Pontiac Fiero 1988 Service Manual page 433

6 E - 6 DRIVEABILITY AND EMISSIONS - FUEL INJECTION
SECTION A
Diagnostic Procedure S u m m a r y
This is the starting point for the diagnostic
procedures or an emissions test failure. The
diagnostic charts are related to the ECM and
w i l l
determine if the ECM is working properly. This
section diagnoses the fuel system controlled by the
ECM and has charts to diagnose a circuit when the
ECM has displayed a trouble code.
The way to approach a problem is to follow three
basic steps (shown in Figure 3):
1.
Are the
On-Vehicle
Diagnostics working? We find
this out by performing the "Diagnostic Circuit
Check". Since this is the starting point for the
diagnostic procedures or finding the cause of
an emissions test failure, always begin here.
If the On-Vehicle Diagnostics aren't working, the
"Diagnostic Circuit Check"
will
lead you to a chart
in Section "A" to correct the problem. If the On-
Vehicle Diagnostics are OK, the next step is:
2. Is there a Trouble Code stored? If a trouble code is
stored, go directly to the numbered code chart in
Section "A". This will determine if the fault is
still present. If no trouble code is stored, then:
3. "Scan" Serial Data.
This involves reading the various pieces of
information available on the Serial Data Stream
with one of the tools available for that purpose.
Information on these tools and the meaning of the
various displays can be found in the succeeding
paragraphs. Expected readings can be found on
the facing page for the Diagnostic Circuit Check.
This short procedure will help lead you to repair
the problem in the least amount of time.
ALDL "SCAN" TOOLS
The ALDL connector under the dash has a variety
of information available on terminal "E" or "M"
(depending on engine). There are several tools on the
market for reading this information.
"Scan" tools do not make the use of diagnostic
charts unnecessary. They do not tell exactly where a
problem is in a given circuit. However, with an
understanding of what each position on the equipment
measures, and knowledge of the circuit involved, the
tools can be very useful in getting information which
would be more time consuming to get with other
equipment.
In some cases, "Scan" tools will provide
information that is either extremely difficult or
impossible to get with other equipment.
A " S C A N "
TOOL
THAT D I S P L A Y S F A U L T Y D A T A
SHOULD NOT BE USED AND THE PROBLEM SHOULD
BE REPORTED TO THE MANUFACTURER. THE USE OF
A F A U L T Y " S C A N " T O O L C A N R E S U L T I N
• IGNITION " O N " , ENGINE STOPPED.
• IS THE "SERVICE ENGINE S O O N " (SES) LIGHT " O N " ?
YES NO
• JUMPER ALDL TERM. B TO A.
® DOES SES LIGHT FLASH CODE 12?
ZL-
YES
I
DOES "SCAN" DISPLAY ECM DATA?
r^rr-
j SEE CHART A-2
YES
1
DOES ENGINE START?
NO
T
r
__» , ....j
s SEE CHART A-2 •
Y E S
NO
ARE ANY CODES DISPLAYED?
r-T-
i
• SEE CHART A-3 i
I . . J
NO
REFER TO APPLICABLE
CODE CHART. START
WITH LOWEST CODE.
" S C A N " SERIAL DATA.
REPAIR AS NECESSARY IF
ALL OK.SEE DRIVEABILITY
SYMPTOMS IN SECTION B
3-26-86
* 7 - S 3380-6E
I
SECTION C SYSTEMS
Figure 3 - Diagnostic Procedure Summary
MISDIAGNOSIS
A N D U N N E C E S S A R Y P A R T S
REPLACEMENT
Trouble Tree Charts incorporate diagnosis
procedures using an ALDL "Scan" tool where possible.
Most charts require use of a "Scan" tool when it is
applicable. Unless instructed otherwise, code charts
in "6E" Section "A" should not be used for diagnosis
unless the fault is still present (a "hard" failure).
Some ECM's have three modes for transmitting
information but some only read data in the open mode.
The following information will describe each of
the three modes where applicable and the effects they
may cause.
Normal (Open) Mode
Not all engines and ECM families will transmit
information on the Serial Data Line while in this
mode.