Home ReviewsRefund
Home/Jeep/Wrangler/Jeep Wrangler II (1996-2006)/Repair manual/Testing & Diagnostics/Engine Controls - Basic Diagnostic Procedures: Other
Contents Wiring diagrams Section: Testing & Diagnostics All sections

Engine Controls - Basic Diagnostic Procedures: Other Jeep Wrangler II

Testing & Diagnostics 6 illustrations ~7883 words

POWERTRAIN CONTROL MODULE

Note. If replacing Powertrain Control Module (PCM), the correct vehicle mileage and Vehicle Identification Number (VIN) must be programmed into PCM to prevent Diagnostic Trouble Codes (DTC) from being stored in Anti-Lock Brake System (ABS) module and Air Bag Control Module (ACM). If replacing PCM on models equipped with a Sentry Key Immobilizer Module (SKIM), the secret key data must also be updated to enable engine starting.

Programming Powertrain Control Module

Connect scan tool to Data Link Connector (DLC) located below instrument panel, near steering column. Using scan tool, enter correct VIN and mileage into PCM. Using scan tool manufacturer's instructions, clear DTCs from ABS module and ACM.

Updating Secret Key Data

  1. Connect scan tool to Data Link Connector (DLC) located below instrument panel, near steering column. Ensure transmission is in Park (A/T) or Neutral (M/T). Turn ignition on.
  2. Using scan tool, select THEFT ALARM, SKIM and then MISCELLANEOUS. Select PCM REPLACED. Place the SKIM in SECURED ACCESS MODE by entering the appropriate Personal Identification Number (PIN) for this vehicle. PIN may be obtained from the owner, vehicle's invoice, or from the manufacturer. Press ENTER to transfer secret key data from Sentry Key Immobilizer Module (SKIM) to the PCM. This will enable the vehicle to start.
  3. If 3 attempts are made to enter the SECURED ACCESS MODE by using an incorrect PIN, the SECURED ACCESS MODE will be locked out for one hour. To exit lock out mode, leave ignition on with all accessories turned off. After one hour, enter correct PIN. It may be necessary to monitor battery voltage and connect a battery charger.

Compression

Ensure battery is fully charged and starter motor is in good operating condition. On 2.5L, disconnect ignition coil connector. On 4.0L, remove coil rail assembly to access spark plugs. On 4.7L, remove coil on plugs. On all models, clean spark plug recesses with compressed air. Remove all spark plugs. Remove fuel pump relay from power distribution center. (Scheme 1), (Scheme 2) or (Scheme 3). Install compression gauge. Hold throttle in Wide Open Throttle (WOT) position. Using a remote starter switch, rotate engine 3 revolutions. Record compression pressure from third revolution. Continue test for remaining cylinders. See COMPRESSION SPECIFICATIONS table for correct engine compression pressures.

ApplicationPsi (kg/cm 2 )
Normal Compression Pressure
2.5L & 4.0L120-150 (8.3-10.5)
4.7L140-180 (9.8-12.7)
Maximum Variation Between Cylinders
2.5L & 4.0L30 (2.1)
4.7L(1)
(1) Information is not available from manufacturer.
(1)

COMPRESSION SPECIFICATIONS

Scheme 1

Scheme 1
Scheme 1

Scheme 2

Scheme 2
Scheme 2

Scheme 3

Scheme 3
Scheme 3

CHECKING ENGINE VACUUM

Note. Normal vacuum readings vary according to altitude.

Connect vacuum gauge to engine vacuum source. Start engine and allow engine to idle. Note engine vacuum reading. Engine vacuum should be steady and 13-22 in. Hg with engine at idle. While monitoring engine vacuum reading, quickly open and close the throttle several times and then allow engine to idle. If engine vacuum is within specification, test is complete. If engine vacuum is not within specification, check for vacuum leaks and repair as necessary. If no vacuum leaks are found, check for engine mechanical problem.

FUEL SYSTEMS

WARNINGALWAYS relieve fuel pressure before disconnecting any fuel injection-related component. DO NOT allow fuel to contact engine or electrical components.
CAUTIONWhen battery is disconnected, vehicle computer and memory systems may lose memory data. Driveability problems may exist until computer systems have completed a relearn cycle. See COMPUTER RELEARN PROCEDURES article in GENERAL INFORMATION before disconnecting battery.

Basic diagnosis of fuel system should begin with determining fuel system pressure.

FUEL SYSTEM PRESSURE RELEASE

WARNINGFuel system is under high pressure. ALWAYS release fuel pressure before attempting to open system for testing or component replacement. DO NOT allow fuel to flow onto engine or electrical parts while testing fuel system components.
  1. Remove fuel pump relay from Power Distribution Center (PDC). PDC is located in right side of engine compartment, next to battery. (Scheme 1), (Scheme 2) or (Scheme 3). Start and run engine until it stalls. Attempt to start engine. Continue restarting engine until it will no longer run. Turn ignition off. NOTE: One or more Diagnostic Trouble Codes (DTC) may set when fuel pump relay is removed.
  2. Disconnect any fuel injector connector. Connect a jumper wire between either fuel injector terminal and positive battery terminal. Connect another jumper wire to other fuel injector terminal. Momentarily touch other end of jumper wire to negative battery terminal. CAUTION: DO NOT supply power to fuel injector for more than 4 seconds, or fuel injector may be damaged.
  3. Place a shop towel under fuel line quick-connector at fuel rail. Use care when disconnecting fuel lines, as some fuel pressure may still exist in fuel lines. Disconnect fuel line quick-connector at fuel rail. Reinstall fuel pump relay in PDC. Reconnect fuel line quick-connector. Using scan tool, erase any DTCs that may have set after fuel pressure release procedure.

Cherokee & Wrangler

Note. Cherokee and Wrangler models are equipped with a mechanical fuel pressure regulator located in top of fuel tank. Excess fuel is returned to tank through fuel pressure regulator.

  1. Release fuel pressure. See «FUEL SYSTEM PRESSURE RELEASE»(ref-12051-S35450755352000120600000) . Remove test port cap. Install a 0-60 psi (0-4.2 kg/cm 2 ) fuel pressure gauge at test port.
  2. Start engine and allow to idle. Fuel pressure should be 44.2-54.2 psi (3.1-3.7 kg/cm 2 ). If no fuel pressure exists, fuel pump relay control circuit may be defective. See DTC P1282: FUEL PUMP RELAY CONTROL CIRCUIT under DIAGNOSTIC TESTS in appropriate SELF-DIAGNOSTICS article.
  3. If engine runs but fuel pressure is less than specified, check for kinked or damaged fuel line between fuel pump module and fuel rail. Repair fuel line as necessary and retest. If fuel line is okay, go to «FUEL PUMP VOLUME TEST»(ref-12051-S22922019072000120600000) .
  4. If fuel pressure is more than specified, fuel pump is okay, but fuel pressure regulator is defective. Release fuel pressure and replace fuel pressure regulator. See FUEL FILTER/FUEL PRESSURE REGULATOR under FUEL SYSTEMS in REMOVAL, OVERHAUL & INSTALLATION article.
  5. If fuel pressure is as specified, release fuel pressure. Remove test gauge hose. Install test port cap.

Grand Cherokee

Note. Grand Cherokee is equipped with a mechanical fuel pressure regulator. Fuel filter/pressure regulator is located in front of fuel tank, above rear axle. (Scheme 4) Excess fuel is returned to tank through fuel return line and fuel pressure regulator.

  1. Release fuel pressure. See «FUEL SYSTEM PRESSURE RELEASE»(ref-12051-S35450755352000120600000). Remove test port cap. Install a 0-60 psi (0-4.2 kg/cm 2 ) fuel pressure gauge at test port.
  2. Start engine and allow it to idle. Fuel pressure should be 44.2-54.2 psi (3.1-3.7 kg/cm 2 ). If no fuel pressure exists, fuel pump relay control circuit may be defective. See DTC P1282: FUEL PUMP RELAY CONTROL CIRCUIT under DIAGNOSTIC TESTS in SELF-DIAGNOSTICS - GRAND CHEROKEE article.
  3. If fuel pressure is less than specified, go to next step. If fuel pressure is more than specified, check fuel return line for kinks or restrictions. (Scheme 4) Repair fuel return line as necessary. If fuel return line is okay, replace fuel filter/pressure regulator. If fuel pressure is as specified, fuel system is okay. Diagnose by symptom. See TROUBLE SHOOTING - NO CODES article.
  4. If engine runs but fuel pressure is less than specified, check for kinked or damaged fuel supply line between fuel pump module and fuel rail. Repair fuel line as necessary and retest. If fuel line is okay, release fuel pressure. Raise and support vehicle. Disconnect fuel pressure line from fuel filter/pressure regulator. (Scheme 4) Connect Fuel Line Pressure Test Adapter Hose (6539) between disconnected fuel line and fuel filter/pressure regulator. Connect fuel pressure gauge to fuel line adapter hose. Turn ignition on, with engine off. Using scan tool, actuate ASD fuel system test and note fuel pressure. Fuel pressure should be 44.2-54.2 psi (3.23-3.96 kg/cm 2 ). If fuel pressure is within specification, stop ASD fuel system activation, release fuel pressure and replace fuel filter/pressure regulator. If fuel pressure is not within specification, stop ASD fuel system activation, release fuel pressure and replace fuel pump module.

Scheme 4

Scheme 4
Scheme 4

Cherokee

  1. Perform «FUEL PRESSURE TEST»(ref-12051-S38318979682000120600000) and «FUEL PUMP VOLUME TEST»(ref-12051-S22922019072000120600000) before performing this test. If fuel pressure and fuel volume are okay, ensure fuel tank has fuel. If fuel tank is empty or near empty, amperage readings will be incorrect. Ensure fuel tank temperature is more than 50°F (10°C). WARNING: With ammeter installed in place of fuel pump relay, fuel pump will be activated even with ignition off. Before connecting ammeter, ensure all fuel lines and fuel system components are connected.
  2. Remove fuel pump relay from Power Distribution Center (PDC). (Scheme 1) Set ammeter to 10-amp scale. Connect negative lead of ammeter to terminal C2 (Dark Green/White wire) at fuel pump relay socket in PDC. (Scheme 1) Connect positive lead of ammeter to terminal C1 (Dark Green/Black wire) at fuel pump relay socket in PDC.
  3. If fuel pump current draw is 10 amps or more, replace fuel pump module. See FUEL PUMP MODULE under FUEL SYSTEMS in REMOVAL, OVERHAUL & INSTALLATION article. If fuel pump current draw is less than 10 amps, fuel pump module is okay.
  1. Perform «FUEL PRESSURE TEST»(ref-12051-S38318979682000120600000) and «FUEL PUMP VOLUME TEST»(ref-12051-S22922019072000120600000) before performing this test. If fuel pressure and fuel volume are okay, ensure fuel tank has fuel. Ensure fuel tank has fuel. If fuel tank is empty or near empty, amperage readings will be incorrect. Ensure fuel tank temperature is more than 50°F (10°C). WARNING: With ammeter installed in place of fuel pump relay, fuel pump will be activated even with ignition off. Before connecting ammeter, ensure all fuel lines and fuel system components are connected.
  2. Remove fuel pump relay from Power Distribution Center (PDC). (Scheme 2) Set ammeter to 10-amp scale. Connect negative lead of ammeter to terminal No. 87 (Dark Green/Black wire) at fuel pump relay socket in PDC. (Scheme 2) Connect positive lead of ammeter to terminal No. 30 (Violet/White wire) at fuel pump relay socket in PDC.
  3. If fuel pump current draw is 10 amps or more, replace fuel pump module. See FUEL PUMP MODULE under FUEL SYSTEMS in REMOVAL, OVERHAUL & INSTALLATION article. If fuel pump current draw is less than 10 amps, fuel pump module is okay.

Wrangler

  1. Perform «FUEL PRESSURE TEST»(ref-12051-S38318979682000120600000) and «FUEL PUMP VOLUME TEST»(ref-12051-S22922019072000120600000) before performing this test. If fuel pressure and fuel volume are okay, ensure fuel tank has fuel. If fuel tank is empty or near empty, amperage readings will be incorrect. Ensure fuel tank temperature is more than 50°F (10°C). WARNING: With ammeter installed in place of fuel pump relay, fuel pump will be activated even with ignition off. Before connecting ammeter, ensure all fuel lines and fuel system components are connected.
  2. Remove fuel pump relay from Power Distribution Center (PDC). (Scheme 3) Set ammeter to 10-amp scale. Connect negative lead of ammeter to terminal C9 (Dark Green/White wire) at fuel pump relay socket in PDC. (Scheme 3) Connect positive lead of ammeter to terminal C10 (Dark Green/Black wire) at fuel pump relay socket in PDC.
  3. If fuel pump current draw is 10 amps or more, replace fuel pump module. See FUEL PUMP MODULE under FUEL SYSTEMS in REMOVAL, OVERHAUL & INSTALLATION article. If fuel pump current draw is less than 10 amps, fuel pump module is okay.

Fuel Pump Relay

For fuel pump relay test, see FUEL PUMP RELAY under MOTORS, RELAYS & SOLENOIDS in SYSTEM & COMPONENT TESTING article. For fuel pump relay circuit testing, see DTC P1282: FUEL PUMP RELAY CONTROL CIRCUIT under DIAGNOSTIC TESTS in appropriate SELF-DIAGNOSTICS article.

CAMSHAFT POSITION SENSOR

For Camshaft Position (CMP) sensor testing, see DTC P0340: NO CAM SIGNAL AT PCM under DIAGNOSTIC TESTS in appropriate SELF-DIAGNOSTICS article.

CRANKSHAFT POSITION SENSOR

For Crankshaft Position (CKP) sensor testing, see DTC P0320: NO CRANK REFERENCE SIGNAL AT PCM under DIAGNOSTIC TESTS in appropriate SELF-DIAGNOSTICS article.

IGNITION COIL

ApplicationPrimarySecondary
2.5L
Diamond Coil.97-1.1811,300-15,300
Toyodenso Coil.95-1.2011,300-13,300
4.0L.71-.88(1)
4.7L.6-.96000-9000
(1) Secondary resistance cannot be checked using an ohmmeter.
(1)Secondary resistance cannot be checked using an ohmmeter.

IGNITION COIL RESISTANCE - Ohms @ 70-80°F (21-27°C)

ENGINE CRANKS BUT DOES NOT START

Note. Diagnostic tests are written specifically for Chrysler's Diagnostic Readout Box (DRB-III(R)) scan tool. A generic scan tool may not be capable of performing all necessary test functions.

Note. For circuit identification and wiring diagram, see WIRING DIAGRAMS article. If Powertrain Control Module (PCM) is replaced, PCM must be reprogrammed. See PROGRAMMING . After each repair procedure has been completed, reconnect all components. Perform POWERTRAIN VERIFICATION TEST VER-1 under VERIFICATION TESTS to ensure system is functioning properly.

  1. The following checks must be performed before continuing with this test. Ensure battery is fully charged and in good condition. Ensure Powertrain Control Module (PCM) power and ground circuits are okay. See COMPUTERIZED ENGINE CONTROLS in SYSTEM & COMPONENT TESTING article. Ensure PCM communicates with scan tool and no Diagnostic Trouble Codes (DTC) are present. See RETRIEVING DIAGNOSTIC TROUBLE CODES under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - CHEROKEE article. Ensure PCI bus is functional. Using scan tool, attempt to communicate with instrument cluster and Sentry Key Immobilizer Module (SKIM). If scan tool does not communicate with instrument cluster or SKIM, diagnose communication failure. See COMMUNICATIONS in BODY CONTROL MODULES - CHEROKEE article in ACCESSORIES & EQUIPMENT. Using scan tool, select CLEAR PCM (BATT DISCONNECT). Crank engine over several times. Using scan tool, check for DTCs. If any DTCs are present, perform appropriate diagnostic test. See SELF-DIAGNOSTICS - CHEROKEE article. If no DTCs exist, go to next step.
  2. Turn ignition off. Check Power Distribution Center (PDC) and junction block for blown fuses. PDC is located on right side of engine compartment, next to battery. Junction block is located behind passenger side kick panel. Replace blown fuses and check related circuits for short to ground. If fuses are okay, go to next step.
  3. Using scan tool, actuate Auto Shutdown (ASD) fuel system test. Using a mechanic's stethoscope, listen for fuel pump operation at fuel tank. If fuel pump operation cannot be heard, stop ASD fuel system actuation and go to step 10. If fuel pump operation can be heard, stop ASD fuel system actuation and go to next step.
  4. Turn engine off. Release fuel pressure. See «FUEL SYSTEM PRESSURE RELEASE»(ref-12051-S35450755352000120600000). Remove test port cap. Install a 0-60 psi (0-4.2 kg/cm 2 ) fuel pressure gauge at test port. Turn ignition on, with engine off. Using scan tool, actuate ASD fuel system test. Allow fuel pressure gauge to stabilize. Stop ASD fuel system activation. Fuel pressure should be 44.2-54.2 psi (3.23-3.96 kg/cm 2 ). If fuel pressure is less than specified, go to next step. If fuel pressure is more than specified, replace fuel filter/pressure regulator. Fuel filter/fuel pressure regulator is located in top of fuel tank. See FUEL FILTER/FUEL PRESSURE REGULATOR under FUEL SYSTEMS in REMOVAL, OVERHAUL & INSTALLATION article. If fuel pressure is as specified, go to step 7.
  5. Release fuel pressure. Raise and support vehicle. Disconnect fuel pressure line from fuel filter/pressure regulator at fuel tank. Connect Fuel Line Pressure Test Adapter Hose (6539) between disconnected fuel line and fuel filter/pressure regulator. Connect fuel pressure gauge to fuel line adapter hose. Turn ignition on. Using scan tool, actuate ASD fuel system test and note fuel pressure. Fuel pressure should be 44.2-54.2 psi (3.23-3.96 kg/cm 2 ). If fuel pressure is as specified, stop ASD fuel system activation. Release fuel pressure, and repair or replace fuel supply line. If fuel pressure is not as specified, stop ASD fuel system activation and go to next step.
  6. Release fuel pressure. Remove fuel pump module and inspect fuel inlet strainer. See FUEL PUMP MODULE under FUEL SYSTEMS in REMOVAL, OVERHAUL & INSTALLATION article. If fuel inlet strainer is plugged, replace fuel pump inlet strainer. If fuel inlet strainer is not plugged, replace fuel pump.
  7. Turn ignition off. Release fuel pressure. Disconnect fuel supply line from fuel rail. Install Fuel Line Pressure Test Adapter Hose (6539 for 5/16" fuel lines or 6631 for 3/8" fuel lines) between disconnected fuel line and fuel rail. Remove fuel fill cap. Insert other end of hose into a graduated container suitable for gasoline.
  8. Using scan tool, actuate ASD fuel system test for 7 seconds. If fuel volume is.5 pt. (.25L) or more, fuel volume is okay. Stop fuel system activation. Remove all test equipment and reconnect fuel supply line to fuel rail. Go to next step. Test is complete. If fuel volume is less than.5 pt. (.25L), check for a kinked fuel line between fuel pump module and fuel rail. Repair fuel lines as necessary and retest. If fuel line is okay, replace fuel pump module assembly. See FUEL PUMP MODULE under FUEL SYSTEMS in REMOVAL, OVERHAUL & INSTALLATION article.
  9. Check the following additional items as possible causes for no-start condition: Check spark plug condition. Fuel must be free of contamination. Engine exhaust system must be free of restrictions. Engine compression must be within specification. Engine valve timing must be within specification. Engine vacuum must be at least 13 in. Hg with shift selector in Neutral. Repair any problems as necessary. If no problems exist, test is complete.
  10. Turn ignition off. Disconnect fuel pump module connector. Turn ignition on. Using scan tool, actuate ASD fuel system test. Using a test light connected to ground, probe Dark Green/White wire at fuel pump module harness connector. If test light illuminates brightly, go to next step. If test light does not illuminate brightly, go to step 13.
  11. Turn ignition off. Disconnect test light. Using a test light connected to positive battery voltage, probe Black wire at fuel pump module harness connector. If test light illuminates brightly, go to next step. If test light does not illuminate brightly, repair open in Black wire between ground and fuel pump module. See WIRING DIAGRAMS article.
  12. At this time, fuel pump module is assumed to be defective. Replace fuel pump module.
  13. Turn ignition off. Ensure fuel pump module is disconnected. Remove fuel pump relay from PDC. Using a test light connected to ground, probe Dark Green/Black wire at terminal C1 at fuel pump relay socket in PDC. (Scheme 1) If test light illuminates, go to next step. If test light does not illuminate, repair open in Dark Green/Black wire between fuel pump relay socket and fuse No. 22 in PDC. Also check fuse No. 22 (15-amp) in PDC.
  14. Measure resistance of Dark Green/White wire between fuel pump module harness connector and terminal C2 at fuel pump relay socket in PDC. (Scheme 1) If resistance is less than 5 ohms, circuit is okay. Replace fuel pump relay. If resistance is 5 ohms or more, repair open in Dark Green/White wire between fuel pump module and PDC.
  1. The following checks must be performed before continuing with this test. Ensure battery is fully charged and in good condition. Ensure Powertrain Control Module (PCM) power and ground circuits are okay. See COMPUTERIZED ENGINE CONTROLS in SYSTEM & COMPONENT TESTING article. Ensure PCM communicates with scan tool and no Diagnostic Trouble Codes (DTC) are present. See RETRIEVING DIAGNOSTIC TROUBLE CODES under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - GRAND CHEROKEE article. Ensure PCI bus is functional. Using scan tool, attempt to communicate with instrument cluster and Sentry Key Immobilizer Module (SKIM). If scan tool does not communicate with instrument cluster or SKIM, diagnose communication failure. See COMMUNICATIONS in BODY CONTROL MODULES - GRAND CHEROKEE article in ACCESSORIES & EQUIPMENT. Using scan tool, select CLEAR PCM (BATT DISCONNECT). Crank engine over several times. Using scan tool, check for DTCs. If any DTCs are present, perform appropriate diagnostic test. See SELF-DIAGNOSTICS - GRAND CHEROKEE article. If no DTCs exist, go to next step.
  2. Turn ignition on. Using scan tool, monitor SECONDARY INDICATORS while cranking the engine. If no SECONDARY INDICATORS exist, go to next step. If any SECONDARY INDICATORS exist, perform appropriate symptom related test. See TROUBLE SHOOTING - NO CODES article.
  3. Turn ignition off. Check Power Distribution Center (PDC) and junction block for blown fuses. PDC is located on right side of engine compartment, next to battery. Junction block is located under left side of instrument panel. Replace blown fuses and check related circuits for short to ground. If fuses are okay, go to next step.
  4. Using scan tool in SENSOR mode, monitor CURRENT CKP COUNT while cranking engine. If CKP count changes while cranking engine, go to next step. If CKP count does not change while cranking engine, go to DTC P0320: NO CRANK REFERENCE SIGNAL AT PCM under DIAGNOSTIC TESTS in SELF-DIAGNOSTICS - GRAND CHEROKEE article.
  5. Using scan tool in SENSOR mode, monitor CURRENT CMP COUNT while cranking engine. If CMP count changes while cranking engine, go to next step. If CMP count does not change while cranking engine, go to DTC P0340: NO CAM SIGNAL AT PCM under DIAGNOSTIC TESTS in SELF-DIAGNOSTICS - GRAND CHEROKEE article.
  6. Using scan tool in INPUTS/OUTPUTS mode, read CURRENT SYNC STATE while cranking engine. If scan tool does not display OUT OF SYNC, go to next step. If scan tool displays OUT OF SYNC, check Crankshaft Position (CKP) sensor signal circuit for short to Camshaft Position (CMP) sensor signal circuit. See WIRING DIAGRAMS article. Repair wiring as necessary. If wiring is okay, check for incorrect valve timing. Repair valve timing as necessary. See appropriate article in ENGINES. Also check for a CMP sensor drive problem.
  7. Using scan tool, actuate Auto Shutdown (ASD) fuel system test. Using a mechanic's stethoscope, listen for fuel pump operation at fuel tank. If fuel pump operation cannot be heard, stop ASD fuel system actuation and go to step 14. If fuel pump operation can be heard, stop ASD fuel system actuation and go to next step.
  8. Turn engine off. Release fuel pressure. See «FUEL SYSTEM PRESSURE RELEASE»(ref-12051-S35450755352000120600000). Remove test port cap. Install a 0-60 psi (0-4.2 kg/cm 2 ) fuel pressure gauge at test port. Turn ignition on, with engine off. Using scan tool, actuate ASD fuel system test. Allow fuel pressure gauge to stabilize. Stop ASD fuel system activation. Fuel pressure should be 44.2-54.2 psi (3.23-3.96 kg/cm 2 ). If fuel pressure is less than specified, go to next step. If fuel pressure is more than specified, check fuel return line for kinks or restrictions. (Scheme 4) Repair fuel return line as necessary. If fuel return line is okay, replace fuel filter/pressure regulator. If fuel pressure is as specified, go to step 11.
  9. Release fuel pressure. Raise and support vehicle. Disconnect fuel pressure line from fuel filter/pressure regulator. Fuel filter/pressure regulator is located in front of fuel tank, above rear axle. (Scheme 4) Connect Fuel Line Pressure Test Adapter Hose (6539) between disconnected fuel line and fuel filter/pressure regulator. Connect fuel pressure gauge to fuel line adapter hose. Turn ignition on. Using scan tool, actuate ASD fuel system test and note fuel pressure. Fuel pressure should be 44.2-54.2 psi (3.23-3.96 kg/cm 2 ). If fuel pressure is as specified, stop ASD fuel system activation. Release fuel pressure, and repair or replace fuel supply line. If fuel pressure is not as specified, stop ASD fuel system activation and go to next step.
  10. Release fuel pressure. Remove fuel pump module and inspect fuel inlet strainer. See FUEL PUMP MODULE under FUEL SYSTEMS in REMOVAL, OVERHAUL & INSTALLATION article. If fuel inlet strainer is plugged, replace fuel pump inlet strainer. If fuel inlet strainer is not plugged, replace fuel pump.
  11. Turn ignition off. Release fuel pressure. Disconnect fuel supply line from fuel rail. Install Fuel Line Pressure Test Adapter Hose (6539 for 5/16" fuel lines or 6631 for 3/8" fuel lines) between disconnected fuel line and fuel rail. Remove fuel fill cap. Insert other end of hose into a graduated container suitable for gasoline.
  12. Using scan tool, actuate ASD fuel system test for 7 seconds. If fuel volume is.5 pt. (.25L) or more, fuel volume is okay. Stop fuel system activation. Remove all test equipment and reconnect fuel supply line to fuel rail. Go to next step. Test is complete. If fuel volume is less than.5 pt. (.25L), check for a kinked fuel line between fuel pump module and fuel rail. Repair fuel lines as necessary and retest. If fuel line is okay, replace fuel pump module assembly. See FUEL PUMP MODULE under FUEL SYSTEMS in REMOVAL, OVERHAUL & INSTALLATION article.
  13. Check the following additional items as possible causes for no-start condition: Check spark plug condition. Fuel must be free of contamination. Engine exhaust system must be free of restrictions. Engine compression must be within specification. Engine valve timing must be within specification. Engine vacuum must be at least 13 in. Hg with shift selector in Neutral. Repair any problems as necessary. If no problems exist, test is complete.
  14. Turn ignition off. Disconnect fuel pump module connector. Turn ignition on. Using scan tool, actuate ASD fuel system test. Using a test light connected to ground, probe Dark Green/Black wire at fuel pump module harness connector. If test light illuminates brightly, go to next step. If test light does not illuminate brightly, go to step 17.
  15. Turn ignition off. Disconnect test light. Using a test light connected to positive battery voltage, probe Black wire at fuel pump module harness connector. If test light illuminates brightly, go to next step. If test light does not illuminate brightly, repair open in Black wire between ground and fuel pump module. See WIRING DIAGRAMS article.
  16. At this time, fuel pump module is assumed to be defective. Replace fuel pump module.
  17. Turn ignition off. Ensure fuel pump module is disconnected. Remove fuel pump relay from PDC. Using a test light connected to ground, probe Violet/Black wire at terminal No. 30 at fuel pump relay socket in PDC. (Scheme 2) If test light illuminates, go to next step. If test light does not illuminate, repair open in Violet/Black wire between fuel pump relay socket and fuse No. 24 in PDC. Also check fuse No. 24 (20-amp) in PDC.
  18. Measure resistance of Dark Green/Black wire between fuel pump module harness connector and terminal No. 87 at fuel pump relay socket in PDC. (Scheme 2) If resistance is less than 5 ohms, circuit is okay. Replace fuel pump relay. If resistance is 5 ohms or more, repair open in Dark Green/Black wire between fuel pump module and PDC.
  1. The following checks must be performed before continuing with this test. Ensure battery is fully charged and in good condition. Ensure Powertrain Control Module (PCM) power and ground circuits are okay. See COMPUTERIZED ENGINE CONTROLS in SYSTEM & COMPONENT TESTING article. Ensure PCM communicates with scan tool and no Diagnostic Trouble Codes (DTC) are present. See RETRIEVING DIAGNOSTIC TROUBLE CODES under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - WRANGLER article. Ensure PCI bus is functional. Using scan tool, attempt to communicate with instrument cluster and Sentry Key Immobilizer Module (SKIM). If scan tool does not communicate with instrument cluster or SKIM, diagnose communication failure. See COMMUNICATIONS in BODY CONTROL MODULES - WRANGLER article in ACCESSORIES & EQUIPMENT. Using scan tool, select CLEAR PCM (BATT DISCONNECT). Crank engine over several times. Using scan tool, check for DTCs. If any DTCs are present, perform appropriate diagnostic test. See SELF-DIAGNOSTICS - WRANGLER article. If no DTCs exist, go to next step.
  2. Turn ignition on. Using scan tool, monitor SECONDARY INDICATORS while cranking the engine. If no SECONDARY INDICATORS exist, go to next step. If any SECONDARY INDICATORS exist, perform appropriate symptom related test. See TROUBLE SHOOTING - NO CODES article.
  3. Turn ignition off. Check Power Distribution Center (PDC) and fuse block for blown fuses. PDC is located on right side of engine compartment, next to battery. Fuse block is located behind glove box. Replace blown fuses and check related circuits for short to ground. If fuses are okay, go to next step.
  4. Using scan tool in SENSOR mode, monitor CURRENT CKP COUNT while cranking engine. If CKP count changes while cranking engine, go to next step. If CKP count does not change while cranking engine, go to DTC P0320: NO CRANK REFERENCE SIGNAL AT PCM under DIAGNOSTIC TESTS in SELF-DIAGNOSTICS - WRANGLER article.
  5. Using scan tool in SENSOR mode, monitor CURRENT CMP COUNT while cranking engine. If CMP count changes while cranking engine, go to next step. If CMP count does not change while cranking engine, go to DTC P0340: NO CAM SIGNAL AT PCM under DIAGNOSTIC TESTS in SELF-DIAGNOSTICS - WRANGLER article.
  6. Using scan tool in INPUTS/OUTPUTS mode, read CURRENT SYNC STATE while cranking engine. If scan tool does not display OUT OF SYNC, go to next step. If scan tool displays OUT OF SYNC, check Crankshaft Position (CKP) sensor signal circuit for short to Camshaft Position (CMP) sensor signal circuit. See WIRING DIAGRAMS article. Repair wiring as necessary. If wiring is okay, check for incorrect valve timing. Repair valve timing as necessary. See appropriate article in ENGINES. Also check for a CMP sensor drive problem.
  7. Using scan tool, actuate Auto Shutdown (ASD) fuel system test. Using a mechanic's stethoscope, listen for fuel pump operation at fuel tank. If fuel pump operation cannot be heard, stop ASD fuel system actuation and go to step 14. If fuel pump operation can be heard, stop ASD fuel system actuation and go to next step.
  8. Turn engine off. Release fuel pressure. See «FUEL SYSTEM PRESSURE RELEASE»(ref-12051-S35450755352000120600000). Remove test port cap. Install a 0-60 psi (0-4.2 kg/cm 2 ) fuel pressure gauge at test port. Turn ignition on, with engine off. Using scan tool, actuate ASD fuel system test. Allow fuel pressure gauge to stabilize. Stop ASD fuel system activation. Fuel pressure should be 44.2-54.2 psi (3.23-3.96 kg/cm 2 ). If fuel pressure is less than specified, go to next step. If fuel pressure is more than specified, replace fuel filter/pressure regulator. Fuel filter/fuel pressure regulator is located in top of fuel tank. See FUEL FILTER/FUEL PRESSURE REGULATOR under FUEL SYSTEMS in REMOVAL, OVERHAUL & INSTALLATION article. If fuel pressure is as specified, go to step 11.
  9. Turn ignition off. Check for restricted fuel supply line between fuel rail and fuel pump module. Fuel pump module is located in fuel tank. Repair fuel line as necessary. If fuel line is okay, go to next step.
  10. Release fuel pressure. Remove fuel pump module and inspect fuel inlet strainer. See FUEL PUMP MODULE under FUEL SYSTEMS in REMOVAL, OVERHAUL & INSTALLATION article. If fuel inlet strainer is plugged, replace fuel pump inlet strainer. If fuel inlet strainer is not plugged, replace fuel pump.
  11. Turn ignition off. Release fuel pressure. Disconnect fuel supply line from fuel rail. Install Fuel Line Pressure Test Adapter Hose (6539 for 5/16" fuel lines or 6631 for 3/8" fuel lines) between disconnected fuel line and fuel rail. Remove fuel fill cap. Insert other end of hose into a graduated container suitable for gasoline.
  12. Using scan tool, actuate ASD fuel system test for 7 seconds. If fuel volume is.5 pt. (.25L) or more, fuel volume is okay. Stop fuel system activation. Remove all test equipment and reconnect fuel supply line to fuel rail. Go to next step. Test is complete. If fuel volume is less than.5 pt. (.25L), check for a kinked fuel line between fuel pump module and fuel rail. Repair fuel lines as necessary and retest. If fuel line is okay, replace fuel pump module assembly. See FUEL PUMP MODULE under FUEL SYSTEMS in REMOVAL, OVERHAUL & INSTALLATION article.
  13. Check the following additional items as possible causes for no-start condition: Check spark plug condition. Fuel must be free of contamination. Engine exhaust system must be free of restrictions. Engine compression must be within specification. Engine valve timing must be within specification. Engine vacuum must be at least 13 in. Hg with shift selector in Neutral. Repair any problems as necessary. If no problems exist, test is complete.
  14. Turn ignition off. Disconnect fuel pump module connector. Turn ignition on. Using scan tool, actuate ASD fuel system test. Using a test light connected to ground, probe Dark Green/White wire at fuel pump module harness connector. If test light illuminates brightly, go to next step. If test light does not illuminate brightly, go to step 17.
  15. Turn ignition off. Disconnect test light. Using a test light connected to positive battery voltage, probe Black wire at fuel pump module harness connector. If test light illuminates brightly, go to next step. If test light does not illuminate brightly, repair open in Black wire between ground and fuel pump module. See WIRING DIAGRAMS article.
  16. At this time, fuel pump module is assumed to be defective. Replace fuel pump module.
  17. Turn ignition off. Ensure fuel pump module is disconnected. Remove fuel pump relay from PDC. Using a test light connected to ground, probe Dark Green/Black wire at terminal C10 at fuel pump relay socket in PDC. (Scheme 3) If test light illuminates, go to next step. If test light does not illuminate, repair open in Dark Green/Black wire between fuel pump relay socket and PDC. Also check fuse No. 23 (20-amp) in PDC.
  18. Measure resistance of Dark Green/White wire between fuel pump module harness connector and terminal C9 at fuel pump relay socket in PDC. (Scheme 3) If resistance is less than 5 ohms, circuit is okay. Replace fuel pump relay. If resistance is 5 ohms or more, repair open in Dark Green/White wire between fuel pump module and PDC.

NO RESPONSE FROM PCM WITH A NO-START CONDITION

Note. For circuit identification and wiring diagram, see WIRING DIAGRAMS article. If Powertrain Control Module (PCM) is replaced, PCM must be reprogrammed. See PROGRAMMING . After each repair procedure has been completed, reconnect all components. Perform POWERTRAIN VERIFICATION TEST VER-1 under VERIFICATION TESTS to ensure system is functioning properly.

  1. Turn ignition off. Disconnect PCM connectors. PCM is located in engine compartment on left front fender, near radiator support. Inspect connectors for damaged pins, corrosion and loose terminals. Repair connectors necessary. Using a test light connected to ground, probe terminal No. 22 (Dark Green/Black wire) at PCM C1 harness connector. (Scheme 5) If test light illuminates brightly, go to next step. If test light does not illuminate brightly, repair open in Dark Green/Black wire between fuse No. 22 in Power Distribution Center (PDC) and PCM. PDC is located in engine compartment, next to battery. Also check fuse No. 22 in PDC.
  2. Turn ignition on. Using a test light connected to ground, probe terminal No. 2 (Dark Blue/White wire) at PCM C1 connector. (Scheme 5) If test light illuminates brightly, power circuits are okay. Go to next step. If test light does not illuminate brightly, repair open fused ignition switch output circuit (Dark Blue/White wire) between PCM and junction block. Junction block is located behind passenger-side kick panel. Also check fuse No. 11 (20-amp) in junction block.
  3. Turn ignition off. Using a test light connected to positive battery voltage, probe terminals No. 31 (Black/Tan wire) and No. 32 (Black/Tan wire) at PCM C1 connector. (Scheme 5) If test light illuminates brightly at both terminals, ground circuits are okay. Test is complete. If test light does not illuminate brightly at one or both terminals, repair open in appropriate Black/Tan wire between PCM and ground. Ground location is located at right front of cylinder block, near generator.

Scheme 5

Scheme 5
Scheme 5
  1. Turn ignition off. Disconnect PCM connectors. PCM is located on firewall in right rear corner of engine compartment. Inspect connectors for damaged pins, corrosion and loose terminals. Repair connectors necessary. Using a test light connected to ground, probe terminal No. 22 (Red/Black wire) at PCM C1 harness connector. (Scheme 5) If test light illuminates brightly, go to next step. If test light does not illuminate brightly, repair open in Red/Black wire between fuse No. 19 (10-amp) in Power Distribution Center (PDC) and PCM. PDC is located in engine compartment, next to battery. Also check fuse No. 19 in PDC.
  2. Turn ignition on. Using a test light connected to ground, probe terminal No. 2 (Orange/Dark Blue wire) at PCM C1 connector. (Scheme 5) If test light illuminates brightly, power circuits are okay. Go to next step. If test light does not illuminate brightly, repair open fused ignition switch output circuit (Orange/Dark Blue wire) between PCM and junction block. Junction block is located under left side of instrument panel. Also check fuse No. 12 (10-amp) in junction block.
  3. Turn ignition off. Using a test light connected to positive battery voltage, probe terminals No. 31 (Black/White wire) and No. 32 (Black/Tan wire) at PCM C1 connector. (Scheme 5) If test light illuminates brightly at both terminals, ground circuits are okay. Test is complete. If test light does not illuminate brightly at one or both terminals, repair open in Black/White wire or Black/Tan wire between PCM and ground. Ground connection is located on right side of cylinder block.
  1. Turn ignition off. Disconnect PCM connectors. PCM is located on firewall in right rear corner of engine compartment. Inspect connectors for damaged pins, corrosion and loose terminals. Repair connectors necessary. Using a test light connected to ground, probe terminal A22 (Red/White wire) at PCM C1 harness connector. (Scheme 6) If test light illuminates brightly, go to next step. If test light does not illuminate brightly, repair open in Red/White wire between fuse No. 9 (30-amp) in Power Distribution Center (PDC) and PCM. PDC is located in engine compartment, next to battery. Also check fuse No. 9 in PDC.
  2. Turn ignition on. Using a test light connected to ground, probe terminal C3 (Dark Blue/Yellow wire) at PCM C3 harness connector. (Scheme 6) If test light illuminates brightly, power circuits to PCM are okay. Go to next step. If test light does not illuminate brightly, repair open fused ignition switch output circuit (Dark Blue/Yellow wire) between fuse No. 12 (10-amp) in fuse block and PCM. Fuse block is located behind glove box.
  3. Turn ignition off. Using a test light connected to positive battery voltage, probe terminals A31 (Black/Tan wire) and A32 (Black/Tan wire) at PCM C1 connector. (Scheme 6) If test light illuminates brightly at both terminals, ground circuits are okay. Test is complete. If test light does not illuminate brightly at one or both terminals, repair open in appropriate Black/Tan wire between PCM and ground. Ground location is located at right front of cylinder block, near generator.

Scheme 6

Scheme 6
Scheme 6

DRIVEABILITY PROBLEMS

Note. The following tests are written specifically for Chrysler's Diagnostic Readout Box (DRBIII(R)) scan tool. A generic scan tool may not be capable of performing all necessary test functions.

START & STALL CONDITION

Note. For circuit identification and wiring diagram, see WIRING DIAGRAMS article. If Powertrain Control Module (PCM) is replaced, PCM must be reprogrammed. See PROGRAMMING . After each repair procedure has been completed, reconnect all components. Perform POWERTRAIN VERIFICATION TEST VER-1 under VERIFICATION TESTS to ensure system is functioning properly.

  1. Turn ignition on. Using scan tool, check for Diagnostic Trouble Codes (DTC). If no DTCs are present, go to next step. If any DTCs are present, perform appropriate diagnostic test. See appropriate SELF-DIAGNOSTICS article.
  2. Using DRB scan tool, read and record Sentry Key Immobilizer Module (SKIM) DTC (fault) messages. If no SKIM DTC messages are present, go to next step. If any SKIM DTC messages are present, a fault exists in anti-theft system. Perform appropriate test. See appropriate ANTI-THEFT SYSTEMS article.
  3. Turn ignition off. Release fuel pressure. See «FUEL SYSTEM PRESSURE RELEASE»(ref-12051-S35450755352000120600000) . Remove test port cap on fuel rail. Install a 0-60 psi (0-4.2 kg/cm 2 ) fuel pressure gauge at test port. Start engine and allow to idle. Fuel pressure should be 44.2-54.2 psi (3.1-3.7 kg/cm 2 ). If fuel pressure is less than specified, go to next step. If fuel pressure is more than specified, fuel pump is okay, but fuel pressure regulator is defective. Release fuel pressure and replace fuel pressure regulator. See FUEL FILTER/FUEL PRESSURE REGULATOR under FUEL SYSTEMS in REMOVAL, OVERHAUL & INSTALLATION article. If fuel pressure is as specified, go to step 6 .
  4. Release fuel pressure. Raise and support vehicle. Disconnect fuel pressure line from fuel filter/pressure regulator at fuel tank. Connect Fuel Line Pressure Test Adapter Hose (6539) between disconnected fuel line and fuel filter/pressure regulator. Connect fuel pressure gauge to fuel line adapter hose. Turn ignition on. Using scan tool, actuate ASD fuel system test and note fuel pressure. Fuel pressure should be 44.2-54.2 psi (3.23-3.96 kg/cm 2 ). If fuel pressure is as specified, stop ASD fuel system activation. Release fuel pressure, and repair or replace fuel supply line. If fuel pressure is not as specified, stop ASD fuel system activation and go to next step.
  5. Release fuel pressure. Remove fuel pump module and inspect fuel inlet strainer. See FUEL PUMP MODULE under FUEL SYSTEMS in REMOVAL, OVERHAUL & INSTALLATION article. If fuel inlet strainer is plugged, replace fuel pump inlet strainer. If fuel inlet strainer is not plugged, replace fuel pump.
  6. Turn ignition off. Release fuel pressure. Disconnect fuel supply line from fuel rail. Install Fuel Line Pressure Test Adapter Hose (6539 for 5/16" fuel lines or 6631 for 3/8" fuel lines) between disconnected fuel line and fuel rail. Remove fuel fill cap. Insert other end of hose into a graduated container suitable for gasoline.
  7. Using scan tool, actuate ASD fuel system test for 7 seconds. If fuel volume is .5 pt. (.25L) or more, fuel volume is okay. Stop fuel system activation. Remove all test equipment and reconnect fuel supply line to fuel rail. Go to next step. If fuel volume is less than .5 pt. (.25L), check for a kinked fuel line between fuel pump module and fuel rail. Repair fuel lines as necessary and retest. If fuel line is okay, replace fuel pump module assembly. See FUEL PUMP MODULE under FUEL SYSTEMS in REMOVAL, OVERHAUL & INSTALLATION article.
  8. Turn ignition on. Using scan tool, monitor TP sensor voltage while slowly depressing throttle pedal from idle position to wide open throttle position. If voltage changes smoothly, go to next step. If voltage does not change smoothly, replace TP sensor.
  9. Ensure throttle is fully closed and against throttle stop. Using scan tool, read TP sensor voltage. If voltage is 0.92 volt or less, go to next step. If voltage is more than 0.92 volt, check for binding throttle linkage. Repair linkage as necessary. If linkage is not binding, replace TP sensor.
  10. Turn ignition on. Using scan tool, read Engine Coolant Temperature (ECT) sensor value. If engine coolant temperature is more than 180°F (82°C), allow engine coolant temperature to cool down to 150°F (66°C) before proceeding. If engine coolant temperature is 150°F (66°C) or less, start engine and monitor scan tool until engine coolant temperature reaches 180°F (82°C). If ECT sensor value increases smoothly, go to next step. If ECT sensor value increase is erratic, check for cooling system problems and repair as necessary. If cooling system is okay, replace ECT sensor.
  11. Check the following additional items as possible causes for start and stall condition: Check for any technical service bulletins that may apply. Fuel must be free of contamination. Engine exhaust system must be free of restrictions. Engine compression must be within specification. Engine valve timing must be within specification. Engine vacuum must be at least 13 in. Hg with shift selector in Neutral. Throttle body must be free of carbon build-up and dirt. Repair any problems as necessary. If no problems exist, test is complete.
  1. Turn ignition on. Using scan tool, check for Diagnostic Trouble Codes (DTC). If no DTCs are present, go to next step. If any DTCs are present, perform appropriate diagnostic test. See appropriate SELF-DIAGNOSTICS article.
  2. Using DRB scan tool, read and record Sentry Key Immobilizer Module (SKIM) DTC (fault) messages. If no SKIM DTC messages are present, go to next step. If any SKIM DTC messages are present, a fault exists in anti-theft system. Perform appropriate test. See appropriate ANTI-THEFT SYSTEMS article.
  3. Turn ignition off. Release fuel pressure. See «FUEL SYSTEM PRESSURE RELEASE»(ref-12051-S35450755352000120600000). Remove test port cap on fuel rail. Install a 0-60 psi (0-4.2 kg/cm 2 ) fuel pressure gauge at test port. Start engine and allow to idle. Fuel pressure should be 44.2-54.2 psi (3.1-3.7 kg/cm 2 ). If fuel pressure is less than specified, go to next step. If fuel pressure is more than specified, check fuel return line for kinks or restrictions. (Scheme 4) Repair fuel return line as necessary. If fuel return line is okay, replace fuel filter/pressure regulator. See FUEL FILTER/FUEL PRESSURE REGULATOR under FUEL SYSTEMS in REMOVAL, OVERHAUL & INSTALLATION article. If fuel pressure is as specified, go to step 6.
  4. If engine runs but fuel pressure is less than specified, check for kinked or damaged fuel supply line between fuel pump module and fuel rail. Repair fuel line as necessary and retest. If fuel line is okay, release fuel pressure. Raise and support vehicle. Disconnect fuel pressure line from fuel filter/pressure regulator. (Scheme 4) Connect Fuel Line Pressure Test Adapter Hose (6539) between disconnected fuel line and fuel filter/pressure regulator. Connect fuel pressure gauge to fuel line adapter hose. Turn ignition on, with engine off. Using scan tool, actuate ASD fuel system test and note fuel pressure. Fuel pressure should be 44.2-54.2 psi (3.23-3.96 kg/cm 2 ). If fuel pressure is within specification, stop ASD fuel system activation, release fuel pressure and replace fuel filter/pressure regulator. If fuel pressure is not within specification, stop ASD fuel system activation and go to next step.
  5. Release fuel pressure. Remove fuel pump module and inspect fuel inlet strainer. See FUEL PUMP MODULE under FUEL SYSTEMS in REMOVAL, OVERHAUL & INSTALLATION article. If fuel inlet strainer is plugged, replace fuel pump inlet strainer. If fuel inlet strainer is not plugged, replace fuel pump.
  6. Turn ignition off. Release fuel pressure. Disconnect fuel supply line from fuel rail. Install Fuel Line Pressure Test Adapter Hose (6539 for 5/16" fuel lines or 6631 for 3/8" fuel lines) between disconnected fuel line and fuel rail. Remove fuel fill cap. Insert other end of hose into a graduated container suitable for gasoline.
  7. Using scan tool, actuate ASD fuel system test for 7 seconds. If fuel volume is.5 pt. (.25L) or more, fuel volume is okay. Stop fuel system activation. Remove all test equipment and reconnect fuel supply line to fuel rail. Go to next step. If fuel volume is less than.5 pt. (.25L), check for a kinked fuel line between fuel pump module and fuel rail. Repair fuel lines as necessary and retest. If fuel line is okay, replace fuel pump module assembly. See FUEL PUMP MODULE under FUEL SYSTEMS in REMOVAL, OVERHAUL & INSTALLATION article.
  8. Turn ignition on. Using scan tool, monitor TP sensor voltage while slowly depressing throttle pedal from idle position to wide open throttle position. If voltage changes smoothly, go to next step. If voltage does not change smoothly, replace TP sensor.
  9. Ensure throttle is fully closed and against throttle stop. Using scan tool, read TP sensor voltage. If voltage is 0.92 volt or less, go to next step. If voltage is more than 0.92 volt, check for binding throttle linkage. Repair linkage as necessary. If linkage is not binding, replace TP sensor.
  10. Turn ignition on. Using scan tool, read Engine Coolant Temperature (ECT) sensor value. If engine coolant temperature is more than 180°F (82°C), allow engine coolant temperature to cool down to 150°F (66°C) before proceeding. If engine coolant temperature is 150°F (66°C) or less, start engine and monitor scan tool until engine coolant temperature reaches 180°F (82°C). If ECT sensor value increases smoothly, go to next step. If ECT sensor value increase is erratic, check for cooling system problems and repair as necessary. If cooling system is okay, replace ECT sensor.
  11. Check the following additional items as possible causes for start and stall condition: Check for any technical service bulletins that may apply. Fuel must be free of contamination. Engine exhaust system must be free of restrictions. Engine compression must be within specification. Engine valve timing must be within specification. Engine vacuum must be at least 13 in. Hg with shift selector in Neutral. Throttle body must be free of carbon build-up and dirt. Repair any problems as necessary. If no problems exist, test is complete.

SUMMARY

If no faults were found while performing basic diagnostic procedures, proceed to appropriate SELF-DIAGNOSTICS article. If no hard codes are found in self-diagnostics, proceed to TROUBLE SHOOTING - NO CODES article for diagnosis by symptom (i.e., ROUGH IDLE, NO START, etc.) or intermittent diagnostic procedures.

More articles — Engine Controls - Basic Diagnostic Procedures