faulty input shaft speed sensor (sensor failure or internal short/open)
2. Damaged sensor wiring or connectors (corrosion, loose terminals, broken wires)
3. Debris or metal shavings on sensor tip (affects magnetic signal pickup)
4. Faulty transmission control module (TCM)
5. Internal transmission mechanical problems (rare: damaged reluctor ring or shaft)

Step-by-Step Diagnostic Guide for C1124 #

Proper diagnosis is key to avoiding unnecessary repairs. Follow these steps to pinpoint the cause of the C1124 code:

1. Record all trouble codes and freeze frame data using a scan tool.
2. Clear codes, then test drive the vehicle to see if C1124 returns.
3. Visually inspect the input shaft speed sensor and wiring harness for obvious damage or corrosion.
4. Check sensor connector for bent, pushed-out, or corroded pins.
5. Test the input shaft speed sensor using a multimeter (verify resistance/specs per OEM manual).
6. Check for debris or metal shavings on the sensor tip and clean if needed.
7. Inspect the wiring from the sensor to the TCM for continuity and shorts.
8. Test the TCM (if all else passes, and code persists—OEM procedure required).

Possible Repairs for C1124 #

Once you’ve identified the root cause, these are the most common repairs for a C1124 code:

• Replace the input shaft speed sensor if faulty or out of spec
• Repair or replace damaged wiring or connectors
• Clean the sensor tip (remove any metal shavings or debris)
• Replace or repair the TCM if it’s determined to be defective
• Address internal transmission issues (rare; may require specialist intervention)

Is It Safe to Drive with Code C1124? #

Limited—While your vehicle may still be drivable with code C1124, it is not recommended to continue regular use. The transmission can enter limp mode (fixed gear), shifts may become harsh or unpredictable, and there’s a risk of further damage if the underlying issue isn’t addressed. Always prioritize diagnosis and repair to avoid expensive transmission repairs down the line.

Vehicles Most Commonly Affected by C1124 #

While code C1124 can appear on a range of vehicles equipped with electronic automatic transmissions, it’s most frequently reported on certain makes and models:

• Nissan (Altima, Maxima, Murano, Pathfinder, Rogue)
• Infiniti (G35, QX60, M35)
• Hyundai (Santa Fe, Sonata, Tucson)
• Kia (Sorento, Optima, Sportage)
• Chrysler, Dodge, Jeep (with electronically controlled transmissions)

Common Mistakes & Best Practices for C1124 #

It’s easy to misdiagnose the root cause of a C1124 code if you skip key diagnostic steps. Avoid these frequent pitfalls, and follow best practices to ensure a proper fix:

• Replacing the sensor without checking wiring or connectors—bad connections are just as common as failed sensors.
• Ignoring sensor contamination—metal shavings can disrupt signal and are easy to clean.
• Not verifying with OEM specs—always compare sensor readings to the manufacturer’s values.
• Overlooking related codes—multiple transmission codes may point to a bigger issue.

Quick FAQ for Code C1124 #

Here are answers to the most common questions about the C1124 input shaft speed sensor code:

Q: How much does it cost to fix C1124?
A: Costs range from $50–$150 for a replacement sensor (parts and labor). Wiring repairs may vary. TCM or internal transmission repairs are more expensive and less common.

Q: Can I clear the code myself?
A: You can clear the code with an OBD-II scanner, but if the underlying problem isn’t fixed, the code will return. Always address the root cause to avoid further issues.