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The diagnostic trouble code E21700 indicates an invalid signal for the vehicle speed, with the transmitter being the ICM (Instrument Cluster Module). Here’s more information about this code:

Definition/Description: E21700 is a code generated when the ICM module detects an invalid or inconsistent signal for the vehicle speed. The vehicle speed is typically obtained from sensors and used by various vehicle systems and functions.

Meaning: The code suggests that the ICM module has received an invalid signal for the vehicle speed, indicating a problem with the accuracy or consistency of the speed signal. This can be caused by issues with the sensors or circuits involved in measuring and transmitting the speed information.

Causes: Some potential causes for this code include:

1. Faulty vehicle speed sensor: The sensor responsible for measuring the vehicle speed may be malfunctioning, providing inaccurate or inconsistent readings.
2. Wiring or connector issues: There may be wiring or connector problems between the vehicle speed sensor and the ICM module, such as loose connections, damaged wires, or corroded terminals, causing signal irregularities.
3. Sensor alignment or calibration issues: The vehicle speed sensor may require alignment or calibration to ensure accurate readings.
4. Faulty ICM module: In some cases, the ICM module itself may have a malfunction or internal issue that affects its ability to interpret the speed signal correctly.

Symptoms: The symptoms associated with this code may include:

1. Illumination of the instrument cluster warning light.
2. Inaccurate or erratic readings displayed for the vehicle speed.
3. Malfunction or incorrect operation of systems or features that rely on accurate vehicle speed information, such as the speedometer, cruise control, or ABS system.

Diagnosis: Diagnosing the exact cause of the invalid vehicle speed signal requires performing a series of tests and inspections, including:

1. Using a diagnostic scanner to retrieve and interpret the E21700 code.
2. Checking for any additional related codes or warnings in other control modules.
3. Inspecting the wiring and connectors between the vehicle speed sensor and the ICM module for damage, loose connections, or corrosion.
4. Testing the vehicle speed sensor separately for proper operation and accurate readings.
5. Verifying the alignment or calibration of the vehicle speed sensor if applicable.
6. Testing the ICM module for proper functionality and communication.

Common Mistakes: Common mistakes when dealing with this code include:

1. Neglecting to check the wiring and connectors for faults before replacing sensors or modules.
2. Assuming the problem is solely related to one component without considering the entire system.
3. Not performing a comprehensive inspection of all relevant components, including the vehicle speed sensor, wiring, connectors, and the ICM module.

How serious is this? The severity of this code depends on the specific vehicle and the systems affected by the invalid vehicle speed signal. It may lead to incorrect readings or malfunctions in various vehicle systems that rely on accurate speed information.

What repairs can fix the code? Possible repairs for this code include:

1. Repairing or replacing damaged wiring or connectors between the vehicle speed sensor and the ICM module.
2. Replacing a faulty vehicle speed sensor if diagnosed as the cause of the invalid signal.
3. Aligning or calibrating the vehicle speed sensor if necessary.
4. Replacing the ICM module if diagnosed as the cause of the problem.

It’s important to note that these are general guidelines, and the exact diagnostic and repair steps may vary depending on the vehicle’s make, model, and year.