1988 PONTIAC FIERO check engine

DRIVEABILITY AND EMISSIONS 2.8L (VIN 5). 5.OL (VIN F) & 5.7L (VIN 8) 6E3-1
SECTION 6E3
TY AND EM
THIS SEC"T0N APPLIES TO:
2.8L LB8 (VlN S) "F" SERIES
5.OL LB9 (VIN F ) "F'" SERIES
5.7L L98 (VIN 8) ""F3"lES
CONTENTS
INTRODUCTION
2.8L (VIN 5). 5.OL (VIN F) & 5.7L (WIN 8)
General Description ................... 8
Diagnosis Procedure ................... 8
SECTION A . DIAGNOSTIC CHARTS
2.8L (VIN S)
Table of Contents .................... A-1
Engine Components and Wiring
Component Locations
............... A-2
Wiring Diagrams (1 of 3) ............. A.3.4. 5
ECM Terminal End View .............. A-6
Diagnostic Circuit Check ................ A-8
No "Service Engine Soon" Light
Chart A-I
......................... A-10
No ALDL Data . "Service Engine Soon"
Light "ON" Steady (Won't Flash Code 12)
Chart A-2
......................... A-12
Engine Cranks But Won't
.... Chart A-3 (1 of 2)
Fuel System Diagnosis Run ................ A-14
. ChartA-7(1 of
2) ................... A-18
Cold Start Valve
Chart A-9
......................... 8-22
. .... Code 13 Oxygen Sensor Circuit (Open) A-24
Code 14 . Coolant Temperature Sensor Circuit
. (High Temp Indicated) .............. A-26
Code 15 . Coolant Temperature Sensor Circuit
(Low Temp
. Indicated) .............. A-28
Code 2 1 . Throttle Position Sensor (TPS) Circuit
(Signal Voltage High)
........ , ...... A-30
Code 22 . Throttle Position Sensor (TPS) Circuit
(Signal Voltage Low)
......... , ...... A-32
Code 23 . Manifold Air Temperature (MAT) Sensor
. Circuit (Low Temp Indicated) .......... A-34
Code 24 . Vehicle Speed Sensor
(VSS) Circuit ....................... A-36
Code 25 . Manifold Air Temperature (MAT)
Sensor Circuit (High Temp
. Indicated) .... A-38
Code 32 . EGRSystem Failure ............ A-40
Code 33 . Mass Air Flow (MAF) Sensor Circuit
(GMISEC High) .................... A-42
Code 34 . Mass Air Flow (MAF) Sensor Circuit
(GMISEC Low) .................... A-44
Code 41 . Cylinder Select Error ........... A-46
Code 42 . Electronic Spark Timing Fault .... A-48
Code 44 . Oxygen Sensor Circuit
(Lean Exhaust Indicated)
............. A-50
Code 45 . Oxygen Sensor Circuit
(Rich Exhaust Indicated)
.............. A-52
Code 54 . Fuel Pump Circuit (Lowvoltage) . . A-54
Code 5 1 . PROM Error
(Faulty or Incorrect PROM)
............ A-56
Code 52 . CALPAK Error
(Faulty or Incorrect CALPAK)
.......... A-56
Code 53 . System Over Voltage ........... A-56
Code 55 . ECM Error ................... A-56
SECTION B . SYMPTOMS
2.8L (WIN 5)
Table of Contents .................... B-1
Before Starting ...................... B-1
Intermittents ........................ B-2
Hard Start .......................... 8-2
Hesitation. Sag. Stumble ............... 8-3
Surges and/or Chuggle ................. 8-3
Lack of Power. Sluggish. or Spongy ........ B-4
DetonationJSpark Knock ............... 6-4
Cuts Out. Misses ...................... 8-5
Backfire ............................ 8-5
Poor Fuel Economy .................... B-6
Dieseling. Run.On ..................... 8-6
Rough. Unstable. or lncorrect Idle. Stalling . . €3-6
Excess~ve Exhaust Emissions or Odors ...... 8-7
Restr~cted Exhaust System Check
Chart
B-I ......................... 8-63

FUNCTIONAL CHECKS/
DIAGNOSTIC CHARTS
2.8L (VIN S)
ECM QDR Check
......................... Chart C-1 C1-10
ParkINeutral Switch
......................... Chart C-1A C1-12
Power Steering Pressure Switch Check
........................ ChartC-1E C1-14
Injector Balance Test
........................ Chart C-2A C2-18
Idle Air Control
........................ Chart C-2C C2-20
Canister Purge Valve Check
......................... Chart C-3 C3-4
Ignition System Check
........................ Chart C-4A C4-4
Electr~c Control (Divert) -(Manual Transmission)
......................... Chart C-6 C6-6
Exhaust Gas Recirculation Check
........................ Chart C-7 C7-6
Automatic Transmission
Converter Clutch (TCC)
. (I of 2)
........................ Chart C-8 C8-2
Transmiss~on Converter Clutch
(TCC) Electrical Diagnosis
. (2 of 2)
........................ Chart C-8 C8-4
A/C Clutch Control
........................ Chart C-10 C10-2
Cooling Fan Control Circuit (I of 2)
........................ Chart C-12 C12-2
Cooling Fan Control Circuit (2 of 2)
........................ Chart C-12 C12-4
ParklNeutral Switch (Auto Only) ...... C1-4
AIC "ON" Signal .................. C1-4
Distributor Reference Signal ......... C1-4
......................... DIAGNOSIS C1-4
............................. ECM C1-4
........................... PROM C1-4
...................... ECM Inputs C1-5
Coolant Temp . Sensor ............. C1-5
..................... MAFSensor C1-5
..................... MAT Sensor C1-5
....................... 02Sensor C1-5
TPS ............................ C1-5
........................... VSS C1-5
...................... PIN Switch C1-5
................ A/C Request Signal C1-5
Power Steering Pressure Switch ...... C1-5
................. Reference Signal C1-5
ON-CAR SERVICE ..................... C1-5
ELECTRONIC CONTROL MODULE (ECM) . . C1-5
ECM & COMPONENTS REPLACEMENT
..................... PROM OR ECM C1-6
................. Functional Check C1-7
CALPAK .......................... C1-7
COOLANT SENSOR .................. C1-7
MAFSENSOR ...................... C1-7
MAF SENSOR POWER & BURN-OFF RELAY . C1-7
................... OXYGEN SENSOR C1-8
Throttle Position Sensor ............ C1-8
PARKINEUTRALSWITCH .............. C1-9
................. PARTS INFORMATION C1-9
ECM QDR Check
................... ... Chart C-1 ... C1-10
ParktNeutral Switch
........................ ChartC-1A C1-12
Power Steering Pressure Switch Check
........................ SECTION C . COMPONENT SYSTEMS ChartC-lE C1-14
2.8L (VIN S) SECTION C2 . 2.8L (WIN S)
FUEL CONTROL SYSTEM
................ 'Table of Contents .................... C-1 GENERAL DESCRIPTION C2-1
SECTION
C1 . 2.8L (VIN S)
ELECTRONIC CONTROL MODULE (ECM)
& SENSORS
ELECTRONIC CONTROL MODULE (ECM) ... C1-1
........................ ECM TYPES C1-1
........................... PROM C1-1
CALPAK .......................... C1-2
.................... ECM Function C1-2
............. INFORMATION SENSORS C1-2
Engine Coolant Temp . Sensor ........ C1-2
Mass Air Flow (MAF) Sensor ......... C1-2
.................. A/C MAF Sensor Cl-2
Manifold Air Temp . (MAT) Sensor ..... C1-2
Oxygen (Oz)Sensor ............... C1-3
Throttle Position Sensor (TPS) ........ C1-3
Vehicle Speed Sensor .............. C1-3
ParkINeutral Switch (Auto Only) ...... C1-4
......................... PURPOSE C2-1
.............. MODES OF OPERATION C2-1
................... Starting Mode C2-2
................. Clear Flood Mode C2-2
...................... Run Mode C2-2
................ Acceleration Mode C2-2
............... Deceleration Mode C2-2
Battery Voltage Correction Mode ..... C2-2
................. Fuel Cutoff Mode C2-3
Fuel Control System Components ..... C2-3
Basic System Operat~on ............. C2-3
THROTTLEBODY UNIT ............... C2-3
......................... FUELRAIL C2-3
..................... FUEL INJECTOR C2-3
............... PRESSURE REGULATOR C2-3
IDLE AIR CONTROL (IAC) VALVE ........ C2-4

6E3-4 2.8L (VIN S) . 5.OL (VIN F) & 5.7L (VIN 8) DRIVEABILITY AND EMISSIONS
ON-CAR SERVICE ..................... C7-3
EGRVALVE
........................ C7-3
EGR Manifold Passage
............... C7-3
EGR Manifold Passage
............... C7-4
ELECTRONIC VACUUM REGULATOR
VALVE
.......................... C7-4
EVRV FILTER REPLACEMENT
.......... C7-4
PARTS INFORMATION
................. C7-4
Exhaust Gas Recirculation Check
Chart C-7
......................... C7-6
SECTION
C8 . 2.8L (VIN S)
TRANSMISISON CONVERTER CLUTCH (TCC) SYSTEM
AND MANUAL TRANSMISSION SHIFT LIGHT
GENERAL DESCRIPTION
................ C8-1
PURPOSE ......................... C8-1
OPERATION ....................... C8-1
DIAGNOSIS
......................... C8-1
SHIFT LIGHT (M/T) DESCRIPTION ........ C8-1
DIAGNOSIS
......................... C8-1
ON-CAR SERVICE ..................... C8-1
Automatic Transmission
Converter Clutch (TCC)
. (1 of 2)
Chart C-8
......................... C8-2
Transmission Converter Clutch
(TCC) Electrical Diagnosis
. (2 of 2)
Chart C-8
......................... C8-4
SECTION C10 . 2.8L (WIN S)
ECM CONTROLLED AIR CONDITIONING
GENERAL DESCRIPTION
................ C10-1
OPERATION ....................... C10-1
DIAGNOSIS ......................... C10-1
ON-CARSERVICE ..................... C10-1
FJC Clutch Control
Chart C-
1 0 ........................ C10-2
SECTION C12 . 2.8L (VlN S)
COOLING FAN CONTROL
GENERAL DESCRIPTION
................ C12-1
OPERATION ....................... C12-1
DIAGNOSIS
......................... C12-1
PARTS INFORMATION ................. C12-1
Cooling Fan Control Circuit (1 of 2)
Chart
C- 12 ........................ C12-2
Cooling Fan Control Circuit (2 of 2)
Chart C-12
........................ C12-4
SECTION C13
. 2.8L (WIN S)
POSITIVE CRANKCASE VENTILATION (PCV)
GENERAL DESCRIPTION
................ C13-1
RESULTS OF INCORRECT OPERATION
.... C13-1
DIAGNOSIS
......................... C13-1
FUNCTIONALCHECK OF PCV VALVE .... C13-1
ON-CAR SERVICE
..................... C13-2
PARTS INFORMATION
................. C13-2
SEC"T0N A . DIAGNOSTIC CHARTS
5.OL (VIN F) & 5.7L (VIN 8)
.................... Table of Contents A-1
Engine Components and Wiring
............... Component Locations A-2
Wiring Diagrams
(1 of 4) ............. A-3
ECM Terminal End View
.............. A-7
Diagnostic Circuit Check
................ A-8
No "Service Engine Soon" Light
......................... Chart A-1 A-10
No ALDL Data
. "Service Engine Soon"
Light "ON" Steady (Won't Flash Code 12)
Chart A-2
......................... A-12
Eng~ne Cranks But Won't Run
Chart A-3
(1 of 2) ................... A-14
Fuel System
Diagnos~s
Chart A-7 (1 of 2) ................... A-18
Cold Start Valve
Chart A-9
......................... A-22
Code 13
. Oxygen Sensor Circuit (Open) .... A-24
Code 14
. Coolant Temperature Sensor Circuit
(High Temp
. Indicated) .............. A-26
Code
1 5 . Coolant Temperature Sensor C~rcuit
. .............. (Low Temp Ind~cated) A-28
Code 21
. Throttle Pos~tlon Sensor (TPS) Circuit
(Signal Voltage High)
............... A-30
Code 22
. Throttle Pos~t~on Sensor (TPS) Circuit
................ (Signal Voltage Low) A-32
Code 23
. Manifold Air Temperature (MAT) Sensor
C~rcuit (Low Temp . Indicated) .......... A-34
Code 24
. Vehicle Speed Sensor
....................... (VSS) Circuit A-36
Code 25
. Manifold Air Temperature (MAT)
Sensor Circuit (High Temp
. Indicated) .... A-38
. ............ Code 32 EGR System Failure A-40
Code 33
. Mass Air Flow (MAF) Sensor Circuit
.................... (GMISECHlgh) A-42
Code 34
. Mass Air Flow (MAF) Sensor Circu~t
.................... (GMISEC Low) A-44
Code 36 Mass Air Flow
(MAF) Sensor
.. ..... ........... Burn-Off Circuit , , A-46
. ........... Code 41 Cyl~nder Select Error A-48
... . Code 42 Electronic Spark Timing Circuit A-50
Code 43 Electronic Spark Control
(ESC)
C~rcuit ....................... A-52
Code 44
. Oxygen Sensor Circu~t
(Lean Exhaust lnd~cated) ............. A-54
Code 45
. Oxygen Sensor Circuit
(Rich Exhaust Indicated)
.............. A-56
Code 54
. Fuel Pump C~rcuit (Lowvoltage) . . 14-58
. ................... Code 51 MEM-CAL A-60
Code 52
. CALPAK Error
.......... (Faulty or Incorrect CALPAK) A-60
. ........... Code 53 System Over Voltage A-60

DRIVEABILITVAND EMISSIONS Z.$L (VIN 5). 5.OL (VIN F) & 5.7L (VIN 8) 6E3-5
SECTION B . SYMPTOMS
5.OL (VIN F) & 5.7L (VIN 8)
.................... Table of Contents B-1
................... Before Starting ... B-1
. lntermittents .................... ... B-2
Hardstart .......................... B-2
............... Hesitation. Sag. Stumble 8-3
Surges andlor Chuggle ................. B-3
........ Lack of Power. Sluggish. or Spongy 8-4
DetonationISpark Knock ............... B-4
...................... Cuts Out. Misses €3-5
Backfire ............................ B-5
Poor Fuel Economy .................... B-6
Dieseling. Run.On ..................... 8-6
Rough. Unstable. or Incorrect Idle. Stalling . . B-6
Excessive Exhaust Emissions or Odors ...... B-7
Restricted Exhaust System Check
Chart
B-1 ......................... B-8
FUNCTIONAL CHECKS1
DIAGNO%"FIC CHARTS
5.OL (VIN F) & 5.7L (WIN 8)
ParkINeutral Switch
. Chart C-1A .................... ... C1-10
Injector Balance Test
Chart C-2A
........................ C2-18
Idle Air Control
Chart C-2C
........................ C2-20
Canister Purge Valve Check
Chart C-3
......................... C3-4
Ignition System Check
ChartC-4
......................... C4-4
Electronic Spark Control System Check
Chart C-5
......................... C5-4
AIR Management Check
Chart C-6
......................... C6-6
Exhaust Gas Recirculation (EGR) Check
Chart C-7
........................ C7-4
Automatic Transmission Converter Clutch (TCC)
Chart
6-814 ........................ C8-6
Manual Transmission Shift Light Diagnosis
Chart C-8B
........................ C8-10
Cooling Fan Control Circuit Diagnosis
Chart C- 1 2
........................ C12-2
SECTION C . COMP0NEN"I"SVSTEMS
5.OL (VIN F) & 5.7L (WIN 8)
Table of Contents .................... C-1
SECTION
C1 . 5.OL (VIN F) & 5.7L (VIN 8)
ELECTRONIC CONTROL MODULE (ECM)
81 SENSORS
GENERAL DESCRIPTION
................ C1-1
ELECTRONIC CONTROL MODULE ....... C1-1
MEM.CAL ......................... C1-1
................... ECM Function. C1-1
INFORMATION SENSORS ............. C1-2
Engine Coolant Temperature Sensor . . C1-2
..................... MAF Sensor C1-2
.................... MAT Sensor C1-2
Oxygen (Oz) Sensor ..............a. C1-3
Throttle Position Sensor ............ C1-3
.................... Knock Sensor C1-3
Vehicle Speed Sensor .............. C1-3
ParkINeutral Switch (Auto Only) ...... C1-3
.................. A/C "ON" Signal C1-4
Distributor Reference Signal ......... C1-4
DIAGNOSIS ......................... C1-4
ECM ............................. C1-4
MEM.CAL ......................... C1-4
ECM INPUTS ....................... C1-4
Coolant Temperature Sensor ........ C1-5
..................... MAF Sensor C1-5
..................... MAT Sensor C1-5
Oxygen (Oz) Sensor ............... C1-5
TPS ........................... C1-5
VSS ........................... C1-5
...................... PIN Switch C1-5
A/C Request Signal ................ C1-5
Reference Signal ................. C1-5
ON-CAR SERVICE ..................... C1-5
ELECTRONIC CONTROL MODULE ....... C1-5
ECM or MEM-CAL REPLACEMENT ....... C1-6
Functional Check ................. C1-7
COOLANTSENSOR .................. C1-7
MAF SENSOR ...................... C1-8
MAF SENSOR POWER & BURN-OFF RELAY . C1-8
OXYGEN SENSOR .................. C1-8
THROTTLE POSITION SENSOR ......... C1-8
PARKINEUTRAL SWITCH ............. C1-9
................. PARTS INFORMATION C1-9
ParkINeutral Switch
Chart
C-1 ..................... ... C1-10
SECTION C2 . 5.0L (WIN F) & 5.7L (WIN 8)
FUEL CONTROL SYSTEM
................ GENERAL DESCRIPTION C2-1
......................... PURPOSE C2-1
.............. MODES OF OPERATION CZ-2
................... Starting Mode C2-2
Clear Flood Mode ................. CZ-2
....................... Run Mode CZ-2
................ Acceleration Mode C2-2
............... Decelerat~on Mode C2-3
Battery Voltage Correction Mode ..... C2-3
................. Fuel Cutoff Mode C2-3
.............. FUEL CONTROL SYSTEM C2-3
............ Basic System Operation CZ-3
................ Throttle Body Unit CZ-3
....................... Fuel Rail C2-3
.................... Fuel Injectors CZ-3
............... Pressure Regulator C2-4
....................... IAC Valve 62-4

6E3-6 2.8L (VIN S). 5.OL (&BIN F) & 5.7L (WIN 8) BRllVEABlhlPY AND EMISSIONS
......... Fuel Pump Electrical Circuit C2-5
DIAGNOSiS ......................... CZ-5
.............. FUEL CONTROL SYSTERA C2.5
............ IDLE AIR CONTROLVALVE CZ-5
......... FUEL SYSTEM PRESSURE TEST C2-5
ON-CAR SERVICE ..................... C2-5
PORT FUEL INJECTION COMPONENTS .... Cf-5
FUEL PRESSURE RELIEF PROCEDURE ..... C2-5
Plenum ......................... C2-5
................ FUEL RAILASSEMBLY CP-6
FUEL RAIL SERVICE ................... C2-7
................... IDENTIFICATION C2-7
........... UNIT SERVICE PROCEDURES C2-7
COLD START .TUBE & VALVE ASSEMBLY ... ~2-7
PARTS INFORMATION ............... CZ-9
.... FUEL PRE5Si.J RE COPdNECl'ION ASSY C2-10
FUEL INJECTORS (Rail Removed) ........ C2-10
PRESSURE REGULATOR (Ball Removed) ... C2-10
COLD START FUEL INJEClION SWITCH ... C2-1%
THROTTLE BODY ................... CZ-11
VWROTTLE BODY SERVICE IDENTIFICATION . C2-12
............ UNIT REPAIR PROCEDURES Cf-112
TPS Adjcistment .............. C2-12
MiNIRilUM IDLE SPEED CHECK ........... CE-'I2
................. PARTS INFORMATION C2-15
IDLE AIR C'NT' L VALVE ASSY (3r: GASKET . . C2-15
CLEAN AIR COVER & GASKET .......... C2-15
SECTION C4 . 5.0h (VIN F) & 5.7L (VIN 8)
lGNITlON SYSTEMIEST
................ GENERAL DESCRIPTION C4-1
......................... PURPOSE C4-1
OPERATION ....................... C4-1
RESULTS OF INCORRECT OPERATION .... C4-1
......................... DIAGNOSIS C4-1
CODE 12 .......................... C4-1
ON-CAR SERVICE ..................... C4-2
SETTING TIMING .................... C4-2
HOW CODE 42 IS DETERMINED ......... C4-2
................. PARTS INFORMATION C4-2
lgn~tion System Check
Chart C-4
......................... C4-4
SECTION C5 . 5.0L (VIM F) & 5.7L JVIN 8)
ELECTRONIC SPARK CONTROL (ESC) SYSTEM
................ GENERAL DESCRIPTION C5-1
......................... PURPOSE C5-1
.............. GENERAL DESCRIPTION C5-1
......................... DlAGNOSiS C5-1
..................... ON-CAR SERVICE C5-1
....................... ESCSENSOR 65-1
.......... E4C MODULE AiYD BRACKET 165-2
................. PARTS INFORMATXBM C5-2
Electronic Spark Control
Chiirt C-5 ......................... C5-4
IDLE AIR CBi\~TROVCOOLANl'CVR . AS57 0
Throlrle Body Reinovecl Froti.1 Engine . .
FUEL PUlVlP RELAY ..................
................ OIL PRESSURE 5WETCI-I
P/%RVS INFORMATION .................
Irilector Halarlce Test
Chart
C-2A ........................
Idle Air Control
Chart
C-%C ........................
C2-I 5 SECYlOM Ct; . 5.0L (VlN F) & 5.7L (VIN 8)
62-1 5 A8W INJECTION REACTION (A.I.R.) SYSTEM
C2-16 GENERAL DESCRbPTION ............... CG-I
C2-16 PURPOSE ....................... C6-1
C2-76 OPE RATION ...................... C6-1
AIR COPJTROL PEDES VALVE ......... C6-I
C2-'18 RESULTS OF INCORRECT OPERATION .... C6-2
DIAGNOSIS ........................ C6-2
............. Cf -20 OPERATIONAL CHECKS C6-2
SbCTIBN C3 . 5.0L (VIN F) h 5.7L (V1N 8)
I:itAPORAIIVE EMISSlON CONTROL (EECS) SYSTEM
LZNERA. L DESCRIP'rION ............... C3-'!
PURPOSE ........................ C3-1
VAPOR CANISTER
.............. $3-1
EVAF'OFt/?ITIVE EMISSION SYSTEM .me.e. C3-4
FUEL TANK PRESSURE CONTROL VALVE . . C3-2
IN-'TANK PRESSURE CONTROL VALVE . . 63-2
RESULTS OF IRiCORRECT OPERATIGN .... C3-2
DIAGNOSIS ........................ C3-2
VISUAL CHECK OF CANIS'rkR .......... C3-2
FUNCPIONAL TEST
Vapor
Can~saer Purge Valve ........ C3-9
Tank Pressure Control Valve ..... C3-2
ON-CAR SERVICE ................. C3-3
FUEL VAPOR CANISTER ............ C3-3
CANISTER HOSES.
................... C3-3
PARTS INFORiblAT%BN ................ C3-3
Canister Purge Valve Check
Chart
C-3 ......................... C3-4
...................... Air Pump C6-2
................. Hoses and Pipes C6-3
.................... Check \/alve C6-3
.................... ON-CAR SERVICE C6-3
...................... DRIVE BELT C6-3
AIR INJECTION PUMP ............... C6-3
AIR INJECTION CONTROL
.................. (PEDES) VALVE C6-3
AIR ~NJECTION CIIECK VALVE ......... ~6-4
................ PARTS INFORMATION C6-4
AIR Management Check (PEDES)
........................ Chart C-6 C6-6
SECTlON C7 . 5.OL (VlN F) & 5.7L (VIN 8)
EXHAUST GAS RECIRCULATION {EGR) SYSTEM
GENERAL DESCRIPI'ION ..............*. C7-1
......................... PURPOSE C7-I
OPERATION
....................... C7-1
EGR
CONTROL .................... C7-1
NEGATIVE BACKPRESSURE EGR VALVE . . C7-2
EGR \/ALVE IDEhITIFICATION ........... C7-2

6E3-8 2.8L (VIM $1, 5.OL (VIN F) & 5.7L(VlN 8) BRlVEABILlTY AND EMISSIOMS
ALL NEW GENERAL MOTORS VEHICLES ARE CERTIFIED BY THE UNITED STAEES
ENVIRONMENTAL PROTECTION AGENCY AS CONFOWMlNG TO "THE REQUIREMENTS QF THE
REGULATIONS FOR THE CONTROL OF AIR POLLUTION FROM NEW MOTOR VEHICLES. THIS
CERTlFlCATlON IS CONTINGENT ON CERTAIN ADJUSTMENTS BEING SET TO FACTORY
STANDARDS. IN MOST CASES, THESE ADJUSTMENT POINTS EITHER HAVE BEEN
PERMANENTLY SEALED ANDIOR MADE
INACCESSlBLE TO PREVENT INDISCRIMINATE OR
ROUTINE ADJUSTM&M"FIN THE FIELD. FOR THIS REASON, THE FACTORY PROCEDURE FOR
TEMPORARILY REMOVING PLUGS, CAPS, ETC., FOR PURPOSES OF SERVICING THE PRODUCT,
MUST
BE STRICTLY FOLLOWED AND, WHEREVER PRACTICABLE, RETURNED TO THE
ORIGINAL INTENT QF THE DESIGN.
INTRODUCTION
GENERAL BESCRIPT18N DIAGNOSIS PROCEDURE
This section applies to engines which have a fuel
injector in the intake manifold near the intake valve
for each cylinder. It is commonly referred to as "Port
Fuel Injection".
These engines have controls to reduce exhaust
emissions, while maintaining good driveability and
fuel economy.
An engine control module
(ECM) is the heart of
this control system and has sensors used to provide
information about engine operation and the various
systems it controls. Details of basic operation,
diagnosis, functional checks, and on-vehicle service
are covered in Section "C", "Component Systems".
The ECM has the ability to do some diagnosis of
itself, and of other parts of the system. When it finds a
problem, it lights a "Service Engine Soon" light on the
instrument panel and
a trouble code will be stored in
the ECM memory. This does not mean that the engine
should be stopped right away, but that the cause of the
light coming
"ON" should be checked as soon as
reasonably possible. The
following
sections(s) are written for specific
engine applications and are clearly indentified. Be
sure to use only the section which applies to the
engine family being diagnosed.
Before using this section of the manual, you
should be familiar with the information and the
proper diagnosing procedures as described in Section
"GE". If the proper diagnosis procedures are not
followed, as described in Section
"6EM, it may result in
unnecessary replacement of good parts.
Trouble tree charts incorporate diagnosis
procedures using an ALDL "SCAN" tool where
possible.
The "SCANJ' tool has the ability to save time
in diagnosis and prevent the replacement of good
parts. The
key to using the "SCAN" tool
successfully for diagnosis lies in the technician's
ability to understand the system he is
trving to
diagnose. as well as an understanding of the
"SCAN" tool's limitations. See Section "6E" for
more information.

DRIVEABILITY AND EMISSIONS f.8b (VIN S) 6E3-A-1
Cold Oxygen Sensor
The "Diagnostic Circuit Check" verifies the On some engines.
the oxygen sensor will cool off
system is functioning correctly . some special after only a short period of operation at idle . This will
considerations to keep in mind while making the put the system into "Open Loop" . To restore "Closed
"Diagnostic Circuit Check" are: Loop"
operation. run the engine
at part throttle
several minutes and accelerate from idle to part
Blocking Drive Wheels throttle a few times .
The vehicle drive wheels should always be blocked Basic Procedure
while checking the system . If you have not reviewed the basic information on
how to
use the diagnostic procedures. go to the
introduction of this section
.
ENGINE COMPONENTS /WIRING DIAGRAMS / DIAGNOSTIC CHARTS
ComponentLocations ........................................................ PageA-2
Wiring Diagrams (1 of 3) ...................................................... Page A.3.4. 5
ECM Connector Terminal End View
.............................................. Page A-6
Diagnostic Circuit Check
...................................................... Page A-8
No "Service Engine Soon" bight
. Chart A-1 ........................................ Page A-10
No
ALBL or Won't Flash Code 12 . "Serv~ce Engine Soon" Light On Steady . Chart A-2 ........ Page A-12
. Engine Cranks But Won't Run Chart A-3 (1 of 2) .................................... Page 8-14
. Fuel System Diagnosis Chart A-7 (1 of
2) .......................................... Page A-18
Cold Start Valve
. Chart A-9 .................................................... Page A-22
Code 13 Oxygen Sensor Circuit (Open Circuit)
...................................... Page A-24
Code 14 Coolant Temperature Sensor Circuit (High Temp
. Indicated) ..................... Page A-26
Code 15 Coolant Temperature Sensor Circuit (Low Temp
. Indicated) ..................... Page A-28
Code 21 Throttle Position Sensor (TPS) Circuit (Signal Voltage High)
...................... Page A-30
Code 22 Throttle Position Sensor (TPS) Circuit (Signal Voltage Low)
...................... Page A-32
Code 23 Manifold Air Temperature (MAT) Sensor Circuit (Low Temp
. Indicated) ............ Page A-34
Code 24 Vehicle Speed Sensor (VSS) Circuit
........................................ Page A-36
Code
25 Manifold Air Temperature (MAT) Sensor Circuit (High Temp . Indicated) ............ Page A-38
Code 32
EGR System Failure .................................................... Page A-40
Code 33 Mass Air Flow (MAF) Sensor Circuit
(GMISEC High) ............................. Page A-42
Code 34 Mass Air Flow (MAF) Sensor Circuit
(GMISEC bow) ............................. Page 8-44
Code
41 Cylinder Select Error .................................................. Page A-46
Code 42 Electronic Spark Timing Fault
................... .... .................... Page 8-48
Code 44 Oxygen Sensor Circuit (Lean Exhaust Indicated)
.............................. Page A-50
Code
45 Oxygen Sensor Circuit (Rich Exhaust Indicated) ............................... Page A-52
Code 54 Fuel Pump Circuit
(Lowvoltage) .......................................... Page A-54
Code
51 PROM Error (Faulty or Incorrect PROM) ..................................... Page A-56
Code 52 CALPAK Error (Faulty or Incorrect CALPAK)
................................. Page 44-56
Code 53 System Over Voltage .................................................. Page A-56
Code55ECMError ............................O.~o.~.~e.~e~e.~e....... .. PageA-56

DIAGNOSTIC CIRCUIT CHECK
The diagnostic circuit check is an organized approach to identifying a problem created by an electronic
engine control system malfunction. It
must be the starting point for any driveability complaint diagnosis,
because it directs the service technician to the next logical step in diagnosing the complaint.
The "Scan Data" listed in the table may be used for comparison, after completing the diagnostic circuit check
and finding the on-board diagnostics functioning properly and no trouble codes displayed. The "Typical Values"
are an average of display values recorded from normally operating vehicles and are intended to represent what a
normally functioning system would typically display.
A "SCAN" TOOL THAT BiSPLAYS FAULTY DATA SHOULD NOT BE USED, AND THE PROBLEM
SHOULD BE REPORTED
TO THE MANUFACTURER. THE USE OF A FAULTY "SCAN" CAN RESULT
IN MISDIAGNOSIS AND UNNECESSARY PARTS REPLACEMENT.
Only the parameters listed below are used in this manual for diagnosis. If a "Scan" reads other parameters,
the values are not recommended by General Motors for use in diagnosis. For more description on the values and
use of the "Scan" to diagnosis
ECM inputs, refer to the applicable diagnosis section in Section "C". If all values
are within the range illustrated, refer to symptoms in Section
"B".
""SCAN" DATA
Coolant Temp. CO 85" - 105"
MAT Temp. C0 10" - 60" (depends on underhood temp.)
TPS
volts 0.35 - 0.67
MAF
gmlsec 4-7
INT (Integrator) Counts Varies
BLM (Block Learn) Counts 118- 138
IAC Counts (steps) 5-50
rPm rPm 1000 ? 50 rpm (depends on temperature)
0 2 volts .I - 1 and varies
OpenIClosed Loop OpenIClosed Closed Loop (may go open with extended idle)
Spark Advance
# of Degrees Varies
BPW (base pulse width) MISec .7 - 2.0
EGR Duty Cycle 0-
100% 0%
(at idle)
NC Request YesINo No (yes, with NC requested)
4th gear
YesINo No (yes, when in 4th gear)
NC Clutch ONIOFF OFF (ON, with NC commanded ON)
PIN Switch PIN
and
RBL ParkINeutral (PIN)
Power Steering Pressure Switch
NormalIHI pressure Normal
TCC
ONIOFF OFF1 (ON, with TCC commanded)
VSS mph 0