Engine Control System Self-Diagnostics: Diagnosis Toyota Celica T230

DIAGNOSTIC TROUBLE CODE DEFINITIONS

DIAGNOSTIC TROUBLE CODE (DTC) IDENTIFICATION

DIAGNOSTIC TESTS

Note. Before performing any diagnostic test, see SELF-DIAGNOSTICS - INTRODUCTION article for diagnostic system functions and system diagnostic procedures. To identify circuits and wire colors referenced in testing, see WIRING DIAGRAMS. Use illustration to identify ECM connector terminals. (Scheme 230) References to California emissions apply to vehicles with California emissions, which may be verified by underhood Emission Control label. Vehicles with California emissions may be available in other states.

Scheme 230

Diagnosis & Repair

1. Connect scan tool to Data Link Connector (DLC) No. 3. (Scheme 231) Start and warm engine to normal operating temperature. Using scan tool, monitor MAF flow rate. If scan tool reading is 0.0 gm/sec., go to next step. If scan tool reading is 271 gm/sec. or more, go to step 5.
2. Turn ignition off. Disconnect MAF meter harness connector. Turn ignition on. Measure voltage between ground and terminal No. 1 (Black/Red wire) at MAF meter harness connector. (Scheme 232) If voltage is 9-14 volts, go to next step. If voltage is not 9-14 volts, repair open in Black/Red wire between engine room junction box and MAF meter. See «WIRING DIAGRAMS»(/toyota/celica/t230-1999-2002/remont/wiring-diagrams-engine-performance/#engine-performance-wiring-diagrams) article.
3. Turn ignition off. Connect MAF meter harness connector. Access ECM in driver's side of engine compartment, next to battery. Ensure shift lever is in Neutral or Park. Ensure A/C switch is off. Start engine and let idle. Using DVOM, backprobe ECM harness connector and measure voltage between ground and terminal No. 11 (Green/White wire) at ECM harness connector E4. (Scheme 230) If voltage is not 1.1-1.5 volts, go to next step. If voltage is 1.1-1.5 volts, replace ECM.
4. Check for open or short in Green/White wire between MAF meter and ECM. See «WIRING DIAGRAMS»(/toyota/celica/t230-1999-2002/remont/wiring-diagrams-engine-performance/#engine-performance-wiring-diagrams) article. If problem exists, repair wiring as necessary. If problem does not exist, replace MAF meter.
5. Turn ignition off. Access ECM in driver's side of engine compartment, next to battery. Using DVOM, backprobe ECM harness connector and measure resistance between ground and terminal No. 1 (Yellow/Green wire) at ECM harness connector E4. (Scheme 230) If resistance is one ohms or less, go to next step. If resistance is greater than one ohm, replace ECM.
6. Check for open in Yellow/Green wire between MAF meter and ECM. See «WIRING DIAGRAMS»(/toyota/celica/t230-1999-2002/remont/wiring-diagrams-engine-performance/#engine-performance-wiring-diagrams) article. If problem exists, repair wiring as necessary. If problem does not exist, replace MAF meter.

Scheme 231

Scheme 232

If only DTC P0101 is displayed, replace MAF meter. If other DTCs are displayed, diagnose and repair those DTCs first and retest.

1. Connect scan tool to Data Link Connector (DLC) No. 3. (Scheme 231) Turn ignition on. Using scan tool, monitor IAT sensor temperature. If temperature displayed on scan tool is same as outside temperature, problem is intermittent. Check component and ECM connections. If temperature displayed on scan tool is 284°F (140°C) or more, go to step 4. If temperature displayed on scan tool is -40°F (-40°C), go to next step.
2. Turn ignition off. Disconnect MAF meter harness connector. Connect a jumper wire between terminals No. 4 (Blue/Red wire) and No. 5 (Brown wire) at MAF meter harness connector. (Scheme 232) Turn ignition on. Using scan tool, monitor IAT sensor temperature. If temperature displayed on scan tool is 284°F (140°C) or more, replace MAF meter. If temperature displayed on scan tool is less than 284°F (140°C), go to next step.
3. Turn ignition off. Remove jumper wire. Access ECM in driver's side of engine compartment, next to battery. Connect a jumper wire by backprobing between terminals No. 22 (Blue/Red wire) and No. 18 (Brown wire) at ECM harness connector E4. (Scheme 230) Temperature displayed on scan tool should be 284°F (140°C) or more. If temperature displayed on scan tool is as specified, repair open in wiring between MAF meter and ECM. See «WIRING DIAGRAMS»(/toyota/celica/t230-1999-2002/remont/wiring-diagrams-engine-performance/#engine-performance-wiring-diagrams) article. If temperature displayed on scan tool is not as specified, replace ECM.
4. Turn ignition off. Disconnect MAF meter harness connector. Turn ignition on. If temperature displayed on scan tool is -40°F (-40°C), replace MAF meter. If temperature displayed on scan tool is not -40°F (-40°C), go to next step.
5. Turn ignition off. Access ECM in driver's side of engine compartment, next to battery. Disconnect ECM harness connector E4. (Scheme 230) Turn ignition on. If temperature displayed on scan tool is -40°F (-40°C), repair short in wiring between MAF meter and ECM. See «WIRING DIAGRAMS»(/toyota/celica/t230-1999-2002/remont/wiring-diagrams-engine-performance/#engine-performance-wiring-diagrams) article. If temperature displayed on scan tool is not -40°F (-40°C), replace ECM.

1. Connect scan tool to Data Link Connector (DLC) No. 3. (Scheme 231) Turn ignition on. Using scan tool, monitor ECT sensor temperature. If temperature displayed on scan tool is same as actual coolant temperature, problem is intermittent. Check component and ECM connections. If temperature displayed on scan tool is 284°F (140°C) or more, go to step 4. If temperature displayed on scan tool is -40°F (-40°C), go to next step.
2. Turn ignition off. Disconnect ECT sensor harness connector. Connect a jumper wire between ECT sensor harness connector terminals. Turn ignition on. Using scan tool, monitor ECT sensor temperature. If temperature displayed on scan tool is 284°F (140°C) or more, replace ECT sensor. If temperature displayed on scan tool is less than 284°F (140°C), go to next step.
3. Turn ignition off. Remove jumper wire. Access ECM in driver's side of engine compartment, next to battery. Connect a jumper wire by backprobing between terminals No. 14 (Green wire) and No. 18 (Brown wire) at ECM harness connector E4. (Scheme 230) Temperature displayed on scan tool should be 284°F (140°C) or more. If temperature displayed on scan tool is as specified, repair open in wiring between ECT sensor and ECM. See «WIRING DIAGRAMS»(/toyota/celica/t230-1999-2002/remont/wiring-diagrams-engine-performance/#engine-performance-wiring-diagrams) article. If temperature displayed on scan tool is not as specified, replace ECM.
4. Turn ignition off. Disconnect ECT sensor harness connector. Turn ignition on. If temperature displayed on scan tool is -40°F (-40°C), replace ECT sensor. If temperature displayed on scan tool is not -40°F (-40°C), go to next step.
5. Turn ignition off. Access ECM in driver's side of engine compartment, next to battery. Disconnect ECM harness connector E4. (Scheme 230) Turn ignition on. If temperature displayed on scan tool is -40°F (-40°C), repair short in wiring between ECT sensor and ECM. See «WIRING DIAGRAMS»(/toyota/celica/t230-1999-2002/remont/wiring-diagrams-engine-performance/#engine-performance-wiring-diagrams) article. If temperature displayed on scan tool is not -40°F (-40°C), replace ECM.

1. If any other DTCs are displayed, diagnose and repair those DTCs first and retest. If only DTC P0116 is displayed, go to next step.
2. Remove and inspect cooling system thermostat. If problem exists, replace thermostat as necessary and retest system. If problem does not exist, replace ECT sensor.

1. Connect scan tool to Data Link Connector (DLC) No. 3. (Scheme 231) Turn ignition on. Using scan tool, monitor throttle valve opening percentage. Opening percentage should be approximately 10 percent with fully closed throttle, and should be approximately 80 percent with throttle fully open (WOT). If percentages are as specified, problem is intermittent. Check component and ECM connections. If percentages are not as specified, go to next step.
2. Turn ignition off. Disconnect TP sensor harness connector. Turn ignition on. Using DVOM, measure voltage between ground and Red wire terminal (terminal No. 1 on 1ZZ-FE; terminal No. 2 on 2ZZ-GE) at TP sensor harness connector. If voltage is 4.5-5.5 volts, go to next step. If voltage is not 4.5-5.5 volts, go to step 5.
3. Check TP sensor. See «ENGINE SENSORS & SWITCHES»(ref-2892-S05206625502000041400000) in SYSTEM & COMPONENT TESTING - 4-CYLINDER article. If problem exists, replace TP sensor. If problem does not exist, go to next step.
4. Access ECM in driver's side of engine compartment, next to battery. Turn ignition on. Using DVOM, backprobe ECM harness connector and measure voltage between terminals No. 18 (Brown wire) and No. 23 (Black/White wire) at ECM harness connector E4. (Scheme 230) Voltage should be.3-.8 volt with throttle fully closed and 3.2-4.9 volts with throttle fully open (WOT). If voltage is as specified, replace ECM. If voltage is not as specified, repair open or short in wiring between TP sensor and ECM. See «WIRING DIAGRAMS»(/toyota/celica/t230-1999-2002/remont/wiring-diagrams-engine-performance/#engine-performance-wiring-diagrams) article.
5. Access ECM in driver's side of engine compartment, next to battery. Turn ignition on. Using DVOM, backprobe ECM harness connector and measure voltage between terminals No. 2 (Red wire) and No. 18 (Brown wire) at ECM harness connector E4. (Scheme 230) Voltage should be 4.5-5.5 volts. If voltage is as specified, repair open in Red wire between TP sensor and ECM. If voltage is not as specified, replace ECM.

Circuit Description

TP sensor is a variable resistor which monitors throttle opening. ECM determines vehicle driving condition and adjusts air/fuel mixture accordingly. DTC is set after vehicle speed has exceeded 19 MPH once and TP sensor output voltage is out of range while vehicle speed is 0-19 MPH. Possible cause is

1. Defective Throttle Position (TP) sensor.

Diagnostic Aids

After confirming DTC P0121, use scan tool to access CURRENT DATA to confirm throttle valve opening percentage with throttle open and closed. If percentage displayed on scan tool is always zero percent, VC circuit may be open or VTA circuit may be shorted. If percentage displayed on scan tool is always 100 percent, check for open in E2 circuit. Using scan tool, read freeze frame data. Freeze frame records engine conditions when malfunction is detected.

If only DTC P0121 is displayed, replace TP sensor. If any other DTCs are displayed, diagnose and repair those DTCs first and retest.

1. If any other DTCs are displayed, diagnose and repair those DTCs first and retest. If only DTC P0125 is displayed, go to next step.
2. Connect scan tool to Data Link Connector (DLC) No. 3. (Scheme 231) Start and warm engine to normal operating temperature. Using scan tool, monitor heated oxygen sensor No. 1. Snap accelerate engine to about 4000 RPM 3 times. Heated oxygen sensor No. 1 should indicate a rich signal (.45 volt or more) at least once. If a rich signal is indicated for heated oxygen sensor No. 1 at least once, go to step 9. If heated oxygen sensor No. 1 does not display a rich signal at least once, go to next step.
3. Check for open or short in wiring between heated oxygen sensor No. 1 and ECM. If problem does not exist, go to next step. If problem exists, repair wiring as necessary. See «WIRING DIAGRAMS»(/toyota/celica/t230-1999-2002/remont/wiring-diagrams-engine-performance/#engine-performance-wiring-diagrams) article.
4. Using scan tool, check if a misfire has occurred by monitoring DTCs and DATA LIST. If a misfire has occurred, perform «DTC P0300: RANDOM MISFIRE DETECTED»(ref-3781-S03630286922000051600000). If misfire has not occurred, go to next step.
5. Ensure oil dipstick, oil filler cap, PCV system and all other air induction system components are intact and operating properly. If problem exists, repair as necessary. If problem does not exist, go to next step.
6. Check fuel pressure. See «FUEL SYSTEMS»(ref-2888-S02687592482000041400000) in BASIC DIAGNOSTIC PROCEDURES - 4-CYLINDER article. If fuel pressure is not within specification, repair as necessary. If fuel pressure is within specification, go to next step.
7. Check fuel injectors. See «FUEL SYSTEMS»(ref-2892-S33566963412000041400000) in SYSTEM & COMPONENT TESTING - 4-CYLINDER article. If problem exists, repair as necessary. If problem does not exist, go to next step.
8. Check exhaust system for leaks. If problem exists, repair as necessary. If problem does not exist, replace defective heated oxygen sensor No. 1.
9. Perform test drive confirmation, then go to next step. See «TEST DRIVE CONFIRMATION»(ref-3781-S00744728032000051600000) under DTC P0130: HEATED OXYGEN SENSOR NO. 1 CIRCUIT.
10. Clear and recheck for DTCs. If DTC P0125 is displayed again, replace ECM. If DTC P0125 is not displayed again, go to next step.
11. Vehicle either ran out of fuel or problem is intermittent. Check component and ECM connections.

Test Drive Confirmation

1. If using OBD-II scan tool, go to step 3. If using Toyota hand-held tester, connect hand-held tester to Data Link Connector (DLC) No. 3. (Scheme 231) Switch hand-held tester to CHECK mode and go to next step.
2. Start and warm engine to normal operating temperature with all accessories off. Drive vehicle at 31-40 MPH for 1-3 minutes. Stop vehicle and allow to idle for one minute. Repeat driving and idling part of test 3 times. If malfunction exists, MIL will illuminate.
3. Start and warm engine to normal operating temperature. Drive vehicle at 31-40 MPH for 1-3 minutes. Stop vehicle and allow to idle for one minute. Turn ignition off. Repeat driving and idle part of test. If malfunction exists, MIL will illuminate.

1. If any other DTCs are displayed, diagnose and repair those DTCs first and retest system. If only DTC P0130 is displayed, go to next step.
2. Connect scan tool to Data Link Connector (DLC) No. 3. (Scheme 231) Start engine and increase engine speed to 2500 RPM for approximately 90 seconds. Let engine idle. Using scan tool, monitor heated oxygen senor No. 1 output voltage. Voltage should alternate repeatedly between less than.4 volt and more than.55 volt. If voltage is as specified, go to step 7. If voltage is not as specified, go to next step.
3. Check for open or short in wiring between ECM and heated oxygen sensor No. 1. See «WIRING DIAGRAMS»(/toyota/celica/t230-1999-2002/remont/wiring-diagrams-engine-performance/#engine-performance-wiring-diagrams) article. If problem exists, repair wiring as necessary. If problem does not exist, go to next step.
4. Ensure oil dipstick, oil filler cap, PCV system and all other air induction system components are intact and operating properly. If problem exists, repair as necessary. If problem does not exist, go to next step.
5. Check fuel pressure. See «FUEL SYSTEMS»(ref-2888-S02687592482000041400000) in BASIC DIAGNOSTIC PROCEDURES - 4-CYLINDER article. If fuel pressure is not within specification, repair as necessary. If fuel pressure is within specification, go to next step.
6. Check fuel injectors. See «FUEL SYSTEMS»(ref-2892-S33566963412000041400000) in SYSTEM & COMPONENT TESTING - 4-CYLINDER article. If problem exists, repair as necessary. If problem does not exist, replace heated oxygen sensor No. 1.
7. Perform test drive confirmation, then go to next step. See «TEST DRIVE CONFIRMATION»(ref-3781-S00744728032000051600000).
8. Clear and recheck for DTCs. If DTC P0130 is displayed again, replace ECM. If DTC P0130 is not displayed again, problem is intermittent. Check component and ECM connections.

1. If any other DTCs are displayed, diagnose and repair those DTCs first and retest system. If only DTC P0133 is displayed, go to next step.
2. Connect scan tool to Data Link Connector (DLC) No. 3. (Scheme 231) Start engine and increase engine speed to 2500 RPM for approximately 90 seconds. Let engine idle. Using scan tool, monitor heated oxygen sensor No. 1 output voltage. Voltage should alternate repeatedly between less than.4 volt and more than.55 volt. If voltage is as specified, go to step 7. If voltage is not as specified, go to next step.
3. Check for open or short in wiring between ECM and heated oxygen sensor No. 1. See «WIRING DIAGRAMS»(/toyota/celica/t230-1999-2002/remont/wiring-diagrams-engine-performance/#engine-performance-wiring-diagrams) article. If problem exists, repair wiring as necessary. If problem does not exist, go to next step.
4. Ensure oil dipstick, oil filler cap, PCV system and all other air induction system components are intact and operating properly. If problem exists, repair as necessary. If problem does not exist, go to next step.
5. Check fuel pressure. See «FUEL SYSTEMS»(ref-2888-S02687592482000041400000) in BASIC DIAGNOSTIC PROCEDURES - 4-CYLINDER article. If fuel pressure is not within specification, repair as necessary. If fuel pressure is within specification, go to next step.
6. Check fuel injectors. See «FUEL SYSTEMS»(ref-2892-S33566963412000041400000) in SYSTEM & COMPONENT TESTING - 4-CYLINDER article. If problem exists, repair as necessary. If problem does not exist, replace heated oxygen sensor No. 1.
7. Perform test drive confirmation, then go to next step. See «TEST DRIVE CONFIRMATION»(ref-3781-S00744728032000051600000) under DTC P0130: HEATED OXYGEN SENSOR NO. 1 CIRCUIT.
8. Clear and recheck for DTCs. If DTC P0133 is displayed again, replace ECM. If DTC P0133 is not displayed again, problem is intermittent. Check component and ECM connections.

1. Access ECM in driver's side of engine compartment, next to battery. Turn ignition on. Using DVOM, backprobe ECM harness connector and measure voltage between ground and terminal No. 3 (Yellow/Red wire) at ECM harness connector E4. (Scheme 230) Voltage should be 9-14 volts. If voltage is as specified, replace ECM. If voltage is not as specified, go to next step.
2. Disconnect heated oxygen sensor No. 1 harness connector. Measure resistance between terminals B+ (Black/White wire) and HT (Yellow/Red wire) at heated oxygen sensor No. 1 (component side). (Scheme 233) Resistance should be 11-16 ohms at 68°F (20°C). If resistance is not as specified, replace heated oxygen sensor No. 1. If resistance is as specified, go to next step.
3. Repair wiring between ECM and heated oxygen sensor No. 1, or between heated oxygen sensor No. 1 and engine room junction box. See «WIRING DIAGRAMS»(/toyota/celica/t230-1999-2002/remont/wiring-diagrams-engine-performance/#engine-performance-wiring-diagrams) article.

Scheme 233

1. If any other DTCs are displayed, diagnose and repair those DTCs first. If only DTC P0136 is displayed, go to next step.
2. Check for open or short in wiring between ECM and heated oxygen sensor No. 2. See «WIRING DIAGRAMS»(/toyota/celica/t230-1999-2002/remont/wiring-diagrams-engine-performance/#engine-performance-wiring-diagrams) article. If problem exists, repair wiring as necessary. If problem does not exist, go to next step.
3. Connect scan tool to Data Link Connector (DLC) No. 3. (Scheme 231) Start and warm engine to normal operating temperature. Monitor heated oxygen sensor No. 2 output voltage. Snap accelerate engine to about 4000 RPM 3 times. Voltage should fluctuate from less than.4 volt to.5 volt or more. If voltage is as specified, problem is intermittent. Check component and ECM connections. If voltage is not as specified, replace heated oxygen sensor No. 2.

1. Access ECM in driver's side of engine compartment, next to battery. Turn ignition on. Using DVOM, backprobe ECM harness connector and measure voltage between ground and terminal No. 16 (Yellow/Green wire) at ECM harness connector E3. (Scheme 230) Voltage should be 9-14 volts. If voltage is as specified, replace ECM. If voltage is not as specified, go to next step.
2. Disconnect heated oxygen sensor No. 2 harness connector. Measure resistance between terminals B+ (Black/White wire) and HT (Yellow/Green wire) at heated oxygen sensor No. 2 (component side). (Scheme 234) Resistance should be 11-16 ohms at 68°F (20°C). If resistance is not as specified, replace heated oxygen sensor No. 2. If resistance is as specified, go to next step.
3. Repair wiring between ECM and heated oxygen sensor No. 2, or between heated oxygen sensor No. 2 and engine room junction box. See «WIRING DIAGRAMS»(/toyota/celica/t230-1999-2002/remont/wiring-diagrams-engine-performance/#engine-performance-wiring-diagrams) article.

Scheme 234

1. Ensure oil dipstick, oil filler cap, PCV system and all other air induction system components are intact and operating properly. If problem exists, repair as necessary. If problem does not exist, go to next step.
2. Check fuel injectors. See «FUEL SYSTEMS»(ref-2892-S33566963412000041400000) in SYSTEM & COMPONENT TESTING - 4-CYLINDER article. If problem exists, repair as necessary. If problem does not exist, go to next step.
3. Check Manifold Absolute Pressure (MAP) sensor and Engine Coolant Temperature (ECT) sensor. See «ENGINE SENSORS & SWITCHES»(ref-2892-S05206625502000041400000) in SYSTEM & COMPONENT TESTING - 4-CYLINDER article. If problem exists, replace appropriate component. If problem does not exist, go to next step.
4. Check spark and ignition system. See «IGNITION SYSTEMS»(ref-2888-S04722060112000041400000) in BASIC DIAGNOSTIC PROCEDURES - 4-CYLINDER article. If problem exists, repair as necessary. If problem does not exist, go to next step.
5. Check fuel pressure. See «FUEL SYSTEMS»(ref-2888-S02687592482000041400000) in BASIC DIAGNOSTIC PROCEDURES - 4-CYLINDER article. If fuel pressure is not within specification, repair as necessary. If fuel pressure is within specification, go to next step.
6. Check exhaust system for leaks. If problem exists, repair as necessary. If problem does not exist, go to next step.
7. Connect scan tool to Data Link Connector (DLC) No. 3. (Scheme 231) Start engine and increase engine speed to 2500 RPM for approximately 90 seconds. Let engine idle. Using scan tool, monitor heated oxygen sensor No. 1 output voltage. Voltage should alternate repeatedly from less than.4 volt to more than.5 volt. If voltage is as specified, go to step 9. If voltage is not as specified, go to next step.
8. Check for open or short in wiring between ECM and heated oxygen sensor No. 1. See «WIRING DIAGRAMS»(/toyota/celica/t230-1999-2002/remont/wiring-diagrams-engine-performance/#engine-performance-wiring-diagrams) article. If problem exists, repair wiring as necessary. If problem does not exist, replace heated oxygen sensor No. 1.
9. Perform test drive confirmation, then go to next step. See «TEST DRIVE CONFIRMATION»(ref-3781-S00744728032000051600000) under DTC P0130: HEATED OXYGEN SENSOR NO. 1 CIRCUIT.
10. Clear and recheck for DTCs. If DTC P0171 and/or P0172 are displayed again, replace ECM. If neither DTC P0171 nor P0172 is displayed again, go to next step.
11. Vehicle either ran out of fuel or problem is intermittent. Check component and ECM connections.

1. Connect scan tool to Data Link Connector (DLC) No. 3. (Scheme 231) Record any DTCs and freeze frame data. Switch scan tool to CHECK mode (Toyota hand-held tester only). Drive vehicle several times with engine speed, load and its surrounding range shown with ENGINE SPD, CALC LOAD in freeze frame data or MISFIRE RPM and MISFIRE LOAD in scan tool data list.
2. Drive vehicle at specified engine speeds. See «DRIVING PATTERN»(ref-3781-S38788432612000051600000) table. Turn ignition off after symptom is simulated the first time, then repeat test drive again (OBD-II scan tool only). If a misfire is detected, a DTC will set and misfire will be indicated in freeze frame data. Turn ignition off and wait a minimum of 5 seconds. DRIVING PATTERN RPM (1) Minutes Idling 3 1/2 1000 3 2000 1 1/2 3000 1 (1) Minimum specification is given.

1. Check vacuum hoses for leaks, blockage and proper routing. See appropriate illustration in «VACUUM DIAGRAMS»(ref-3029) article. Also, check wiring and connectors for damage or poor connections. If problem exists, repair as necessary and perform «TEST DRIVE CONFIRMATION»(ref-3781-S18164663652000051600000). If problem does not exist, go to next step.
2. Check spark and ignition system. See «IGNITION SYSTEMS»(ref-2888-S04722060112000041400000) in BASIC DIAGNOSTIC PROCEDURES - 4-CYLINDER article. If problem exists, repair as necessary. If problem does not exist, go to next step.
3. Access ECM in driver's side of engine compartment, next to battery. Turn ignition on. Using DVOM, backprobe ECM connector and measure voltage between ground and fuel injector terminals at ECM harness connector E5. See «IDENTIFYING ECM FUEL INJECTOR TERMINALS»(ref-3781-S29033083422000051600000) table. (Scheme 230) If voltage is 9-14 volts at each terminal, go to step 6. If voltage is not 9-14 volts at each terminal, go to next step. IDENTIFYING ECM FUEL INJECTOR TERMINALS Fuel Injector No. (1) Terminal No. Wire Color 1 1 Red 2 2 Red/Blue 3 3 Red/White 4 4 Red/Black (1) Terminals are located at ECM harness connector E5. (Scheme 230)
4. Disconnect fuel injector harness connector at misfiring cylinder. Measure resistance between fuel injector terminals (component side). Resistance should be 13.4-14.2 ohms at 68°F (20°C). If resistance is as specified, go to next step. If resistance is not as specified, replace fuel injector.
5. Check for open or short in wiring between ECM and fuel injector. See «WIRING DIAGRAMS»(/toyota/celica/t230-1999-2002/remont/wiring-diagrams-engine-performance/#engine-performance-wiring-diagrams) article. If problem exists, repair as necessary. If problem does not exist, repair open or short in injector power source circuit. See «WIRING DIAGRAMS»(/toyota/celica/t230-1999-2002/remont/wiring-diagrams-engine-performance/#engine-performance-wiring-diagrams) article.
6. Check fuel pressure. See «FUEL SYSTEMS»(ref-2888-S02687592482000041400000) in BASIC DIAGNOSTIC PROCEDURES - 4-CYLINDER article. If fuel pressure is not within specification, repair as necessary. If fuel pressure is within specification, go to next step.
7. Check fuel injectors. See «FUEL SYSTEMS»(ref-2892-S33566963412000041400000) in SYSTEM & COMPONENT TESTING - 4-CYLINDER article. If problem exists, repair as necessary. If problem does not exist, go to next step.
8. Check Manifold Absolute Pressure (MAP) sensor and Engine Coolant Temperature (ECT) sensor. See «ENGINE SENSORS & SWITCHES»(ref-2892-S05206625502000041400000) in SYSTEM & COMPONENT TESTING - 4-CYLINDER article. If problem exists, replace appropriate component. If problem does not exist, go to next step.
9. Check engine compression. See «BASIC DIAGNOSTIC PROCEDURES - 4-CYLINDER»(ref-2888) article. If engine compression is okay, check valve clearance. See «ON-VEHICLE ADJUSTMENTS - 4-CYLINDER»(ref-2883) article. If valve clearance is okay, it may be necessary to check valve timing. See appropriate article in ENGINES.

ECM uses signals provided by crankshaft and camshaft position sensors. If engine speed rate has changed enough to equal a preset number, a misfire is detected and MIL is illuminated. If misfire rate is high enough, and driving conditions will cause catalytic converter damage or overheating, MIL blinks when a misfire is occurring. DTC is set during any particular 200 revolutions of engine during which misfiring is detected which can cause catalytic converter overheating and/or damage, or during any particular 1000 revolutions of engine during which misfiring is detected which can cause a deterioration in emission levels. Possible causes are

1. Open or short in wiring.
2. Poor contact at ECM or component.
3. Disconnect, blocked or damaged vacuum hose(s).
4. Ignition system malfunction.
5. Defective fuel injector(s).
6. Improper fuel pressure.
7. Defective Manifold Absolute Pressure (MAP) sensor.
8. Defective Engine Coolant Temperature (ECT) sensor.
9. Improper engine compression.
10. Improper valve clearance.
11. Improper valve timing.
12. VVTL system malfunction.
13. Defective ECM.

When 2 or more codes for misfiring cylinder are recorded repeatedly but no random misfire code is recorded, it indicates misfires were detected and recorded at different times. If misfire cannot be reproduced, reason may be because of driving with lack of fuel, improper fuel, fouled spark plug, etc. Using scan tool, read freeze frame data. Freeze frame records engine conditions when malfunction is detected.

For diagnosis and repair procedure, see DTC P0300: RANDOM MISFIRE DETECTED.

1. Access ECM in driver's side of engine compartment, next to battery. Disconnect ECM harness connector E5. (Scheme 230) Use DVOM, backprobe ECM harness connector and measure resistance between ground and terminal No. 27 (White wire) at ECM harness connector E5. Resistance should be one megohm or more. If resistance is as specified, go to step 3. If resistance is not as specified, go to next step.
2. Disconnect knock sensor harness connector. Check continuity between knock sensor terminal and knock sensor housing. If continuity does not exist, go to next step. If continuity exists, replace knock sensor.
3. Check for open or short in wiring between knock sensor and ECM. See «WIRING DIAGRAMS»(/toyota/celica/t230-1999-2002/remont/wiring-diagrams-engine-performance/#engine-performance-wiring-diagrams) article. If problem exists, repair wiring as necessary. If problem does not exist, substitute knock sensor with known-good knock sensor. Clear and then retrieve DTCs. If DTC P0325 is still displayed, replace ECM. If DTC P0325 is no longer displayed, replace knock sensor.

1. Disconnect CKP sensor harness connector. Measure resistance between CKP sensor terminals (component side). Resistance should be 1630-2740 ohms (cold sensor) or 2065-3225 ohms (hot sensor). If problem exists, replace CKP sensor. If problem does not exist, go to next step.
2. Check for open or short in wiring between ECM and CKP sensor. See «WIRING DIAGRAMS»(/toyota/celica/t230-1999-2002/remont/wiring-diagrams-engine-performance/#engine-performance-wiring-diagrams) article. If problem exists, repair wiring as necessary. If problem does not exist, go to next step.
3. Remove and inspect CKP sensor. Also inspect crankshaft timing pulley teeth. If problem exists, replace CKP sensor and/or crankshaft timing pulley as necessary. If problem does not exist, replace ECM.

1. Disconnect CMP sensor harness connector. Measure resistance between CMP sensor terminals (component side). Resistance should be 835-1400 ohms (cold sensor) or 1060-1645 ohms (hot sensor). If resistance is not as specified, replace CMP sensor. If resistance is as specified, go to next step.
2. Check for open or short in wiring between ECM and CMP sensor. See «WIRING DIAGRAMS»(/toyota/celica/t230-1999-2002/remont/wiring-diagrams-engine-performance/#engine-performance-wiring-diagrams) article. If problem exists, repair wiring as necessary. If problem does not exist, go to next step.
3. Remove and inspect CMP sensor. Also inspect camshaft timing pulley. If problem exists, replace CMP sensor and/or camshaft timing pulley as necessary. If problem does not exist, replace ECM.

1. If any other DTCs are displayed, diagnose and repair those DTCs first. If only DTC P0420 is displayed, go to next step.
2. Check exhaust system for leaks. If problem exists, repair as necessary. If problem does not exist, go to next step.
3. Check heated oxygen sensor No. 1. See «DTC P0130: HEATED OXYGEN SENSOR NO. 1 CIRCUIT»(ref-3781-S09895159932000051600000). If problem exists, repair as necessary. If problem does not exist, go to next step.
4. Check heated oxygen sensor No. 2. See «DTC P0136: HEATED OXYGEN SENSOR NO. 2 CIRCUIT»(ref-3781-S36863784752000051600000) test. If problem exists, repair as necessary. If problem does not exist, replace catalytic converter.

1. Check for cracks, deformations in fuel tank, charcoal canister and fuel tank filler pipe. Check for disconnected hoses and tubes around fuel tank and charcoal canister. If problem exists, repair as necessary. If problem does not exist, go to next step.
2. Check fuel cap. If fuel cap is not an OEM cap, replace cap with an OEM cap. If fuel cap is an OEM cap, go to next step.
3. Check if fuel cap is properly installed. If problem exists, install fuel cap properly. If fuel cap is properly installed, go to next step.
4. Check for damaged fuel cap and gasket. If problem exists, replace fuel cap with OEM cap. If problem does not exist, go to next step.
5. Remove fuel cap. Visually inspect fuel tank filler neck for damage. If problem exists, replace fuel tank filler neck as necessary. If problem does not exist, go to next step.
6. Check vacuum hoses between vapor pressure sensor and fuel tank, and between charcoal canister and pressure switching valve VSV. Check hoses for correct installation, looseness and damage. If problem exists, repair vacuum hoses as necessary. If problem does not exist, go to next step.
7. Check hose and tube between fuel tank and charcoal canister for correct installation and damage. If problem exists, repair as necessary. If problem does not exist, go to next step.
8. Check charcoal canister for damage. If problem exists, repair or replace as necessary. If problem does not exist, go to next step.
9. Access ECM in driver's side of engine compartment, next to battery. Turn ignition on. Using DVOM, backprobe ECM harness connector and measure voltage between terminals No. 2 (Red wire) and No. 18 (Brown wire) at ECM harness connector E4. (Scheme 230) Voltage should be 4.5-5.5 volts. If voltage is not as specified, replace ECM. If voltage is as specified, go to next step.
10. Using DVOM, backprobe ECM harness connector and measure voltage between terminal No. 4 (Blue/Black wire) at ECM harness connector E2 and terminal No. 18 (Brown wire) at ECM harness connector E4. Remove fuel cap. Turn ignition on. Voltage should be 3.3 volts. If voltage is as specified, go to step 12. If voltage is not as specified, go to next step.
11. Check for an open or short in wiring between vapor pressure sensor and ECM. See «WIRING DIAGRAMS»(/toyota/celica/t230-1999-2002/remont/wiring-diagrams-engine-performance/#engine-performance-wiring-diagrams) article. If problem exists, repair wiring as necessary. If problem does not exist, replace vapor pressure sensor.
12. Check fuel tank and fuel tank over fill valve for damage. If problem exists, repair or replace fuel tank or fuel tank over fill valve as necessary. If problem does not exist, no fault is indicated at this time. Probable cause of DTC to set was an incorrectly installed fuel cap.

1. Check for cracks, deformations in fuel tank, charcoal canister and fuel tank filler pipe. Check for disconnected hoses and tubes around fuel tank and charcoal canister. If problem exists, repair as necessary. If problem does not exist, go to next step.
2. Check fuel cap. If fuel cap is not an OEM cap, replace cap with an OEM cap. If fuel cap is an OEM cap, go to next step.
3. Check if fuel cap is properly installed. If problem exists, install fuel cap properly. If fuel cap is properly installed, go to next step.
4. Check for damaged fuel cap and gasket. If problem exists, replace fuel cap with OEM cap. If problem does not exist, go to next step.
5. Remove fuel cap. Visually inspect fuel tank filler neck for damage. If problem exists, replace fuel tank filler neck as necessary. If problem does not exist, go to next step.
6. Check vacuum hoses between vapor pressure sensor and fuel tank, and between charcoal canister and pressure switching valve VSV. Check hoses for correct installation, looseness and damage. If problem exists, repair vacuum hoses as necessary. If problem does not exist, go to next step.
7. Check hose and tube between fuel tank and charcoal canister for correct installation and damage. If problem exists, repair as necessary. If problem does not exist, go to next step.
8. Check all EVAP system electrical component connections. If problem exists, repair as necessary. If problem does not exist, go to next step.
9. Check vacuum hoses between charcoal canister and fuel tank, and between fuel filler neck and fuel tank. If problem exists, repair as necessary. If problem does not exist, go to next step.
10. Access ECM in driver's side of engine compartment, next to battery. Turn ignition on. Using DVOM, backprobe ECM harness connector and measure voltage between terminals No. 2 (Red wire) and No. 18 (Brown wire) at ECM harness connector E4. (Scheme 230) Voltage should be 4.5-5.5 volts. If voltage is not as specified, replace ECM. If voltage is as specified, go to next step.
11. Using DVOM, backprobe ECM harness connector and measure voltage between terminal No. 4 (Blue/Black wire) at ECM harness connector E2 and terminal No. 18 (Brown wire) at ECM harness connector E4. Remove fuel cap. Turn ignition on. Voltage should be 3.3 volts. If voltage is as specified, go to step 13. If voltage is not as specified, go to next step.
12. Check for an open or short in wiring between vapor pressure sensor and ECM. See «WIRING DIAGRAMS»(/toyota/celica/t230-1999-2002/remont/wiring-diagrams-engine-performance/#engine-performance-wiring-diagrams) article. If problem exists, repair wiring as necessary. If problem does not exist, replace vapor pressure sensor.
13. Disconnect EVAP VSV vacuum hoses. Turn ignition on. Access ECM in driver's side of engine compartment, next to battery. Connect a jumper wire by backprobing between ground and terminal No. 4 (Green/Orange wire) at ECM harness connector E4. (Scheme 230) With jumper wire connected air applied to EVAP VSV port "E" should flow from port "F". (Scheme 235) Remove jumper wire. With jumper wire removed, air applied to EVAP VSV port "E" should not flow from port "F". If EVAP VSV functions as specified, go to step 16. If EVAP VSV does not function as specified, go to next step.
14. Check EVAP VSV operation. See «FUEL EVAPORATION SYSTEM»(ref-2892-S06317964532000041400000) under EMISSION SYSTEMS & SUB-SYSTEMS in appropriate SYSTEM & COMPONENT TESTING article. If EVAP VSV is okay, go to next step. If EVAP VSV is not okay, replace EVAP VSV. Also clean vacuum hose between throttle body and EVAP VSV, and between EVAP VSV and charcoal canister, then check charcoal canister. See «FUEL EVAPORATION SYSTEM»(ref-2892-S06317964532000041400000) under EMISSION SYSTEMS & SUB-SYSTEMS in appropriate SYSTEM & COMPONENT TESTING article.
15. Check for an open or short in wiring between engine room junction box and EVAP VSV, and between EVAP VSV and ECM. See «WIRING DIAGRAMS»(/toyota/celica/t230-1999-2002/remont/wiring-diagrams-engine-performance/#engine-performance-wiring-diagrams) article. If problem exists, repair wiring as necessary. If problem does not exist, replace ECM.
16. Disconnect canister closed valve VSV vacuum hoses. Turn ignition on. Access ECM in driver's side of engine compartment, next to battery. Connect a jumper wire by backprobing between ground and terminal No. 17 (Violet/White wire) at ECM harness connector E5. With jumper wire connected air applied to canister closed valve VSV port "E" should not flow from port "F". (Scheme 236) Remove jumper wire. With jumper wire removed, air applied to canister closed valve VSV port "E" should flow from port "F". If canister closed valve VSV does not function as specified, go to next step. If canister closed valve VSV functions as specified, go to step 19.
17. Check canister closed valve VSV. See «FUEL EVAPORATION SYSTEM»(ref-2892-S06317964532000041400000) under EMISSION SYSTEMS & SUB-SYSTEMS in SYSTEM & COMPONENT TESTING - 4-CYLINDER article. If canister closed valve VSV is okay, go to next step. If canister closed valve VSV is defective, replace canister closed valve VSV and charcoal canister. Also clean vacuum hose between charcoal canister and canister closed valve VSV.
18. Check for an open or short in wiring between engine room junction box and canister closed valve VSV, and between canister closed valve VSV and ECM. See «WIRING DIAGRAMS»(/toyota/celica/t230-1999-2002/remont/wiring-diagrams-engine-performance/#engine-performance-wiring-diagrams) article. If problem exists, repair wiring as necessary. If problem does not exist, replace ECM.
19. Disconnect pressure switching valve VSV vacuum hoses. Turn ignition on. Access ECM in driver's side of engine compartment, next to battery. Connect a jumper wire by backprobing between ground and terminal No. 23 (Green/Orange wire) at ECM harness connector E3. With jumper wire connected air applied to pressure switching valve VSV port "E" should flow from port "F". (Scheme 237) Remove jumper wire. With jumper wire removed, air applied to pressure switching valve VSV port "E" should not flow from port "F". If pressure switching valve VSV functions as specified, go to step 22. If pressure switching valve VSV does not function as specified, go to next step.
20. Check pressure switching valve VSV. See «FUEL EVAPORATION SYSTEM»(ref-2892-S06317964532000041400000) under EMISSION SYSTEMS & SUB-SYSTEMS in appropriate SYSTEM & COMPONENT TESTING article. If pressure switching valve VSV is defective, replace pressure switching valve VSV and charcoal canister. Also clean vacuum hose between charcoal canister and pressure switching valve VSV, and between pressure switching valve VSV and fuel tank. If pressure switching valve VSV is okay, go to next step.
21. Check for an open or short in wiring between engine room junction box and pressure switching valve VSV, and between pressure switching valve VSV and ECM. See «WIRING DIAGRAMS»(/toyota/celica/t230-1999-2002/remont/wiring-diagrams-engine-performance/#engine-performance-wiring-diagrams) article. If problem exists, repair wiring as necessary. If problem does not exist, replace ECM.
22. Charcoal canister or fuel tank overfill check valve maybe defective. Check fuel evaporation system. See «FUEL EVAPORATION SYSTEM»(ref-2892-S06317964532000041400000) under EMISSION SYSTEMS & SUB-SYSTEMS in appropriate SYSTEM & COMPONENT TESTING article. Repair as necessary. If no problem is indicated, replace ECM.

Scheme 235

Scheme 236

Scheme 237

1. Access ECM in driver's side of engine compartment, next to battery. Turn ignition on. Using DVOM, backprobe ECM harness connector and measure voltage between terminals No. 2 (Red wire) and No. 18 (Brown wire) at ECM harness connector E4. (Scheme 230) Voltage should be 4.5-5.5 volts. If voltage is not as specified, replace ECM. If voltage is as specified, go to next step.
2. Using DVOM, backprobe ECM harness connector and measure voltage between terminal No. 4 (Blue/Black wire) at ECM harness connector E2 and terminal No. 18 (Brown wire) at ECM harness connector E4. Remove fuel cap. Turn ignition on. Voltage should be 3.3 volts. If voltage is as specified, replace ECM. If voltage is not as specified, go to next step.
3. Check for open or short in wiring between vapor pressure sensor and ECM. See «WIRING DIAGRAMS»(/toyota/celica/t230-1999-2002/remont/wiring-diagrams-engine-performance/#engine-performance-wiring-diagrams) article. If problem exists, repair wiring as necessary. If problem does not exist, replace vapor pressure sensor.

1. Test drive vehicle and check operation of speedometer. If speedometer is not operating correctly, repair speedometer as necessary. See appropriate INSTRUMENT PANELS article in ACCESSORIES & EQUIPMENT. If speedometer is operating correctly, go to next step.
2. Access ECM in driver's side of engine compartment, next to battery. Raise and support one front wheel. Turn ignition on. Shift transaxle lever into Neutral. Using DVOM, backprobe ECM harness connector and measure voltage between ground and terminal No. 22 (White/Red wire) at ECM harness connector E3. (Scheme 230) Observe voltage reading while rotating front wheel. Voltage should pulse between zero volts and 4.5-5.5 volts. If voltage is as specified, replace ECM. If voltage is not as specified, repair open or short in wiring between instrument cluster and ECM. See «WIRING DIAGRAMS»(/toyota/celica/t230-1999-2002/remont/wiring-diagrams-engine-performance/#engine-performance-wiring-diagrams) article.

1. Start engine and warm to normal operating temperature. Turn all accessories off. Ensure A/C is off. Shift transaxle lever into Neutral. Note engine RPM. Using a jumper wire, connect terminals No. 4 (White/Black wire) and No. 13 (Pink/Black wire) at DLC No. 3. (Scheme 238) Note engine RPM and compare RPM readings. If difference in engine speed is more than 100 RPM, go to step 7. If difference in engine speed is 100 RPM or less, go to next step.
2. Turn ignition off. Turn ignition on. Using DVOM, backprobe ECM harness connector and measure voltage between ground and terminal No. 18 (Black/White wire) at ECM harness connector E5. Voltage should be 9-14 volts. If voltage is as specified, go to step 5. If voltage is not as specified, go to next step.
3. Check IAC valve. See «IDLE CONTROL SYSTEMS»(ref-2892-S18717829272000041400000) in SYSTEM & COMPONENT TESTING - 4-CYLINDER article. If problem exists, replace IAC valve. If problem does not exist, go to next step.
4. Check for open or short in wiring between IAC valve and engine room junction box, and between IAC valve and ECM. See «WIRING DIAGRAMS»(/toyota/celica/t230-1999-2002/remont/wiring-diagrams-engine-performance/#engine-performance-wiring-diagrams) article. If problem exists, repair wiring as necessary. If problem does not exist, problem is intermittent. Check component and ECM connections.
5. Check IAC valve operation. See «IDLE CONTROL SYSTEMS»(ref-2892-S18717829272000041400000) in SYSTEM & COMPONENT TESTING - 4-CYLINDER article. If problem exists, replace IAC valve. If problem does not exist, go to next step.
6. Remove IAC valve from throttle body. Check IAC valve and passages for carbon build-up and blockage. If problem exists, repair or replace as necessary. If problem does not exist, replace ECM.
7. Ensure oil dipstick, oil filler cap, PCV system and all other air induction system components are intact and operating properly. If problem exists, repair as necessary. If problem does not exist, an open or short in A/C switch signal circuit may exist. Check A/C amplifier. See appropriate MANUAL or AUTOMATIC A/C-HEATER SYSTEMS article in AIR CONDITIONING & HEATING. Repair as necessary.

Scheme 238

1. Check for spark at misfiring cylinder. See «IGNITION SYSTEMS»(ref-2888-S04722060112000041400000) in BASIC DIAGNOSTIC PROCEDURES - 4-CYLINDER article. If spark exists, go to next step. If spark does not exist, go to step 4.
2. Check for open or short in Black/Yellow wire between ECM and ignition coil/ignitor No. 1. Also, check for open or short in Red/Black wire between ECM and ignition coil/ignitor No. 1. See «WIRING DIAGRAMS»(/toyota/celica/t230-1999-2002/remont/wiring-diagrams-engine-performance/#engine-performance-wiring-diagrams) article. If problem exists, repair wiring as necessary. If problem does not exist, go to next step.
3. Disconnect ignition coil/ignitor No. 1 harness connector. Access ECM in driver's side of engine compartment, next to battery. Turn ignition on. Using DVOM, backprobe ECM harness connector and measure voltage between ground and terminal No. 25 (Black/Yellow wire) at ECM harness connector E5. (Scheme 230) Voltage should be 4.5-5.5 volts. If voltage is as specified, replace ignition coil/ignitor No. 1. If voltage is not as specified, replace ECM.
4. Check for open or short in Red/Black wire between ECM and ignition coil/ignitor No. 1. See «WIRING DIAGRAMS»(/toyota/celica/t230-1999-2002/remont/wiring-diagrams-engine-performance/#engine-performance-wiring-diagrams) article. If problem exists, repair wiring as necessary. If problem does not exist, go to next step.
5. Access ECM in driver's side of engine compartment, next to battery. Using DVOM, backprobe ECM harness connector and measure voltage between ground and terminal No. 10 (Red/Black wire) at ECM harness connector E5 while cranking engine. (Scheme 230) Voltage should be.1-4.5 volts. If voltage is not as specified, go to next step. If voltage is as specified, go to step 7.
6. Disconnect ignition coil/ignitor No. 1 harness connector. Using DVOM, backprobe ECM harness connector and measure voltage between ground and terminal No. 10 (Red/Black wire) at ECM harness connector E5 while cranking engine. Voltage should be.1-5.0 volts. If voltage is as specified, replace ignition coil/ignitor No. 1. If voltage is not as specified, replace ECM
7. Turn ignition on. Measure voltage between ground and terminal No. 1 (Black wire) at ignition coil/ignitor No. 1 harness connector. (Scheme 239) If voltage is 9-14 volts, go to next step. If voltage is not 9-14 volts, check and repair ignition coil/ignitor No. 1 power source circuit. See «WIRING DIAGRAMS»(/toyota/celica/t230-1999-2002/remont/wiring-diagrams-engine-performance/#engine-performance-wiring-diagrams) article.
8. Check for open or short in wiring between ground and terminal No. 4 (White/Black wire) at ignition coil/ignitor No. 1 harness connector. See «WIRING DIAGRAMS»(/toyota/celica/t230-1999-2002/remont/wiring-diagrams-engine-performance/#engine-performance-wiring-diagrams) article. If problem exists, repair wiring as necessary. If problem does not exist, replace ignition coil/ignitor No. 1.

Scheme 239

1. Check for spark at misfiring cylinder. See «IGNITION SYSTEMS»(ref-2888-S04722060112000041400000) in BASIC DIAGNOSTIC PROCEDURES - 4-CYLINDER article. If spark exists, go to next step. If spark does not exist, go to step 4.
2. Check for open or short in Black/Yellow wire between ECM and ignition coil/ignitor No. 2. Also, check for open or short in Red/White wire between ECM and ignition coil/ignitor No. 2. See «WIRING DIAGRAMS»(/toyota/celica/t230-1999-2002/remont/wiring-diagrams-engine-performance/#engine-performance-wiring-diagrams) article. If problem exists, repair wiring as necessary. If problem does not exist, go to next step.
3. Disconnect ignition coil/ignitor No. 2 harness connector. Access ECM in driver's side of engine compartment, next to battery. Turn ignition on. Using DVOM, backprobe ECM harness connector and measure voltage between ground and terminal No. 25 (Black/Yellow wire) at ECM harness connector E5. (Scheme 230) Voltage should be 4.5-5.5 volts. If voltage is as specified, replace ignition coil/ignitor No. 2. If voltage is not as specified, replace ECM.
4. Check for open or short in Red/White wire between ECM and ignition coil/ignitor No. 2. See «WIRING DIAGRAMS»(/toyota/celica/t230-1999-2002/remont/wiring-diagrams-engine-performance/#engine-performance-wiring-diagrams) article. If problem exists, repair wiring as necessary. If problem does not exist, go to next step.
5. Access ECM in driver's side of engine compartment, next to battery. Using DVOM, backprobe ECM harness connector and measure voltage between ground and terminal No. 11 (Red/White wire) at ECM harness connector E5 while cranking engine. (Scheme 230) Voltage should be.1-4.5 volts. If voltage is not as specified, go to next step. If voltage is as specified, go to step 7.
6. Disconnect ignition coil/ignitor No. 2 harness connector. Using DVOM, backprobe ECM harness connector and measure voltage between ground and terminal No. 11 (Red/White wire) at ECM harness connector E5 while cranking engine. Voltage should be.1-5.0 volts. If voltage is as specified, replace ignition coil/ignitor No. 2. If voltage is not as specified, replace ECM.
7. Turn ignition on. Measure voltage between ground and terminal No. 1 (Black wire) at ignition coil/ignitor No. 2 harness connector. (Scheme 239) If voltage is 9-14 volts, go to next step. If voltage is not 9-14 volts, check and repair ignition coil/ignitor No. 2 power source circuit. See «WIRING DIAGRAMS»(/toyota/celica/t230-1999-2002/remont/wiring-diagrams-engine-performance/#engine-performance-wiring-diagrams) article.
8. Check for open or short in wiring between ground and terminal No. 4 (White/Black wire) at ignition coil/ignitor No. 2 harness connector. See «WIRING DIAGRAMS»(/toyota/celica/t230-1999-2002/remont/wiring-diagrams-engine-performance/#engine-performance-wiring-diagrams) article. If problem exists, repair wiring as necessary. If problem does not exist, replace ignition coil/ignitor No. 2.

1. Check for spark at misfiring cylinder. See «IGNITION SYSTEMS»(ref-2888-S04722060112000041400000) in BASIC DIAGNOSTIC PROCEDURES - 4-CYLINDER article. If spark exists, go to next step. If spark does not exist, go to step 4.
2. Check for open or short in Black/Yellow wire between ECM and ignition coil/ignitor No. 3. Also, check for open or short in Green/Red wire between ECM and ignition coil/ignitor No. 3. See «WIRING DIAGRAMS»(/toyota/celica/t230-1999-2002/remont/wiring-diagrams-engine-performance/#engine-performance-wiring-diagrams) article. If problem exists, repair wiring as necessary. If problem does not exist, go to next step.
3. Disconnect ignition coil/ignitor No. 3 harness connector. Access ECM in driver's side of engine compartment, next to battery. Turn ignition on. Using DVOM, backprobe ECM harness connector and measure voltage between ground and terminal No. 25 (Black/Yellow wire) at ECM harness connector E5. (Scheme 230) Voltage should be 4.5-5.5 volts. If voltage is as specified, replace ignition coil/ignitor No. 3. If voltage is not as specified, replace ECM.
4. Check for open or short in Green/Red wire between ECM and ignition coil/ignitor No. 3. See «WIRING DIAGRAMS»(/toyota/celica/t230-1999-2002/remont/wiring-diagrams-engine-performance/#engine-performance-wiring-diagrams) article. If problem exists, repair wiring as necessary. If problem does not exist, go to next step.
5. Access ECM in driver's side of engine compartment, next to battery. Using DVOM, backprobe ECM harness connector and measure voltage between ground and terminal No. 12 (Green/Red wire) at ECM harness connector E5 while cranking engine. (Scheme 230) Voltage should be.1-4.5 volts. If voltage is not as specified, go to next step. If voltage is as specified, go to step 7.
6. Disconnect ignition coil/ignitor No. 3 harness connector. Using DVOM, backprobe ECM harness connector and measure voltage between ground and terminal No. 12 (Green/Red wire) at ECM harness connector E5 while cranking engine. Voltage should be.1-5.0 volts. If voltage is as specified, replace ignition coil/ignitor No. 3. If voltage is not as specified, replace ECM.
7. Turn ignition on. Measure voltage between ground and terminal No. 1 (Black wire) at ignition coil/ignitor No. 3 harness connector. (Scheme 239) If voltage is 9-14 volts, go to next step. If voltage is not 9-14 volts, check and repair ignition coil/ignitor No. 3 power source circuit. See «WIRING DIAGRAMS»(/toyota/celica/t230-1999-2002/remont/wiring-diagrams-engine-performance/#engine-performance-wiring-diagrams) article.
8. Check for open or short in wiring between ground and terminal No. 4 (White/Black wire) at ignition coil/ignitor No. 3 harness connector. See «WIRING DIAGRAMS»(/toyota/celica/t230-1999-2002/remont/wiring-diagrams-engine-performance/#engine-performance-wiring-diagrams) article. If problem exists, repair wiring as necessary. If problem does not exist, replace ignition coil/ignitor No. 3.

1. Check for spark at misfiring cylinder. See «IGNITION SYSTEMS»(ref-2888-S04722060112000041400000) in BASIC DIAGNOSTIC PROCEDURES - 4-CYLINDER article. If spark exists, go to next step. If spark does not exist, go to step 4.
2. Check for open or short in Black/Yellow wire between ECM and ignition coil/ignitor No. 4. Also, check for open or short in Red/Yellow wire between ECM and ignition coil/ignitor No. 4. See «WIRING DIAGRAMS»(/toyota/celica/t230-1999-2002/remont/wiring-diagrams-engine-performance/#engine-performance-wiring-diagrams) article. If problem exists, repair wiring as necessary. If problem does not exist, go to next step.
3. Disconnect ignition coil/ignitor No. 4 harness connector. Access ECM in driver's side of engine compartment, next to battery. Turn ignition on. Using DVOM, backprobe ECM harness connector and measure voltage between ground and terminal No. 25 (Black/Yellow wire) at ECM harness connector E5. (Scheme 230) Voltage should be 4.5-5.5 volts. If voltage is as specified, replace ignition coil/ignitor No. 4. If voltage is not as specified, replace ECM.
4. Check for open or short in Red/Yellow wire between ECM and ignition coil/ignitor No. 4. See «WIRING DIAGRAMS»(/toyota/celica/t230-1999-2002/remont/wiring-diagrams-engine-performance/#engine-performance-wiring-diagrams) article. If problem exists, repair wiring as necessary. If problem does not exist, go to next step.
5. Access ECM in driver's side of engine compartment, next to battery. Using DVOM, backprobe ECM harness connector and measure voltage between ground and terminal No. 13 (Red/Yellow wire) at ECM harness connector E5 while cranking engine. (Scheme 230) Voltage should be.1-4.5 volts. If voltage is not as specified, go to next step. If voltage is as specified, go to step 7.
6. Disconnect ignition coil/ignitor No. 4 harness connector. Using DVOM, backprobe ECM harness connector and measure voltage between ground and terminal No. 13 (Red/Yellow wire) at ECM harness connector E5 while cranking engine. Voltage should be.1-5.0 volts. If voltage is as specified, replace ignition coil/ignitor No. 4. If voltage is not as specified, replace ECM.
7. Turn ignition on. Measure voltage between ground and terminal No. 1 (Black wire) at ignition coil/ignitor No. 4 harness connector. (Scheme 239) If voltage is 9-14 volts, go to next step. If voltage is not 9-14 volts, check and repair ignition coil/ignitor No. 4 power source circuit. See «WIRING DIAGRAMS»(/toyota/celica/t230-1999-2002/remont/wiring-diagrams-engine-performance/#engine-performance-wiring-diagrams) article.
8. Check for open or short in wiring between ground and terminal No. 4 (White/Black wire) at ignition coil/ignitor No. 4 harness connector. See «WIRING DIAGRAMS»(/toyota/celica/t230-1999-2002/remont/wiring-diagrams-engine-performance/#engine-performance-wiring-diagrams) article. If problem exists, repair wiring as necessary. If problem does not exist, replace ignition coil/ignitor No. 4.

Check valve timing. Check for loose, stretched or jumped teeth of timing chain. See appropriate article in ENGINES. If problem exists, repair as necessary. If problem does not exist, replace ECM.

Diagnosis & Repair (Using Toyota Hand-Held Tester)

1. Check valve timing. See appropriate article in ENGINES. If problem exists, repair as necessary. If problem does not exist, go to next step.
2. Connect hand-held tester to Data Link Connector (DLC) NO. 3. (Scheme 231) Using hand-held tester, select ACTIVE TEST mode. Select VVT. Note idle speed when VVT OCV is activated by hand-held tester. Idle speed should be normal with OCV off and engine should idle rough or stalls when VVT OCV is on. If idle speed functions as specified, VVT is functioning properly at this time. DTC may have been set because of a foreign object that was temporarily caught in the engine oil system but after a short time system returned to normal. If idle speed does not function as specified, go to next step.
3. Access ECM in driver's side of engine compartment, next to battery. Using oscilloscope, backprobe ECM harness connector and connect oscilloscope between terminals No. 23 (White wire) and No. 24 (Green/Orange wire) at ECM harness connector E5. (Scheme 230) Start engine and let idle. Ensure oscilloscope pattern is as shown in illustration. (Scheme 240) As engine speed is increased, waveform frequency ("A") should lengthen. If waveform pattern is as shown, go to next step. If waveform pattern is not as shown, replace ECM.
4. Check VVT controller assembly for proper operation. See appropriate article in ENGINES. If problem exists, replace VVT controller assembly and go to next step. If problem does not exist, go to next step.
5. Disconnect VVT OCV harness connector. Measure resistance between VVT OCV terminals (component side). (Scheme 241) Resistance should be 6.9-7.9 ohms at 68°F (20°C). If resistance is as specified, go to next step. If resistance is not as specified, replace OCV and go to next step.
6. Check blockage in VVT OCV. Check oil check valve and oil pipe located under VVT OCV. If problem exists, repair as necessary. If problem does not exist, go to next step.
7. Install all remove components and connect all disconnected harness connectors. Using hand-held tester, clear DTCs. Start engine and allow it to idle. Turn ignition off. Turn ignition on and check for DTCs. If DTC P1349 is not present, no problem is indicated at this time. DTC may have been set because of a foreign object that was temporarily caught in the engine oil system but after a short time system returned to normal. If DTC P1349 is present, replace ECM.

Scheme 240

Scheme 241

Diagnosis & Repair (Using OBD-II Scan Tool)

1. Check valve timing. See appropriate article in ENGINES. If problem exists, repair as necessary. If problem does not exist, go to next step.
2. Start engine and allow it to idle. Disconnect Variable Valve Timing (VVT) Oil Control Valve (OCV) and note idle speed. OCV is located on front cylinder head, next to intake manifold. Engine idle speed should not change. Using jumper wires, apply battery voltage and ground to VVT OCV terminals (component side). Engine should idle rough or stall. If VVT OCV operates as specified, go to next step. If VVT OCV does not operate as specified, go to step 4.
3. Access ECM in driver's side of engine compartment, next to battery. Using oscilloscope, backprobe ECM harness connector and connect oscilloscope between terminals No. 23 (White wire) and No. 24 (Green/Orange wire) at ECM harness connector E5. (Scheme 230) Start engine and let idle. Ensure oscilloscope pattern is as shown in illustration. (Scheme 240) As engine speed is increased, waveform frequency ("A") should lengthen. If waveform pattern is as shown, go to next step. If waveform pattern is not as shown, replace ECM.
4. Check VVT controller assembly for proper operation. See appropriate article in ENGINES. If problem exists, replace VVT controller assembly and go to next step. If problem does not exist, go to next step.
5. With VVT OCV removed, connect a fused jumper wire between positive battery terminal and terminal No. 1 at VVT OCV. (Scheme 241) Connect another jumper wire between negative battery terminal and terminal No. 2 at VVT OCV and note VVT OCV plunger operation. With battery voltage applied, plunger on end of VVT OCV should extend. Disconnect a jumper wire. Without battery voltage applied, plunger should retract. If VVT OCV operates as specified, go to next step. If VVT OCV does not operate as specified, replace VVT OCV and go to next step.
6. Check blockage in VVT OCV. Check oil check valve and oil pipe located under VVT OCV. If problem exists, repair as necessary. If problem does not exist, go to next step.
7. Install remove components all and connect all disconnected harness connectors. Using scan tool, clear DTCs. Start engine and allow it to idle. Turn ignition off. Turn ignition on and check for DTCs. If DTC P1349 is not present, no problem is indicated at this time. DTC may have been set because of a foreign object that was temporarily caught in the engine oil system but after a short time system returned to normal. If DTC P1349 is present, replace ECM.

1. Check stoplight operation. If stoplights do not operate properly, repair as necessary and retest system. See EXTERIOR LIGHTS article in ACCESSORIES & EQUIPMENT. If stoplights operate properly, go to next step.
2. Access ECM in driver's side of engine compartment, next to battery. Turn ignition on. Using DVOM, backprobe ECM harness connector and measure voltage between ground and terminal No. 6 (Green/White wire) at ECM harness connector E3. (Scheme 230) With brake pedal depressed voltage should be 7.5-14.0 volts. With brake pedal released, voltage should be less than 1.5 volts. If voltage is not as specified, go to next step. If voltage is as specified, problem is intermittent. Check component and ECM connections.
3. Check for short in wiring between ECM and stoplight switch. If problem exists, repair wiring as necessary. If problem does not exist, replace ECM.

1. Turn ignition off. Access ECM in driver's side of engine compartment, next to battery. Using DVOM, backprobe ECM harness connector and measure voltage between ground and terminal No. 1 (White wire) at ECM harness connector E2. (Scheme 230) Voltage should be 9-14 volts. If voltage is as specified, replace ECM. If voltage is not as specified, go to next step.
2. Remove and inspect EFI fuse (15-amp). EFI fuse is located in engine room junction box. Replace fuse as necessary. If fuse is okay, check circuit between EFI fuse and ECM. See «WIRING DIAGRAMS»(/toyota/celica/t230-1999-2002/remont/wiring-diagrams-engine-performance/#engine-performance-wiring-diagrams) article. Repair wiring as necessary.

ECM receives the operating condition of A/C system from the A/C ECU. ECM also receives electrical load information from the body ECM over the bus communications system from the instrument cluster. ECM uses this information to control engine idles speed. Possible causes are

1. Defective body ECU.
2. Defective A/C ECU.
3. Bus communications circuit is open or shorted.
4. Defective ECM.

Using scan tool, read freeze frame data. Freeze frame records engine conditions when malfunction is detected.

Information is not available from manufacturer. Check bus communication circuits. See DATA LINK CONNECTORS article in WIRING DIAGRAMS.

1. Connect hand-held tester to Data Link Connector (DLC) NO. 3. (Scheme 231) Using hand-held tester, select ACTIVE TEST mode. Select VVT. Note idle speed when Variable Valve Timing (VVT) Oil Control Valve (OCV) is activated by hand-held tester. If idle speed is normal with VVT OCV off and engine idles rough or stalls when VVT OCV is on, VVT is functioning properly at this time. DTC may have been set because of a foreign object that was temporarily caught in engine oil system but after a short time system returned to normal. If idle speed does not function as specified, go to next step.
2. Start engine and allow it to idle. Disconnect VVT OCV harness connector and note idle speed. Engine idle speed should not change. Using jumper wires, apply battery voltage and ground to VVT OCV terminals. Engine should idle rough or stall. If VVT OCV operates as specified, go to next step. If VVT OCV does not operate as specified, replace VVT OCV.
3. Turn ignition off. Connect VVT OCV harness connector. Access ECM in driver's side of engine compartment, next to battery. Using oscilloscope, backprobe ECM harness connector. Connect oscilloscope between terminals No. 23 (White wire) and No. 24 (Green/Orange wire) at ECM harness connector E5. (Scheme 230) Start engine and let idle. Ensure oscilloscope pattern is as shown in illustration. (Scheme 240) As engine speed is increased, waveform frequency ("A") should lengthen. If waveform pattern is as shown, go to next step. If waveform pattern is not as shown, replace ECM.
4. Check for an open or short in wiring between VVT OCV and ECM. If problem exists, repair wiring as necessary. If problem does not exist, problem is intermittent. Check component and ECM connections.

1. Start engine and allow it to idle. Disconnect Variable Valve Timing (VVT) Oil Control Valve (OCV) harness connector and note idle speed. VVT OCV is located on timing chain side of cylinder head. Engine idle speed should not change. Using jumper wires, apply battery voltage and ground to VVT OCV. Engine should idle rough or stall. If VVT OCV operates as specified, go to next step. If VVT OCV does not operate as specified, replace OCV.
2. Turn ignition off. Connect VVT OCV harness connector. Access ECM in driver's side of engine compartment, next to battery. Using oscilloscope, backprobe ECM harness connector. Connect oscilloscope between terminals No. 23 (White wire) and No. 24 (Green/Orange wire) at ECM harness connector E5. (Scheme 230) Start engine and let idle. Ensure oscilloscope pattern is as shown in illustration. (Scheme 240) As engine speed is increased, waveform frequency ("A") should lengthen. If waveform pattern is as shown, go to next step. If waveform pattern is not as shown, replace ECM.
3. Check for an open or short in wiring between VVT OCV and ECM. If problem exists, repair wiring as necessary. If problem does not exist, problem is intermittent. Check component and ECM connections.

1. Connect hand-held tester to Data Link Connector (DLC) NO. 3. (Scheme 231) Start engine and increase engine speed to 1500-2000 RPM. Using hand-held tester, select ACTIVE TEST mode. Select VVTL. Note engine speed when Variable Valve Lift (VVL) Oil Control Valve (OCV) is activated by hand-held tester. If engine speed is normal with VVL OCV off and engine runs rough or stalls when VVL OCV is on, VVTL is functioning properly at this time. DTC may have been set because of a foreign object that was temporarily caught in the engine oil system but after a short time system returned to normal. If idle speed does not function as specified, go to next step.
2. Increase engine speed to 1500-2000 RPM. Disconnect VVL OCV harness connector and note engine speed. Engine speed should not change. Using jumper wires, apply battery voltage and ground to VVL OCV terminals. Engine should run rough or stall. If VVL OCV operates as specified, go to next step. If VVL OCV does not operate as specified, replace VVL OCV.
3. Check for an open or short in wiring between VVL OCV and ECM. If problem exists, repair wiring as necessary. If problem does not exist, replace ECM.

1. Start engine and increase engine speed to 1500-2000 RPM. Disconnect Variable Valve Lift (VVL) Oil Control Valve (OCV) harness connector and note engine speed. VVL OCV is located on flywheel side of cylinder head. Engine idle speed should not change. Using jumper wires, apply battery voltage and ground to VVL OCV. Engine should run rough or stall. If VVL OCV operates as specified, go to next step. If VVL OCV does not operate as specified, replace VVL OCV.
2. Turn ignition off. Connect VVL OCV harness connector. Access ECM in driver's side of engine compartment, next to battery. Using DVOM, backprobe ECM harness connector and measure voltage between terminals No. 6 (Blue/Black wire) and No. 7 (Blue/White wire) at ECM harness connector E4. (Scheme 230) Start engine and increase engine speed to 6000 RPM. Voltage should be 9-14 volts when engine speed is 6000 RPM or more. If voltage is as specified, go to next step. If voltage is not as specified, replace ECM.
3. Turn ignition off. Check for an open or short in wiring between VVL OCV and ECM. If problem exists, repair wiring as necessary. If problem does not exist, problem is intermittent. Check component and ECM connections.

1. Connect hand-held tester to Data Link Connector (DLC) NO. 3. (Scheme 231) Disconnect oil pressure switch for Variable Valve Lift (VVL) Oil Control Valve (OCV) harness connector. Oil pressure switch for VVL OCV is located on flywheel side of cylinder head. Using hand-held tester, select ACTIVE TEST mode. Check continuity between ground and terminal at oil pressure switch for VVL OCV. Start engine and increase engine speed to 6500 RPM. When VVL OCV is activated by hand-held tester, continuity should exist. When VVL OCV is not activated by hand-held tester, continuity should not exist. If continuity is as specified, go to next step. If continuity is not as specified, replace oil pressure switch for VVL OCV.
2. Turn ignition off. Check continuity between ground and terminal at oil pressure switch for VVL OCV. If continuity does not exist, go to next step. If continuity exists, replace oil pressure switch for VVL OCV.
3. Check for an open or short in wiring between oil pressure switch for VVL OCV and ECM. If problem exists, repair wiring as necessary. If problem does not exist, go to next step.
4. Check oil filter. Check VVL OCV. See «VARIABLE VALVE TIMING (VVT) SYSTEMS»(ref-2892-S00410426782000041400000) in SYSTEM & COMPONENT TESTING - 4-CYLINDER article. If problem exists, repair as necessary. If problem does not exist, go to next step.
5. Check for an open or short in wiring between VVL OCV and ECM. If problem exists, repair wiring as necessary. If problem does not exist, replace ECM.

Note. Toyota hand-held tester can be used to confirm PNP switch signal from CURRENT DATA.

1. Access ECM in driver's side of engine compartment, next to battery. Turn ignition on. Using DVOM, backprobe and measure voltage between ground and specified terminal at appropriate ECM harness connector. See «PARK/NEUTRAL POSITION SWITCH VOLTAGE»(ref-3781-S14048506762000051600000) table. (Scheme 230) If voltage is as specified, no problem is indicated at this time. If voltage is not as specified, go to next step. PARK/NEUTRAL POSITION SWITCH VOLTAGE Shift Lever Position Terminal No. Volts Park (1) 2 Zero (2) 8 Zero (2) 9 Zero (2) 19 Zero (2) 20 9-14 (1) 24 Zero Reverse (1) 2 (3) 9-14 (2) 8 Zero (2) 9 Zero (2) 19 Zero (2) 20 Zero (1) 24 Zero Neutral (1) 2 Zero (2) 8 9-14 (2) 9 Zero (2) 19 Zero (2) 20 Zero (1) 24 Zero Drive (1) 2 Zero (2) 8 Zero (2) 9 Zero (2) 19 Zero (2) 20 Zero (1) 24 9-14 2 (1) 2 Zero (2) 8 Zero (2) 9 Zero (2) 19 9-14 (2) 20 Zero (1) 24 Zero Low (1) 2 Zero (2) 8 Zero (2) 9 9-14 (2) 19 Zero (2) 20 Zero (1) 24 Zero (1) Measure voltage between ground and terminal listed, at ECM harness connector E3. (Scheme 230) (2) Measure voltage between ground and terminal listed, at ECM harness connector E4. (Scheme 230) (3) Voltage may be slightly less due to lighting of reverse lights.
2. Disconnect PNP switch harness connector. Check continuity between appropriate PNP switch terminals (component side) with shift lever in appropriate position. See «PARK/NEUTRAL POSITION SWITCH CONTINUITY»(ref-3781-S14576862902000051600000) table. (Scheme 242) If problem exists, replace PNP switch. If problem does not exist, go to next step. PARK/NEUTRAL POSITION SWITCH CONTINUITY Shift Lever Position Continuity Between Terminals No. Park 1 & 3; 6 & 9 Reverse 2 & 3 Neutral 3 & 5; 6 & 9 Drive 3 & 7 2 3 & 4 Low 3 & 8
3. Check wiring between battery and PNP switch. Check wiring between PNP switch and ECM. See «WIRING DIAGRAMS»(/toyota/celica/t230-1999-2002/remont/wiring-diagrams-engine-performance/#engine-performance-wiring-diagrams) article. If problem exists, repair wiring as necessary. If problem does not exist, replace ECM.

Scheme 242

See also:
• WIRING DIAGRAMS