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Retrieving Codes
OVERVIEW OF FAULT CODES
23 Chapter 4
OVERVIEW OF FAULT CODES
IMPORTANT:
Retrieving and utilizing Diagnostic Trouble
Codes (DTC's) for troubleshooting vehicle operation problems is
only one part of an overall diagnostic strategy. Never replace
a part based only on the Diagnostic Trouble Code Definition.
Always consult the vehicle's service manual for more detailed
testing instructions. Each DTC has a set of testing procedures,
instructions and flow charts that must be followed to confirm
the exact location of the problem. This type of information is
found in the vehicle's service manual.
a. Fault Codes are called "Diagnostic Trouble Codes" (DTCs),
"Trouble Codes", “Fault Codes” or "Service Codes" (these
terms are used interchangeably throughout this manual).
These numeric codes are used to identify a problem in any
of the systems that are monitored by the vehicle's on-
board computer.
b. Each Fault Code is assigned a message that identifies the
circuit, component or system area where the problem was
detected.
c. Ford Diagnostic Trouble Codes are composed of two- or
three-digit numbers.
■ Most early model Ford vehicles (up to 1991) use a two-
digit code system.
■ Most late model Ford vehicles (1992 to 1995) use a
three-digit code system.
The computer records codes for three types of
conditions:
1. It records Fault Codes for problems that are present at the
time the Self-Tests are performed (the Code Reader is
used to place the vehicle's computer in Self-Test Mode; the
procedures are described in detail later in this manual).
These types of codes are usually called "Hard Codes".
Hard Codes will make the check engine light or
Malfunction Indicator Lamp (MIL), if equipped, on the
dash to come on and stay on solid.
2. It records and saves Fault Codes for "Intermittent
Problems" (not applicable to MCU systems). These
problems come and go intermittently. Intermittent Fault
Codes may cause the Check Engine/Malfunction Indicator
Lamp (MIL) light to flicker on dash.
4
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