Designation of trouble codes

The diagnostics tool VIDA shows the diagnostic trouble code in plain text according to the following example:

TCM-001F Speed sensor Signal missing Permanent malfunction

This diagnostic trouble code consists of the following parts:

Prefix for control system in question (TCM ) to show what system the diagnostic trouble code belongs to. *
- If the qualifier is, e. g., "Too high signal", the control module interprets that the signal from the sensor is too high. This may mean that, e. g., the voltage is too high, current is too high, frequency is too high, or the pulse ratio (% duty) is too high, all depending on which type of signal it is. Malfunction causes may be, e. g., open circuit or short-circuiting to voltage.
- If the qualifier is "Too low signal", the control module interprets that the signal from the sensor is too low. Malfunction causes may be, e. g., open circuit, short-circuiting to ground, contact resistance in connections.
  NOTE: Information about which type of signal that the control module detects and what conditions are required to detect that a malfunction is found again in the diagnostic trouble code information.
Diagnostic trouble code number (001F ) to decide which diagnostic trouble code is stored. Number of digits in the diagnostic trouble code number may vary. *, **
- If the qualifier is, e. g., "Too high signal", the control module interprets that the signal from the sensor is too high. This may mean that, e. g., the voltage is too high, current is too high, frequency is too high, or the pulse ratio (% duty) is too high, all depending on which type of signal it is. Malfunction causes may be, e. g., open circuit or short-circuiting to voltage.
- If the qualifier is "Too low signal", the control module interprets that the signal from the sensor is too low. Malfunction causes may be, e. g., open circuit, short-circuiting to ground, contact resistance in connections.
  NOTE: Information about which type of signal that the control module detects and what conditions are required to detect that a malfunction is found again in the diagnostic trouble code information.
Title (Speed sensor ) is a text that shows to which component/function the diagnostic trouble code refers.*
- If the qualifier is, e. g., "Too high signal", the control module interprets that the signal from the sensor is too high. This may mean that, e. g., the voltage is too high, current is too high, frequency is too high, or the pulse ratio (% duty) is too high, all depending on which type of signal it is. Malfunction causes may be, e. g., open circuit or short-circuiting to voltage.
- If the qualifier is "Too low signal", the control module interprets that the signal from the sensor is too low. Malfunction causes may be, e. g., open circuit, short-circuiting to ground, contact resistance in connections.
  NOTE: Information about which type of signal that the control module detects and what conditions are required to detect that a malfunction is found again in the diagnostic trouble code information.
Qualifier (Signal missing ) is used to show how the control module has perceived the signal from, e. g., the sensor, or how it detected the monitored function. In this case, the control module has perceived that the signal is missing. There a re a number of other qualifiers for, e. g., too high signal, incorrect signal, too high flow, too low flow, etc. *, **.
- If the qualifier is, e. g., "Too high signal", the control module interprets that the signal from the sensor is too high. This may mean that, e. g., the voltage is too high, current is too high, frequency is too high, or the pulse ratio (% duty) is too high, all depending on which type of signal it is. Malfunction causes may be, e. g., open circuit or short-circuiting to voltage.
- If the qualifier is "Too low signal", the control module interprets that the signal from the sensor is too low. Malfunction causes may be, e. g., open circuit, short-circuiting to ground, contact resistance in connections.
  NOTE: Information about which type of signal that the control module detects and what conditions are required to detect that a malfunction is found again in the diagnostic trouble code information.
Status (Permanent malfunction ) to show the malfunction's status, that is, if the malfunction has been detected in the present driving cycle or not. There are two different status texts, permanent or intermittent. When the control module's diagnosis cannot decide the malfunction's status, the diagnostic trouble code is shown without status text.*

*When reading out diagnostic trouble codes using diagnostic socket with light-emitting diode, you get a three-digit flash code. Then this code is translated to a diagnostic trouble code text using the service information.

For example, if the control module flashes the code 1-2-3 from Engine control module (ECM), it can be translated to, e. g., diagnostic trouble code 1-2-3 Engine temperature sensor. Volvo Diagnostic Key and Volvo System Tester translate these flash codes directly to plain text (add a title). In these diagnostic systems it is not possible to show qualifier or status.

**For systems with diagnostic version called Generic Global Diagnostics (GGD) (adheres to standard ISO/DIS 15031-6.4) the diagnostic trouble code number consists of a letter and six characters. The letter alternatives are B, C, P and N, which means Body, Chassis, Powertrain and Network and indicate to which "function" in the vehicle the diagnostic trouble code belongs. The six following characters may consist of both letters (A-F) and digits (0-9) and indicate the component to which the malfunction refers as well as what type of malfunction. See following example.

BCM-C006A16 Multi-axial acceleration sensor. General electric malfunction. Too low voltage

Fig 1: Identifying Detected Malfunction

Courtesy of VOLVO CARS OF NORTH AMERICA.

A malfunction that is detected is assessed by the control module's self-diagnosis. First after, e. g., a certain time, a certain number of driving cycles, certain driving/operation or other conditions, the control module decides if it is a real malfunction or not.

When self-diagnosis has determined that a real malfunction exists, you can say that the malfunction is confirmed and the malfunction is stored in the control module's trouble code memory in the form of diagnostic trouble codes.

If a malfunction disappears, the diagnostic trouble code will remain for a tome in the diagnostic trouble code memory, but the status of the diagnostic trouble code changes. How long the diagnostic trouble code is stored in the diagnostic trouble code memory is different from control module to control module, as well as between different vehicle models (generation of vehicle model).

In some systems the diagnostic trouble code will be stored until it is erased with the diagnostics tool. In other systems the diagnostic trouble code is erased automatically by the control module after, e. g., a certain number of malfunction-free driving cycles. A new driving cycle (operation cycle) is usually started every time the ignition is turned on.

Information about the nature of the malfunction is stored for every diagnostic trouble code:

when the malfunction was detected (frozen values, counters)
what the driving conditions were at the time (frozen values)
status for the test (diagnosis) (status identifier)
how frequent the malfunction is (counter).

Exactly what is stored is different from control module to control module, as well as between different vehicle models (generation of vehicle model).

If the system is provided with warning light, it is lit when the ignition key is turned to position II. The warning light will go off after a certain number of seconds when no malfunction is detected on the control system.

The warning light will be on in case of a malfunction of the control system. The warning light will be lit first after the malfunction is confirmed as a real malfunction.