GM Service Manual Online
For 1990-2009 cars only

The DTCs for this vehicle include DTC symptoms. A DTC symptom is a 2-digit number which adds additional detail to a DTC. The DTC symptom provides the technician additional information without requiring a large increase in the number of new DTCs.

DTC Symptom Categories

The DTC symptom is made up of 2 alphanumeric digits. The first digit following the DTC indicates the DTC symptom category. There are 16 possible categories available in the range of 0 through the letter F. Currently there are 8 categories in use, 0 through 7. These 8 categories together with their definitions are given below.

Category #

Category name

Category Description

0

General Electrical Failures

This category includes standard wiring failure modes, direct current quantities related by Ohm's Law and quantities related to amplitude, frequency or rate of change, and wave shape.

1

Additional General Electrical Failures

This category includes the overflow from the previous category.

2

FM/PWM (Frequency/Pulse Width Modulated) Failures

This category includes faults related to frequency modulated and pulse width modulated inputs and outputs of the ECU. This category also includes faults where position is determined by counts.

3

ECU internal failures

This category includes faults related to memory, software, and internal electrical circuitry requiring ECU replacement.

4

ECU Programming Failures

This category includes faults related to operational software, calibrations, and options remedied by programming the ECU.

5

Algorithm Based Failures

This category includes faults based on comparing two or more input parameters for plausibility or comparing a single parameter to itself with respect to time.

6

Mechanical Failures

This category includes faults detected by inappropriate motion in response to an ECU controlled output.

7

Bus Signal / Message Failures

This category includes faults related to bus hardware and signal integrity. This category is also used when the physical input for a signal is located in one ECU and another ECU diagnoses the circuit.

8-F

Reserved by Document

Not in use at this time.

DTC Symptom Subtypes

The second digit of the DTC symptom is the subtype of the DTC symptom. These subtypes and their categories, together with their definitions, are given in the following table. DTC symptom 00 is a special case. If 00 is displayed, only the base code number and its description apply. Information regarding the fault will be provided in the code setting criteria.

DTC Symptom

DTC Symptom Description

00

no additional information

01

short to battery

02

short to ground

03

voltage below threshold

04

open circuit

05

short to battery or open

06

short to ground or open

07

voltage above threshold

08

signal invalid

09

rate of change above threshold

0A

rate of change below threshold

0B

current above threshold

0C

current below threshold

0D

resistance above threshold

0E

resistance below threshold

OF

erratic

10

reserved

11

above maximum threshold

12

below minimum threshold

13

voltage low/high temperature

14

voltage high/low temperature

15

signal rising time failure

16

signal falling time failure

17

signal shape/waveform failure

18

signal amplitude < minimum

19

signal amplitude < maximum

1A

bias level out of range

1F

intermittent

21

incorrect period

22

low time < minimum

23

low time > maximum

24

high time < minimum

25

high time > maximum

26

frequency too low

27

frequency too high

28

incorrect frequency

29

too few pulses

2A

too many pulses

2B

missing reference

2C

reference compare error

31

general checksum failure

32

general memory failure

33

special memory failure

34

RAM failure

35

ROM failure

36

EEPROM failure

37

watchdog/safety processor failure

38

supervision software failure

39

internal electronic failure

41

operational software/calibration data set not programmed

42

calibration data set not programmed

43

EEPROM error

44

security access not activated

45

variant not programmed

46

vehicle configuration not programmed

47

VIN not programmed

48

theft/security data not programmed

49

RAM error

4A

checksum error

4B

calibration not learned

51

calculation failure

52

compare failure

53

temperature low

54

temperature high

55

expected number of transitions/events not reached

56

allowable number of transitions/events exceeded

57

expected reaction after event didn't occur

58

incorrect reaction after event

59

circuit/component protection time-out

61

actuator stuck

62

actuator stuck open

63

actuator stuck closed

64

actuator slipping

65

emergency position not reachable

71

invalid serial data received (signal validity bit indicates failure)

72

alive counter incorrect/not updated

73

parity error

74

value of signal protection calculation incorrect

75

signal above allowable range

76

signal below allowable range

7F

erratic

Example

The DTC symptoms associated with each DTC provide more information about the fault that caused that DTC. An example of a DTC displayed can be B1451 05 where the B1451 is the DTC, and 05 after the space represents the DTC symptom. While the DTC indicates that the fault is in the accessory power circuit, this DTC symptom indicates the circuit is shorted to battery or open. Another possible symptom for this code is B1451 02, where B1451 indicates the accessory power circuit, and 02 indicates the circuit is shorted to ground.