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Home >> Toyota >> 2001 >> Sienna CE >> Repair and Diagnosis >> External Pages >> Different car >> Section 125 (Engine Control System Self Diagnostics (2UZ-FE)) >> Diagnostic Tests >> DTC P0300, DTC P0301, DTC P0302, DTC P0303, DTC P0304, DTC P0305, DTC P0306, DTC P0307 &/Or DTC P0308 >> Diagnosis & Repair

Diagnosis & Repair

WARNING: This page is about a different car, the 2003 Toyota 4Runner. However, it is still accessible from the selected car via links, so may be relevant.
  1. Check for any loose or defective PCV valve hose connections. PCV valve is located on top of passenger's side valve cover near front corner of valve cover. If PCV valve hose connections are okay, go to next step. If PCV valve hose connections are defective, repair or replace components as necessary.
  2. Check vacuum hoses for leaks, restrictions, poor connections and proper routing. See VACUUM DIAGRAMS article for proper vacuum hose routing. Also, check engine wiring harness and electrical connectors for damage or poor connections. If no problems exist, go to next step. If problem exists, repair as necessary and perform TEST DRIVE CONFIRMATION .
  3. Connect Toyota hand-held tester or scan tool to Data Link Connector (DLC3) at driver's side of instrument panel. See Figure. Check number of MISFIRE COUNTS in the DATA LIST for all cylinders. If there is a high misfire count on 1 or 2 cylinders only, go to next step. If there is a high misfire count for more than 3 cylinders, go to step  13.
  4. Remove spark plug for misfiring cylinder. Ensure no carbon deposits exist, spark plug is not fouled and spark plug gap is .043" (1.10 mm). Check ignition system by performing spark test on misfiring cylinder. Disconnect each fuel injector connector while performing spark test.  See SPARK TEST under IGNITION SYSTEMS in BASIC DIAGNOSTIC PROCEDURES - V6 & V8 article. If ignition system operates properly and spark exists, go to step  8. If ignition system does not operate properly and spark does not exist, go to next step.
  5. Replace spark plugs and check ignition system by performing spark test again. Disconnect each fuel injector connector while performing spark test.  See SPARK TEST under IGNITION SYSTEMS in BASIC DIAGNOSTIC PROCEDURES - V6 & V8 article. If ignition system operates properly and spark exists, perform TEST DRIVE CONFIRMATION . If ignition system does not operate properly and spark does not exist, go to next step.
  6. Turn ignition off. Remove glove box for access to ECM with connectors. See Figure. Disconnect all 8 ignition coil 4-pin connectors and ECM 34-pin connector E4. See Figure & Fig 2 . Check continuity between ignition coil 4-pin connector terminal and ECM 34-pin connector E4 terminals. See IDENTIFYING ECM (IGF) TO IGNITION COILS TERMINALS  for appropriate ignition coil and ECM 34-pin connector E4 terminal selections. Continuity should exist. Then, check continuity between body ground and ECM 34-pin connector E4 terminals No. 23 (Red/White wire) and No. 24 (Red/Yellow wire) individually. There should be no continuity. Go to next step.
    IDENTIFYING ECM (IGF) TO IGNITION COILS TERMINALS

    Ignition Coil No. (1) (3) ECM 34-Pin Connector E4 Terminal No. Wire Color
    1 (2) No. 24 Red/Yellow
    2 (2) No. 23 Red/White
    3 (2) No. 23 Red/White
    4 (2) No. 24 Red/Yellow
    5 (2) No. 23 Red/White
    6 (2) No. 24 Red/Yellow
    7 (2) No. 24 Red/Yellow
    8 (2) No. 23 Red/White
    (1) Ignition coil No. 1 is front ignition coil on passenger's side of engine. Ignition coil No. 2 is front ignition coil on driver's side of engine. Ignition coils No. 1, 3, 5 and 7 are on passenger's side of engine. Ignition coils No. 2, 4, 6 and 8 are on driver's side of engine.
    (2) For all continuity checks, use ignition coil 4-pin connector terminal No. 2.
    (3) For ECM electrical connector terminal identification, see Figure.
  7. Check continuity between ignition coil 4-pin connector terminal and ECM 34-pin connector E4 terminals. See IDENTIFYING ECM (IGT) TO IGNITION COILS TERMINALS  for appropriate ignition coil and ECM 34-pin connector E4 terminal selections. Continuity should exist. Then, check continuity between body ground and ignition coil 4-pin connector terminals No. 3, individually. There should be no continuity. If continuity is as specified, replace ignition coil(s) assembly. Then, perform TEST DRIVE CONFIRMATION . If continuity is not as specified, repair or replace harness and/or connectors as necessary. Then, perform TEST DRIVE CONFIRMATION .
    IDENTIFYING ECM (IGT) TO IGNITION COILS TERMINALS

    Ignition Coil No. (1) (2) ECM 34-Pin Connector E4 Terminal No. Wire Color
    1 (3) No. 9 Light Green
    2 (3) No. 8 Light Green/Black
    3 (3) No. 25 Blue/White
    4 (3) No. 11 Blue/Yellow
    5 (3) No. 12 Black/Blue
    6 (3) No. 26 Green
    7 (3) No. 13 Green/White
    8 (3) No. 10 Green/Black
    (1) Ignition coil No. 1 is front ignition coil on passenger's side of engine. Ignition coil No. 2 is front ignition coil on driver's side of engine. Ignition coils No. 1, 3, 5 and 7 are on passenger's side of engine. Ignition coils No. 2, 4, 6 and 8 are on driver's side of engine.
    (2) For ECM electrical connector terminal identification, see Figure.
    (3) For all continuity checks, use ignition coil 4-pin connector terminal No. 3.
  8. Remove glove box for access to ECM with electrical connectors still installed on ECM. See Figure. Turn ignition on. With negative (-) probe of voltmeter on ECM 34-pin connector E4 terminal No. 7 (EO1) (White/Black wire), place positive (+) probe and check voltage at appropriate ECM connector (fuel injector driver) terminal. See IDENTIFYING ECM FUEL INJECTOR DRIVER TERMINALS  for ECM injector driver circuit terminal selections. For ECM electrical connector terminal identification, see Figure & Fig 2 . If voltage is not 9-14 volts at fuel injector driver terminal, go to next step. If voltage is 9-14 volts at fuel injector driver terminal, go to step  11.
    NOTE: With engine idling, using same connections as described above, an oscilloscope can be used to show each injector's waveform pattern. Fuel injector signal waveform pattern and fuel injector duration signal waveform pattern should be properly displayed within proper intervals. See Fig 1.
    IDENTIFYING ECM FUEL INJECTOR DRIVER TERMINALS

    Fuel Injector No. (1) ECM Electrical Connector & Terminal (2) Wire Color
    1 E4 Terminal No. 1 Red/Blue
    2 E4 Terminal No. 2 Blue
    3 E4 Terminal No. 3 White
    4 E4 Terminal No. 4 Yellow
    5 E4 Terminal No. 5 Green
    6 E5 Terminal No. 3 Red
    7 E6 Terminal No. 6 White
    8 E6 Terminal No. 5 Brown
    (1) Fuel injector No. 1 is front fuel injector on passenger's side of engine. Fuel injector No. 2 is front fuel injector on driver's side of engine. Fuel injectors No. 1, 3, 5 and 7 are on passenger's side of engine. Fuel injectors No. 2, 4, 6 and 8 are on driver's side of engine.
    (2) For ECM electrical connector terminal identification, see Figure.
    Fig 1: Identifying Fuel Injector Signal Waveform Pattern & Fuel Injector Duration Signal Waveform Pattern
    G00023165Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
  9. Disconnect electrical connector at fuel injector for misfiring cylinder. Using ohmmeter, check resistance between electrical terminals on fuel injector. Resistance should be about 13.4-14.2 ohms at 68°F (20°C). If resistance is within specification, go to next step. If resistance is not within specification, replace fuel injector. See FUEL RAILS & FUEL INJECTORS under FUEL SYSTEMS in REMOVAL, OVERHAUL & INSTALLATION - V6 & V8 article.
  10. Disconnect ECM connectors E4, E5, and E6. Check continuity between each injector connector terminal No. 2 and ECM connector. See IDENTIFYING ECM FUEL INJECTOR DRIVER TERMINALS  for terminal selections. Here, continuity should exist. Then, check continuity between each injector connector terminal No. 2 and body ground. Continuity should not exist. Check that continuity exists between ignition switch connector terminal No. 6 and injector connector terminal No. 1. If continuity is not as specified, repair as necessary. See appropriate WIRING DIAGRAM under ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article. If continuity is as specified, go to next step.
  11. Check operation of fuel injector for misfiring cylinder. See FUEL CONTROL under FUEL SYSTEMS in SYSTEM & COMPONENT TESTING - V6 & V8 article. Fuel injector volume should be 0.20-0.25 oz. (60-73 cc) within 15 seconds and difference in volume between each fuel injector should be less than 0.04 oz. (13 cc). Fuel injectors should not leak more than one drop every 12 minutes. If fuel injectors are okay, go to next step. If fuel injectors are defective, replace fuel injectors as necessary.
  12. Check engine compression on misfiring cylinder. See ENGINE MECHANICAL under PRELIMINARY INSPECTION & ADJUSTMENTS in BASIC DIAGNOSTIC PROCEDURES - V6 & V8 article. Check valve clearance on misfiring cylinder. See V8 VALVE CLEARANCE under ENGINE MECHANICAL in ON-VEHICLE ADJUSTMENTS - V6 & V8 article.
  13. Check valve timing belt for loose or jumped teeth. See appropriate article in ENGINES. Repair engine as necessary. If valve timing and timing belt are OK, go to next step.
  14. Check fuel pressure. See FUEL PRESSURE under FUEL SYSTEMS in BASIC DIAGNOSTIC PROCEDURES - V6 & V8 article. If fuel pressure is within specification, go to next step. If fuel pressure is not within specification, repair fuel system as necessary.
  15. Connect Toyota hand-held tester or scan tool to Data Link Connector (DLC3) at driver's side of instrument panel. See Figure. Start engine and maintain engine speed at 2500 RPM for about 90 seconds to fully warm the HO2S. Allow engine to idle.
  16. Check Intake Air Temperature (IAT ) sensor. See INTAKE AIR TEMPERATURE SENSOR under ENGINE SENSORS & SWITCHES in SYSTEM & COMPONENT TESTING - V6 & V8 article. If IAT sensor is okay, go to next step. If IAT sensor is defective, replace components as necessary (IAT and MAF are combined into one unit)  . See AIRFLOW METER under ENGINE SENSORS & SWITCHES in REMOVAL, OVERHAUL & INSTALLATION - V6 & V8 article.
  17. Check Mass Airflow (MAF) meter. MAF meter may also be referred to as airflow meter. See AIRFLOW METER under ENGINE SENSORS & SWITCHES in SYSTEM & COMPONENT TESTING - V6 & V8 article. If MAF meter is okay, go to next step. If MAF meter is defective, replace components as necessary. See AIRFLOW METER under ENGINE SENSORS & SWITCHES in REMOVAL, OVERHAUL & INSTALLATION - V6 & V8 article.
  18. Check Engine Coolant Temperature (ECT) sensor. See ENGINE COOLANT TEMPERATURE SENSOR under ENGINE SENSORS & SWITCHES in SYSTEM & COMPONENT TESTING - V6 & V8 article. If ECT sensor is okay, go to next step. If ECT sensor is defective, replace components as necessary. See ENGINE COOLANT TEMPERATURE SENSOR under ENGINE SENSORS & SWITCHES in REMOVAL, OVERHAUL & INSTALLATION - V6 & V8 article.
  19. Connect Toyota hand-held tester or scan tool to Data Link Connector (DLC3) at driver's side of instrument panel. See Figure. Check number of MISFIRE COUNTS in the DATA LIST for all cylinders. If there is a high misfire count on 1 or 2 cylinders only, go to next step. If there is a high misfire count for more than 3 cylinders, go to step  13 and recheck.
  20. Verify if vehicle ran out of fuel. If vehicle ran out of fuel, DTC P0300 and DTCs P0301-P0308 was caused by the vehicle running out of fuel. If vehicle did not run out of fuel, problem is intermittent. Check for defective connections or intermittent problem in wiring. ECM is located behind glove box. See Figure.
Fig 2: Identifying Ignition Coil, Ignition Switch & Fuel Injector Connectors
G00228907Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
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