ProScan Help - What is a Diagnostic Trouble Code? (DTC)

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ProScan Help - What is a Diagnostic Trouble Code? - DTC

What is a Diagnostic Trouble Code?

Diagnostic trouble codes are alphanumeric codes that are used to identify a problem that is present on any of the systems that are monitored by the on-board computer (PCM).

OBD-II diagnostic codes are composed of five characters; one letter followed by 4 digits.

Example DTCs:

P0134
P1155
B0042

First Digit = System Identifier

Digit 1	System
B	Body
C	Chassis
P	Powertrain
U	Network (UART)

Second Digit = Type of Code

Digit 2	Type of Code
0	Generic. Same definition for all manufacturers.
1	Manufacturer-specific. Definition will vary depending on manufacturer.
2+	Will vary depending upon System Identifier. See full breakdown below.

Powertrain Codes Body Codes

P0xxx = Generic B0xxx = Generic

P1xxx = Manufacturer-specific B1xxx = Manufacturer-specific

P2xxx = Generic B2xxx = Manufacturer-specific

P30xx-P33xx = Manufacturer-specific B3xx = Generic

P34xx-P39xx = Generic

Chassis Codes Network Codes

C0xxx = Generic U0xxx = Generic

C1xxx = Manufacturer-specific U1xxx = Manufacturer-specific

C2xxx = Manufacturer-specific U2xxx = Manufacturer-specific

C3xxx = Generic U3xx = Generic

Third Digit = Sub-System

Digit 3 Sub-System

1 Fuel and Air Metering

2 Fuel and Air Metering (Injector Circuit Malfunction Only)

3 Ignition System or Misfire

4 Auxiliary Emission Control System

5 Vehicle Speed Control and Idle Control System

6 Computer Output Circuits

7,8 Transmission

Digits Four and Five

The fourth and fifth digits identify the specific problem.