A Comprehensive Guide to DTC Fault Type Bytes (FTB) Lists and their Descriptions

In the world of automotive diagnostics, understanding the language of Diagnostic Trouble Codes (DTCs) is crucial for technicians and enthusiasts alike. These alphanumeric codes help p

inpoint issues within a vehicle’s electronic control systems, sensors, and components. One essential component of DTCs is the Fault Type Byte (FTB), which provides vital information about the nature and severity of a problem. In this article, we’ll provide a comprehensive list of common Diagnostic Trouble Code Fault Type Bytes, along with detailed descriptions for each one.

Unlock the mysteries of vehicle diagnostics with our comprehensive ‘List of DTC FTB (Fault Type Byte) with Descriptions.’ Decode fault codes and troubleshoot efficiently for a seamless understanding of automotive issues.

List of all the DTC FTB bytes with their Descriptions

This article describes the list of all the 16 categories DTC FTB Bytes. Understanding the DTC FTB description is crucial for technicians to interpret Diagnostic Trouble Codes accurately and address specific faults within vehicle systems. Either it is a OBD-II or UDS standard DTC, FTB is the main core of any format of DTC. We can read any DTC code with their FTB Byte by using the Read DTC information (0x19) service of UDS Protocol.

FTB (Hex)	Sub-Type Name	FTB Description
0x00	No Sub Type Information	This particular subtype is applied in cases of failures for which the primary DTC text string offers a comprehensive description of the failure itself, without any utilization of Category or Subtype information. For example, an emissions-related DTC (012700 hex) is represented as follows: P0127 Intake Air Temperature Too High.
0x01	General Electrical Failure	This particular category is employed to address General Electrical Failures that do not have a specific subcategory assigned (lacking category information and specific subtype data, for instance, DTC (803901): BO039-01 Second Row Right Frontal Stage 1 Deployment Control – General Electrical Failure).
0x02	General Signal Failure	This subtype is employed for general signal failures that defy classification into a specific subtype. These cases lack both category and subtype information, as exemplified by DTC (403002): C0030 Left Front Tone Wheel – General Signal Failure.
0x03	FM (Frequency Modulated) /PWM (Pulse Width Modulated)Failure	“This particular subtype is employed to address FM/PWM failures that defy classification into a specific subcategory.”
0x04	System Internal Failure	This particular subtype is employed to address internal failures within the control module that cannot be categorized under a specific subtype.
0x05	System Programming Failure	This subtype is employed to categorize system programming failures that defy classification into a specific subtype.
0x06	Algorithm-Based Failure	This subtype is employed to categorize Algorithm-Based Failures that defy classification under a specific subtype.
0x07	Mechanical Failure	“This subtype is designated for mechanical failures that defy categorization under any specific subcategory.”
0x08	Bus Signal / Message Failure	“This subtype is employed to address bus signal or message failures that defy classification under a specific subtype.”
0x09	Component Failure	This subtype is employed to categorize Bus Signal/Message Failures that defy allocation to a particular subtype.
0A – 0F	ISO/SAE Reserved	This value is reserved by the document for future expansion.
0x10	ISO/SAE Reserved	This value is reserved by the document for future expansion.
0x11	Circuit Short To Ground	This particular category is employed to address failures in which the control module detects a ground (battery negative) potential exceeding a specified duration or when an anticipated value deviates.
0x12	Circuit Short To Battery	This particular category is employed to address malfunctions in which the control module monitors the vehicle system’s (battery-positive) voltage potential for an extended duration or when an anticipated value is not met.
0x13	Circuit Open	This specific category is employed to address failures in situations where the control module identifies an open circuit due to the absence of bias voltage, minimal current flow, a lack of alteration in the input state in response to an output, and similar conditions.
0x14	Circuit Short To Ground or Open	This particular subtype is employed in cases of failures in which the condition identified by the control module remains consistent across both indicated failure modes.
0x15	Circuit Short To Battery or Open	This subtype is employed for situations in which the condition identified by the control module remains consistent across multiple indicated failure modes.
0x16	Circuit Voltage Below	This particular subtype is applied in cases of failures, in which the control module’s Threshold monitors a voltage level falling below a designated range, without necessarily indicating a short circuit to ground.
0x17	Circuit Voltage Above Threshold	This particular subtype is employed in cases where the control module detects a voltage reading exceeding a defined range, without necessarily indicating a short to the battery.
0x18	Circuit Current Below Threshold	This subtype is employed to identify failures when the control module detects current flow falling below a specified range.
0x19	Circuit Current Above Threshold	This particular category is employed for instances of failure, wherein the control module detects a current flow exceeding a predetermined range.
0x1A	Circuit Resistance Below Threshold	This particular category is employed for instances of failures in which the control module deduces a circuit resistance falling below a predefined threshold.
0x1B	Circuit Resistance Above Threshold	This particular category is applied to instances of failure in which the control module detects a circuit resistance exceeding a specified range.
0x1C	Circuit Voltage Out of Range	This particular category is employed in cases of failures where the control module detects a voltage level that falls outside the anticipated range but doesn’t specify whether it’s excessively high or excessively low.
0x1D	Circuit Current Out of Range	This subtype is employed to address instances of failure when the control module detects a current that falls outside the anticipated range but is not classified as excessively high or excessively low.
0x1E	Circuit Resistance Out of Range	This particular subtype is employed to address instances of control module failures, in which the module detects a resistance level outside the anticipated range but does not categorize it as excessively high or excessively low.
0x1F	Circuit Intermittent	This particular subtype is employed to address instances of failures in which the control module briefly detects one of the previously specified conditions, albeit not for a duration sufficient to establish a distinct subtype.
0x20	ISO/SAE Reserved	This value is reserved by the document for future expansion.
0x21	Signal Amplitude < Minimum	This subtype is employed in cases of control module failures when it detects a signal voltage below a specified range, without necessarily indicating a short to ground (e.g., low gain).
0x22	Signal Amplitude > Maximum	This subtype is employed to address failures in which the control module detects a signal voltage exceeding a defined range, without necessarily indicating a short to the battery (for instance, due to excessive gain).
0x23	Signal Stuck Low	This subtype is employed for instances of failure in which the control module detects a signal that persists at a low level when transitions are anticipated.
0x24	Signal Stuck High	This particular category is employed in cases where the control module detects a signal that remains in a high state when transitions should be occurring.
0x25	Signal Shape / Waveform Failure	This particular category is employed to describe instances of failure characterized by an incorrect signal shape, such as deviations in amplitude over time due to issues like improper circuit impedance.
0x26	Signal Rate of Change Below Threshold	This particular subtype is employed for instances of signal transitions that occur at a slower rate than what is considered reasonably permissible.
0x27	Signal Rate of Change Above Threshold	This particular subtype is employed to address failures characterized by signal transitions that occur more rapidly than what is considered reasonably permissible.
0x28	Signal Bias Level Out of Range	This specific subtype is employed in cases of control module failures where it applies a bias voltage for zero adjustment failure or a zero signal level to a circuit. This circuit typically carries a signal voltage, such as a bias voltage for an oxygen sensor circuit, or a filtered digital meters per second (m/s) signal when the vehicle is stationary and in use with a lateral accelerator sensor module.
0x29	Signal Invalid	This particular subtype is employed to categorize failures that occur when the signal’s value appears implausible within the context of the operational conditions.
0x2A	Signal Stuck In Range	This particular category is employed to describe instances of failure in which the signal’s value falls within the typical operating range but is not suitable for the present operating conditions.
0x2B	Signal Cross Coupled	This particular category is employed when a signal is determined to be improperly associated with another signal under the server’s monitoring, suggesting that the signals are connected or linked inappropriately.
0x2C	ISO/SAE Reserved	This value is reserved by the document for future expansion.
0x2D	ISO/SAE Reserved	This value is reserved by the document for future expansion.
0x2E	ISO/SAE Reserved	This value is reserved by the document for future expansion.
0x2F	Signal Erratic	This subcategory is employed to address instances of signal momentarily appearing implausible (without reaching the duration for a “signal invalid” status) or displaying discontinuity.
0x30	ISO/SAE Reserved	This value is reserved by the document for future expansion.
0x31	No Signal	“This sub-type is employed in cases where the control module fails to detect an expected signal, such as instances where wheel speed signals are expected for three out of four wheels, and the brakes are not engaged.”
0x32	Signal Low Time < Minimum	This subtype is employed for instances in which the control module identifies that the duration of the low pulse is excessively short in relation to time.
0x33	Signal Low Time > Maximum	This subcategory is employed for instances where the control module identifies that the duration of the low pulse is excessively extended in relation to time.
0x34	Signal High Time < Minimum	“This sub-category is utilized to identify instances where the control module detects that the high pulse duration is insufficient in relation to time.”
0x35	Signal High Time > Maximum	“This sub-category is employed to address instances in which the control module identifies that the high pulse is excessively wide concerning time.”
0x36	Signal Frequency Too Low	“This sub-type is employed in cases where the control module identifies an extended duration for a single cycle of output within a specified sample size.”
0x37	Signal Frequency Too High	“This subcategory is applied to instances where the control module identifies a deficiency in the duration of a single output cycle within a specified sample size.”
0x38	Signal Frequency Incorrect	“This subtype is employed for instances in which the control module registers an inaccurate count of cycles within a specified time frame.”
0x39	Signal Has Too Few Pulses	This sub-category is applied in cases of failures where the control module registers an insufficient number of pulses, such as when the position is calibrated using counts spanning from one extreme to the other.
0x3A	Signal Has Too Many Pulses	“This particular subtype is employed to identify failures in which the control module registers an excessive number of pulses, such as when position calibration is recorded in counts spanning from one extreme to the other.”
0x3B-0x3F	ISO/SAE Reserved	This value is reserved by the document for future expansion.
0x40	ISO/SAE Reserved	This value is reserved by the document for future expansion.
0x41	General Checksum Failure	“This particular sub-type is employed by the control module to signal an inaccurate checksum calculation in cases where the memory type is unspecified.”
0x42	General Memory Failure	This sub-type is utilized by the control module to signal a memory failure without specifying the memory type.
0x43	Special Memory Failure	The control module utilizes this sub-type to signify a memory failure, especially when the particular memory type is not specified within this category.
0x44	Data Memory Failure	The control module utilizes this sub-type to signal a failure in data or working memory within embedded systems that employ FLASH memory. This type of memory serves a similar function as RAM does in embedded systems featuring RAM/ROM/EEPROM configurations.
0x45	Program Memory Failure	The sub-type is employed by the control module to signal a program memory malfunction in embedded systems utilizing FLASH memory. This is analogous to ROM in embedded systems that feature RAM/ROM/EEPROM.
0x46	Calibration / Parameter Memory	The control module employs this sub-type to signal a malfunction in the calibration or failure parameter memory of embedded systems utilizing FLASH memory. This is analogous to EEPROM in embedded systems that use RAM or ROM in addition to FLASH memory.
0x47	Watchdog / Safety uC Failure	“The control module employs this subcategory to signal the occurrence of a watchdog or safety microcontroller (uC) failure.”
0x48	Supervision Software Failure	“The control module utilizes this sub-type to signal a software failure in its supervisory function.”
0x49	Internal Electronic Failure	“This particular sub-type is employed by the control module to signal the identification of an internal circuit malfunction.”
0x4A	Incorrect Component Installed	This sub-type is employed by the control module to signal a disparity between the hardware connected to the control module and the hardware anticipated by the control module.
0x4B	Over Temperature	“This subcategory is employed by the control module to signal the identification of an internal temperature exceeding the anticipated range.”
0x4C – 0x4F	ISO/SAE Reserved	This value is reserved by the document for future expansion.
0x50	ISO/SAE Reserved	This value is reserved by the document for future expansion.
0x51	Not Programmed	This subtype serves as a signal to the control module, indicating the necessity for programming.
0x52	Not Activated	This subtype is employed by the control module to signify that a segment of the program remains disabled.
0x53	Deactivated	“This subtype serves as an indicator for the control module, signaling that a specific section of the program has been deactivated.”
0x54	Missing Calibration	This subtype is employed by the control module to signal the necessity of instructing the control module about operational parameters, such as the range, for a sensor or actuator. This instruction can be achieved through methods like programming or learning.
0x55	Not Configured	This subtype is employed by the control module to signal the requirement for accessing (programming) the sub-system option details or the vehicle option details.
0x56	Invalid / Incompatible	This subtype denotes a control module or system configuration that is invalid. For example, it may involve mutually exclusive options being enabled simultaneously or a setup that is not compatible with the currently installed hardware or software.
0x57	Invalid / Incompatible Software	This subtype is employed by the control module to signal the detection of an invalid component software component (calibration or program) for the control module or its incompatibility with other hardware or software identified by the control module. For example, a downloaded calibration software component may be incompatible with a permanent or downloaded strategy software component.
0x58 – 0x60	ISO/SAE Reserved	This value is reserved by the document for future expansion.
0x61	Signal Calculation Failure	This subtype is used for algorithm-based calculation failures.
0x62	Signal Compare Failure	This particular subtype is employed in situations where the control module assesses the plausibility of two or more input parameters.
0x63	Circuit / Component Protection Time-Out	“This particular subtype is employed for instances in which the control module identifies that a function has been active for a duration exceeding a predefined time threshold.”
0x64	Signal Plausibility Failure	This subtype is employed for instances in which the control module identifies a single input parameter for plausibility assessment.
0x65	Signal Has Too Few Transitions / Events	This subtype is employed for instances of failure where the control module continuously monitors a parameter over a defined period, maintaining it within specified limits, and identifies a lower count of transitions than what is expected.
0x66	Signal Has Too Many Transitions / Events	This particular subtype is employed in cases of failures where the control module continuously monitors a parameter over a defined time frame, and identifies an excessive number of transitions beyond the anticipated threshold.
0x67	Signal Incorrect After Event	This subtype is employed to address failures in which the control module fails to detect the appropriate alteration of a parameter or a set of parameters in response to a specific event.
0x68	Event Information	This subtype is employed by the control module to signal the detection of a system event that was initiated not by the control module itself but compels the control module to record a Diagnostic Trouble Code (DTC), for instance, due to a deficiency in functionality from another system or control module.
0x69 – 0x6F	ISO/SAE Reserved	This value is reserved by the document for future expansion.
0x70	ISO/SAE Reserved	This value is reserved by the document for future expansion.
0x71	Actuator Stuck	This particular category is applied to situations in which the control module fails to register any movement when attempting to activate a motor, solenoid, relay, and similar components.
0x72	Actuator Stuck Open	This specific category is employed to describe instances of failure in which the control module fails to detect any movement when it instructs the activation of a motor, solenoid, relay, or any other component to engage a piece of equipment.
0x73	Actuator Stuck Closed	This particular category is employed to address instances in which the control module fails to detect any movement when instructing a motor, solenoid, relay, or other components to activate and initiate the operation of a piece of equipment.
0x74	Actuator Slipping	This particular category pertains to instances in which the control module identifies a prolonged period required to instruct a motor, solenoid, relay, or similar component to execute the task of positioning a piece of equipment as intended.
0x75	Emergency Position Not Reachable	This specific category pertains to situations in which the control module cannot establish communication with a motor, solenoid, relay, or similar device, preventing it from carrying out the critical task of moving a piece of equipment to the emergency position.
0x76	Wrong Mounting Position	Utilization of this subcategory pertains to instances in which the control module identifies incorrectly installed components, such as an acceleration sensor exhibiting a 90° positional error.
0x77	Commanded Position Not Reachable	This particular category is employed to address instances in which the control module cannot establish communication with a motor, solenoid, relay, or similar device in order to initiate the movement of a piece of equipment, often as a result of either actuator malfunction or adverse mechanical conditions.
0x78	Alignment or Adjustment Incorrect	This particular category pertains to failures in which the control module identifies inaccurately adjusted or misaligned components.
0x79	Mechanical Linkage Failure	This particular subtype pertains to instances in which the control module identifies the actuator as functional, but the driven device remains non-operational. An example of such a failure is a broken drive cable for a power sliding door.
0x7A	Fluid Leak or Seal Failure	This particular category pertains to instances of malfunction in which the control module identifies an abnormal flow of gas or liquid into, out of, or through a mechanical component.
0x7B	Low Fluid Level	This particular category pertains to instances in which the control module identifies insufficient fluid levels that could impede the system’s optimal functioning.
0x7C-0x7F	ISO/SAE Reserved	This value is reserved by the document for future expansion.
0x80	ISO/SAE Reserved	This value is reserved by the document for future expansion.
0x81	Invalid Serial Data Received	This particular subcategory is employed by the control module to signify that a signal has been received, and either its associated validity bit is set to ‘invalid,’ or the signal has been determined as invalid through post-processing.
0x82	Alive / Sequence Counter Incorrect / Not Updated	This subtype serves as a signal to the control module, indicating that it has received an incorrect or outdated signal without the accompanying rolling count value being appropriately refreshed.
0x83	Value of Signal Protection Calculation Incorrect	This particular subtype is employed by the control module to signify that a message has undergone incorrect protection (checksum) calculation during processing.
0x84	Signal Below Allowable Range	This particular category is employed to address instances of failures in which a circuit parameter, communicated through serial data, falls short of a predefined threshold.
0x85	Signal Above Allowable Range	This particular category is employed to address instances of circuit failures characterized by an excess of a specific range in the data reported through serial communication.
0x86	Signal Invalid	This subcategory is employed to address instances of circuit failures in which the reported serial data does not align with the expected operating conditions.
0x87	Missing Message	This particular category pertains to instances of failure in which one or more anticipated messages are not successfully received. This can occur in situations such as periodic transmissions with extended repetition intervals or when messages fail to be delivered due to unforeseen reset events involving the relevant component, such as the engine control unit communicating with the ABS.
0x88	Bus off	This subtype is used for failures where a data bus is not available.
0x89-0x8E	ISO/SAE Reserved	This value is reserved by the document for future expansion.
0x8F	Erratic	This particular category is employed to address instances of signal failures in which the data transmitted through a serial connection briefly exhibits implausibility or interruptions.
0x90	ISO/SAE Reserved	This value is reserved by the document for future expansion.
0x91	Parametric	This subtype pertains to instances of malfunction where the control module identifies that a component parameter (such as capacitance or inductance) deviates from its anticipated range.
0x92	Performance or Incorrect	This particular category is applied to instances in which the control module has identified that the component’s performance is either beyond the anticipated range or operating in an improper manner.
0x93	No Operation	This subcategory pertains to malfunctions in which the control module identifies that the component is not functioning as intended.
0x94	Unexpected Operation	This subcategory is employed to address instances in which the control module identifies that the component is functioning in a manner or at a moment when it hasn’t been instructed to do so.
0x95	Incorrect Assembly	This particular category pertains to instances in which the control module identifies that a component has been installed incorrectly, such as situations involving hydraulic pipes being crossed over, circuits being wired incorrectly, or polarity errors.
0x96	Component Internal Failure	This particular category is applied to situations in which the control module has detected a signal indicating an internal fault within a component, such as an intelligent actuator or sensor, signaling a failure.
0x97	Component or System Operation Obstructed or Blocked	This particular category pertains to instances in which the control module identifies that a component’s operation is impeded due to an obstruction, such as the radar beam of an advanced cruise system being blocked.
0x98	Component or System Over Temperature	Utilization of this particular subcategory is for instances where the control module identifies an elevated temperature that could impede the proper functioning of a component or system, such as an obstruction, such as the advanced cruise system radar beam being obstructed.
0x99	ISO/SAE Reserved	This value is reserved by the document for future expansion.
0x9A	Component or System Operating Conditions	Utilization of this category is for instances in which the control module identifies environmental or operational conditions that deviate, whether temporarily or permanently, from the prescribed parameters for proper functionality. Consequently, this leads to the partial or complete failure of a component’s function. For instance, a radio may be rendered inoperative due to its LCD display or CD mechanism being unable to function under extremely cold ambient temperatures.
0x9B-0xEF	ISO/SAE Reserved	This value is reserved by the document for future expansion.
C2	ISO/SAE Reserved	This value is reserved by the document for future expansion.
C3	ISO/SAE Reserved	This value is reserved by the document for future expansion.
C4	ISO/SAE Reserved	This value is reserved by the document for future expansion.
C5	ISO/SAE Reserved	This value is reserved by the document for future expansion.
0xF0-0xFF	Manufacturer Defined	This value is reserved for vehicle manufacturer/system supplier use.

DTC Fault Type Byte Guide

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DTC fault type bytes are invaluable tools for automotive technicians, enabling them to quickly and accurately identify and address issues within a vehicle. Understanding the structure and meaning of these fault type bytes is essential for effective diagnostics and efficient repairs. As technology continues to advance, the role of DTCs in vehicle maintenance will only become more critical, underscoring the importance of staying informed about these diagnostic tools.