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Engine Controls - Basic Diagnostic Procedures: Diagnosis Isuzu Axiom I

Testing & Diagnostics 2 illustrations ~8313 words

VISUAL INSPECTION

Visually inspect all electrical wiring, looking for chafed, stretched, cut or pinched wiring. Check for any blown fuses. Ensure electrical connectors fit tightly and are not corroded. For connector and wiring identification, see WIRING DIAGRAMS . Ensure vacuum hoses are properly routed and not pinched or cut. See appropriate vacuum diagram in VACUUM DIAGRAMS article to verify routing and connections (if necessary). Inspect air induction system for possible vacuum leaks.

MECHANICAL INSPECTION

WARNINGDO NOT use ignition switch during compression tests on fuel injected vehicles. Use a remote starter switch to crank engine. Fuel injectors on many models are triggered by ignition switch during cranking mode, which can create a fire hazard or contaminate the engine's oiling system.

Circuit Description

The electronic ignition system uses a dual coil method of spark distribution. In this type of ignition system, PCM triggers the correct Ignition Control Module (ICM) driver, which triggers correct ignition coil based on 58X signal received from the Crankshaft Position Sensor (CKP). Spark plug connected to coil fires when ICM opens ground circuit for ignition coil's primary circuit. During cranking, PCM monitors CKP 58X signal. CKP signal is used to determine which cylinder will fire first. After CKP 58X signal has been processed by the PCM, it will command all four injectors to allow a priming shot of fuel for all cylinders. After priming, fuel injectors are left OFF during the next four 58X reference pulses from CKP. This allows each cylinder a chance to use fuel from priming shot. During this waiting period, a Camshaft Position (CMP) sensor signal pulse will have been received by PCM. CMP sensor signal allows PCM to operate fuel injectors sequentially based on camshaft position. If camshaft position signal is not present at start-up, PCM will begin sequential fuel delivery with a 1-in-4 chance that fuel delivery is correct. Engine will run without a CMP sensor signal, but will set a DTC code.

Diagnostic Aids

An intermittent problem may be caused by a poor connection, rubbed-through wire insulation or a wire broken inside the insulation. Check for poor connection or damaged harness. Inspect PCM harness and connectors for improper mating, broken locks, improperly formed or damaged terminals, poor terminal-to-wire connection, and damaged harness. Faulty Engine Coolant Temperature (ECT) sensor. Using scan tool, compare engine coolant temperature with intake air temperature on a completely cool engine. Engine coolant temperature should be within 50 °F (10 °C) of intake air temperature. If not, replace the ECT sensor.

Testing Procedure

  1. Perform On-Board Diagnostic II (OBD-II) System Check. See «ON-BOARD DIAGNOSTIC II SYSTEM CHECK»(ref-133138-S20220920332002021300000) in SELF-DIAGNOSTICS - RODEO & RODEO SPORT 2.2L article. After performing OBD-II system check, go to next step.
  2. Connect Tech 2 or equivalent scan tool to Data Link Connector (DLC). DLC is located under small cover on left side of dash. Following manufacturer's instructions, check for stored DTCs. If no DTCs are stored, go to next step. If any DTCs are stored, perform appropriate test. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-133138-S22707626342002081900000) in SELF-DIAGNOSTICS - 2.2L article.
  3. Check CB-13 IG. COIL (15-amp) fuse and CB-12 ENGINE IG. fuse (15-amp) located in dashboard fuse block. Check EB-13 ECM fuse (15-amp) located in underhood fuse/relay block. If any fuse is blown, go to next step. If fuses are okay, go to step 5 .
  4. Check for short to ground in suspect fuse circuits. See «WIRING DIAGRAMS»(ref-133147) article. If problem is found, repair as necessary. Replace any blown fuses and recheck system.
  5. Turn ignition on. With a test light connected to ground, probe CB-13 IG. COIL (15-amp), CB-12 ENGINE IG. fuse (15-amp) and ECM fuse (15-amp) fuses. If test light illuminates at all fuses, go to step 7 . If test light does not illuminate at all fuses, go to next step.
  6. Repair open in appropriate ignition feed circuit to suspect fuse. See «WIRING DIAGRAMS»(ref-133147) article. After repair, retest system.
  7. Turn ignition off. Disconnect spark plug wire from cylinder No. 1. Install spark tester. While cranking engine, check for crisp, Blue spark. If poor or no spark is found, go to next step. If spark is okay, go to step 16 .
  8. Disconnect Ignition Control Module (ICM) 4-pin harness connector. ICM is located on rear of cylinder head. Check for open or short in circuits between ICM and PCM. See «WIRING DIAGRAMS»(ref-133147) article. If problem is found, go to next step. If no problem is found, go to step 10 .
  9. Repair open or short circuit in wires between ICM and PCM as necessary. After repair, retest system.
  10. Turn ignition on. Using DVOM, measure voltage between ground and ICM harness connector terminal No. 1 (Black/Orange wire). See «WIRING DIAGRAMS»(ref-133147) article. If battery voltage is present, go to step 12 . If battery voltage is not present, go to next step.
  11. Repair open in Black/Orange wire (ICM ignition voltage) between CB-13 IG COIL fuse and ICM. After repair, retest system.
  12. Turn ignition switch off. Check for open in Black/Red wire between ground point E-28 and ICM ground circuit. Ground point is located on intake manifold, at right rear of engine. If no problem is found, go to step 14 . If problem is found, go to next step.
  13. Locate and repair open circuit in Black/Red wire (ICM ground) between ground point and ICM. After repair, retest system.
  14. Replace ICM. See IGNITION SYSTEM in «REMOVAL, OVERHAUL & INSTALLATION»(ref-133146) article. Attempt to start engine. If engine starts, testing is complete. If engine still does not start, go to next step.
  15. Replace and reprogram PCM. See «POWERTRAIN CONTROL MODULE REPLACEMENT»(ref-133138-S03776365552002081900000) under POWERTRAIN CONTROL MODULE in SELF-DIAGNOSTICS - RODEO & RODEO SPORT 2.2L article. After repair, retest system.
  16. Turn ignition off. Using DVOM, measure ignition coil primary resistance. Resistance should be .8-18 ohms. If primary resistance is as specified, go to next step. If primary resistance is not as specified, go to step 18 .
  17. Measure ignition coil secondary resistance. Resistance should be 9000-12,000 ohms. If secondary resistance is as specified, go to step 19 . If secondary resistance is not as specified, go to next step.
  18. Replace ignition coil. After repair, retest system.
  19. Measure resistance of each coil-to-spark plug secondary ignition wire. Resistance should be 10 k/ohms per foot. If resistance is more than specified, go to next step. If resistance less than specified, go to step 21 .
  20. Replace any spark plug wires with resistance more than 10 k/ohms per foot. If problem still exists, go to next step. If problem no longer exists, testing is complete.
  21. Remove all spark plugs. Inspect spark plugs for fouling, loose or missing electrodes, or cracked insulators. Clean or replace spark plugs as necessary, and go to next step. If spark plugs are okay, go to step 33 .
  22. Attempt to start engine. If problem is still present, go to next step.
  23. Turn ignition off. Install fuel pressure gauge to fuel supply line test fitting. Turn ignition on. Fuel pressure should be 42-55 psi (283-376 kPa) and hold steady for 2 seconds. If fuel pressure is as specified, leave fuel pressure gauge connected and go to step 25 . If fuel pressure is not as specified, go to next step.
  24. If fuel pressure is not present, go to «FUEL SYSTEM DIAGNOSIS»(ref-133136-S33194148372002021300000) under FUEL SYSTEM. If any fuel pressure is present, go to «FUEL SYSTEM ELECTRICAL TEST»(ref-133136-S17205019162002021300000) under FUEL SYSTEM.
  25. Disconnect fuel injector 5-pin in-line harness connector. In-line harness connector is located under air intake pie, near air filter. Install Injector Tester (J-39021) and switch box at injector test connector. While observing fuel pressure gauge activate fuel injector. If fuel pressure drops, go to next step. If fuel pressure does not drop, go to «FUEL SYSTEM DIAGNOSIS»(ref-133136-S33194148372002021300000) under FUEL SYSTEM.
  26. Pressurize system by turning ignition on. Using injector switch box, test each injector for pressure drop. If a pressure drop is present at each injector, go to next step. If a pressure drop is not present at each injector, go to «FUEL SYSTEM DIAGNOSIS»(ref-133136-S33194148372002021300000) under FUEL SYSTEM.
  27. Remove Injector Tester (J-39021) and switch box. Connect Injector Test Light (J-39021-45) to injector test harness connector. Crank engine. If any tester lights blink while engine is cranking, go to step 33 . If no tester lights blink while engine is cranking, go to next step.
  28. Raise and support vehicle. Disconnect Crankshaft Position (CKP) sensor 3-pin harness connector. Turn ignition on. Using a test light connected to ground, probe ignition feed circuit at CKP sensor harness terminal No. 2 (Blue wire). If test light illuminates, go to next step. If test light does not illuminate, go to step 30 .
  29. Connect test light between CKP sensor harness connector terminals No. 2 (Blue wire) and No. 3 (Black wire). Turn ignition on. If test light illuminates, go to step 31 . If test light does not illuminate, go to step 32 .
  30. Check for open or short to ground in Green wire (CKP sensor high circuit) between CKP sensor and PCM. If problem is found, repair as necessary. After repair, retest system. If no problem is found, go to step 33 .
  31. Replace CKP sensor. See ENGINE SENSORS & SWITCHES in «REMOVAL, OVERHAUL & INSTALLATION»(ref-133146) article. After repair, retest system. If problem still exists, go to step 34 .
  32. Check for open or short to ground in Yellow wire (CKP sensor low circuit) between CKP sensor and PCM. If problem was found, repair as necessary. After repair, retest system. If no problem is found, go to next step.
  33. Replace and reprogram PCM. See «POWERTRAIN CONTROL MODULE REPLACEMENT»(ref-133138-S03776365552002081900000) under POWERTRAIN CONTROL MODULE in SELF-DIAGNOSTICS - RODEO & RODEO SPORT 2.2L article. After repair, retest system.
  34. Test for fuel contamination. If fuel is contaminated, clean fuel system as necessary. Replace fuel filter and verify all fuel injectors are delivering fuel. If no problem is found, go to next step.
  35. Check for these possible conditions: Faulty camshaft timing belt. Leaking or sticking valves or rings. Excessive valve deposits. Loose or worn rocker arms. Weak valve springs. Leaking head gasket. If problem is found, repair as necessary. See appropriate article in ENGINES. After repair, retest system.

Isuzu V6 electronic ignition systems use a coil-at-plug method of spark distribution. In this type of ignition system, the PCM triggers correct driver outside the Ignition Current Sense System (ICSS), which then triggers correct ignition coil based on the 58X signal received from Crankshaft Position (CKP) sensor. Spark plug connected to coil fires when ICSS opens ground circuit for appropriate ignition coil primary circuit. During cranking, PCM monitors CKP sensor 58X signal. CKP sensor signal is used to determine which cylinder will fire first. After CKP sensor 58X signal has been processed by the PCM, it will command all six injectors On to allow a priming shot of fuel for all cylinders. After priming, injectors are left Off during the next six 58X reference pulses from the CKP sensors. This allows each cylinder a chance to use fuel from priming shot during cranking. The ION sensor signal allows the PCM to operate fuel injectors sequentially based on camshaft position. If camshaft position signal is not present at start-up, PCM will begin sequential fuel delivery with a 1-in-6 chance that fuel delivery is correct. Engine will run without a ION sensor signal, but will set an appropriate DTC.

An intermittent problem may be caused by a poor connection, rubbed-through wire insulation or a wire broken inside the insulation. Check for poor connection or damaged harness. Inspect PCM harness and connectors for improper mating, broken locks, improperly formed or damaged terminals, poor terminal-to-wire connection, and damaged harness. Faulty Engine Coolant Temperature (ECT) sensor. Using scan tool, compare engine coolant temperature with intake air temperature on a completely cool engine. Engine coolant temperature should be within 50 °F (10 °C) of intake air temperature. If not, replace the ECT sensor.

  1. Perform On-Board Diagnostic II (OBD-II) System Check. See «ON-BOARD DIAGNOSTIC II SYSTEM CHECK»(ref-142539-S02067822572002080800000) under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - AXIOM 3.5L, PASSPORT & RODEO 3.2L article. After performing OBD-II system check, go to next step.
  2. Check CB-13 IG. COIL (15-amp) fuse located in dashboard fuse box. If any fuse is blown, go to next step. If fuses are okay, go to step 4.
  3. Check for short to ground in Black/Orange wire (ignition feed circuit) between fuse and ION sensing module. See «WIRING DIAGRAMS»(ref-133147) article. If problem is found, repair as necessary. Replace any blown fuses.
  4. Turn ignition off. Install fuel pressure gauge to fuel supply line test fitting. Turn ignition on. Fuel pressure should be 42-55 psi (283-376 kPa) and hold steady for 2 seconds. If fuel pressure is as specified, leave fuel pressure gauge connected and go to step 6. If fuel pressure is not as specified, go to next step.
  5. If no fuel pressure is indicated, go to «FUEL SYSTEM DIAGNOSIS»(ref-133136-S33194148372002021300000) under FUEL SYSTEM. If any fuel pressure is indicated, go to «FUEL SYSTEM ELECTRICAL TEST»(ref-133136-S17205019162002021300000) under FUEL SYSTEM.
  6. Install Injector Tester (J-39021) and switch box at injector test connector Gray 7-pin in-line harness connector. In-line harness connector is bolted to front of right valve cover, below where air duct attaches to MAF sensor. While observing fuel pressure gauge activate fuel injector. If fuel pressure drops, go to next step. If fuel pressure does not drop, go to 18.
  7. Install fuel injector test light (noid light) at cylinder No. 2 injector harness connector. Crank engine. If noid light blinks, go to next step. If noid light does not blink, go to step 24.
  8. Turn ignition off. Disconnect ION sensing 11-pin harness connector. ION sensor is located on top of intake manifold. Using a test light connected to battery voltage, probe each of the 6 exposed pins while cranking engine. If test light flashes at each pin, connect disconnected harness connectors and go to step 12. If test light does not flash at each pin, go to next step.
  9. Turn ignition off. Disconnect ION sensing module 4-pin harness connector. Turn ignition on. Using a test light connected to ground, probe ION sensing module harness connector E-16 terminal No. 7 (Black/Orange wire). See «WIRING DIAGRAMS»(ref-133147) article. Connect test light to battery voltage, probe ION sensing module harness connector E-16 terminal No. 1 (Black wire). If test light does not illuminate at both terminals, go to next step. If test light illuminates at both terminals, go to step 11.
  10. Repair open in Black/Orange wire (ION sensing module ignition feed) between ISM and CB-13 IG. COIL fuse, or in Black wire (ION sensing module ground) between ground point E-29 and ISM. Ground point is forward of 2 grounds located on right side of intake manifold. After repair, retest system.
  11. Replace ION sensing module. After repair, test drive vehicle to confirm repair.
  12. Disconnect 3-pin harness connector from each ignition coil. Using a test light connected to battery voltage, probe each ignition coil harness connector terminal No. 1. See «IDENTIFYING IGNITION COIL TO ISM WIRES»(ref-133136-S25432502522002021300000) table. While cranking engine, observe test light. If test light flashes at each ignition coil, leave harness connectors disconnected and go to step 14. If test light does not flash at each ignition coil, go to next step. IDENTIFYING IGNITION COIL TO ISM WIRES Ignition Coil/Cylinder No. (1) Wire Color 1 Red 2 Red/Black 3 Red/Blue 4 Red/White 5 Red/Yellow 6 Red/Green (1) Test each ignition coil at harness connector terminal No. 1.
  13. Check for and repair open in circuits between ignition coil and ION sensing module. See «WIRING DIAGRAMS»(ref-133147) article. If problem is found, repair as necessary. After repair, test drive vehicle to confirm repair.
  14. Turn ignition on. Using a test light connected to ground, probe Black/Orange wire (ignition feed circuit) at each ignition coil harness connector. If test light illuminates at each terminal, leave harness connectors disconnected and go to step 16. If test light does not illuminate at each terminal, go to next step.
  15. Repair open in Black/Orange wire (ignition feed circuit) between suspect ignition coil and CB-13 IG. COIL fuse. After repair, test drive vehicle to confirm repair.
  16. Using a test light connected to battery voltage, probe secondary ground circuit of each ignition coil at harness connector (Black wire). If test light does not illuminate at each terminal, go to next step. If test light does illuminate at each terminal, go to step 18.
  17. Repair open circuit in Black wire between appropriate ignition coil and ground. After repair, test drive vehicle to confirm repair.
  18. Test for fuel contamination. If fuel is contaminated, clean fuel system as necessary. Replace fuel filter and verify all fuel injectors are delivering fuel. After repair, test drive vehicle to confirm repair. If fuel is not contaminated, go to next step.
  19. Remove any ignition coil. Install spark tester at spark plug end of coil. While cranking engine, check ignition coil for crisp, Blue spark. If weak spark or no spark is present, go to next step. If spark is okay, go to step 21.
  20. Replace faulty ignition coil. Repeat test from previous step for each ignition coil. If problem is found, replace coil(s) as necessary. After repair, test drive vehicle to confirm repair.
  21. Repeat test from step 19 for each ignition coil. Test one coil at a time, and reinstall each coil on its spark plug when testing is complete (DO NOT install screws). Attempt to start engine. If engine does not start, go to next step. If engine starts, install ignition coil screws and test drive vehicle to confirm repair.
  22. Remove all spark plugs. Inspect spark plugs for fouling, loose or missing electrodes, or cracked insulators. Clean or replace spark plugs as necessary. If spark plugs are okay, go to next step.
  23. Check for these possible conditions: Faulty or incorrect camshaft timing belt. Leaking or sticking valves or rings. Excessive valve deposits. Loose or worn rocker arms. Weak valve springs. Incorrect valve timing. Leaking head gasket. If problem is found, repair as necessary. See appropriate article in ENGINES. If no problem is found, go to step 25.
  24. Using scan tool, select ENGINE SPEED parameter. While cranking engine, observe scan tool. If RPM is indicated on scan tool, go to next step. If engine RPM is not indicated, go to step 34.
  25. Turn ignition off. Disconnect fuel injector tester Gray 7-pin in-line harness connector. In-line harness connector is bolted to front of right valve cover, below where air duct attaches to MAF sensor. Turn ignition on. Using a test light connected to ground, on female side of connector probe fuel injector tester in-line harness connector terminal No. 1 (Red/Green wire). (Scheme 1) If test light illuminates, go to next step. If test light does not illuminate, go to step 32.
  26. Connect test light between female side of fuel injector tester in-line harness connector terminals No. 1 (Red/Green wire) and specified terminal. See «IDENTIFYING FUEL INJECTOR TESTER IN-LINE HARNESS CONNECTOR TERMINALS»(ref-133136-S21383449552002021300000) table. (Scheme 1) Turn ignition on. If test light illuminates and stays on at any terminal, leave test light connected and go to next step. If test light does not illuminate and stay on at any terminal, go to step 29. IDENTIFYING FUEL INJECTOR TESTER IN-LINE HARNESS CONNECTOR TERMINALS Application Wire Color Injector No. 1 Green/White Injector No. 2 Green/Orange Injector No. 3 Green Injector No. 4 Green/Red Injector No. 5 Green/Black Injector No. 6 Green/Yellow
  27. Turn ignition off. Disconnect PCM 80-pin harness connector E-35. PCM is located on fenderwell at right side of engine compartment. Turn ignition on. If test light illuminates, go to next step. If test light does not illuminate, go to step 33.
  28. Repair short to ground in suspect fuel injector driver circuit. See «WIRING DIAGRAMS»(ref-133147) article. After repair, test drive vehicle to confirm repair.
  29. Connect test light between female side of fuel injector tester in-line harness connector terminals No. 1 (Red/Green wire) and specified terminal. See «IDENTIFYING FUEL INJECTOR TESTER IN-LINE HARNESS CONNECTOR TERMINALS»(ref-133136-S21383449552002021300000) table. (Scheme 1) Observing test light crank engine. If test light flashes at any terminal, leave harness connector disconnected and go to step 31. If test light does not flash at any terminal, go to next step.
  30. Check for open in suspect injector driver circuit. See «WIRING DIAGRAMS»(ref-133147) article. If problem is found, repair as necessary. After repair, test drive vehicle to confirm repair. If no problem was found, go to step 33.
  31. Turn ignition off. Connect DVOM between male side of fuel injector tester Gray 7-pin in-line harness connector terminals No. 1 and specified terminal. See «IDENTIFYING FUEL INJECTOR TESTER IN-LINE HARNESS CONNECTOR TERMINALS»(ref-133136-S21383449552002021300000) table. (Scheme 1) Resistance should be about 12.5 ohms at all pins. If resistance is as specified, repeat test starting in step 8. If resistance is not as specified at all pins, check for an open, shorted or faulty fuel injector. Repair or replace fuel injector(s) as necessary. After repair, test drive vehicle to confirm repair.
  32. Repair open in Black/Orange wire (ignition feed) between CB-13 IG. COIL fuse and PCM. See «WIRING DIAGRAMS»(ref-133147) article. After repair, test drive vehicle to confirm repair.
  33. Replace and reprogram PCM. See «POWERTRAIN CONTROL MODULE REPLACEMENT»(ref-142539-S05860400612002080800000) under POWERTRAIN CONTROL MODULE in SELF-DIAGNOSTICS - AXIOM 3.5L, PASSPORT & RODEO SPORT 3.2L article. After repair, test drive vehicle to confirm repair.
  34. Turn ignition off. Raise and support vehicle. Disconnect Crankshaft Position (CKP) sensor connector. Turn ignition on. Using a test light connected to ground, probe CKP sensor harness connector terminal No. 1 (White wire). If test light does illuminate, leave harness connector and go to step 36. If test light does not illuminate, go to next step.
  35. Check for and repair open or short to ground in White wire (ignition feed) between CKP sensor and PCM. See «WIRING DIAGRAMS»(ref-133147) article. After repair, test drive vehicle to confirm repair.
  36. Turn ignition on. Connect a test light between CKP sensor harness connector terminals No. 1 (White wire) and No. 2 (Yellow/Black wire). If test light illuminates, go to step 38. If test light does not illuminate, go to next step.
  37. Check for and repair open or short to voltage in Yellow/Black wire (CKP ground) between CKP sensor and PCM. See «WIRING DIAGRAMS»(ref-133147) article. After repair, test drive vehicle to confirm repair.
  38. Check for open, short to ground or short to voltage in White/Blue wire (CKP signal circuit) between CKP sensor and PCM. If problem is found, repair as necessary. After repair, test drive vehicle to confirm repair. If no problem is found, go to next step.
  39. Replace CKP sensor. See «ENGINE SENSORS & SWITCHES»(ref-133146-S28034503012002021300000) in REMOVAL, OVERHAUL & INSTALLATION article. After repair, test drive vehicle to confirm repair. If system is still not operating properly, repeat test starting in step 33.

Scheme 1

Scheme 1
Scheme 1

Isuzu V6 electronic ignition systems use a coil-at-plug method of spark distribution. In this type of ignition system, the PCM triggers correct driver outside the Ignition Current Sense System (ICSS), which then triggers correct ignition coil based on the 58X signal received from Crankshaft Position (CKP) sensor. Spark plug connected to coil fires when ICSS opens ground circuit for appropriate coil's primary circuit. During cranking, PCM monitors CKP sensor 58X signal. CKP sensor signal is used to determine which cylinder will fire first. After CKP sensor 58X signal has been processed by the PCM, it will command all six injectors On to allow a priming shot of fuel for all cylinders. After priming, injectors are left Off during the next six 58X reference pulses from the CKP sensors. This allows each cylinder a chance to use fuel from priming shot during cranking. The ION sensor signal allows the PCM to operate fuel injectors sequentially based on camshaft position. If camshaft position signal is not present at start-up, PCM will begin sequential fuel delivery with a 1-in-6 chance that fuel delivery is correct. Engine will run without a ION sensor signal, but will set an appropriate DTC.

An intermittent problem may be caused by a poor connection, rubbed-through wire insulation or a wire broken inside the insulation. Check for poor connection or damaged harness. Inspect PCM harness and connectors for improper mating, broken locks, improperly formed or damaged terminals, poor terminal-to-wire connection, and damaged harness. Faulty Engine Coolant Temperature (ECT) sensor. Using scan tool, compare engine coolant temperature with intake air temperature on a completely cool engine. Engine coolant temperature should be within 50 °F (10 °C) of intake air temperature. If not, replace the ECT sensor.

  1. Perform On-Board Diagnostic II (OBD-II) System Check. See «ON-BOARD DIAGNOSTIC II SYSTEM CHECK»(ref-133137-S18795492482002021300000) under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - TROOPER 3.5L article. After performing OBD-II system check, go to next step.
  2. Check C-9 IG. COIL (15-amp) and C-8 ENGINE (15-amp) fuse located in dashboard fuse box. Check FL-3 ECM (30-amp) fuse located in underhood fuse/relay box. If any fuse is blown, go to next step. If fuses are okay, go to step 4.
  3. Check for short to ground in ignition feed circuit between suspect fuse and ION sensing module or PCM. See «WIRING DIAGRAMS»(ref-133147) article. If problem is found, repair as necessary. Replace any blown fuses. After repair, test drive vehicle to confirm repair.
  4. Turn ignition off. Install fuel pressure gauge to fuel supply line test fitting. Turn ignition on. Fuel pressure should be 42-55 psi (283-376 kPa) and hold steady for 2 seconds. If fuel pressure is as specified, leave fuel pressure gauge connected and go to step 6. If fuel pressure is not as specified, go to next step.
  5. If no fuel pressure is indicated, go to «FUEL SYSTEM DIAGNOSIS»(ref-133136-S33194148372002021300000) under FUEL SYSTEM. If any fuel pressure is indicated, go to «FUEL SYSTEM ELECTRICAL TEST»(ref-133136-S17205019162002021300000) under FUEL SYSTEM.
  6. Install Injector Tester (J-39021) and switch box at injector test connector Gray 7-pin in-line harness connector. In-line harness connector is bolted to front of right valve cover, below where air duct attaches to MAF sensor. While observing fuel pressure gauge activate fuel injector. If fuel pressure drops, go to next step. If fuel pressure does not drop, go to 18.
  7. Install fuel injector test light (noid light) at cylinder No. 2 injector harness connector. Crank engine. If noid light blinks, go to next step. If noid light does not blink, go to step 24.
  8. Turn ignition off. Disconnect ION sensing 11-pin harness connector. ION sensor is located on top of intake manifold. Using a test light connected to battery voltage, probe each of the 6 exposed pins while cranking engine. If test light flashes at each pin, connect disconnected harness connectors and go to step 12. If test light does not flash at each pin, go to next step.
  9. Turn ignition off. Disconnect ION sensing module 4-pin harness connector. Turn ignition on. Using a test light connected to ground, probe ION sensing module harness connector E-16 terminal No. 7 (Black/Orange wire). See «WIRING DIAGRAMS»(ref-133147) article. Connect test light to battery voltage, probe ION sensing module harness connector E-16 terminal No. 1 (Black wire). If test light does not illuminate at both terminals, go to next step. If test light illuminates at both terminals, go to step 11.
  10. Repair open in Black/Orange wire (ION sensing module ignition feed) between ISM and C-9 IG. COIL fuse, or in Black wire (ION sensing module ground) between ground point E-29 and ISM. Ground point is forward of 2 grounds located on right side of intake manifold. After repair, test drive vehicle to confirm repair.
  11. Replace ION sensing module. After repair, test drive vehicle to confirm repair.
  12. Disconnect 3-pin harness connector from each ignition coil. Using a test light connected to battery voltage, probe each ignition coil harness connector terminal No. 1. See «IDENTIFYING IGNITION COIL TO ISM WIRES»(ref-133136-S00624990312002091700000) table. While cranking engine, observe test light. If test light flashes at each ignition coil, leave harness connectors disconnected and go to step 14. If test light does not flash at each ignition coil, go to next step. IDENTIFYING IGNITION COIL TO ISM WIRES Ignition Coil/Cylinder No. (1) Wire Color 1 Red 2 Red/Black 3 Red/Blue 4 Red/White 5 Red/Yellow 6 Red/Green (1) Test each ignition coil at harness connector terminal No. 1.
  13. Check for and repair open in circuits between suspect ignition coil and ION sensing module. See «WIRING DIAGRAMS»(ref-133147) article. If problem is found, repair as necessary. After repair, test drive vehicle to confirm repair.
  14. Turn ignition on. Using a test light connected to ground, probe Black/Orange wire (ignition feed circuit) at each ignition coil harness connector. If test light illuminates at each terminal, leave harness connectors disconnected and go to step 16. If test light does not illuminate at each terminal, go to next step.
  15. Repair open in Black/Orange wire (ignition feed circuit) between suspect ignition coil and C-9 IG. COIL fuse. After repair, test drive vehicle to confirm repair.
  16. Using a test light connected to battery voltage, probe secondary ground circuit of each ignition coil at harness connector (Black wire). If test light does not illuminate at each terminal, go to next step. If test light does illuminate at each terminal, go to step 18.
  17. Repair open circuit in Black wire between appropriate ignition coil and ground. After repair, test drive vehicle to confirm repair.
  18. Test for fuel contamination. If fuel is contaminated, clean fuel system as necessary. Replace fuel filter and verify all fuel injectors are delivering fuel. After repair, test drive vehicle to confirm repair. If fuel is not contaminated, go to next step.
  19. Remove any ignition coil. Install spark tester at spark plug end of coil. While cranking engine, check ignition coil for crisp, Blue spark. If weak spark or no spark is present, go to next step. If spark is okay, go to step 21.
  20. Replace faulty ignition coil. Repeat test from previous step for each ignition coil. If problem is found, replace coil(s) as necessary. After repair, test drive vehicle to confirm repair.
  21. Repeat test from step 19 for each ignition coil. Test one coil at a time, and reinstall each coil on its spark plug when testing is complete (DO NOT install screws). Attempt to start engine. If engine does not start, go to next step. If engine starts, install ignition coil screws and test drive vehicle to confirm repair.
  22. Remove all spark plugs. Inspect spark plugs for fouling, loose or missing electrodes, or cracked insulators. Clean or replace spark plugs as necessary. If spark plugs are okay, go to next step.
  23. Check for these possible conditions: Faulty or incorrect camshaft timing belt. Leaking or sticking valves or rings. Excessive valve deposits. Loose or worn rocker arms. Weak valve springs. Incorrect valve timing. Leaking head gasket. If problem is found, repair as necessary. See appropriate article in ENGINES. If no problem is found, go to step 25.
  24. Using scan tool, select ENGINE SPEED parameter. While cranking engine, observe scan tool. If RPM is indicated on scan tool, go to next step. If engine RPM is not indicated, go to step 34.
  25. Turn ignition off. Disconnect fuel injector tester Gray 7-pin in-line harness connector. In-line harness connector is bolted to front of right valve cover, below where air duct attaches to MAF sensor. Turn ignition on. Using a test light connected to ground, on female side of connector probe fuel injector tester in-line harness connector terminal No. 1 (Red/Blue wire). (Scheme 1) If test light illuminates, go to next step. If test light does not illuminate, go to step 32.
  26. Connect test light between female side of fuel injector tester in-line harness connector terminals No. 1 (Red/Blue wire) and specified terminal. See «IDENTIFYING FUEL INJECTOR TESTER IN-LINE HARNESS CONNECTOR TERMINALS»(ref-133136-S42695917572002091700000) table. (Scheme 1) Turn ignition on. If test light illuminates and stays on at any terminal, leave test light connected and go to next step. If test light does not illuminate and stay on at any terminal, go to step 29. IDENTIFYING FUEL INJECTOR TESTER IN-LINE HARNESS CONNECTOR TERMINALS Application Wire Color Injector No. 1 Green/White Injector No. 2 Green/Orange Injector No. 3 Green Injector No. 4 Green/Red Injector No. 5 Green/Black Injector No. 6 Green/Yellow
  27. Turn ignition off. Disconnect PCM 80-pin harness connector E-22. PCM is located on fenderwell at right side of engine compartment. Turn ignition on. If test light illuminates, go to next step. If test light does not illuminate, go to step 33.
  28. Repair short to ground in suspect fuel injector driver circuit. See «WIRING DIAGRAMS»(ref-133147) article. After repair, test drive vehicle to confirm repair.
  29. Connect test light between female side of fuel injector tester in-line harness connector terminals No. 1 (Red/Blue wire) and specified terminal. See «IDENTIFYING FUEL INJECTOR TESTER IN-LINE HARNESS CONNECTOR TERMINALS»(ref-133136-S42695917572002091700000) table. (Scheme 1) Observe test light while cranking engine. If test light flashes at any terminal, leave harness connector disconnected and go to step 31. If test light does not flash at any terminal, go to next step.
  30. Check for open in suspect injector driver circuit. See «WIRING DIAGRAMS»(ref-133147) article. If problem is found, repair as necessary. After repair, test drive vehicle to confirm repair. If no problem was found, go to step 33.
  31. Turn ignition off. Using DVOM, measure resistance between male side of fuel injector tester Gray 7-pin in-line harness connector terminals No. 1 and specified terminal. See «IDENTIFYING FUEL INJECTOR TESTER IN-LINE HARNESS CONNECTOR TERMINALS»(ref-133136-S42695917572002091700000) table. (Scheme 1) Resistance should be about 12.5 ohms at all pins. If resistance is as specified, repeat test starting in step 8. If resistance is not as specified at all pins, check for an open, shorted or faulty fuel injector. Repair or replace fuel injector(s) as necessary. After repair, test drive vehicle to confirm repair.
  32. Repair open in Black/Orange wire (ignition feed) between CB-13 IG. COIL fuse and PCM. See «WIRING DIAGRAMS»(ref-133147) article. After repair, test drive vehicle to confirm repair.
  33. Replace and reprogram PCM. See «POWERTRAIN CONTROL MODULE REPLACEMENT»(ref-133137-S39205857452002062800000) under POWERTRAIN CONTROL MODULE in SELF-DIAGNOSTICS - TROOPER 3.5L article. After repair, test drive vehicle to confirm repair.
  34. Turn ignition off. Raise and support vehicle. Disconnect Crankshaft Position (CKP) sensor 3-pin harness connector. Turn ignition on. Using a test light connected to ground, probe CKP sensor harness connector terminal No. 1 (Blue wire). If test light does illuminate, leave harness connector and go to step 36. If test light does not illuminate, go to next step.
  35. Check for and repair open or short to ground in Blue wire (ignition feed) between CKP sensor and PCM. See «WIRING DIAGRAMS»(ref-133147) article. After repair, test drive vehicle to confirm repair.
  36. Turn ignition on. Connect a test light between CKP sensor harness connector terminals No. 1 (Blue wire) and No. 2 (Green wire). If test light illuminates, go to step 38. If test light does not illuminate, go to next step.
  37. Check for and repair open or short to voltage in Green wire (CKP ground) between CKP sensor and PCM. See «WIRING DIAGRAMS»(ref-133147) article. After repair, test drive vehicle to confirm repair.
  38. Check for open, short to ground or short to voltage in Yellow/Red wire (CKP signal circuit) between CKP sensor and PCM. If problem is found, repair as necessary. After repair, test drive vehicle to confirm repair. If no problem is found, go to next step.
  39. Replace CKP sensor. See «ENGINE SENSORS & SWITCHES»(ref-133146-S28034503012002021300000) in REMOVAL, OVERHAUL & INSTALLATION article. After repair, test drive vehicle to confirm repair. If system is still not operating properly, repeat test starting in step 33.

When ignition switch is turned on, PCM will turn in-tank fuel pump on. In-tank fuel pump will remain running as long as engine is cranking or running and PCM is receiving 58X crankshaft position pulses. If there are no 58X crankshaft position pulses, PCM will turn in-tank fuel pump off 2 seconds after ignition switch is turned on, or 2 seconds after engine stops running. In-tank fuel pump is an electric pump within an integral reservoir. In-tank fuel pump supplies fuel through an in-line fuel filter to fuel rail assembly. Fuel pump is designed to provide fuel at pressure above pressure needed by fuel injectors. Fuel pressure regulator, attached to fuel rail, keeps fuel available to fuel injectors at a regulated pressure. Unused fuel is returned to fuel tank by a separate fuel return line.

  1. Perform On-Board Diagnostic II (OBD-II) System Check. See ON-BOARD DIAGNOSTIC II SYSTEM CHECKunder SELF-DIAGNOSTIC SYSTEM in appropriate SELF-DIAGNOSTICS article. After performing OBD-II system check, go to next step.
  2. Turn ignition off. Turn A/C off. Relieve fuel system pressure. See «FUEL SYSTEM PRESSURE RELEASE»(ref-133136-S41554429242002021300000) . Connect fuel pressure gauge as outlined in «FUEL PUMP PRESSURE TEST»(ref-133136-S39650653832002021300000) . Turn ignition on (fuel pump will run for about two seconds). Using scan tool, command fuel pump On. Fuel pressure should be 42-55 psi (283-376 kPa). If fuel pressure is as specified, go to next step. If fuel pressure is not within specifications, go to step 17 .
  3. Fuel pressure will drop when fuel pump stops running. It should then stabilize and remain constant. If fuel pressure remains constant, go to next step. If fuel pressure does not remain constant, go to step 12 .
  4. With engine warmed up to operating temperature, turn ignition on and observe fuel pressure. Continue to observe fuel pressure while starting engine. Reading should drop 3-15 psi (21-105 kPa). If fuel pressure drops as specified, go to next step. If fuel pressure does not drop as specified, leave pressure gauge connected and go to step 9 .
  5. Test drive vehicle to determine if fuel pressure drops off during acceleration, cruise or hard cornering. If fuel pressure drops, go to next step. If fuel pressure does not drop, check for improper fuel in vehicle. If problem is found, drain fuel and replace as necessary.
  6. Check for restricted fuel filter or fuel feed line. If problem is found, repair as necessary. After repair, test drive vehicle to confirm repair. If no problem was found, go to next step.
  7. Remove fuel tank to inspect for restricted fuel pump strainer, leaking fuel line or incorrect fuel pump. If problem is found, repair as necessary. If no problem was found, go to next step.
  8. Replace fuel pump. See «FUEL SYSTEM»(ref-133146-S21790669332002021300000) in REMOVAL, OVERHAUL & INSTALLATION article. After repair, test drive vehicle to confirm repair.
  9. Disconnect fuel pressure regulator vacuum hose. With engine idling, use hand-held vacuum pump to apply 12-14 in. Hg. while observing fuel pressure gauge. Fuel system pressure should drop 3-15 psi (21-105 kPa). If fuel pressure drops as specified, go to next step. If fuel pressure does not drop as specified, go to step 11 .
  10. Inspect fuel pressure regulator vacuum hose for leaks. If problem is found, repair or replace as necessary. Test drive vehicle to confirm repair.
  11. Replace fuel pressure regulator. See «FUEL SYSTEM»(ref-133146-S21790669332002021300000) in REMOVAL, OVERHAUL & INSTALLATION article. After repair, test drive vehicle to confirm repair.
  12. Using scan tool command fuel pump On. After pressure builds up, turn off pump and clamp fuel supply hose with locking pliers that will not damage fuel line. Observe fuel pressure. If pressure remains constant, go to next step. If fuel pressure does not remain constant, go to step 15 .
  13. Inspect fuel supply hose for leaks. If problem is found, repair as necessary. If no problem is found, go to next step.
  14. Remove fuel tank and inspect for leaking hose or in-tank fuel line. If problem is found, repair as necessary. If no problem is found, repeat test starting in step 8 .
  15. Remove locking pliers from fuel supply hose, and clamp them to fuel return hose. Using scan tool command fuel pump On. After pressure has built up, turn off power and observe fuel pressure gauge. If fuel pressure reading remains constant, repeat test starting in step 11 . If fuel pressure reading does not remain constant, go to next step.
  16. Locate and replace any leaking fuel injectors. See «FUEL SYSTEM»(ref-133146-S21790669332002021300000) in REMOVAL, OVERHAUL & INSTALLATION article. After repair, test drive vehicle to confirm repair.
  17. If fuel pressure indicated on gauge is 55 psi (376 kPa), go to next step. If fuel pressure is less than specified, go to step 21 .
  18. Relieve fuel pressure. See «FUEL SYSTEM PRESSURE RELEASE»(ref-133136-S41554429242002021300000) . Disconnect fuel return line from fuel rail. Attach an auxiliary length of flexible fuel hose to fuel rail return outlet and place other end into a suitable container. Using scan tool command fuel pump On. Observe fuel pressure while fuel pump is running. Fuel pressure should be 42-55 psi (290-376 kPa). If fuel pressure is as specified, go to next step. If fuel pressure is not as specified, go to step 20 .
  19. Locate and repair restriction in fuel return line. After repair, test drive vehicle and confirm repair.
  20. Visually inspect fuel rail outlet passages for restriction. If problem is found, repair or replace as necessary. After repair, test drive vehicle and confirm repair. If no problem was found, go back to step 11 .
  21. If indicated fuel pressure is more than 0 psi (0 kPa), go to next step. If indicated fuel pressure is 0 psi (0 kPa), go to step 23 .
  22. Using scan tool command fuel pump On. Observe fuel pressure reading while slowly pinching off fuel return hose. If fuel pressure rises above 55 psi (376 kPa), repeat testing starting in step 11 . If fuel pressure does not rise above 55 psi (376 kPa), repeat testing starting in step 7 .
  23. Using scan tool command fuel pump On. Remove fuel filler cap and listen for fuel pump operation. If fuel pump is running, repeat testing starting in step 7 . If fuel pump is not running, go to «FUEL SYSTEM ELECTRICAL TEST»(ref-133136-S17205019162002021300000) .

FUEL SYSTEM ELECTRICAL TEST

WARNINGRelieve fuel pressure before connecting fuel pressure gauge. See FUEL SYSTEM PRESSURE RELEASE under FUEL SYSTEM.

When ignition switch is first turned On, PCM energizes fuel pump relay which then applies power to in-tank fuel pump. Fuel pump relay will remain On as long as engine is running or cranking and PCM is receiving 58X crankshaft position pulses. If no 58X crankshaft position pulses are present, PCM de-energizes fuel pump relay within 2 seconds after ignition is turned On or engine is stopped. Fuel pump delivers fuel to fuel rail and injectors, then to fuel pressure regulator. Fuel pressure regulator controls fuel pressure by allowing excess fuel to be returned to fuel tank. With ignition on, fuel pump can be turned on by command from scan tool.

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

  1. Perform On-Board Diagnostic II (OBD-II) System Check. See ON-BOARD DIAGNOSTIC II (OBD-II) SYSTEM CHECK under SELF-DIAGNOSTIC SYSTEM in appropriate SELF-DIAGNOSTICS article. After performing OBD-II system check, go to next step.
  2. Release fuel pressure. See «FUEL SYSTEM PRESSURE RELEASE»(ref-133136-S41554429242002021300000) . Connect fuel pressure gauge as outlined in «FUEL PUMP PRESSURE TEST»(ref-133136-S39650653832002021300000) . Using scan tool, command fuel pump On. Fuel pressure should build up immediately. If fuel pressure builds up immediately, go to next step. If fuel pressure does not build up, go to step 4 .
  3. Verify fuel pump is not running by removing gas cap and listening for fuel pump motor. Using scan tool, command fuel pump On. If fuel pump runs for 2 seconds and turns off, fuel electrical system is operating properly. Testing is complete. If fuel pump does not run or runs continuously, go to step 12 .
  4. Turn ignition off. Remove fuel pump relay from underhood fuse/relay box. Using a test light connected to ground, probe battery feed circuit at fuel pump relay socket cavity. See «FUEL PUMP RELAY BATTERY FEED WIRE IDENTIFICATION»(ref-133136-S03510868342002021300000) table. If test light illuminates, go to step 6 . If test light does not illuminate, go to next step. FUEL PUMP RELAY BATTERY FEED WIRE IDENTIFICATION Application Wire Color (1) Except Trooper White/Black Trooper White (1) Test battery feed circuit is at fuel pump relay socket cavity No. 5 (Except Trooper) or No. 4 (Trooper). See «WIRING DIAGRAMS»(ref-133147) article.
  5. Repair open or short in battery feed wire between fuel pump relay and fuse box. See «FUEL PUMP RELAY BATTERY FEED WIRE IDENTIFICATION»(ref-133136-S03510868342002021300000) table. After repair, retest system.
  6. Connect a test light between fuel pump relay pull-in coil socket cavities. See «FUEL PUMP RELAY PULL-IN COIL WIRE IDENTIFICATION»(ref-133136-S16164572192002021300000) table. Turn ignition on. If test light illuminates for 2 seconds then turns off, go to step 12 . If test light does not illuminate, go to next step. FUEL PUMP RELAY PULL-IN COIL WIRE IDENTIFICATION Application Wire From PCM Ground Wire Rodeo & Rodeo Sport 2.2L (1) Pink/White (3) Black/Blue Axiom 3.5L, Passport, Rodeo & Rodeo Sport 3.2L (1) Pink/White (4) Black Trooper (2) Red/White (5) Black (1) Measure between fuel pump relay socket cavities No. 2 and 4. See «WIRING DIAGRAMS»(ref-133147) article. (2) Measure between fuel pump relay socket cavities No. 1 and 3. See «WIRING DIAGRAMS»(ref-133147) article. (3) Ground point E-28 is located on rear of intake manifold, near ignition coil. (4) Ground point C-16 (Passport, Rodeo & Rodeo Sport) C-26 (Axiom) is located on fenderwell just above PCM. (5) Ground point C-39 is located on fenderwell, next to PCM.
  7. Using test light connected to ground, probe PCM input to fuel pump relay socket cavity. See «FUEL PUMP RELAY PULL-IN COIL WIRE IDENTIFICATION»(ref-133136-S16164572192002021300000) table. Turn ignition on. If test light illuminates for 2 seconds and then turns off, go to next step. If test light does not illuminate, go to step 9 .
  8. Repair open in ground circuit between ground point and fuel pump relay. See «FUEL PUMP RELAY PULL-IN COIL WIRE IDENTIFICATION»(ref-133136-S16164572192002021300000) table. After repair, retest system.
  9. Check for open or short in PCM input to fuel pump relay. See «WIRING DIAGRAMS»(ref-133147) article. For PCM pin and terminal identification, see «PIN VOLTAGE CHARTS»(ref-133142) article. If problem is found, repair as necessary. After repair, retest system. If no problem was found, go to next step.
  10. Check for poor, loose or damaged terminal connections in PCM harness connectors. For PCM pin and terminal identification, see «PIN VOLTAGE CHARTS»(ref-133142) article. If problem is found, repair or replace as necessary. After repair, retest system. If no problem was found, go to next step.
  11. Replace and reprogram PCM. See POWERTRAIN CONTROL MODULE REPLACEMENTunder POWERTRAIN CONTROL MODULE in appropriate SELF-DIAGNOSTICS article. After repair, test drive vehicle to confirm repair.
  12. Install fuel pump relay. Disconnect fuel pump harness connector at fuel tank. Using a test light connected to ground, probe fuel pump harness connector feed wire. See «FUEL PUMP POWER FEED WIRE IDENTIFICATION»(ref-133136-S40960144852002021300000) table. Using scan tool, command fuel pump On. If test light illuminates for 2 seconds, go to step 15 . If test light does not illuminate for 2 seconds, go to next step. FUEL PUMP POWER FEED WIRE IDENTIFICATION Application Wire Color Except Trooper Black/Orange Trooper Black/Red
  13. Operate horn to verify horn relay is functional. Substitute horn relay for fuel pump relay. Repeat test procedure in step 12 . If test light does not illuminate for 2 seconds, go to next step. If test light does illuminate for 2 seconds, go to step 17 .
  14. Check for open or short circuit in feed wire between fuel pump relay and fuel pump harness connector at fuel tank. See «WIRING DIAGRAMS»(ref-133147) article. Check for blown FUEL PUMP fuse (20-amp on Axiom, Passport, Rodeo and Rodeo Sport, 15-amp onTrooper) located in underhood fuse/relay box. If problem is found, repair or replace as necessary. Reinstall horn relay. After repair, retest system.
  15. Connect a test light between fuel pump harness connector terminals No. 1 and 2. See «FUEL PUMP POWER FEED WIRE IDENTIFICATION»(ref-133136-S40960144852002021300000) table. Using scan tool, command fuel pump On. If test light illuminates for 2 seconds, go to step 18 . If test light does not illuminate for 2 seconds, go to next step.
  16. Repair open circuit in Black wire (fuel pump ground) between ground point and fuel pump. Ground point is located on floor under parking brake handle. After repair, test drive vehicle to confirm repairs.
  17. Replace fuel pump relay. Reinstall horn relay to its original position. After repair, test drive vehicle to confirm repairs.
  18. Replace fuel pump. See «FUEL SYSTEM»(ref-133146-S21790669332002021300000) in REMOVAL, OVERHAUL & INSTALLATION article. After repair, test drive vehicle to confirm repair.

FUEL PUMP PRESSURE TEST

Note. If scan tool is not available use following procedure to operate fuel pump On. Remove fuel pump relay from underhood fuse/relay box. Using fused jumper, jumper fuel pump relay socket cavities No. 1 and 5. (Scheme 2)

  1. Turn ignition off. Ensure A/C is off (if equipped). Release fuel system pressure. See «FUEL SYSTEM PRESSURE RELEASE»(ref-133136-S41554429242002021300000) . Install Fuel Pressure Gauge Set (J-34730-1) or equivalent to fuel rail or fuel supply line. Install fuel pump relay. Connect Tech 2 or equivalent scan tool to Data Link Connector (DLC). DLC is located under small cover on left side of dash. Turn ignition on. Using scan tool, command fuel pump On. Observe fuel pressure gauge. Fuel pressure on all models should be 42-55 psi (290-376 kPa). If fuel pressure is not as specified, see appropriate «FUEL SYSTEM DIAGNOSIS»(ref-133136-S33194148372002021300000) procedure. If fuel pressure is as specified, testing is complete.
  2. Start engine let fuel pressure build to maximum pressure. Observe fuel pressure gauge. When engine is running, fuel system pressure should drop 3-15 psi (21-105 kPa) from engine off fuel pump running specification. If pressure does not drop as specified, see appropriate «FUEL SYSTEM DIAGNOSIS»(ref-133136-S33194148372002021300000) procedure. If fuel pressure drops as specified, testing is complete.

Scheme 2

Scheme 2
Scheme 2

FUEL PUMP FLOW TEST

Note. If scan tool is not available use following procedure to operate fuel pump On. Remove fuel pump relay from underhood fuse/relay box. Using fused jumper, jumper fuel pump relay socket cavities No. 1 and 5. (Scheme 2)

If fuel flow or supply problem is suspected, perform following

  1. Turn ignition off. Ensure A/C is off (if equipped). Release fuel system pressure. See «FUEL SYSTEM PRESSURE RELEASE»(ref-133136-S41554429242002021300000) . Remove fuel feed pipe to fuel rail. Place fuel feed pipe into an appropriate sized clean container. Connect Tech 2 or equivalent scan tool to Data Link Connector (DLC). DLC is located under small cover on left side of dash. Turn ignition on. Using scan tool, command fuel pump On.
  2. Fuel pump should run, and in 15 seconds deliver at least .40 qts. (.38 ltrs.). If fuel pump does not perform as specified, check for plugged fuel filter, kinked or blocked fuel lines. If problem is found, repair as necessary. After repair, recheck fuel pump delivery.

More articles — Engine Controls - Basic Diagnostic Procedures