Equus 3110 - CanOBD2 Diagnostic Tool - Manual (Page 23)

CAN OBD2 21
E
Onboard Diagnostics
DIAGNOSTIC TROUBLE CODES (DTCs)
DTCs and MIL Status
When the vehicle’s on-board computer detects
a failure in an emissions-related component
or system, the computer’s internal diagnostic
program assigns a diagnostic trouble code
(DTC) that points to the system (and sub-
system) where the fault was found. The diag-
nostic program saves the code in the com-
puter’s memory. It records a “Freeze Frame” of
conditions present when the fault was found, and lights the Malfunction
Indicator Lamp (MIL). Some faults require detection for two trips in a
row before the MIL is turned on.
The “Malfunction Indicator Lamp” (MIL) is the accepted term
used to describe the lamp on the dashboard that lights to
warn the driver that an emissions-related fault has been
found. Some manufacturers may still call this lamp a “Check
Engine” or “Service Engine Soon” light.
P 0 2 0 1
B
C
P
U -
-
-
- Body
Chassis
Powertrain
Network
-
-
-
- Generic
Manufacturer Specific
Generic
Includes both Generic and Manufacturer
Specific Codes 0
1
2
3
Identifies what section of the system
is malfunctioning
Identifies the system where the
problem is located:
1
2
3
4
5
6
7
8
-
-
-
-
-
-
-
-
Fuel and Air Metering
Fuel and Air Metering (injector circuit
malfunction only)
Ignition System or Misfire
Auxiliary Emission Control System
Vehicle Speed Control and Idle Control
System
Computer Output Circuits
Transmission
Transmission
OBD 2 DTC EXAMPLE
P0201 - Injector Circuit Malfunction, Cylinder 1