1988 PONTIAC FIERO Service Repair Manual

6E3-C3-4 2.8L (VIN S) DRIVEABILITY AND EMISSIONS
TO CANISTER
I.P. HARNESS CONNECTOR (FRONT VIEW)
428 DK GRNNEL
CHART C-3
CARIISXE PURGE VALVE CHECK
2.88 (VIN S) ""F4 SERIES (PORT)
Circuit Description:
Canister purge is controlled by a solenoid that allows manifold vacuum to purge the canister when cle-
energized. The ECM supplies
a ground to energize the solenoid (purge "OFFJ').
If the diagnostic test terminal is ungrounded with the engine stopped or the following is met with the
engine running, the purge solenoid is de-energized (purge
"ON").
Engine run time after start more than 1 minute.
@ Coolant temperature above 75°C.
Vehicle speed above 15 mph.
@ Throttle off idle.
Test Description: Numbers below refer to circled
numbers on the diagnostic chart.
1. Checks to see if the solenoid is opened or close.
The solenoid is normally energized in this step;
so
it should be closed.
2. Checks for a complete circuit. Normally there is
ignition voltage on CKT
39 and the ECM provicles
a ground on CKT
428.
A shorted solenoid could cause an opet! circuit i11
the ECM.
3. Completes functional check by ungrounding test
terminal. This should normally de-energize the
solenoid
and allow the vacuum to drop (purge
"ON").

DRIVEABILITY AND EMISSIONS f.8L (VIN 5) 6E3-C3-5
NOTE: THIS CHART ONLY COVERS THE SOLENOID
PORTION OF THE CANISTER CONTROL PURGE
SYSTEM. TO TEST THE CONTROL
VALVE(S) SEE
DIAGNOSIS UNDER GENERAL DESCRIPTION
@ IGNITION "ON". ENGINE STOPPED.
@ GROUND DIAGNOSTIC TERMINAL.
AT THE SOLENOID, APPLY VACUUM
( 10" Hg OR 34 kPa )
STIC TERMINAL.
TERMINAL
WITH A
TEST LIGHT TO
CONNECTION OR
FAULTY ECM. SEE
GROUND OR FAULTY ECM.
SEE QUAD DRIVER CHECK

BLANK

DRIVEABILITY AND EMISSIONS 2.8L (VIN S) 6E3-C4-1
SECTION C4
IGNI"F0N SYSTEM / EST
CONTENTS
GENERAL DESCRIPTION ................ C4-1 ON-CAR SERVICE ..................... C4-2
PURPOSE ......................... C4-1 SETTING TIMING.. .................. C4-2
OPERATION ....................... C4-1 HOW CODE 42 IS DETERMINED.. ....... C4-2
RESULTS OF INCORRECT OPERATION .... C4-2 PARTS INFORMATION ................. C4-2
DIAGNOSIS
......................... C4-2
CODEIZ.......................... C4-2
GENERAL DESCRIPTION
PURPOSE
The High Energy Ignition ([-IEI) system controls
fuel combustion by providing a spark to ignite the
compressed
airlfuel mixture at the correct time. To
provide improved engine performance, fuel economy,
and control of exhaust emissions, the
ECM controls
distributor spark advance (timing) with the Electronic
Spark Timing (EST) system.
Only the Electronic Spark Timing (EST) system
will be described here. Additional information on the
tIEI system is found in Section "6D".
To properly control ignition/combustion timing
the ECM needs to know:
@ Crankshaft position
@ Engine speed (rpm)
@ Mass Air Flow
@ Engine temperature
OPERATION
The EST system consists of the distributor
module, ECM, and connecting wires. The connector
terminals are lettered as shown in Figure C4-1 for the
2.8L.
These circuits perform the following functions:
@ Distributor reference (CKT 430).
This provides the ECM with rpm ancl crankshaft
position information. If
the wire becomes open or
grounded the engine will not run, because the
ECM
will not operate the injectors. If the engine cranks hut
won't run, see CHART A-3.
@ Reference ground (C KT 453).
This wire is grounded in the distributor and
makes sure the ground circuit has no voltage drop
which could affect performance. If it is open, it
rnay
cause poor performance.
MODULE USED WITH INTEGRAL COlL DISTRIBUTOR
MODULE USED
WITH REMOTE COlL DISTRIBUTOR
MODULE USED
WITH NEW 72 AND 80 MM REMOTE COlL DISTRIBUTORS.
Figure C4-1 Distributor Modules
@ By-Pass (CKT 424).
At about 400 rpm, the ECM applies
5 volts to this
circuit to switch spark timing control from the
HE1
module to the ECM. The wire gocs through a
connector between the
4 wire connector and the ECM.
This is disconnectcd to the set base timing. An open or
grounded bypass circuit will set
a Code 42 and the
engine will run at hase timing, plus a small amount of
advance built into the
HE1 n~odule.
@ EST (CKT423).
This circuit triggers the FIE1 module. The ECM
does not know what the actual timing is, but it does
know when it gets the reference signal. It then
udva~ces or retards the spark from that point.
Therefore, if the
hase timing is set incorrectly, the
entire spark curve will be incorrect.

6E3-C4-2 2.8L (WIN S) DRIVEABILITY AND EMISSIONS
RESULTS OF INCORRECT OPERATION
An open or ground in the EST circuit will set a
Code 42 and cause the engine to run on the HE1
module timing. This will cause reduced performance
and poor fuel economy.
The ECM uses information from the
MAF and
coolant sensors in addition to rpm to calculate spark
~tdvance as follows:
@ Cold engine = more spark advance.
@ Engine under minimum load based on rpm
and low amount of air flow- more spark
advance. Hot engine
= less spark advance.
@ Engine under heavy load based on rprn and
high amount of air flow- less spark advance.
The description, operation, and diagnosis of the
HE1 system are found in Section "GD" of this manual.
CODE 12
Code 12 is used during the Diagnostic Circuit
Check procedure to test the code display ability of the
ECM. This code indicates that the ECM is not
receiving the engine
rpnl (REFERENCE) signal. This
occurs with the ignition key "ON" and the engine not
running.
The "Reference" signal also triggers the fuel
injection system. Without the "Reference" signal the
engine cannot run.
OM-CAR SERVICE
SETTING TIMING
The initial base timing is set by disconnecting the
timing connector, located near the blower motor.
Refer to Emission Control Information Label for
procedure.
This will cause Code 42 to store in the code
memory of the ECM.
The memory must be cleared
after setting timing.
How Code 42 Is Determined
When the system is running on the HE1 module,
that is no voltage on the bypass line, the
HE1 module
grounds the EST signal.
The ECk1 expects to see no
voltage
on the EST line during this condition. If it sees
a voltage, it sets code 42 and will not go into the EST
mode.
When the rpm for EST
is reachecl bout 300 rprn)
the ECM applies 5 volts to the bypass line and the E:SrI'
should no longer be grounded in the tIEI nodule so
the EST voltage should be varying.
If the bypass line is open or grounclecl, the IIEI
tnod~lle will not switch to EST mode so the EST
voltage will be low
and Code 42 will be set. Refer to
Section
"611" for on vehicle service.
PARTS INFORMATION
PART NAME GROUP
Controller, ECM
(Remanufi~ctured) ................ 3.670
.......................... Distributor 2.36 1
Module, Distr ........................ 3.380
........................... Coil, Distr 2.170

DRIVEABILITY AND EMISSIONS f.8L (VIN 5) 6E3-C4-3
BLANK

6E3-C4-4 2.8L (VIN S) DRIVEABILITY AND EMISSIONS
430 PPLMlHT - 85 - REFERENCE
424
TANIBLK
453 BLWRED
CHART C-4A
IGNITION SYSTEM CHECK
(REMOTE COIL / SEALED MODULE CONNECTOR DISTRIBUTOR)
2.8L (VIN 5) "F" SERIES (PORT)
Test Description: Numbers below refer to circled
numbers on the diagnostic chart.
1. Two wires are checked, to ensure that an open is
not present in
a spark plug wire.
1A. If spark occurs with EST connector disconnected,
pick-up coil output is too low for
EST operation.
2. A spark indicates the problem must be the
distributor cap or rotor.
3. Normally, there should he battery voltage at the
"C" and "+" terminals. Low voltage would
indicktte an open or a high resistance circuit from
the distributor to the coil or ignition switch. If
"C"
term. voltage was low, but " +" term. voltage is 10
volts or more, circuit from "C" term. to Ign. coil or
ignition coil primary winding is open.
4. Checks for a shorted module or grounded circuit
from the ignition coil to the module. The
distributor
nodule should be turned "OFF", so
normal voltage should be about
1% volts.
If the module is turned "ON", the voltage would be
low, but above
1 volt. 'I'his could cause the ig~lition
coil to fail from excessive heat.
With an open ignition coil primary
winding, i~
small amount of voltage will leak through the
module from the "Rat." to the tach terminal.
5. Applying a voltage (1.5 to 8V) to module terminal
"P" should turn the nlodule "ON" and the tach.
term. voltage should drop to about
7-9 volts. This
test will determine whether the module or coil is
faulty or if the pick-up coil is not generating the
proper signal to turn the
rnodule "ON". 'Phis test
can be performed by using a I)C battery with a
rating of
1.5 to 8 volts. The i~sc of the test light is
mainly to allow the
"P" terminal to be probed
more easily.
Some digital multi-meters can also be used t,o
trigger the module by selecting ohms, i~sually the
diode position. In this position the meter
may
have a voltage across it's terminals which can be
used to trigger the module.
'I'he voltage in the
ohm's position can be checked by
using a second
meter or by checking the manufacture's
specification of the tool being used.
6. This should turn "OFF" the nlodule and cause a
spark. If no
spark occurs, the fault is most likely in
the ignition coil because most module problems
would have been found before this point in the
procedure.
A moclule tester could determine
which is at fault.

DRlVEABlLlTY AND EMISSIONS 2.8L (VIN S) 6E3-C4-5
r J-26792 or equivalent (ST-125) while IGNI"PION SYSTEM CHECK
eck a second wire) A few sparks and
POWER SUPPLY
coil connector from module.
from tach. term. to ground.