Innova 3120d, Owner'S Manual, Page: 72 / 131

Ford OBD1 Systems
CODE RETRIEVAL PROCEDURES - OVERVIEW - REVIEWING DTCs
70 3120d
fault code will be stored in memory as a history DTC. If the
malfunction that caused the history DTC to set does not recur within
a predetermined length of time (usually within 40-80 ignition key
start cycles), the computer will automatically erase the related fault
code from its memory.
CODE RETRIEVAL PROCEDURES
Overview of Ford Code Retrieval Process
Ford's computer self-diagnostic system is divided into four main
sections:
1. "Key On Engine Off" (KOEO) Self-Test
2. "Continuous Memory" (CM) Self-Test
3. "Key On Engine Running" (KOER) Self-Test
4. Other EEC-IV System tests
These Self-Tests are specially designed to monitor and/or test the
various components and circuits that are controlled by the vehicle's
computer, and to save and/or transmit diagnostic test results to the
Diagnostic Tool in the form of numerical fault codes.
The "Continuous Memory" Self-Test is designed to run continuously
whenever the vehicle is normal operation. If a fault is detected by the
"Continuous Memory" Self-Test, a fault code is saved in the vehicle's
computer memory for later retrieval.
Ford’s On-Board Diagnostic Self-Tests are designed in such a way that
in order to properly diagnose a problem, you must perform all the Self-
Tests, in the proper sequence.
As described previously, some tests are designed to detect problems
only when the vehicle is in normal operation. Some tests are designed
to activate components and detect problems only with the Key On and
Engine Off. Other tests are designed to activate components and test
their operation only with the Key On and Engine Running. Do not take
short cuts. If you fail to perform a test, or you perform a test out of
sequence, you might miss a problem that is only detected during that
part of the test.
Reviewing DTCs
To view codes in the Diagnostic Tool’s memory:
1. Locate the vehicle’s Data Link Connector (DLC). See TEST
CONNECTORS on page 68 for connector location.
Some DLCs have a plastic cover that must be removed before
connecting the Diagnostic Tool’s cable connector.