PONTIAC FIERO 1988 Service Repair Manual

6E2-C4-2 5.8L (VIN E) DRIVEABILIW AND EMISSIONS
Therefore, detonation could be caused by low MAP
output or high resistance in the coolant sensor circuit.
Poor performance could be caused by high MAP
o~~tput or low resistance in the coolant sensor circuit.
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 ECM 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 reached (about
400 rpm),
the ECM applies 5 volts to the bypass line and the EST
should no longer be grounded in the
HE1 module, so,
the EST voltage should be varying.
If the bypass line is open, the
HE1 module will not
switch to EST mode, so, the EST voltage will be low
and Code
42 will be set.
If the EST line is grounded, the HE1 module will
switch to EST but, because the line is grounded, there
will be no EST signal and the engine will not run. A
Code
42 may, or may not, be set.
The description, operation, and diagnosis of the
HE1 system are found in Section 6D of this manual.
This section will address diagnosis of that portion of
the Ignition System pertaining to the EST operation.
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 rpm (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.
ON-CAR SERVICE
SETTING TIMING
Set timing according to instructions on Vehicle
Emission Control Information label.
PARTS INFORMATION
PART NAME GROUP
....................... Module, Distr 2.383
......................... Coil, Distr 2.170

BLANK

6E2-C4-4 5.OL (VIN E) DRIVEABILITY AND EMISSIONS
CONNECTOR
430 PPUWHf
424 TANIBLK
CHART C-4
IGMB"$IIQN SYSTEM CHECK
(REMOTE COILSEALED MODULE CONNECTOR DISTRIBUTOR)
5.OL (VIN E) 'TF"7SEWBES (TBi)
Test De~driptian: Siin~bers below refer to circled
numbers
on the diagilostic chart.
1. 'Two wires are checkecl, to ensure that ti11 open is
not present
in a spark plug wire.
IA. If spark occurs with EST connector disconnected,
pick-LIP coil
oiltp~it is too !OW for l,:SrI' operation.
2. A spark indicates t,he problem must be the
distributor cap or rotor.
3. Normally, there should be battery voltage at the "c" ailti " -I-" terminals. Low voltage would
indicate 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.
'I'hc
distributor module should be turned "OFF", so
normal voltage should be
about 12 volts.
If the module is turned "ON", the voltage would be
low, but above
1 volt. This could cause the ignition
coil to fail from excessive heat.
With an open ignition coil primary winding,
a
small amount of voltage will leak throtrgh the
module from the "Bat." to the tach terminal.
5. Applying a voltage (1.5 to 8 volts) to module
terminal
"P" should turn the module "ON" and the
tach. term. voltage should drop to about 7-9 volts.
'I'his 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 module "ON". This
test can be performed by using a DC battery with a
rating of 1.5 to
8 volts. The use of the test light is
~nainly to tillow the "P" terminal to be probed
tilore easily. Some digital multi-meters can also
be used to trigger the
module by selecting ohms,
i~sually the diode position. 111 this position the
meter may have a voltage across it's terminals
which can be
used to trigger the module. The
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. 'I'his should turn "OFF" the module 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 modulc tester could determine
which is at fault.

DRIVEABILITY AND EMISSIONS 5.0L (VIM E) 6E2-C4-5
TEST LIGHT
TO
D.C. POWER SUPPLY (1.5 to 8V)
0 dist. harn. conn.
L~oth term's. 10 volts or more 1 ,=-.-.-

6E2-C4-6 5.BL (VIN E) DRIVEABILITY AND EMISSIONS
BLANK

DRIVEABILITY AND EMISSIONS 5.OL (VIN E) 6E2-C5-1
ELECmONIC SPARK CONTROL (ESC) SYSTEM
CONTENTS
GENERAL DESCRIPTION ................ C5-1 ON-CAR SERVICE ..................... C5-1
PURPOSE
......................... C5-1 ESC KNOCK SENSOR ................ C5-1
OPERATION
....................... C5-1 ESC MODULE ...........e..e.e..... C5-1
DIAGNOSIS
......................... C5-1 PARTS INFORMATION ................. C5-2
RESULTS OF INCORRECT ESC OPERATION
. C5-1
GENERAL DESCRIPTION
PURPOSE
To control spark knock, an electronic spark control
(ESC) system has been added. This system is designed
to retard spark timing up to
20°, to reduce spark knock
in the engine. This allows the engine to use maximum
spark advance to
improve driveability and fuel
economy. Varying octane levels in today's gasoline can
cause detonation in high performance engines.
Detonation is called spark knock. Loss
of the ESC signal to the ECM would cause the
ECM to constantly retard EST. This could result in
sluggish performance and cause a Code
43 to set.
A "Scan" tool will read knock signal in
AID
counts. When detonation is detected, knock signal
counts will increment,
as long as knock is present.
"Scan" tools will indicate knock being present either
by showing
AID counts, or displaying Yes (knock
present), or No (knock not present). If Code
43 is
present, use that chart to diagnose system. If no code
is present and ESC system is suspected, use CHART
C-5.
ON-CAR SERVICE
OPERATION
ESC KNOCK SENSOR
'I'he ESC system has two major components:
e ESC Module
@ ESC Knock Sensor
The sensor is mounted in the engine block near
the cylinders, or in the intake manifold at the rear of
the engine. When the ESC knock sensor detects
abnormal vibration (spark knocking) in the engine, it
produced
a voltage that is received by the ESC
module. As long as the ESC module sees no voltage
from the knock sensor (knock not present), it sends a
signal voltage
(8 to 10 volts) to the ECM and the ECM
provides normal spark advance.
When the module
d'etects voltage from the knock
sensor (knock present), it turns "OFF" the signal to
the ECM and the voltage at terminal
B7 goes to 0
volts: The ECM then retards EST to reduce spark
knock.
DIAGNOSIS
See Figure C5-1.
Remove or Disconnect
1. Negative battery cable.
2. ESC wiring harness connector from ESC sensor.
3. ESC sensor from engine block.
Install or Connect
I. ESC sensor into engine block. Apply thread
sealer, such as soft tape, to the ESC sensor
threads.
2. ESC wiring harness connector to the ESC sensor.
3. Negative battery cable.
ESC MODULE
RESULTS OF INCORRECT ESC OPERATION
Refer to Figure C5- 1
Loss of the ESC knock sensor signal or loss of
ground at ESC module would cause the signal to the a Remove or Disconnect
ECM to remain hiph. This condition would cause the 1. ESC module connector. L. ECM to control EST, as if no spark knocking were 2. Attachingscrews.
happening. No retard would occur, and spark 3. p;SCmodule.
knocking could become severe under heavy engine
load conditions.

6E2-C5-2 5.OL (WIN E) DRIVEABILITY AND EMISSIONS
Install or Connect
1, ESC module.
2. Attaching screws.
3. ESC module connector.
PARTS INFORMATION
PART NAME GROUP
Sensor, ESC Knock . . . . . . . . . . . . . . . . . 2.383
Module, Elek Spark Cont . . . . . . . . . . . . . 2.383

DRIVEABILITY AND EMISSIONS 5.OL (VIN E) 6EZ-C5-3

CHART C-5
ELECTRONIC SPARK CONTROL (ESC) SYSTEM CHECK
(ENGINE KNOCK, POOR PERFORMANCE, OR POOR ECONOMV)
5.OL (VIN E) "F" SERIES (TBI)
Circuit Description:
Electronic spark control is accomplished with a module that sends a voltage signal to the ECM. As the
knock sensor detects engine knock, the voltage from the ESC module to the ECM is shut "OFF" and this
signals the ECM to retard timing, if engine rpm is over about 900.
Test Description: Numbers below refer to circled
numbers on the diagnostic chart.
1. If a Code
43 is not set, but a knock signal is
indicated while running at 1500 rpm, listen for an
internal engine noise. Under a no load condition,
there should not be any detonation, and if knock is
indicated, an internal engine problem may exist.
2. Usually a knock signal can be generated by tapping
on the right exhaust manifold. This test can also be
performed at idle. Test number 1 was run at 1500
rpm, to determine if a constant knock signal was
present, which would affect engine performance.
3. This tests whether the knock signal is due to the
sensor, a basic engine problem, or the ESC module.
4. If the module ground circuit is faulty, the ESC
module will not function correctly. The test light
should light indicating the ground circuit is OK.
5. Contacting CKT 496, with a test light to 12 volts,
should generate a knock signal to determine
whether the knock sensor is faulty, or the ESC
module can't recognize a knock signal.
Diagnostic Aids:
If the ESC system checks OK, but detonation is the
complaint, refer to
Detonation1 Spark knock in Section
"B".

DRIVEABILIW AND EMISSIONS 5.OL (VIN E) 6E2-C5-5
THIS CHART SHOULD BE USED AFTER ALL OTHER CAUSES OF SPARK KNOCK HAVE BEEN CHECKED. I.E., TIMING. EGR, ENGINE
TEMPERATURE OR EXCESSIVE ENGINE NOISE,ETC. IF CODE 43 IS SET, USE THAT CHART FIRST.
@ PROBE HARNESS TERMINAL "D" (CKT 486) EVlEW "DIAGNOSTIC
WITH A TEST LIGHT TO 12 V.
IDS" ON FACING PAGE