Engine Control System & Engine Component Tests: Diagnosis Chevrolet Tracker II

Fuel Injector Balance Test

Note. Allow engine to cool down to avoid irregular reading due to "hot soak" condition. To prevent flooding, the fuel injector balance test should not be performed more than once without starting and running engine.

Note. If injectors are dirty, they should be cleaned using approved injector cleaning procedure before performing fuel injector balance test.

1. If powertrain diagnostic system check has been performed, go to next step. If powertrain diagnostic system check has been performed, perform powertrain diagnostic system check. See POWERTRAIN DIAGNOSTIC SYSTEM CHECK under SELF-DIAGNOSTIC SYSTEM in appropriate SELF-DIAGNOSTICS article.
2. If fuel injector coil test has been performed, go to next step. If fuel injector coil test has not been performed, perform fuel injector coil test. See «INJECTOR COIL TEST - ECT IS 50-95°F (2.0L)»(ref-128963-S05701188392001110800000) or «INJECTOR COIL TEST (2.5L)»(ref-128963-S17381326472001110900000) . Go to next step.
3. If engine coolant temperature is greater than 201°F (94°C), go to next step. If engine coolant temperature is less than 201°F (94°C), go to step 5 .
4. Allow engine to cool to less than 201°F (94°C) and go to next step.
5. Install fuel pressure gauge. Turn ignition on, and then off to energize fuel pump. Place fuel pressure gauge bleed hose into a container. Bleed air from fuel pressure gauge. Turn ignition on, and then off to energize fuel pump again. Observe fuel pressure gauge reading. If fuel pressure reading is 39-45 psi (2.7-3.2 kg/cm 2 ), go to next step. If fuel pressure reading is not 39-45 psi (2.7-3.2 kg/cm 2 ), perform fuel system diagnosis. See appropriate BASIC DIAGNOSTIC PROCEDURES article.
6. Disconnect fuel injectors harness connector. Using appropriate fuel injector adapter, connect Fuel Injector Tester (J-39021) to fuel injector. Connect fuel injector tester power leads to appropriate battery terminals. Set amperage supply selector switch on fuel injector tester to Balance Test 0.5-2.5-amp position. Turn ignition on, and then off. Record fuel pressure reading (first reading). Energize injector by depressing PUSH TO START TEST button on injector tester and hold until fuel pressure gauge stabilizes. Record fuel pressure reading (second reading). Subtract first reading from second reading (this result is pressure drop value). Add pressure drop value for each injector together and divide total by total number of injectors. If any injector's drop value is greater or less than average drop value by 1.5 psi (0.10 kg/cm), replace faulty injector(s) as necessary. If no injector's drop value is greater or less than average drop value by 1.5 psi (0.10 kg/cm), repair by symptom. See appropriate TROUBLE SHOOTING - NO CODES article.

Fuel Injector Circuit Diagnosis

1. If powertrain diagnostic system check has been performed, go to next step. If powertrain diagnostic system check has been performed, perform powertrain diagnostic system check. See POWERTRAIN DIAGNOSTIC SYSTEM CHECK under SELF-DIAGNOSTIC SYSTEM in appropriate SELF-DIAGNOSTICS article.
2. Turn ignition off. Disconnect all fuel injector harness connectors. Install Fuel Injector Test Light (J-34730-2B) to each fuel injector harness connector one at a time. Observe injector test light for each injector while cranking engine. If injector test light flashes for each injector while cranking engine, perform fuel injector coil test. See «INJECTOR COIL TEST - ECT IS 50-95°F (2.0L)»(ref-128963-S05701188392001110800000) or «INJECTOR COIL TEST (2.5L)»(ref-128963-S17381326472001110900000) . If injector test light does not flash for each injector while cranking engine, go to next step.
3. If injector test light remained illuminated for any injector while cranking engine, go to next step. If injector test light does not remain illuminated for any injector while cranking engine, go to step 5 .
4. Check for short to ground in faulty fuel injector control circuit between fuel injector and PCM. See WIRING DIAGRAMS article. If problem exists, repair as necessary and go to step 11 . If problem does not exist, go to step 10 .
5. Remove fuel injector test light from fuel injector harness connector. Connect a test light between ground and ignition feed circuit of fuel injector harness that did not flash. See WIRING DIAGRAMS article. Turn ignition on, engine off. If test light illuminates, go to next step. If test light does not illuminate, go to step 8 .
6. Connect a test light between battery voltage and fuel injector control circuit of fuel injector harness that did not flash. See WIRING DIAGRAMS article. Observe test light while cranking engine. If test light flashes while cranking engine, go to next step. If test light does not flash while cranking engine, go to step 9 .
7. Repair poor connections at fuel injector harness connector. After repairs, go to step 11 .
8. Repair open in ignition feed circuit between fuel injector and main relay. After repairs, go to step 11 .
9. Check for open in faulty fuel injector control circuit. If problem exists, repair as necessary and repeat test procedure beginning at step 2 until test light flashes for all injectors. After repairs, go to step 11 . If a circuit malfunction does not exist and test light does not flash at all injectors, go to next step.
10. Replace PCM. After repairs, go to next step.
11. Operate vehicle within conditions under which original symptom was observed. If system operates properly, system is okay. If system does not operate properly, check for contaminated fuel, faulty injector spray pattern, leaking or stuck closed injector, poor connections or terminals in wiring harness connectors.

Injector Coil Test - ECT Is 50-95°F (2.0L)

1. If powertrain diagnostic system check has been performed, go to next step. If powertrain diagnostic system check has been performed, perform powertrain diagnostic system check. See POWERTRAIN DIAGNOSTIC SYSTEM CHECK under SELF-DIAGNOSTIC SYSTEM in appropriate SELF-DIAGNOSTICS article.
2. Using scan tool, check engine coolant temperature. If scan tool displays 50-95°F (10-35°C), go to next step. If scan tool does not display 50-95°F (10-35°C), see «INJECTOR COIL TEST - ECT IS NOT 50-95°F»(ref-128963-S42903018022001110800000) .
3. Turn ignition off. Relieve fuel pressure. Disconnect fuel injector harness connectors. Using fuel injector adapter, connect Fuel Injector Tester (J-39021) to fuel injector. Connect fuel injector tester power leads to appropriate battery terminals. Set amperage supply selector switch on fuel injector tester to Coil Test 0.5-amp position. Connect DVOM to injector tester. Depress PUSH TO START TEST button on injector tester. Record lowest voltage reading within first second of test. If any injector has erratic voltage reading or reading is not 6.5-8.0 volts, go to next step. If no injector has erratic voltage reading or reading is not 6.5-8.0 volts, perform fuel injector balance test. See «FUEL INJECTOR BALANCE TEST»(ref-128963-S25983683002001110800000) .
4. Replace faulty injector(s) and perform fuel injector balance test. See «FUEL INJECTOR BALANCE TEST»(ref-128963-S25983683002001110800000) .

Injector Coil Test - ECT Is Not 50-95°F (2.0L)

1. If powertrain diagnostic system check has been performed, go to next step. If powertrain diagnostic system check has been performed, perform powertrain diagnostic system check. See POWERTRAIN DIAGNOSTIC SYSTEM CHECK under SELF-DIAGNOSTIC SYSTEM in appropriate SELF-DIAGNOSTICS article.
2. Install scan tool. Using scan tool, check engine coolant temperature. If scan tool does not display 50-95°F (10-35°C), go to next step. If scan tool displays 50-95°F (10-35°C), see «INJECTOR COIL TEST - ECT IS 50-95°F (2.0L)»(ref-128963-S05701188392001110800000) .
3. Turn ignition off. Relieve fuel pressure. Disconnect fuel injector harness connectors. Using fuel injector adapter, connect Fuel Injector Tester (J-39021) to fuel injector. Connect fuel injector tester power leads to appropriate battery terminals. Set amperage supply selector switch on fuel injector tester to Coil Test 0.5-amp position. Connect DVOM to injector tester. Depress PUSH TO START TEST button on injector tester. Record highest voltage reading other than those greater than 9.5 volts. Subtract any other voltage reading observed from highest voltage reading. If difference is greater than one volt, go to next step. If difference is not greater than one volt, perform fuel injector balance test. See «FUEL INJECTOR BALANCE TEST»(ref-128963-S25983683002001110800000) .
4. Replace any injector(s) with an initial reading greater than 9.5 volts, erratic reading or difference greater than 0.6 volt. After repairs, perform fuel injector balance test. See «FUEL INJECTOR BALANCE TEST»(ref-128963-S25983683002001110800000) .

Injector Coil Test (2.5L)

1. If powertrain diagnostic system check has been performed, go to next step. If powertrain diagnostic system check has been performed, perform powertrain diagnostic system check. See POWERTRAIN DIAGNOSTIC SYSTEM CHECK under SELF-DIAGNOSTIC SYSTEM in appropriate SELF-DIAGNOSTICS article.
2. Using scan tool, check engine coolant temperature. Ensure scan tool displays 50-95°F (10-35°C) before performing test, then go to next step.
3. Turn ignition off. Relieve fuel pressure. Disconnect fuel injector harness connectors. Using fuel injector adapter, connect Fuel Injector Tester (J-39021) to fuel injector. Connect fuel injector tester power leads to appropriate battery terminals. Set amperage supply selector switch on fuel injector tester to Coil Test 0.5-amp position. Connect DVOM to injector tester. Depress PUSH TO START TEST button on injector tester. Record lowest voltage reading within first second of test. If any injector has erratic voltage reading or reading is not 4.5-7.0 volts, go to next step. If no injector has erratic voltage reading or reading is not 4.5-7.0 volts, perform fuel injector balance test. See «FUEL INJECTOR BALANCE TEST»(ref-128963-S25983683002001110800000) .
4. Replace faulty injector(s) and perform fuel injector balance test. See «FUEL INJECTOR BALANCE TEST»(ref-128963-S25983683002001110800000) .

ELECTRICAL/ACCESSORY LOAD IDLE-UP CIRCUIT DIAGNOSIS

1. If powertrain diagnostic system check has been performed, go to next step. If powertrain diagnostic system check has been performed, perform powertrain diagnostic system check. See POWERTRAIN DIAGNOSTIC SYSTEM CHECK under SELF-DIAGNOSTIC SYSTEM in appropriate SELF-DIAGNOSTICS article.
2. Start and warm engine to normal operating temperature. Turn off all accessories. Using scan tool, monitor engine RPM and IAC duty cycle while turning each of the following accessories on and off: Headlights HVAC blower motor Rear window defogger If scan tool indicates increase in IAC duty cycle when each accessory is turned on, go to next step. If scan tool does not indicate increase in IAC duty cycle when each accessory is turned on, go to step 20 .
3. Turn all accessories off. Turn A/C switch to ON position and blower speed selector switch to any position except OFF. Using scan tool, monitor engine RPM and the IAC duty cycle while operating A/C system. If IAC duty cycle increases when A/C compressor in operating, go to next step. If IAC duty cycle does not increase when A/C compressor in operating, go to step 10 .
4. Turn all accessories off. Using scan tool, monitor engine RPM and IAC duty cycle while turning steering wheel fully right and left. If IAC duty cycle increases when turning steering wheel fully right and left, see appropriate TROUBLE SHOOTING - NO CODES article. If IAC duty cycle does not increase, go to next step.
5. Turn all accessories off. Using scan tool, monitor power steering switch. Turn steering wheel fully right and left. If scan tool indicates high pressure when steering wheel was turned fully in either direction, see «IDLE AIR CONTROL SYSTEM DIAGNOSIS»(ref-128963-S36448754902001110800000) . If high pressure is not indicated when steering wheel was turned fully in either direction, go to next step.
6. Turn ignition on, engine off. Disconnect Power Steering Pump (PSP) switch connector. Using DVOM, measure voltage from PSP switch connector (harness side) to ground. See WIRING DIAGRAMS article. If about battery voltage exists, go to next step. If about battery voltage does not exist, go to step 8 .
7. Connect a test light to battery voltage. Probe PSP switch connector (switch side) with test light. Start engine. Observe test light while turning steering wheel fully to right and left. If test light illuminates when steering wheel was turned fully in either direction, go to «DIAGNOSTIC AIDS»(ref-128963-S23982083252001110900000) . If test light does not illuminate when steering wheel was turned fully in either direction, go to step 9 .
8. Check for open or short to ground in PSP circuit between PCM connector C2 terminal No. 7 (Blue/Orange wire) on 2.0L or PCM connector C1 terminal No. 26 (Blue/Orange wire) on 2.5L and PSP switch. Repair as necessary. After repairs, go to step 30 . If circuit is okay, go to step 29 .
9. Check for poor ground connection at power steering pump. Repair as necessary. After repairs, go to step 30 . If circuit is okay, go to step 28 .
10. Using scan tool, monitor A/C relay command. Turn A/C switch to ON position and blower speed selector switch to any position except OFF. If scan tool indicates ON when A/C compressor is operating, see «IDLE AIR CONTROL SYSTEM DIAGNOSIS»(ref-128963-S36448754902001110800000) . If scan tool does not indicate ON when A/C compressor is operating, go to next step.
11. Start engine. Turn A/C on. Using DVOM connected to ground, backprobe A/C ON circuit at PCM connector C1 terminal No. 17 (Yellow/Black wire) on 2.0L or PCM connector C2 terminal No. 27 (Yellow/Black wire) on 2.5L. If voltage is zero, go to next step. If voltage is not zero, go to step 14 .
12. Start engine. Turn A/C off. Using DVOM connected to ground, backprobe A/C idle-up circuit at PCM connector C1 terminal No. 17 (Yellow/Black wire) on 2.0L or PCM connector C2 terminal No. 27 (Yellow/Black wire) on 2.5L. If battery voltage exists on 2.0L or 4.5-5.0 volts exists on 2.5L, go to step 15 . If voltage is not as specified, go to next step.
13. Turn ignition off. Disconnect PCM connector C1. Back out terminal No. 17 (Yellow/Black wire) on 2.0L or terminal No. 27 (Yellow/Black wire) on 2.5L (A/C idle-up signal wire) from PCM connector. Reconnect PCM connector C1. Turn ignition on, engine off. Using DVOM connected to ground, backprobe through PCM connector slot to PCM terminal to ground. Measure voltage. If battery voltage exists on 2.0L or 4.5-5.0 volts exists on 2.5L, go to next step. If voltage is not as specified, go to step 29 .
14. Check for open or a short in A/C idle up circuit between PCM and A/C compressor control module. Repair as necessary. After repairs, go to step 30 . If circuit is okay, go to step 19 .
15. Start engine. Turn A/C off. Using DVOM connected to ground, backprobe A/C cut-out circuit at PCM connector C1 terminal No. 8 (Gray/White wire) on 2.0L or PCM connector C1 terminal No. 28 (Gray/White wire) on 2.5L. If voltage does not exist, go to next step. If voltage exists, go to step 29 .
16. Start engine. Turn A/C on (A/C operating). Using DVOM connected to ground, backprobe A/C cut-out circuit at PCM connector C1 terminal No. 8 (Gray/White wire) on 2.0L or PCM connector C1 terminal No. 28 (Gray/White wire) on 2.5L. If battery voltage exists, go to «DIAGNOSTIC AIDS»(ref-128963-S23982083252001110900000) . If battery voltage does not exist, go to next step.
17. Check for open or short to ground in A/C cut-out circuit between PCM and A/C compressor control module. Repair as necessary. After repairs, go to step 30 . If circuit is okay, go to next step.
18. Disconnect A/C compressor control module connector. Turn ignition on, engine off. Using DVOM, measure voltage at A/C compressor control module connector terminal No. 5 and ground. If battery voltage exists, go to step 29 . If battery voltage does not exist, go to next step.
19. A/C compressor control module is malfunctioning. Inspect A/C compressor control module and circuits for a fault. See appropriate MANUAL A/C-HEATER SYSTEMS article in AIR CONDITIONING & HEATING. Repair as necessary. After repairs, go to step 30 .
20. If scan tool indicated an increase in IAC duty cycle when HVAC blower motor was turned on, go to step 22 . If scan tool did not indicate an increase in IAC Motor Command when HVAC blower motor was turned on, go to next step.
21. Turn ignition off. Disconnect PCM connectors. Turn ignition on, engine off. Using test light connected to battery voltage, probe harness side of HVAC Blower Idle-Up circuit PCM connector C1 terminal No. 16 (Pink/White wire) on 2.0L or PCM connector C1 terminal No. 13 (Pink/White wire) on 2.5L. Observe test light while operating HVAC blower motor switch. If test light illuminates when HVAC blower motor switch is turned to ON position, go to step 29 . If test light does not illuminate when HVAC blower motor switch is turned to ON position, go to step 25 .
22. If scan tool indicated an increase in IAC duty cycle when rear window defogger switch was turned to ON position, go to next step. If scan tool did not indicate an increase in IAC duty cycle when rear window defogger switch was turned to ON position, go to step 24 .
23. Using test light connected to ground, backprobe taillight idle-up circuit at PCM connector C1 terminal No. 32 (Red/Yellow wire) on 2.0L or PCM connector C1 terminal No. 29 (Red/Yellow wire) on 2.5L. Observe test light while operating headlight switch. If test light illuminates when headlight switch is turned to ON position, go to step 29 . If test light does not illuminate when headlight switch is turned to ON position, go to step 26 .
24. Using test light connected to ground, backprobe rear defogger idle-up circuit at PCM connector C1 terminal No. 15. Observe test light while operating rear defogger switch. If test light illuminates when rear defogger switch is turned to ON position, go to step 29 . If test light does not illuminate when rear defogger switch is turned to ON position, go to step 27 .
25. Check for correct operation of HVAC blower circuit. See appropriate MANUAL A/C-HEATER SYSTEMS article in AIR CONDITIONING & HEATING. Check HVAC blower idle-up signal circuit for open or short. Repair as necessary. After repairs, go to step 30 . If all HVAC circuits are okay, go to step 29 .
26. Check for correct operation of exterior lighting. See EXTERIOR LIGHTS article in ACCESSORIES & EQUIPMENT. Check for open or short in taillight idle-up circuit. Repair as necessary. After repairs, go to step 30 . If all exterior light circuits are okay, go to step 29 .
27. Check for correct operation of rear defogger. Check for open or short rear defogger idle-up circuit. See appropriate REAR WINDOW DEFOGGERS article in ACCESSORIES & EQUIPMENT. Repair as necessary. After repairs, go to step 30 . If all rear window defogger circuits are okay, go to step 29 .
28. Replace PSP switch. After repairs, go to step 30 .
29. Replace PCM. After repairs, go to next step.
30. Operate vehicle within conditions under which original symptom was observed. System should operate properly. If system does not operate properly, see «DIAGNOSTIC AIDS»(ref-128963-S23982083252001110900000) .

Diagnostic Aids

Check for any of the following conditions

1. High electrical load parameter on scan tool can indicate if PCM has received rear defogger or parking lamps on signal. Scan tool should indicate YES when rear defogger or parking lamps are turned on and engine speed should increase slightly. Check for fault in IAC system or short to ground in diagnostic request circuit if engine speed does not increase.
2. Malfunctioning taillight circuit may cause erratic performance of electrical load idle-up circuit.
3. Shorted PSP switch can cause engine idle speed to remain high even when driving straight ahead.
4. Incorrectly calibrated PSP switch can cause engine idle speed to remain low when steering pump hydraulic pressure is high.
5. Faulty ground for PSP switch can cause erratic switch operation. Ensure power steering pump and bracket are secure, insuring a good ground path. Check PSP switch for tight installation.
6. Scan tool will display A/C relay command on when air conditioning control is turned on, blower switch is on, and A/C compressor is operating.
7. Observe IAC duty cycle on scan tool while operating A/C. IAC duty cycle should increase 4 to 12 percent when A/C compressor is engaged. If scan tool indicates IAC duty cycle is increasing, but idle quality is unsatisfactory, inspect IAC system for proper operation.
8. Check for a poor connection, rubbed-through wire insulation, or a wire broken inside insulation. Inspect PCM harness connector for backed-out terminals, improper mating, improperly formed or damaged terminals, poor terminal-to-wire connection and damaged harness.

IDLE AIR CONTROL SYSTEM DIAGNOSIS

1. If powertrain diagnostic system check has been performed, go to next step. If powertrain diagnostic system check has been performed, perform powertrain diagnostic system check. See POWERTRAIN DIAGNOSTIC SYSTEM CHECK under SELF-DIAGNOSTIC SYSTEM in appropriate SELF-DIAGNOSTICS article.
2. If DTC P0505 is present or pending, see appropriate SELF-DIAGNOSTICS article. If DTC P0505 is not present or pending, go to next step.
3. Start and warm engine to normal operating temperature. Using scan tool, observe IAC duty cycle. If IAC duty cycle is 10-30 percent at 700-800 RPM in Park or Neutral, go to step 5 . If IAC duty is not 10-30 percent at 700-800 RPM in Park or Neutral, go to next step.
4. Start and warm engine to normal operating temperature. Select RPM control, under IAC system, in SPECIAL FUNCTIONS menu of scan tool. Command IAC valve to increase and decrease engine RPM. If engine RPM increases and decreases as commanded, go to next step. If engine RPM does not increase or decrease as commanded, go to step 8
5. Start engine. Place transmission in Park or Neutral. Operate headlights, HVAC blower motor (AC off) and rear window defogger (if equipped) one at a time, while observing engine RPM and IAC duty cycle on scan tool. If engine stays within 700-800 RPM and IAC duty cycle increases 2 to 3 percent, go to next step. If engine RPM and IAC duty cycle are not as specified, see «ELECTRICAL/ACCESSORY LOAD IDLE-UP CIRCUIT DIAGNOSIS»(ref-128963-S42647317112001110800000) .
6. Turn HVAC blower motor and AC on (if equipped). If engine RPM is 750-850 RPM and IAC duty cycle increases 4 to 12 percent, go to next step. If engine RPM and IAC duty cycle are not as specified, see «ELECTRICAL/ACCESSORY LOAD IDLE-UP CIRCUIT DIAGNOSIS»(ref-128963-S42647317112001110800000) .
7. Turn all accessories off. Ensure engine is at normal operating temperature. Using scan tool, observe engine RPM and IAC duty cycle. If engine RPM is 700-800 RPM and IAC duty cycle is 10-30 percent system is okay. If engine RPM and IAC duty cycle are not as specified, see TROUBLE SHOOTING - NO CODES article.
8. Turn off ignition and disconnect IAC valve connector. On 2.0L models, measure resistance between the following IAC valve terminals. See WIRING DIAGRAMS article. Terminals No. 1 (Purple/Black wire) and No. 2 (Blue/Black wire). Terminals No. 3 (Light Green/Black wire) and No. 2 (Blue/Black wire). Terminals No. 4 (Gray/Blue wire) and No. 5 (Blue/Black wire). Terminals No. 6 (Purple/Yellow wire) and No. 5 (Blue/Black wire). If resistance is 35-43 ohms at 68°F (20°C), go to next step. If resistance is not 35-43 ohms, go to step 15 . On 2.5L models, measure resistance between the following IAC valve terminals. See WIRING DIAGRAMS article. Terminals No. 1 (Gray/Blue wire) and No. 2 (Blue/Black wire). Terminals No. 3 (Light Green/Black wire) and No. 2 (Blue/Black wire). Terminals No. 4 (Purple/Yellow wire) and No. 5 (Blue/Black wire). Terminals No. 6 (Purple/Black wire) and No. 5 (Blue/Black wire). If resistance is 21-23 ohms at 68°F (20°C), go to next step. If resistance is not 21-23 ohms, go to step 15 .
9. Turn ignition on, engine off. Disconnect IAC valve connector. Using test light connected to ground, probe IAC valve connector (harness side) terminals No. 2 (Blue/Black wire) and No. 5 (Blue/Black wire). If test light illuminates on both circuits, go to next step. If test light does not illuminate on both circuits, go to step 12 .
10. Turn ignition off. Reconnect IAC valve connector. Disconnect PCM connector C4. Turn ignition on, engine off. On 2.0L models, measure voltage at PCM connector C4 terminals No. 3 (Light Green/Black wire), No. 10 (Purple/Yellow wire), No. 11 (Gray/Blue wire) and No. 12 (Purple/Black wire). On 2.5L models, measure voltage at PCM connector C4 terminals No. 14 (Purple/Black wire), No. 15 (Light Green/Black wire), No. 24 (Purple/Yellow wire) and No. 25 (Gray/Blue wire). If about battery voltage exists at all terminals, go to next step. If about battery voltage does not exist at all terminals, go to step 13 .
11. Turn ignition off. Reconnect PCM connector C4. Start and warm engine to normal operating temperature. On 2.0L models, using DVOM connected to ground, backprobe PCM connector C4 terminals No. 3 (Light Green/Black wire), No. 10 (Purple/Yellow wire), No. 11 (Gray/Blue wire) and No. 12 (Purple/Black wire) and on 2.5L models, measure voltage at PCM connector C4 terminals No. 14 (Purple/Black wire), No. 15 (Light Green/Black wire), No. 24 (Purple/Yellow wire) and No. 25 (Gray/Blue wire). Observe voltage display on DVOM for each IAC coil control circuit while increasing and decreasing engine RPM with scan tool RPM control function. If voltage of each circuit changes from high to low with increase and decrease in engine RPM, go to step 14 . If voltage of each circuit does not change from high to low with increase and decrease in engine RPM, go to step 16 .
12. Repair high resistance or open in ignition voltage circuit. See WIRING DIAGRAMS article. After repairs, go to step 17 .
13. Repair open, short to ground or high resistance in any IAC coil control circuit that did not measure battery voltage. After repairs, go to step 17 .
14. Remove IAC valve. Inspect idle air passage for restrictions or blockage. Repair as necessary. After repairs, go to step 17 . If idle air passages are not restricted, go to next step.
15. Replace IAC valve. After repairs, go to step 17 .
16. Replace PCM. After repairs, go to next step.
17. Operate vehicle within conditions under which original symptom was observed. Using scan tool, retrieve DTCs. If no DTCs are set, system is okay. If any DTCs are set, perform appropriate DTC test. See appropriate SELF-DIAGNOSTICS article.

EVAP Canister Purge System Diagnosis

1. Start engine (cold). Disconnect purge hose from EVAP canister. Place finger over end of disconnected hose and check for vacuum. Vacuum should not be felt with engine below normal operating temperature. If vacuum exists, check vacuum hose routing for proper installation. If vacuum does not exist, go to next step.
2. Reconnect purge hose to EVAP canister. Warm engine to normal operating temperature. Disconnect purge hose from EVAP canister. Place finger over end of disconnected hose and check for vacuum. Vacuum should be felt with engine running at normal operating temperature.

EVAP Canister Purge Valve Diagnosis (2.0L)

1. Disconnect electrical connector from EVAP canister purge valve.
2. Using a DVOM, measure resistance of EVAP canister purge valve. Resistance should be 28-36 ohms at 68°F (20°C).
3. Replace EVAP canister purge valve if resistance is not 28-36 ohms at 68°F (20°C). If the resistance is within specification, go to next step.
4. Disconnect purge valve vacuum hoses from intake manifold and vacuum pipe from EVAP canister.
5. Blow air into purge valve vacuum hose that was disconnected from the vacuum pipe. Air should NOT pass through EVAP canister purge valve and exit from intake manifold hose. (Scheme 12)
6. Connect 12 volts to EVAP canister purge valve terminals.
7. Blow air into purge valve vacuum hose that was disconnected from EVAP canister. Air should pass through EVAP canister purge valve and exit from intake manifold hose.
8. Replace EVAP canister purge valve if valve failed inspection.
9. Connect purge valve vacuum hoses and electrical connector.

Scheme 12

EVAP Canister Purge Valve Diagnosis (2.5L)

1. Disconnect electrical connector from EVAP canister purge valve.
2. Using a DVOM, measure resistance of EVAP canister purge valve. Resistance should be 28-36 ohms at 68°F (20°C).
3. Replace EVAP canister purge valve if resistance is not 28-36 ohms at 68°F (20°C). If the resistance is within specification, go to next step.
4. Disconnect purge valve vacuum hoses.
5. Blow air into lower port of purge valve. Air should NOT pass through EVAP canister purge valve and exit from upper port. (Scheme 13)
6. Connect 12 volts DC to EVAP canister purge valve terminals. (Scheme 13)
7. Blow air into lower port of purge valve. Air should pass through EVAP canister purge valve and exit from upper port.
8. Replace EVAP canister purge valve if valve failed inspection.
9. Connect purge valve vacuum hoses and electrical connector.

Scheme 13

EVAP Canister Diagnosis

Disconnect vacuum hoses from EVAP canister. Blow air into bottom vacuum port. Air should escape from both top vacuum ports. If EVAP canister does not operate as described, replace EVAP canister.

EVAP Canister Vent Solenoid Diagnosis (2.0L)

1. Remove EVAP canister vent valve. (Scheme 14)
2. Using DVOM, measure resistance between terminals of EVAP canister vent valve. Resistance should be 25-30 ohms at 68°F (20°C).
3. Replace EVAP canister vent valve if resistance is not 25-30 ohms at 68°F (20°C). If resistance is within specification, go to next step.
4. Disconnect EVAP canister vent valve hose from EVAP canister.
5. Blow air into vent valve hose that was disconnected from EVAP canister. Air should pass through EVAP canister vent valve
6. Connect 12 volts to terminals of EVAP canister vent valve. (Scheme 14)
7. Blow air into vent valve vacuum hose that was disconnected from EVAP canister. Air should not pass through vent valve and exit from other end.
8. Replace EVAP canister vent valve if vent valve failed inspection.
9. Connect vent valve vacuum hoses and electrical connector.

Scheme 14

EVAP Canister Vent Solenoid Diagnosis (2.5L)

1. Remove EVAP canister vent valve.
2. Using DVOM, measure resistance between terminals of EVAP canister vent valve. Resistance should be 25-30 ohms at 68°F (20°C). (Scheme 15)
3. Replace EVAP canister vent valve if resistance is not 25-30 ohms at 68°F (20°C). If resistance is within specification, go to next step.
4. Blow air into vent valve port that was connected to EVAP canister air filter. Air should pass through EVAP canister vent valve.
5. Connect 12 volts to terminals of EVAP canister vent valve. (Scheme 15)
6. Blow air into vent valve port that was connected to EVAP canister air filter. Air should not pass through vent valve and exit from other end.
7. Replace the EVAP canister vent valve if vent valve failed inspection.

Scheme 15

EVAP Tank Pressure Control Solenoid Vacuum Valve Diagnosis (2.0L)

1. Disconnect EVAP tank pressure control solenoid vacuum valve harness connector. Using DVOM, measure resistance between EVAP tank pressure control solenoid vacuum valve terminals. If resistance is 28-36 ohms at 68°F (20°C), go to next step. If resistance is not as specified, replace EVAP tank pressure control solenoid vacuum valve.
2. Disconnect EVAP tank pressure control solenoid vacuum valve vacuum hoses from intake manifold and vacuum pipe (fuel tank pressure control valve). Blow air into vacuum hose that was disconnected from vacuum pipe. (Scheme 16) Air should not flow through EVAP tank pressure control solenoid vacuum valve and exit intake manifold port. Apply battery voltage and ground across EVAP tank pressure control solenoid vacuum valve terminals. Blow air into vacuum hose that was disconnected from vacuum pipe. Air should flow through EVAP tank pressure control solenoid vacuum valve and exit intake manifold port. If operation is as specified, check EVAP tank pressure control solenoid vacuum valve harness for open or short. Repair as necessary. If operation is not as specified, replace EVAP tank pressure control solenoid vacuum valve.

Scheme 16

Fuel Tank Pressure Control Valve Diagnosis (2.0L)

1. Connect a length of hose to fuel tank pressure control valve vacuum port marked TANK. (Scheme 17) Blow hard into hose. Air should slowly escape through fuel tank pressure control valve vacuum port marked CAN. Go to next step.
2. Remove hose from TANK port and connect to CAN port. (Scheme 17) Blow easily into hose. Air should escape through fuel tank pressure control valve vacuum port marked TANK. Go to next step.
3. Connect a hand-held vacuum pump to fuel tank pressure control valve vacuum port and apply vacuum. (Scheme 17) With vacuum applied, blow into port marked TANK. Air should slowly escape through fuel tank pressure control valve vacuum port marked CAN. If operation is not as specified, replace fuel tank pressure control valve.

Scheme 17

Fuel Tank Pressure Control Valve Diagnosis (2.5L)

1. Connect hose to fuel tank side of pressure control valve on fuel tank. (Scheme 18)
2. Blow hard into hose. Some air should pass through valve from fuel tank side to canister side when blown hard.
3. Remove hose from fuel tank side and connect hose to canister side of pressure control valve.
4. Blow easily into hose. Even lightly blown air should pass smoothly through valve from canister side to fuel tank side.
5. Replace pressure control valve if valve fails any checks.

Scheme 18

Fuel Tank Pressure Sensor Diagnosis

A malfunction in fuel tank pressure sensor, or circuit can set DTCs P0450 and P0451. For testing procedures with DTC set, see appropriate SELF-DIAGNOSTICS article.

POWER STEERING PRESSURE SWITCH CIRCUIT DIAGNOSIS

1. If powertrain diagnostic system check has been performed, go to next step. If powertrain diagnostic system check has been performed, perform powertrain diagnostic system check. See POWERTRAIN DIAGNOSTIC SYSTEM CHECK under SELF-DIAGNOSTIC SYSTEM in appropriate SELF-DIAGNOSTICS article.
2. Start and warm engine to normal operating temperature. Turn off all accessories. Using scan tool, monitor PSP switch. Turn steering wheel all the way to the right, and then all the way to the left. If scan tool indicates ON when steering wheel is turned all the way in either direction, PSP switch is operating properly. If scan tool does not indicate ON when steering wheel is turned all the way in either direction, go to next step.
3. Turn ignition on, engine off. Disconnect PSP switch connector. Using DVOM, measure voltage between ground and PSP switch connector terminal (harness side). If battery voltage exists, go to next step. If battery voltage does not exist, go to step 5 .
4. Using a test light connected to battery voltage, probe PSP switch connector terminal (component side). Start engine. Observe test light while turning steering wheel all the way to the right, and then all the way to the left. If test light illuminates when steering wheel is turned all the way in either direction, check for shorted PSP switch, incorrectly calibrated PSP switch or faulty ground in PSP switch. If test light does not illuminate when steering wheel is turned all the way in either direction, go to step 6 .
5. Check for open or short to ground in PSP switch signal circuit between PSP switch and PCM. See WIRING DIAGRAMS article. If problem exists, repair as necessary and go to step 9 . If problem does not exist, go to step 8 .
6. Check for a poor ground connection at power steering pump. If problem exists, repair as necessary and go to step 9 . If problem does not exist, go to next step.
7. Replace PSP switch. After repairs, go to step 9 .
8. Replace PCM. After repairs, go to next step.
9. Operate vehicle within conditions under which original symptom was observed. System should operate properly. If system does not operate properly, check for shorted PSP switch, incorrectly calibrated PSP switch or faulty ground in PSP switch.