Toyota's with the
electronic fuel injection utilize the Toyota EFI or TCCS engine management
system. This system helps to enhance the performance, emissions, and
drivability of the vehicle. The Self-Diagnostic System, which
monitors engine operations, is just one of the features of this system.
The Check Engine light will appear when a particular sensor or
input varies out of the specified operation parameters.
The check engine light alerts the user that there is a
possible problem in the EFI / TCCS Engine Control Unit. This is an
indication of a problem in the engine management system. A code that
pinpoints a possible component in the EFI / TCCS system may be stored in
the ECU at this time. The problem can be narrowed down to a number
of possible causes just by checking the trouble codes at this time.
The self-diagnostic system allows the user to zero in on the possible
fault.
The chart on the following page contains 1 and 2 digit
trouble codes that will help to diagnose problems in the EFI / TCCS
system. The chart also contains possible causes of the problem.
Keep in mind this is a tool to help narrow down the problem and may not be
exact. Other components failures have been known to cause similar
symptoms that can hide the actual fault.
Be sure to do a complete inspection before you do any
repairs on the computer of the vehicle. The last step to an engine
diagnose should always be a computer interrogation.
Remember to be cautious with the electrical system
within the vehicle. Serious injury can occur if the user or
technician is now careful. the electrical system can be damaged if
not careful; water and static electricity can easily cause damage.
Also keep in mind that the ignition system does put out high voltage.
Always put your safety first when dealing with these components of your
vehicle.
The diagnostic trouble codes are easy to read.
All you need is a simple paperclip to short the check connectors of the
diagnostic connector. There are two different types of diagnostic
connectors. For those of you who own an early model vehicle, check
on the inner-left fender well for a round green connector close to the air
cleaner. With the ignition key on, but the motor off, jump the two
terminals in the connector. On the later models, 87 and newer, there
is a multiple terminal "Diagnostic" connector which is located in the
engine compartment on the right fender. Look for a small rectangular
shaped gray box. In order to get the codes from this connector you
need to jump the "TE1" and "E1" terminals. To find the terminals,
look at the inside of the diagnostic connector. Here you will find a
schematic, which labels the connector pinouts. There is also a (VECI)
emissions decal located under the hood, which also outlines the terminals.
The trouble codes will appear as flashes of the check
engine light. When reading the codes, make sure your foot is OFF the
accelerator, the ignition key ON and the engine is OFF. There
are two different codes that will appear, one digit and two digit.
The one digit codes have and approximate 4.5 sec. delay between flashes
with the check engine light illuminating for around a half second.
On the two digit codes you will have a 2.5 sec. delay
between them. Here are some example codes to follow. A code
two flashes the check engine light two times in little over one second;
I I. When multiple codes are stored,
like a code 2 and code 4, the light will flash the following; ....I
I....I I I I. Two digit codes
are real similar, but will flash the light with the first number first
then the second dumber last. For example, a code 12 will flash;
I....I I.
A code 24 is; I I....I
I I I. The examples are a little crude but you get the idea.
(In these examples, the ..I..
represents the check engine flashing once.)
An ECI failure is not common, although many
possible faults might seem to point to the EFI system. Only if all
diagnoses points to a faulty ECU should it be replaced. Typically
EFI problems result from poor grounds, shorted wiring and bad connections
at sensors.
For more comprehensive diagnostic information and
electrical wiring diagrams, carefully consult your factory repair manual. |