Engine Controls - Tests W/codes: Diagnosis Geo Prizm II

SELF-DIAGNOSTIC SYSTEM

Prizm LSi uses a Powertrain Control Module (PCM). All other models use a Engine Control Module (ECM). All references to ECM include PCM unless specified otherwise.

The ECM is equipped with a self-diagnostic system, which detects system failures or abnormalities. When a malfunction occurs, ECM will illuminate the CHECK ENGINE light located on instrument cluster. This light is also referred to as the Malfunction Indicator Light (MIL). When malfunction is detected and MIL is turned on, a corresponding trouble code will be stored in ECM memory. To retrieve stored codes, see READING TROUBLE CODES or RETRIEVING CODES (NON-SCAN). Malfunctions are recorded as HARD FAILURES or as INTERMITTENT FAILURES.

DIAGNOSTIC PROCEDURE

Diagnosis of the computerized engine control system should be performed in the following order

1. Ensure all engine systems not related to the computer are operating properly. DO NOT proceed with testing unless all other problems have been repaired. Perform on-board diagnostic system check chart before using trouble code charts.
2. If trouble codes were displayed (other than Code 12), determine whether codes are hard or intermittent. Hard codes cause Malfunction Indicator Light (MIL) to illuminate continuously with engine running. For diagnosing hard codes, proceed to appropriate diagnostic code chart. For diagnosing intermittent codes, proceed to INTERMITTENTS in TESTS W/O CODES article in the ENGINE PERFORMANCE Section.
3. If trouble codes were not displayed and a driveability problem exists, refer to SYMPTOMS in TESTS W/O CODES article in the ENGINE PERFORMANCE Section. From there you will be sent to the appropriate area in I - SYS/COMP TESTS article.
4. After repairs are made, clear trouble codes, confirm closed loop operation and ensure MIL is not illuminated.

READING TROUBLE CODES

1. Perform on-board diagnostic system check before diagnosing vehicle using self-diagnostic system. See appropriate ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK chart under DIAGNOSTIC CODE CHARTS.
2. Ensure ignition is off. Using a jumper wire, connect between Data Link Connector (DLC) terminals TE1 and E1. (Scheme 23) DLC is located on left strut tower. Turn ignition on and observe Malfunction Indicator Light (MIL) to read fault code(s). If fault codes are stored, code will flash 3 times starting with the lowest code. Proceed to appropriate chart(s) under DIAGNOSTIC CODE CHARTS to diagnose fault codes. See SELF-DIAGNOSTICS DIRECTORY table.
3. If no fault codes are stored, remove jumper wire from DLC terminal TE1. Turn ignition switch to LOCK position. Reconnect jumper wire between DLC terminals TE2 and E1. (Scheme 23) Turn ignition on. MIL will flash on and off rapidly.
4. Start and run engine until normal operating temperature is obtained. Test drive vehicle at condition at which problem occurred. With ignition still on, connect jumper wire between Data Link Connector (DLC) terminals TE1 and E1, and observe MIL. Code(s) will flash if present. Proceed to appropriate chart(s) under DIAGNOSTIC CODE CHARTS to diagnose fault codes. See SELF-DIAGNOSTICS DIRECTORY table.
5. If fault codes are not present, ECM and wiring are okay. Proceed to INTERMITTENTS in TESTS W/O CODES article in the ENGINE PERFORMANCE Section.

Note. Test diagnostic mode will not function if DLC terminal TE2 is grounded with ignition switch in any other position than LOCK. When in test diagnostic mode, Code 42 will set if vehicle is not driven above 3 MPH, and Code 43 will set if engine is not cranked. This is considered normal. Code 51 will set if accelerator pedal depressed off the idle position for 3 seconds, gear selector in Park or Neutral (A/T), or if A/C is on (if equipped). Systems are properly functioning if Code 51 sets under these conditions.

Scheme 23

TROUBLE CODE DEFINITIONS

Note. Trouble codes will be recorded at various operating times. Some codes require sensor or switch operation for 5 seconds and others may require longer under certain conditions. Some codes may not set in a service bay operational mode.

TROUBLE CODE IDENTIFICATION

Diagnostic Aids

Diagnostic aids (located in many trouble code charts) are provided as additional tips to help with diagnosis when inspected circuit is okay.

SPECIAL TOOLS (DIAGNOSTIC)

Note. A special scan tester, plugged into the DLC, can read trouble codes, check system voltages on the serial data line and save a great deal of diagnostic time. For additional information, see tester owner's manual. Also, see SCAN TESTER USAGE and SCAN TESTER DATA.

The computerized engine control system is most easily diagnosed using a scan tester. However, other tools may aid in diagnosing problems if a scan tester is unavailable. These tools are a tachometer, test light, ohmmeter, digital voltmeter with 10-megohm input impedance (minimum), vacuum pump, vacuum gauge, fuel injector test lights and 6 jumper wires 6" long (one wire with female connectors at both ends, one wire with male connector at both ends and 4 wires with male and female connectors at opposite ends). A test light, rather than a voltmeter, must be used when indicated by a diagnostic code chart.

DIAGNOSTIC CODE CHARTS (PRIZM)

Note. The following Schematics and Flow Charts are Courtesy of General Motors Corp.

ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK (PRIZM)

On-board diagnostic system check is an organized approach in identifying a problem created by an electronic engine 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 a complaint. Understanding the chart and using it correctly will reduce diagnostic time and prevent unnecessary replacement of good parts.

Note. Test numbers refer to test numbers on diagnostic chart.

1. Checks Malfunction Indicator Light (MIL) operation with ignition switch in ON position.
2. Checks if ECM's normal diagnostic mode is operating.
3. Checks if ECM's test diagnostic mode is operating.
4. Checks if engine will start.
5. Checks for any codes that are stored in ECM's memory with engine running.
6. Checks for any codes that are stored in ECM's memory with engine off. If no other codes than Code 42 are set and engine won't start, go to appropriate CHART A1-3 in BASIC TESTING article in the ENGINE PERFORMANCE Section.
7. Checks if Code 51 (Switch Condition Signal) is functioning.
8. This step checks if code(s) are intermittent problems.

On-Board Diagnostic (OBD) System Check - Schematic Prizm. Scheme 24

On-Board Diagnostic (OBD) System Check - Flow Chart (1 OF 2) Prizm. Scheme 25

On-Board Diagnostic (OBD) System Check - Flow Chart (2 OF 2) Prizm. Scheme 26

Check for open in EFI F-HTR, IGN and GAUGE fuses. Ensure EFI F-HTR relay is securely mounted in fuse/relay box. An intermittent condition may be caused by poor connection, rubbed-through insulation, or a broken wire inside insulation. Check ECM harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal-to-wire connections before component replacement.

CHART A1-1 - Flow Chart (Prizm) (1 OF 2) No Malfunction Indicator Light. Scheme 27

CHART A1-1 - Flow Chart (Prizm) (2 OF 2) No Malfunction Indicator Light. Scheme 28

An intermittent condition may be caused by poor connection, rubbed-through insulation, or a broken wire inside insulation. Check ECM harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal-to-wire connections before component replacement.

CHART A1-2 - Flow Chart (Prizm) MIL Won't Flash Any Codes, Or On Steady. Scheme 29

Check for cracks in distributor cap and rotor. Check for properly adjusted signal rotor air gap. An intermittent condition may be caused by poor connection, rubbed-through insulation, or a broken wire inside insulation. Check ECM harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal-to-wire connections before component replacement.

CODE 12 - Schematic (Prizm) No RPM Signal. Scheme 30

CODE 12 - Flow Chart (Prizm) No RPM Signal. Scheme 31

Check for cracks in distributor cap and rotor. Check for properly adjusted signal rotor air gap. An intermittent condition may be caused by poor connection, rubbed-through insulation, or a broken wire inside insulation. Check ECM harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal-to-wire connections before component replacement.

CODE 13 - Flow Chart (Prizm) No RPM Signal. Scheme 32

An intermittent condition may be caused by poor connection, rubbed-through insulation, or a broken wire inside insulation. Check ECM harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal-to-wire connections before component replacement.

CODE 1 - Flow Chart (Prizm) (1 OF 2) No Ignition Signal. Scheme 33

CODE 14 - Flow Chart (Prizm) (2 OF 2) No Ignition Signal. Scheme 34

Verify clean, tight connection on G106 (Brown wire).

An intermittent condition may be caused by poor connection, rubbed-through insulation, or a broken wire inside insulation. Check ECM harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal-to-wire connections before component replacement.

CODE 21 - Schematic (Prizm) Oxygen Sensor, Open Or Shorted Circuit. Scheme 35

CODE 21 - Flow Chart (Prizm) Oxygen Sensor, Open Or Shorted Circuit. Scheme 36

Ensure engine is not overheating and has not been subjected to conditions which would create an overheating condition (i.e., overload, trailer towing, hilly terrain, heavy stop and go traffic, etc.). When replacing ECT sensor, check TEMPERATURE TO RESISTANCE VALUES table. A "shifted" (mis-scaled) sensor could result in poor driveability complaints. If Codes 24, 31 and 41 are also set, problem is open in sensor ground circuit. An intermittent condition may be caused by poor connection, rubbed-through insulation, or a broken wire inside insulation. Check ECM harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal-to-wire connections before component replacement.

CODE 22 - Schematic (Prizm) Engine Coolant Temperature Sensor, Open Or Shorted Circuit. Scheme 37

CODE 22 - Flow Chart (Prizm) Engine Coolant Temperature Sensor, Open Or Shorted Circuit. Scheme 38

When replacing IAT sensor, check TEMPERATURE TO RESISTANCE VALUES table. A "shifted" (mis-scaled) sensor could result in poor driveability complaints. If Codes 22, 31 and 41 are also set, problem is open in sensor ground circuit.

An intermittent condition may be caused by poor connection, rubbed-through insulation, or a broken wire inside insulation. Check ECM harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal-to-wire connections before component replacement.

CODE 24 - Schematic (Prizm) Intake Air Temperature Sensor, Open Or Shorted Circuit. Scheme 39

CODE 24 - Flow Chart (Prizm) Intake Air Temperature Sensor, Open Or Shorted Circuit. Scheme 40

Verify clean, tight connection on G106 (Brown wire). A lean air/fuel condition may be caused by contaminated fuel, low fuel pressure or vacuum and exhaust leaks. An intermittent condition may be caused by poor connection, rubbed-through insulation, or a broken wire inside insulation. Check ECM harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal-to-wire connections before component replacement.

CODE 25 - Flow Chart (Prizm) Oxygen Sensor, Lean Exhaust Indicated. Scheme 41

Verify clean, tight connection on G106 (Brown wire). A rich air/fuel condition may be caused by high fuel pressure, faulty EVAP canister purge system, faulty MAP sensor, or faulty EGR system (Calif. emissions only).

An intermittent condition may be caused by poor connection, rubbed-through insulation, or a broken wire inside insulation. Check ECM harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal-to-wire connections before component replacement.

CODE 26 - Flow Chart (Prizm) Oxygen Sensor, Rich Exhaust Indicated. Scheme 42

Verify clean, tight connection on G106 (Brown wire).

An intermittent condition may be caused by poor connection, rubbed-through insulation, or a broken wire inside insulation. Check ECM harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal-to-wire connections before component replacement.

CODE 27 - Schematic (PRIZM - CALIF. EMISSIONS) Sub-oxygen Sensor, Open Or Shorted Circuit. Scheme 43

CODE 27 - Flow Chart (PRIZM - CALIF. EMISSIONS) Sub-oxygen Sensor, Open Or Shorted Circuit. Scheme 44

If Codes 22, 24 and 41 are also set, problem is open in sensor ground circuit. An intermittent condition may be caused by poor connection, rubbed-through insulation, or a broken wire inside insulation. Check ECM harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal-to-wire connections before component replacement.

CODE 31 - Schematic (Prizm) Manifold Absolute Pressure Sensor, Open Or Shorted Circuit. Scheme 45

CODE 31 - Flow Chart (Prizm) Manifold Absolute Pressure Sensor, Open Or Shorted Circuit. Scheme 46

Check for properly adjusted TP sensor before replacement of TP sensor. If Codes 22, 24 and 31 are also set, problem is open in sensor ground circuit. An intermittent condition may be caused by poor connection, rubbed-through insulation, or a broken wire inside insulation. Check ECM harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal-to-wire connections before component replacement.

CODE 41 - Schematic (Prizm) Throttle Position Sensor, Open Or Shorted Circuit. Scheme 47

CODE 41 - Flow Chart (Prizm) Throttle Position Sensor, Open Or Shorted Circuit. Scheme 48

Verify clean, tight connection on G202 (Brown wire).

An intermittent condition may be caused by poor connection, rubbed-through insulation, or a broken wire inside insulation. Check ECM harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal-to-wire connections before component replacement.

CODE 42 - Schematic (Prizm) Vehicle Speed Sensor Circuit, Open Or Shorted Circuit. Scheme 49

CODE 42 - Flow Chart (Prizm) (1 OF 2) Vehicle Speed Sensor Circuit, Open Or Shorted Circuit. Scheme 50

CODE 42 - Flow Chart (Prizm) (2 OF 2) Vehicle Speed Sensor Circuit, Open Or Shorted Circuit. Scheme 51

An intermittent condition may be caused by poor connection, rubbed-through insulation, or a broken wire inside insulation. Check ECM harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal-to-wire connections before component replacement.

CODE 43 - Schematic (Prizm) Crank Signal, No Signal. Scheme 52

CODE 43 - Flow Chart (Prizm) Crank Signal, No Signal. Scheme 53

Check EGR vacuum modulator and EGR valve for sticking open or closed.

An intermittent condition may be caused by poor connection, rubbed-through insulation, or a broken wire inside insulation. Check ECM harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal-to-wire connections before component replacement.

CODE 71 - Schematic (Prizm) Exhaust Gas Recirculation (EGR) System. Scheme 54

CODE 71 - Flow Chart (Prizm) (1 OF 2) Exhaust Gas Recirculation (EGR) System. Scheme 55

CODE 71 - Flow Chart (Prizm) (2 OF 2) Exhaust Gas Recirculation (EGR) System. Scheme 56

DIAGNOSTIC CODE CHARTS (PRIZM LSi)

Note. The following Schematic (Prizm)s and Flow Charts are Courtesy of General Motors Corp.

ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK - (PRIZM LSi)

On-board diagnostic system check is an organized approach in identifying a problem created by an electronic engine 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 a complaint. Understanding the chart and using it correctly will reduce diagnostic time and prevent unnecessary replacement of good parts.

Note. Test numbers refer to test numbers on diagnostic chart.

1. Checks Malfunction Indicator Light (MIL) operation with ignition switch in ON position.
2. Checks if PCM's normal diagnostic mode is operating.
3. Checks if PCM's test diagnostic mode is operating.
4. Checks if engine will start.
5. Checks for any codes that are stored in PCM's memory with engine running.
6. Checks for any codes that are stored in PCM's memory with engine off. If no other codes than Code 42 are set and engine won't start, go to appropriate CHART A2-3 in BASIC TESTING article in the ENGINE PERFORMANCE Section.
7. Checks if Code 51 (Switch Condition Signal) is functioning.
8. Checks if code(s) are intermittent problems.

ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK - Schematic (Prizm LSi). Scheme 57

ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK - Flow Chart (1 OF 2) (Prizm LSi). Scheme 58

ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK - Flow Chart (2 OF 2) (Prizm LSi). Scheme 59

Check for open in EFI F-HTR, IGN and GAUGE fuses. Ensure EFI F-HTR relay is securely mounted in fuse/relay box. An intermittent condition may be caused by poor connection, rubbed-through insulation, or a broken wire inside insulation. Check PCM harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal-to-wire connections before component replacement.

CHART A2-1 - Flow Chart (Prizm LSi) (1 OF 2) No Malfunction Indicator Light. Scheme 60

CHART A2-1 - Flow Chart (Prizm LSi) (2 OF 2) No Malfunction Indicator Light. Scheme 61

An intermittent condition may be caused by poor connection, rubbed-through insulation, or a broken wire inside insulation. Check PCM harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal-to-wire connections before component replacement.

CHART A2-2 - Flow Chart (Prizm LSi) (MIL) Won't Flash Any Codes, On Steady. Scheme 62

Check for cracks in distributor cap and rotor. Check for properly adjusted signal rotor air gap. An intermittent condition may be caused by poor connection, rubbed-through insulation, or a broken wire inside insulation. Check PCM harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal-to-wire connections before component replacement.

CODES 12 - Schematic (Prizm LSi) No RPM Signal. Scheme 63

CODES 12 - Flow Chart (Prizm LSi) No RPM Signal. Scheme 64

Check for cracks in distributor cap and rotor. Check for properly adjusted signal rotor air gap. An intermittent condition may be caused by poor connection, rubbed-through insulation, or a broken wire inside insulation. Check PCM harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal-to-wire connections before component replacement.

CODES 13 - Flow Chart (Prizm LSi) No RPM Signal. Scheme 65

An intermittent condition may be caused by poor connection, rubbed-through insulation, or a broken wire inside insulation. Check PCM harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal-to-wire connections before component replacement.

CODE 14 - Flow Chart (Prizm LSi) (1 OF 2) No Ignition Signal. Scheme 66

CODE 14 - Flow Chart (Prizm LSi) (2 OF 2) No Ignition Signal. Scheme 67

Verify clean, tight connection on G106 (Brown wire). An intermittent condition may be caused by poor connection, rubbed-through insulation, or a broken wire inside insulation. Check PCM harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal-to-wire connections before component replacement.

CODE 21 - Schematic (Prizm LSi) Oxygen Sensor Circuit, Open Or Shorted Circuit. Scheme 68

CODE 21 - Flow Chart (Prizm LSi) Oxygen Sensor Circuit, Open Or Shorted Circuit. Scheme 69

Ensure engine is not overheating and has not been subjected to conditions which would create an overheating condition (i.e., overload, trailer towing, hilly terrain, heavy stop and go traffic, etc.). When replacing ECT sensor, check TEMPERATURE TO RESISTANCE VALUES table. A "shifted" (mis-scaled) sensor could result in poor driveability complaints. If Codes 24, 31 and 41 are also set, problem is open in sensor ground circuit. An intermittent condition may be caused by poor connection, rubbed-through insulation, or a broken wire inside insulation. Check PCM harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal-to-wire connections before component replacement.

CODE 22 - Schematic (Prizm LSi) Engine Coolant Temperature Sensor, Open Or Shorted Circuit. Scheme 70

CODE 22 - Flow Chart (Prizm LSi) Engine Coolant Temperature Sensor, Open Or Shorted Circuit. Scheme 71

When replacing IAT sensor, check TEMPERATURE TO RESISTANCE VALUES table. A "shifted" (mis-scaled) sensor could result in poor driveability complaints. If Codes 22, 31 and 41 are also set, problem is open in sensor ground circuit. An intermittent condition may be caused by poor connection, rubbed-through insulation, or a broken wire inside insulation. Check PCM harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal-to-wire connections before component replacement.

CODE 24 - Schematic (Prizm LSi) Intake Air Temperature Sensor, Open Or Shorted Circuit. Scheme 72

CODE 24 - Flow Chart (Prizm LSi) Intake Air Temperature Sensor, Open Or Shorted Circuit. Scheme 73

Verify clean, tight connection on G106 (Brown wire). A lean air/fuel condition may be caused by contaminated fuel, low fuel pressure or vacuum and exhaust leaks. An intermittent condition may be caused by poor connection, rubbed-through insulation, or a broken wire inside insulation. Check PCM harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal-to-wire connections before component replacement.

CODE 25 - Flow Chart (Prizm LSi) Oxygen Sensor, Lean Exhaust Indicated. Scheme 74

Verify clean, tight connection on G106 (Brown wire). A rich air/fuel condition may be caused by high fuel pressure, faulty EVAP canister purge system, faulty MAP sensor, or faulty EGR system (Calif. emissions). An intermittent condition may be caused by poor connection, rubbed-through insulation, or a broken wire inside insulation. Check PCM harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal-to-wire connections before component replacement.

CODE 26 - Flow Chart (Prizm LSi) Oxygen Sensor, Rich Exhaust Indicated. Scheme 75

Verify clean, tight connection on G106 (Brown wire). An intermittent condition may be caused by poor connection, rubbed-through insulation, or a broken wire inside insulation. Check PCM harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal-to-wire connections before component replacement.

CODE 27 - Schematic (Prizm LSi) Sub-Oxygen Sensor, Open Or Shorted Circuit. Scheme 76

CODE 27 - Flow Chart (Prizm LSi) Sub-Oxygen Sensor, Open Or Shorted Circuit. Scheme 77

If Codes 22, 24 and 41 are also set, problem is open in sensor ground circuit. An intermittent condition may be caused by poor connection, rubbed-through insulation, or a broken wire inside insulation. Check PCM harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal-to-wire connections before component replacement.

CODE 31 - Schematic (Prizm LSi) Manifold Absolute Pressure Sensor, Open Or Shorted Circuit. Scheme 78

CODE 31 - Flow Chart (Prizm LSi) Manifold Absolute Pressure Sensor, Open Or Shorted Circuit. Scheme 79

Check for properly adjusted TP sensor before replacement of TP sensor. If Codes 22, 24 and 31 are also set, problem is open in sensor ground circuit. An intermittent condition may be caused by poor connection, rubbed-through insulation, or a broken wire inside insulation. Check PCM harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal-to-wire connections before component replacement.

CODE 41 - Schematic (Prizm LSi) Throttle Position (TP) Sensor, Open Or Shorted Circuit. Scheme 80

CODE 41 - Flow Chart (Prizm LSi) Throttle Position (TP) Sensor, Open Or Shorted Circuit. Scheme 81

Verify clean, tight connection on G202 (Brown wire). An intermittent condition may be caused by poor connection, rubbed-through insulation, or a broken wire inside insulation. Check PCM harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal-to-wire connections before component replacement.

CODE 42 - Schematic (Prizm LSi) Vehicle Speed Sensor, Open Or Shorted Circuit. Scheme 82

CODE 42 - Flow Chart (Prizm LSi) (1 OF 2) Vehicle Speed Sensor, Open Or Shorted Circuit. Scheme 83

CODE 42 - Flow Chart (Prizm LSi) (2 OF 2) Vehicle Speed Sensor, Open Or Shorted Circuit. Scheme 84

An intermittent condition may be caused by poor connection, rubbed-through insulation, or a broken wire inside insulation. Check PCM harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal-to-wire connections before component replacement.

CODE 43 - Schematic (Prizm LSi) No Crank Signal. Scheme 85

CODE 43 - Flow Chart (Prizm LSi) No Crank Signal. Scheme 86

Ensure no mechanical failures are inducing engine knock. See TESTS W/O CODES article in the ENGINE PERFORMANCE Section. An intermittent condition may be caused by poor connection, rubbed-through insulation, or a broken wire inside insulation. Check PCM harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal-to-wire connections before component replacement.

CODE 52 - Schematic (Prizm LSi) Knock Sensor, Open Or Shorted Circuit. Scheme 87

CODE 52 - Flow Chart (Prizm LSi) Knock Sensor, Open Or Shorted Circuit. Scheme 88

Check EGR vacuum modulator and EGR valve for sticking open or closed. An intermittent condition may be caused by poor connection, rubbed-through insulation, or a broken wire inside insulation. Check PCM harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal-to-wire connections before component replacement.

CODE 71 - Schematic (Prizm LSi) Exhaust Gas Recirculation (EGR) System. Scheme 89

CODE 71 - Flow Chart (Prizm LSi) (1 OF 2) Exhaust Gas Recirculation (EGR) System. Scheme 90

CODE 71 - Flow Chart (Prizm LSi) (2 OF 2) Exhaust Gas Recirculation (EGR) System. Scheme 91