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Engine Controls - Self-Diagnostics - 2.0: Diagnosis Infiniti G20 II

Testing & Diagnostics 5 illustrations ~7342 words

DTC Confirmation Test "A"

Malfunction is detected when ECM receives an excessively high voltage from MAF sensor when engine is not running. Possible causes are

  1. MAF sensor circuit open or shorted.
  2. Defective MAF sensor.

To set DTC, turn ignition on. Select DATA MONITOR with scan tool. Wait at least 6 seconds.

DTC Confirmation Test "B" & "E"

Malfunction "B" is detected when ECM receives an excessively low voltage from MAF sensor when engine is running. ECM will enter fail-safe mode. Malfunction "E" is detected when ECM receives a constant voltage signal of about one volt from MAF sensor. Possible causes are

  1. MAF sensor circuit open or shorted.
  2. Intake air leaks.
  3. Defective MAF sensor.

To set DTC, turn ignition on. Select DATA MONITOR with scan tool. Start engine and run for no more than 5 seconds. If DTC sets after 5 seconds, malfunction "C" may be present.

DTC Confirmation Test "C"

Malfunction is detected when ECM receives a high voltage from MAF sensor under light-load driving conditions. Possible causes are

  1. MAF sensor circuit open or shorted.
  2. Defective MAF sensor.

To set DTC, turn ignition on. Select DATA MONITOR with scan tool. Start engine and warm to normal operating temperature. Let engine idle for at least 10 seconds.

DTC Confirmation Test "D" (Overall Function Check)

Note. Use the following test to check overall function of MAF sensor circuit. During this test, DTC may not be confirmed.

Malfunction is detected when ECM receives a low voltage from MAF sensor under heavy-load driving conditions. Possible causes are

  1. MAF sensor circuit open or shorted.
  2. Intake air leaks.
  3. Defective MAF sensor.

Start engine and warm to normal operating temperature. Select MODE 1 with scan tool. Observe MAF reading on scan tool while increasing engine speed to 4000 RPM. MAF reading should increase in response to engine speed.

DTC Confirmation Test

Malfunction is detected when ECM receives an excessively low or high voltage from AP sensor. Possible causes are

  1. AP sensor circuit open or shorted.
  2. Defective AP sensor.

To set DTC, turn ignition on. Select DATA MONITOR with scan tool. Wait at least 6 seconds.

Malfunction is detected when ECM receives an excessively low or high voltage from IAT sensor. Possible causes are

  1. IAT sensor circuit open or shorted.
  2. Defective IAT sensor.

To set DTC, turn ignition on. Select DATA MONITOR with scan tool. Wait at least 5 seconds.

DTC Confirmation Test "B"

Malfunction is detected when ECM receives a rationally incorrect voltage from IAT sensor compared to Engine Coolant Temperature (ECT) sensor voltage. Possible causes are

  1. IAT sensor circuit open or shorted.
  2. Defective IAT sensor.

Note. Ensure engine coolant temperature is less then 194°F (90°C) for entire test.

To set DTC, ensure engine coolant temperature is less than 194°F (90°C). Turn ignition on. Select DATA MONITOR with scan tool. Drive vehicle at a speed of more than 44 MPH for 105 consecutive seconds.

DTC Confirmation Test (DTC P0115)

Malfunction is detected when ECM receives an excessively high or low voltage from ECT sensor. ECM will enter fail-safe mode. Possible causes are

  1. ECT sensor circuit open or shorted.
  2. Defective ECT sensor.

To set DTC, turn ignition on. Select DATA MONITOR with scan tool. Wait at least 5 seconds.

DTC Confirmation Test (DTC P0125)

Malfunction is detected when voltage received from ECT sensor is incorrect based on engine run time, or engine coolant temperature is insufficient for closed-loop fuel control. Possible causes are

  1. High resistance in ECT sensor circuit.
  2. Defective ECT sensor.
  3. Stuck open thermostat.

To set DTC, turn ignition on. Select DATA MONITOR with scan tool. Ensure engine coolant temperature is less than 59°F (15°C). Start engine and let it idle. DTC will set if engine coolant temperature does not increase to more than 59°F (15°C) within 65 minutes.

Malfunction is detected when ECM receives an excessively low or high voltage from TP sensor. ECM will enter fail-safe mode. Possible causes are

  1. TP sensor circuit open or shorted.
  2. Defective TP sensor.

To set DTC, turn ignition on. Select DATA MONITOR with scan tool. Start engine and drive vehicle for at least 5 seconds at 2 MPH or more.

Malfunction is detected when ECM receives a high voltage from TP sensor under light-load driving conditions. Possible causes are

  1. TP sensor circuit open or shorted.
  2. Defective TP sensor.
  3. Defective fuel injector.
  4. Defective Camshaft Position (CMP) Sensor.
  5. Defective Mass Airflow (MAF) sensor.

To set DTC, turn ignition on. Select DATA MONITOR with scan tool. Start engine and let it idle for at least 10 seconds. On A/T models, if idle speed is more than 1000 RPM, depress brake pedal and shift transmission into Drive. On M/T models, if idle speed is more than 1000 RPM, drive vehicle as slow as possible with transmission in 3rd or 4th gear.

Malfunction is detected when ECM receives a low voltage from TP sensor under heavy-load driving conditions. Possible causes are

  1. TP sensor circuit open or shorted.
  2. Intake air leaks.
  3. Defective TP sensor.

To set DTC, start engine and warm to normal operating temperature. Ensure engine coolant temperature is more than 158°F (70°C). Measure voltage between ground and ECM terminal No. 61 (MAF sensor signal) by backprobing. see scheme 1and see scheme 2. While observing voltmeter, drive vehicle at a suitable speed to increase voltage to more than 3 volts for at least 10 consecutive seconds. Select MODE 7 with scan tool.

DTC Confirmation Test (Overall Function Check)

Note. Use the following test to check overall function of front HO2S circuit. During this test, DTC may not be confirmed.

Malfunction is detected when ECM receives a constant .3 volt from front HO2S. When ECM is not using front HO2S signal as an input, ECM circuits read a continuous .3 volt. Therefore, ECM monitors the time that front HO2S voltage is .2-.4 volt. DTC will set if time is too long. Possible causes are

  1. HO2S circuit open or shorted.
  2. Defective HO2S.

To check overall function of front HO2S circuit, start engine and warm to normal operating temperature. Measure voltage between engine ground and ECM terminal No. 62 by backprobing. see scheme 1and see scheme 2. While observing voltmeter, increase engine speed to 2000 RPM. Voltage should not stay in the.2-.4 volt range.

Note. Use the following test to check overall function of front HO2S circuit. During this test, DTC may not be confirmed.

Malfunction is detected when front HO2S "rich" output is not high enough or "lean" output is not low enough. DTC P0131 will set if both "rich" and "lean" outputs are shifted to the lean side. DTC P0132 will set if both "rich" and "lean" outputs are shifted to the rich side. Possible causes are

  1. Defective HO2S.
  2. Defective HO2S heater.
  3. Fuel pressure incorrect.
  4. Defective injectors.
  5. Intake air leaks.

To check overall function of front HO2S circuit, start engine and warm to normal operating temperature. Measure voltage between engine ground and ECM terminal No. 62 by backprobing. see scheme 1and see scheme 2. While observing voltmeter, increase engine speed to 2000 RPM. The following conditions should exist

  1. Maximum voltage should be more than .6 volt at least once.
  2. Minimum voltage should be more than .1 volt at least once.
  3. Maximum voltage should be less than .8 volt at least once.
  4. Minimum voltage should be less than .35 volt at least once.

Note. Use the following test to check overall function of front HO2S circuit. During this test, DTC may not be confirmed.

Malfunction is detected when HO2S response time is too long. Possible causes are

  1. HO2S circuit open or shorted.
  2. Defective HO2S.
  3. Defective HO2S heater.
  4. Fuel pressure incorrect.
  5. Defective injectors.
  6. Intake air leaks.
  7. Exhaust leaks.
  8. Defective PCV valve.
  9. Defective Mass Airflow (MAF) sensor.

To check overall function of front HO2S circuit, start engine and warm to normal operating temperature. Measure voltage between engine ground and ECM terminal No. 62 by backprobing. see scheme 1and see scheme 2. While observing voltmeter, increase engine speed to 2000 RPM. Voltage should cycle from 0-0.3 volt to 0.6-1.0 volt more than 5 times within 10 seconds.

Malfunction is detected when HO2S voltage is too high. Possible causes are

  1. HO2S circuit open or shorted.
  2. Defective HO2S.

To set DTC, start engine and warm to normal operating temperature. Turn ignition off and wait at least 5 seconds. Start engine and let it idle for 2 minutes. Turn ignition off and wait at least 5 seconds. Start engine and let it idle for 2 minutes. Select MODE 3 with scan tool.

Malfunction is detected when front HO2S heater circuit current is out of normal range. Possible causes are

  1. HO2S heater circuit open or shorted.
  2. Defective HO2S heater.

To set DTC, start engine and let it idle for at least 6 seconds. Turn ignition off and wait at least 5 seconds. Start engine and let it idle for at least 6 seconds. Select MODE 3 with scan tool.

Note. Use the following test to check overall function of rear HO2S circuit. During this test, DTC may not be confirmed.

DTC P0137 will set if rear HO2S minimum voltage is too high. DTC P0138 will set if rear HO2S maximum voltage is too low. DTC P0139 will set if rear HO2S response time is too long. DTC P0140 will set if rear HO2S voltage is too high. Possible causes are

  1. HO2S circuit open or shorted.
  2. Defective HO2S.
  3. Fuel pressure incorrect.
  4. Defective injectors.
  5. Intake air leaks.

To check overall function of rear HO2S circuit, drive vehicle at a speed of more than 43 MPH for 2 consecutive minutes. Stop vehicle and leave engine running. Measure voltage between engine ground and ECM terminal No. 63 by backprobing. see scheme 1and see scheme 2. While monitoring voltmeter, quickly increase engine speed to 4000 RPM. Repeat 10 times.

  1. Voltage should be less than .43 volt at least once.
  2. Voltage should be more than .48 volt at least once.
  3. Voltage should change at least .06 volt in one second.
  4. Voltage should be less than 2 volts during test.

If voltage is not as specified, allow engine to idle for 10 minutes and recheck voltage. If voltage is still not as specified, allow vehicle to coast at 50 MPH with transmission in 3rd gear (M/T) or Drive with Overdrive Off (A/T) and recheck voltage.

Malfunction is detected when rear HO2S heater circuit current is out of normal range. Possible causes are

  1. HO2S heater circuit open or shorted.
  2. Defective HO2S heater.

To set DTC, drive vehicle at a speed of more than 43 MPH for 2 consecutive minutes. Stop vehicle and let engine idle for at least 6 seconds. Turn ignition off and wait at least 5 seconds. Drive vehicle at a speed of more than 43 MPH for 2 consecutive minutes. Stop vehicle and let engine idle for at least 6 seconds. Select MODE 3 with scan tool.

Malfunction is detected when mixture ratio compensation amount is too large (mixture is too lean or too rich). Possible causes are

  1. Intake air leaks.
  2. Defective front HO2S.
  3. Defective injectors.
  4. Exhaust leaks.
  5. Fuel pressure incorrect.
  6. Lack of fuel.
  7. Defective Mass Airflow (MAF) sensor.

To set DTC, start engine and warm to normal operating temperature. Turn ignition off and wait at least 5 seconds. Disconnect MAF sensor harness connector located near air cleaner housing. Start engine and let it idle for at least 3 seconds. Turn ignition off and reconnect MAF sensor harness connector. Select MODE 7 and ensure DTC P0100 is set. Select MODE 4 and erase DTC. Start engine and let it idle for at least 10 minutes. Select MODE 7. If engine does not start, fuel injection system has a malfunction. Attempt to start engine while depressing accelerator pedal. If engine still does not start, check for intake or exhaust leaks or spark plug fouling.

Malfunction is detected when ECM receives an excessively low or high voltage from FTT sensor, or when voltage received is rationally incorrect compared to ECT sensor and IAT sensor. Possible causes are

  1. FTT sensor circuit open or shorted.
  2. Defective FTT sensor.

To set DTC, turn ignition on. Select DATA MONITOR with scan tool and wait at least 10 seconds. If DTC sets, go to PROCEDURE . If DTC does not set, check engine coolant temperature with scan tool. If engine coolant temperature is 140°F (60°C) or more, allow engine to cool until engine coolant temperature is less than 140°F (60°C). Wait at least 10 seconds.

Note. Use the following test to check overall function of cooling system. During this test, DTC may not be confirmed.

For DTC P0217, malfunction is detected when engine coolant temperature is excessively high under light engine load conditions. Possible causes are

  1. Cooling fan circuit open or shorted.
  2. Defective cooling fan motor.
  3. Defective thermostat.
  4. Incorrect ignition timing.
  5. Defective Engine Coolant Temperature (ECT) sensor.
  6. Radiator plugged.
  7. Blocked air passage.

For DTC P1217, malfunction is detected when engine overheats. Possible causes are

  1. Cooling fan circuit open or shorted.
  2. Defective cooling fan motor.
  3. Coolant leak.
  4. Radiator plugged.
  5. Defective water pump.
  6. Defective thermostat.
  1. To check overall function of cooling system, allow engine to cool. Check coolant level in reservoir tank and radiator. If coolant level is low, go to «PROCEDURE»(ref-3086-S00302659202000050300000). If coolant level is okay, go to next step.
  2. Check coolant mixture ratio. If coolant mixture ratio is not 45-55 percent, change coolant. Start engine and run until air is purged from system. Ensure A/C is turned off and compressor is not operating. If compressor is operating, repair A/C system. See appropriate A/C-HEATER SYSTEMS article in AIR CONDITIONING & HEATING. If compressor is not operating, go to next step.
  3. Turn ignition off. Disconnect ECT sensor harness connector. see scheme 6 Connect a 150 ohm resistor between ECT sensor harness connector terminals. Start engine. If cooling fan operates, go to next step. If cooling fan does not operate, go to «PROCEDURE»(ref-3086-S00302659202000050300000).
  4. Ensure coolant is flowing through radiator. Check for blocked radiator or condenser fins. Check for damaged grille or improper air dam installation. Repair as necessary. If no problems are found, go to next step.
  5. Check operation of ECT sensor. See step 4 under PROCEDURE. Repair as necessary. If ECT sensor is okay, check ignition timing. See «ON-VEHICLE ADJUSTMENTS»(ref-4039) article. Adjust, if necessary.

Misfire is detected when Crankshaft Position (CKP) sensor detects a fluctuation in engine speed. Possible causes are

  1. Incorrect spark plugs.
  2. Insufficient compression.
  3. Incorrect fuel pressure.
  4. Defective EGR volume control valve.
  5. Injector circuit open or shorted.
  6. Defective injectors.
  7. Intake air leak.
  8. Secondary ignition circuit open or shorted.
  9. Lack of fuel.
  10. Defective drive plate or flywheel.
  11. Defective front HO2S.
  12. Incorrect distributor rotor.

To set DTC, turn ignition on. Select DATA MONITOR with scan tool. Start engine and warm to normal operating temperature. Turn ignition off and wait at least 5 seconds. Drive vehicle for at least 3 minutes with engine at 1500-3000 RPM. Hold accelerator pedal as steady as possible. If DTC does not set, refer to freeze-frame data, and duplicate conditions present when DTC was set.

Malfunction is detected when ECM receives an excessively low or high voltage from knock sensor. Possible causes are

  1. Knock sensor circuit open or shorted.
  2. Defective knock sensor.

To set DTC, turn ignition on. Select DATA MONITOR with scan tool. Start engine and let it idle for at least 5 seconds.

DTC Confirmation Test (DTC P0335)

Malfunction is detected when ECM does not receive proper pulse signal from CKP sensor when engine is running. Possible causes are

  1. CKP sensor circuit open or shorted.
  2. Defective CKP sensor.

To set DTC, turn ignition on. Select DATA MONITOR with scan tool. Start engine and let it idle for at least 10 seconds.

DTC Confirmation Test (DTC P1336)

Malfunction is detected when ECM detects chipping of flywheel or drive plate teeth. Possible causes are

  1. CKP sensor circuit open or shorted.
  2. Defective CKP sensor.
  3. Damaged flywheel or drive plate.

To set DTC, turn ignition on. Select DATA MONITOR with scan tool. Start engine and let it idle for at least 4 minutes.

Malfunction is detected when either one-degree or 180-degree signal from CMP sensor is not sent to ECM during engine cranking. Possible causes are

  1. CMP sensor circuit is open or shorted.
  2. Defective CMP sensor.
  3. Defective starter.
  4. Starter circuit fault.
  5. Weak battery.

To set DTC, turn ignition on. Select DATA MONITOR with scan tool. Crank engine for at least 2 seconds.

DTC Confirmation Test "B" & "C"

Malfunction "B" is detected when either one-degree or 180-degree signal from CMP sensor is not sent to ECM often enough when engine is running at a certain speed. Malfunction "C" is detected when relationship between one-degree signal and 180-degree signal is abnormal. Possible causes are

  1. CMP sensor circuit is open or shorted.
  2. Defective CMP sensor.
  3. Defective starter.
  4. Starter circuit fault.
  5. Weak battery.

To set DTC, turn ignition on. Select DATA MONITOR with scan tool. Start engine and let it idle for at least 2 seconds.

Malfunction is detected when no EGR flow is detected by EGR temperature sensor under conditions that call for EGR. Possible causes are

  1. EGR Volume Control Valve (EGR-VCV) circuit open or shorted.
  2. EGR-VCV stuck closed.
  3. Weak battery.
  4. EGR passage clogged.
  5. EGR temperature sensor or circuit fault.
  6. Exhaust leaks.

To set DTC, turn ignition off and wait at least 5 seconds. Turn ignition on. Using scan tool, select MODE 1 and read engine coolant temperature. Ensure engine coolant temperature is less than 104°F (40°C). While monitoring engine coolant temperature, start engine and let it idle. Measure voltage between ground and ECM terminal No. 92 (TP sensor signal) by backprobing. see scheme 1and see scheme 2. When engine coolant temperature reaches 158°F (70°C), immediately drive vehicle at a suitable speed with engine at 1800-2800 RPM and TP sensor voltage at.86-2.00 volts for at least one minute. Repeat test and select MODE 3 with scan tool.

Malfunction is detected when an improper voltage signal is sent to ECM through EGR-VCV. ECM will enter fail-safe mode. Possible causes are

  1. EGR-VCV circuit open or shorted.
  2. Defective EGR-VCV.

To set DTC, turn ignition on. Select DATA MONITOR with scan tool. Start engine and warm to normal operating temperature. Quickly increase engine speed to 2000 RPM 10 times.

Note. Use the following test to check overall function of 3-way catalyst. During this test, DTC may not be confirmed.

Malfunction is detected when switching frequency of rear HO2S increases to a specified value, indicating that 3-way catalyst is not operating properly. Possible causes are

  1. Defective 3-way catalyst.
  2. Exhaust leak.
  3. Intake air leaks.
  4. Defective injectors.
  5. Defective spark plugs.
  6. Incorrect ignition timing.

To check overall function of 3-way catalyst, drive vehicle at a speed of more than 43 MPH for 2 consecutive minutes. Stop vehicle and leave engine running. Measure voltage between engine ground and ECM terminals No. 62 (front HO2S) and No. 63 (rear HO2S) by backprobing. see scheme 1and see scheme 2. Increase engine speed to 2000 RPM. Ensure switching frequency of rear HO2S is less than 75 percent of front HO2S switching frequency. If front HO2S does not switch more than 5 times within 10 seconds, diagnose and repair front HO2S. See DTC P0133: FRONT HEATED OXYGEN SENSOR (HO2S).

Malfunction is detected when EVAP system has a leak or does not operate properly. Possible causes are

  1. Incorrect fuel tank vacuum relief valve.
  2. Incorrect fuel filler cap.
  3. Fuel filler cap open or leaking.
  4. Foreign matter in fuel filler cap.
  5. Leak in hose between intake manifold and EVAP Canister Purge Volume Control Valve (EVAP-CPVCV).
  6. Foreign matter in EVAP Canister Vent Control Valve (EVAP-CVCV).
  7. Leak in EVAP canister or fuel tank.
  8. Leak or blockage in EVAP purge line.
  9. Leak or blockage in hose to EVAP Control System Pressure Sensor (EVAP-CSPS).
  10. Defective EVAP-CVCV or circuit.
  11. Defective EVAP-CPVCV or circuit.
  12. Defective absolute pressure senor.
  13. Defective fuel tank temperature sensor.
  14. Missing or damaged EVAP-CVCV "O" ring.
  15. Defective water separator.
  16. EVAP canister saturated with water.
  17. Defective EVAP-CSPS.
  18. Defective fuel level sensor or circuit.
  19. Defective refueling control valve.
  20. Leak in On-Board Refueling Vapor Recovery (ORVR) system.

Note. Before performing test, ensure fuel tank level is 1/4-3/4, ambient temperature is 32-86°F (0-32°C) and EVAP-CPVCV hoses are installed correctly.

  1. To set DTC, drive vehicle according to specified driving pattern to set System Readiness Test (SRT) codes. See «SYSTEM READINESS TEST (SRT)»(ref-3085-S42640548892000041700000) under ADDITIONAL SYSTEM FEATURES in SELF-DIAGNOSTICS - INTRODUCTION article. Stop vehicle and go to next step.
  2. Select MODE 1 on scan tool and check SRT status of EVAP system. If EVAP system SRT is complete, system is okay at this time. Problem may be intermittent. See «TESTING PROCEDURE»(ref-3085-S33644654112000041700000) under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - INTRODUCTION article. If EVAP system SRT is incomplete, turn ignition off, wait at least 10 seconds and go to next step.
  3. Perform driving pattern again. Select MODE 3. If DTC P0440, P0455, P1440 or P1447 is set, perform appropriate diagnostic procedure. If DTC P0440, P0455 P1440 or P1447 is not set, go to step 2 .

Procedure (DTC P0440 & P1440)

  1. Ensure fuel cap is original equipment. Attempt to turn fuel cap clockwise. If fuel cap was tightened properly, go to next step. If fuel cap was not tightened properly, clean fuel cap and filler neck with compressed air. Reinstall cap and retest system.
  2. While removing fuel cap, listen for air escaping from fuel tank. If air escaped from fuel tank, go to step 4. If air did not escape from fuel tank, go to next step.
  3. Using a suitable hand vacuum/pressure pump with fuel cap adapter, apply pressure and vacuum to fuel cap. Fuel cap vacuum relief valve should open when pressure reaches 2.22-2.90 psi (15.3-20.0 kPa) and when vacuum reaches.98-1.78 in. Hg (3.3-6.0 kPa). If operation is as specified, go to next step. If operation is not as specified, replace fuel cap and retest system.
  4. Check EVAP system for leaks. See «FUEL EVAPORATION (EVAP) CONTROL SYSTEM»(ref-3089-S11434001382000041700000) under EMISSION SYSTEMS & SUB-SYSTEMS in SYSTEM & COMPONENT TESTING article. Repair as necessary and retest system. If no leaks are found, go to next step.
  5. Remove water separator and inspect for cracks or blockage. (Scheme 5) With water separator port "A" plugged, blow air into port "B". (Scheme 6) Air should flow out of port "C". With port "C" plugged, blow air into port "B". Air should flow out of port "A". If operation is as specified, go to next step. If operation is not as specified, replace water separator and retest system.
  6. Check EVAP-CVCV and circuit. See «DTC P0446: EVAP CANISTER VENT CONTROL VALVE (EVAP-CVCV)»(ref-3086-S16701810302000041700000). Repair as necessary and retest system. If EVAP-CVCV and circuit are okay, go to next step.
  7. Remove EVAP canister with EVAP-CVCV attached. Attempt to drain water from EVAP canister. If water does not drain from EVAP canister, go to step 9. If water drains from EVAP canister, weigh EVAP canister with EVAP-CVCV attached. If weight is more than 4.0 lbs. (1.8 kg), go to next step. If weight is less than 4.0 lbs. (1.8 kg), go to step 9.
  8. Inspect EVAP canister for damage. Replace, if necessary. Also check hose between water separator and EVAP canister for blockage or leak. Repair as necessary and retest system. If EVAP canister and hose are okay, go to next step.
  9. Start engine and warm to normal operating temperature. Turn ignition off. Disconnect EVAP-CPVCV hose from EVAP service port. (Scheme 7)and (Scheme 8). Start engine and let it idle for at least 80 seconds. While quickly increasing engine speed to 2000 RPM, check for vacuum at EVAP-CPVCV hose. Vacuum should exist. If vacuum does not exist, go to next step. If vacuum exists, go to step 12.
  10. Check EVAP system vacuum hoses for blockages or leaks. See «VACUUM DIAGRAMS»(ref-3092) article. Repair as necessary and retest system. If vacuum hoses are okay, go to next step.
  11. Turn ignition off. Remove EVAP-CPVCV. Using jumper wires, apply battery voltage to EVAP-CPVCV terminals. (Scheme 9) Air should flow between ports "A" and "B". Remove jumper wires. Air should not flow. If operation is as specified, go to next step. If operation is not as specified, replace EVAP-CPVCV and retest system.
  12. Remove Absolute Pressure (AP) sensor located on top of air cleaner housing. Leave AP sensor harness connector connected. Turn ignition on. Measure voltage between engine ground and ECM terminal No. 80 by backprobing. see scheme 1and see scheme 2. Voltage should be 3.2-4.8 volts. Using a hand vacuum pump, apply 7.88 in. Hg (26.7 kPa) of vacuum to AP sensor. Voltage should be 1.0-1.4 volts less than voltage measured with no vacuum applied. Voltage should decrease as vacuum is applied. see scheme 4 If voltage is as specified, go to next step. If voltage is not as specified, replace AP sensor and retest system.
  13. Remove rear seat. Remove Fuel Tank Temperature (FTT) sensor assembly from fuel tank. Measure resistance between fuel level sensor/FTT sensor assembly terminals No. 1 (Black wire) and No. 2 (Light Green/Red wire), with sensor at specified temperatures. See «FTT SENSOR RESISTANCE»(ref-3086-S38842819322000050800000) table. If resistance is as specified, go to next step. If resistance is not as specified, replace FTT sensor and retest system.
  14. Remove EVAP-CSPS with its harness connector connected. (Scheme 5) Turn ignition on. Using a hand vacuum pump, apply 2.76 in. Hg (9.3 kPa) of vacuum to EVAP-CSPS. Measure voltage between ground and ECM terminal No. 84 by backprobing. see scheme 1and see scheme 2. Voltage should be.4-.6 volt. Disconnect vacuum pump. Voltage should be 3.0-3.6 volts. If voltage is as specified, go to next step. If voltage is not as specified, replace EVAP-CSPS and retest system.
  15. Check EVAP purge line at fuel tank and EVAP canister for leaks or improper connection. Repair as necessary and retest system. If purge line is okay, clean with compressed air, and go to next step.
  16. Measure resistance between fuel level sensor/FTT sensor assembly terminals No. 1 (Black wire) and No. 2 (Green/Red wire), with float in specified positions. See «FUEL LEVEL SENSOR RESISTANCE»(ref-3086-S19456590982000050800000) table. If resistance is as specified, go to next step. If resistance is not as specified, replace fuel level sensor and retest system.
  17. No problem is indicated at this time. Problem may be intermittent. See «TESTING PROCEDURE»(ref-3085-S33644654112000041700000) under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - INTRODUCTION article.
Temperature °F (°C)(1) Ohms
68 (20)2300-2700
122 (50)790-970
(1) Resistance should decrease as temperature increases. see scheme 5
(1)Resistance should decrease as temperature increases. see scheme 5

FTT SENSOR RESISTANCE

Float Position(1) Ohms
Full (2)4-6
1/230-34
Empty (2)80-83
(1) Approximate resistance. (2) When float rod is in contact with stop.
(1)Approximate resistance.
(2)When float rod is in contact with stop.

FUEL LEVEL SENSOR RESISTANCE

Scheme 5

Scheme 5
Scheme 5

Scheme 6

Scheme 6
Scheme 6

Scheme 7

Scheme 7
Scheme 7

Scheme 8

Scheme 8
Scheme 8

Scheme 9

Scheme 9
Scheme 9

Procedure (DTC P0455)

  1. Ensure fuel cap is original equipment. Attempt to turn fuel cap clockwise. If fuel cap was tightened properly, go to next step. If fuel cap was not tightened properly, clean fuel cap and filler neck with compressed air. Reinstall cap and retest system.
  2. While removing fuel cap, listen for air escaping from fuel tank. If air escaped from fuel tank, go to step 4. If air did not escape from fuel tank, go to next step.
  3. Using a suitable hand vacuum/pressure pump with fuel cap adapter, apply pressure and vacuum to fuel cap. Fuel cap vacuum relief valve should open when pressure reaches 2.22-2.90 psi (15.3-20.0 kPa) and when vacuum reaches.98-1.78 in. Hg (3.3-6.0 kPa). If operation is as specified, go to next step. If operation is not as specified, replace fuel cap and retest system.
  4. Check EVAP purge line at fuel tank and EVAP canister for leaks or improper connection. Repair as necessary and retest system. If purge line is okay, clean with compressed air, and go to next step.
  5. Check EVAP-CVCV, "O" ring and circuit. See «DTC P0446: EVAP CANISTER VENT CONTROL VALVE (EVAP-CVCV)»(ref-3086-S16701810302000041700000). Repair as necessary and retest system. If no problems are found, go to next step.
  6. Check EVAP system for leaks. See «FUEL EVAPORATION (EVAP) CONTROL SYSTEM»(ref-3089-S11434001382000041700000) under EMISSION SYSTEMS & SUB-SYSTEMS in SYSTEM & COMPONENT TESTING article. Repair as necessary and retest system. If no leaks are found, go to next step.
  7. Start engine and warm to normal operating temperature. Turn ignition off. Disconnect EVAP-CPVCV hose from EVAP service port. (Scheme 7)and (Scheme 8). Start engine and let it idle for at least 80 seconds. While quickly increasing engine speed to 2000 RPM, check for vacuum at EVAP-CPVCV hose. Vacuum should exist. If vacuum does not exist, go to next step. If vacuum exists, go to step 10.
  8. Check EVAP system vacuum hoses for blockages or leaks. See «VACUUM DIAGRAMS»(ref-3092) article. Repair as necessary and retest system. If vacuum hoses are okay, go to next step.
  9. Turn ignition off. Remove EVAP-CPVCV. Using jumper wires, apply battery voltage to EVAP-CPVCV terminals. (Scheme 9) Air should flow between ports "A" and "B". Remove jumper wires. Air should not flow. If operation is as specified, go to next step. If operation is not as specified, replace EVAP-CPVCV and retest system.
  10. Remove Absolute Pressure (AP) sensor located on top of air cleaner housing. Leave AP sensor harness connector connected. Turn ignition on. Measure voltage between engine ground and ECM terminal No. 80 by backprobing. see scheme 1and see scheme 2. Voltage should be 3.2-4.8 volts. Using a hand vacuum pump, apply 7.88 in. Hg (26.7 kPa) of vacuum to AP sensor. Voltage should be 1.0-1.4 volts less than voltage measured with no vacuum applied. Voltage should decrease as vacuum is applied. see scheme 4 If voltage is as specified, go to next step. If voltage is not as specified, replace AP sensor and retest system.
  11. Remove rear seat. Remove Fuel Tank Temperature (FTT) sensor assembly from fuel tank. Measure resistance between fuel level sensor/FTT sensor assembly terminals No. 1 (Black wire) and No. 2 (Light Green/Red wire), with sensor at specified temperatures. See «FTT SENSOR RESISTANCE»(ref-3086-S38842819322000050800000) table. If resistance is as specified, go to next step. If resistance is not as specified, replace FTT sensor and retest system.
  12. Remove EVAP-CSPS with its harness connector connected. (Scheme 5) Turn ignition on. Using a hand vacuum pump, apply 2.76 in. Hg (9.3 kPa) of vacuum to EVAP-CSPS. Measure voltage between ground and ECM terminal No. 84 by backprobing. see scheme 1and see scheme 2. Voltage should be.4-.6 volt. Disconnect vacuum pump. Voltage should be 3.0-3.6 volts. If voltage is as specified, go to next step. If voltage is not as specified, replace EVAP-CSPS and retest system.
  13. No problem is indicated at this time. Problem may be intermittent. See «TESTING PROCEDURE»(ref-3085-S33644654112000041700000) under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - INTRODUCTION article.

Malfunction is detected when improper voltage is sent to ECM through EVAP-CPVCV. Possible causes are

  1. EVAP-CPVCV circuit open or shorted.
  2. Defective EVAP-CPVCV.

To set DTC, turn ignition on. Select DATA MONITOR with scan tool. Start engine and let it idle for at least 13 seconds.

Malfunction is detected when improper voltage is sent to ECM through EVAP-CVCV. Possible causes are

  1. EVAP-CVCV circuit open or shorted.
  2. Defective EVAP-CVCV.

To set DTC, turn ignition on. Select DATA MONITOR with scan tool. Start engine and wait at least 8 seconds.

Malfunction is detected when improper voltage is sent to ECM from EVAP-CSPS. Possible causes are

  1. EVAP-CSPS circuit open or shorted.
  2. EVAP-CSPS hose plugged or leaking.
  3. Defective EVAP-CSPS.
  4. Defective EVAP Canister Vent Control Valve (EVAP-CVCV).
  5. Defective EVAP Canister Purge Volume Control Valve (EVAP-CPVCV).
  6. Defective EVAP canister.
  7. Hose between EVAP canister and water separator plugged or leaking.

To set DTC, start engine and warm to normal operating temperature. Measure voltage between ground and ECM terminal No. 82 (fuel tank temperature sensor signal) by backprobing. see scheme 1and see scheme 2. Ensure voltage is less than 4.2 volts. Turn ignition off and wait at least 5 seconds. Start engine and wait at least 20 seconds. Select MODE 7 with scan tool.

Malfunction is detected when ECM receives a varied signal from fuel level sensor while vehicle is parked. Possible causes are

  1. Fuel level sensor circuit open or shorted.
  2. Defective fuel level sensor.

To set DTC, turn ignition on. Select DATA MONITOR with scan tool. Start engine and wait no more than 2 minutes.

Note. Use the following test to check overall function of fuel level sensor circuit. During this test, DTC may not be confirmed.

Malfunction is detected when fuel level sensor output does not change when vehicle has been driven a long distance. Possible causes are

  1. Fuel level sensor circuit open or shorted.
  2. Defective fuel level sensor.
  1. To check overall function of fuel level sensor circuit, release fuel system pressure. See FUEL SYSTEM in BASIC DIAGNOSTIC PROCEDURES article. Remove fuel feed hose from fuel level sensor unit located behind access cover, under rear seat.
  2. Connect a fuel hose to fuel level sensor unit. Place other end of hose into a suitable fuel container. Turn ignition off. Set voltmeter probes between ground and ECM terminal No. 83 (fuel level sensor signal) by backprobing. See Turn ignition on and monitor voltmeter.
  3. Using suitable equipment, drain 7.93 Gals. (30.0 L) of fuel from tank. Refill tank with drained fuel. Voltage should change more than .03 volt during draining and refilling.

Malfunction is detected when ECM receives an excessively low or high voltage from fuel level sensor. Possible causes are

  1. Fuel level sensor circuit open or shorted.
  2. Defective fuel level sensor.

To set DTC, turn ignition on. Select DATA MONITOR with scan tool. Wait at least 5 seconds.

Note. Use the following test to check overall function of VSS circuit. During this test, DTC may not be confirmed.

Malfunction is detected when zero MPH signal is sent to ECM while vehicle is moving. Possible causes are

  1. VSS circuit open or shorted.
  2. Defective VSS.

To check overall function of VSS circuit, raise drive wheels and support vehicle. Start engine and select MODE 1 with scan tool. VSS reading on scan tool should be able to exceed 6 MPH.

Malfunction "A" is detected when IACV-AAC valve does not operate properly. Possible causes are

  1. IACV-AAC valve circuit open.
  2. Defective IACV-AAC valve.

To set DTC, turn ignition on. Select DATA MONITOR with scan tool. Start engine and let it idle. Increase engine speed to 2500 RPM for 3 seconds. Release throttle and let engine idle for 3 seconds. Increase engine speed to 2500 RPM for 3 seconds. Release throttle and let engine idle for 3 seconds.

Note. Ensure ambient temperature is more than 14°F (-10°C) when performing test.

Malfunction is detected when IACV-AAC valve does not operate properly. Possible causes are

  1. IACV-AAC valve circuit shorted.
  2. Defective IACV-AAC valve.

To set DTC, start engine and warm to normal operating temperature. Turn ignition off and wait at least 5 seconds. Turn ignition on and select DATA MONITOR with scan tool. Start engine and let it idle for at least one minute.

Note. Use the following test to check overall function of TP switch circuit. During this test, DTC may not be confirmed.

Malfunction is detected when battery voltage is sent to ECM from closed TP switch when throttle valve is opened. Possible causes are

  1. Closed TP switch circuit shorted.
  2. Defective closed TP switch.
  3. Defective TP sensor.

To check overall function of closed TP switch circuit, start engine and warm to normal operating temperature. Measure voltage between ground and ECM terminal No. 40 (closed TP switch signal) by backprobing. see scheme 1and see scheme 2. With engine idling, battery voltage should exist. With engine at 2000 RPM, about zero volts should exist.

A/T control circuits are used to control transmission shifting during hard acceleration or deceleration. Malfunction is detected when ECM receives incorrect voltage from Transmission Control Module (TCM) continuously. Only possible cause is an open or short circuit between ECM and TCM.

To set DTC, turn ignition on. Select DATA MONITOR with scan tool. Wait at least 10 seconds.

Malfunction is detected when ECM calculation function is malfunctioning. Only possible cause is a faulty ECM. To set DTC, turn ignition on. Select DATA MONITOR with scan tool. Start engine and let it idle for at least 30 seconds.

Malfunction is detected when engine coolant temperature has not increased to normal operating temperature within a certain amount of engine run time. Possible causes are

  1. Thermostat stuck closed.
  2. Thermostat seal leaking.
  3. Defective Engine Coolant Temperature (ECT) sensor.

To set DTC, replace thermostat with an OEM thermostat. Turn ignition on. Using scan tool, select DATA MONITOR, and read COOLAN TEMP/S value. If value is more than 140°F (60°C), allow engine to cool until value is less than 140°F (60°C). Drive vehicle at 50-75 MPH for 10 consecutive minutes.

Note. Use the following test to check closed-loop fuel control. During this test, DTC may not be confirmed.

Malfunction is detected when ECM does not operate in closed loop. Possible causes are

  1. Front HO2S circuit open or shorted.
  2. Defective front HO2S.
  3. Defective front HO2S heater.

To check closed-loop operation, start engine and warm to normal operating temperature. Measure voltage between ground and ECM terminal 62 (front HO2S signal), by backprobing. see scheme 1and see scheme 2. Monitor voltmeter with engine at 2000 RPM. Voltage should be less than.21 volt at least once and more than.70 volt at least once.

Malfunction is detected when ECM does not receive signal from ignition primary circuit during engine cranking or running. Possible causes are

  1. Ignition primary circuit open or shorted.
  2. Defective power transistor (integral with ignition coil).
  3. Defective resistor (part of distributor cap).
  4. Defective Camshaft Position (CMP) sensor.
  5. CMP sensor circuit open or shorted.

To set DTC, turn ignition on. Select DATA MONITOR with scan tool. Start engine and wait at least 4 seconds. If engine does not start, crank engine for at least 5 seconds.

Malfunction is detected when ECM receives an excessively low voltage from EGR temperature sensor when engine coolant temperature is low. Possible causes are

  1. EGR temperature sensor circuit shorted.
  2. Defective EGR temperature sensor.
  3. EGR malfunction.

To set DTC, turn ignition on. Using scan tool, select DATA MONITOR and read COOLAN TEMP/S value. If value is more than 122°F (50°C), allow engine to cool. Start engine and let it idle for at least 8 seconds.

Malfunction is detected when ECM receives an excessively high voltage from EGR temperature sensor when engine coolant temperature is high. Possible causes are

  1. EGR temperature sensor circuit open.
  2. Defective EGR temperature sensor.
  3. EGR malfunction.

To set DTC, start engine and warm to normal operating temperature. Turn ignition off and wait at least 5 seconds. Select MODE 1 with scan tool. Measure voltage between ground and ECM terminal No. 92 (throttle position sensor signal) by backprobing. see scheme 1and see scheme 2. While observing voltmeter, drive vehicle at 6 MPH or more with engine speed at 1800-2800 RPM and TP sensor voltage at.86-2.00 volts for at least 5 consecutive seconds. Select MODE 7.

Malfunction is detected when EGR flow is detected under conditions that do not call for EGR. Possible causes are

  1. EGR Volume Control Valve (EGR-VCV) circuit open or shorted.
  2. EGR-VCV leaking or stuck open.
  3. Defective EGR temperature sensor.
  1. To set DTC, turn ignition on. Select MODE 1 with scan tool. Ensure engine coolant temperature is 14-95°F (-10-35°C). Measure voltage between ground and ECM terminal No. 72 (EGR temperature sensor signal) by backprobing. see scheme 1and see scheme 2. Ensure voltage is less than 4.8 volts. Start engine and let it idle for at least 80 seconds.
  2. Turn ignition off and wait at least 5 seconds. Repeat step 1. Select MODE 3.

Malfunction is detected when canister purge flow is detected when EVAP-CPVCV is closed. Possible causes are

  1. Defective EVAP Control System Pressure Sensor (EVAP-CSPS).
  2. EVAP-CPVCV stuck open.
  3. Defective EVAP Canister Vent Control Valve (EVAP-CVCV).
  4. Defective EVAP canister.
  5. EVAP system hoses plugged or misrouted.

Note. Before performing test, ensure ambient temperature is 41°F (5°C) or more.

To set DTC, start engine and warm to normal operating temperature. Turn ignition off and wait at least 5 seconds. Start engine and let it idle for at least 20 seconds. Select MODE 7 with scan tool.

Malfunction is detected when EVAP-CVCV remains closed under certain driving conditions. Possible causes are

  1. Defective EVAP-CVCV.
  2. Faulty EVAP Control System Pressure Sensor (EVAP-CSPS) or circuit.
  3. Blockage in hose connected to EVAP-CVCV.
  4. Defective water separator.
  5. EVAP canister saturated with water.

To set DTC, turn ignition on. Select DATA MONITOR with scan tool. Start engine and drive vehicle at 50 MPH. If a malfunction exists, DTC will set within 15 minutes.

Note. Use the following test to check overall function of EVAP purge flow monitoring system. During this test, DTC may not be confirmed.

Malfunction is detected when EVAP system is not functioning properly or there is a leak in hose between EVAP-CSPS and intake manifold. Possible causes are

  1. EVAP Canister Purge Volume Control Valve (EVAP-CPVCV) stuck closed.
  2. Faulty EVAP Control System Pressure Sensor (EVAP-CSPS) or circuit.
  3. Leak or blockage in EVAP-CSPS hose.
  4. EVAP canister cracked.
  5. Fault in EVAP-CPVCV circuit.
  6. Defective closed throttle position switch.
  7. Plugged purge port.
  8. Defective EVAP Canister Vent Control Valve (EVAP-CVCV).
  1. To check overall function of EVAP purge flow monitoring system, raise drive wheels and support vehicle. Start engine and warm to normal operating temperature. Ensure Traction Control System (TCS) is turned off. Turn ignition off and wait at least 5 seconds.
  2. Start engine and wait at least 70 seconds. With engine idling, measure and record voltage between ground and ECM terminal No. 84 (EVAP-CSPS signal) by backprobing. see scheme 1and see scheme 2.
  3. With transmission in a forward gear, turn A/C headlights and rear window defogger on. Hold steering wheel in the fully turned position. Increase engine speed to about 3000 RPM.
  4. While observing voltmeter, maintain conditions in step 3) for at least one minute. Voltage should remain.1 volt less than voltage measured at idle.

Note. Use the following test to check overall function of EVAP-CVCV circuit. During this test, DTC may not be confirmed.

Malfunction is detected when EVAP-CVCV remains open under certain driving conditions. Possible causes are

  1. Defective EVAP-CVCV.
  2. Faulty EVAP Control System Pressure Sensor (EVAP-CSPS) or circuit.
  3. EVAP Canister Vent Control Valve (EVAP-CVCV) hose plugged.
  4. Defective water separator.
  5. EVAP canister saturated with water.
  6. Defective vacuum cut valve.

To check overall function of EVAP-CVCV circuit, disconnect hose from water separator. (Scheme 5) Disconnect EVAP-CVCV harness connector. Using jumper wires, apply battery voltage to EVAP-CVCV terminals. see scheme 22 Air should not flow through EVAP-CVCV. Remove jumper wires. Air should flow. If operation is not as specified, go to PROCEDURE. If operation is as specified, go to DTC P0440, P0455 OR P1440: EVAP CONTROL SYSTEM.

Malfunction is detected when ECM receives a high voltage from fuel level sensor. Possible causes are

  1. Fuel level sensor circuit open or shorted.
  2. Defective fuel level sensor.

To set DTC, turn ignition on. Select DATA MONITOR with scan tool. Wait at least 5 seconds.

Malfunction is detected when ECM receives an improper voltage signal from vacuum cut valve by-pass valve. Possible causes are

  1. Vacuum cut valve by-pass valve circuit open or shorted.
  2. Defective vacuum cut valve by-pass valve.

To set DTC, turn ignition on. Select DATA MONITOR with scan tool. Start engine and wait at least 5 seconds.

Note. Use the following test to check overall function of vacuum cut valve by-pass valve. During this test, DTC may not be confirmed.

Malfunction is detected when vacuum cut valve by-pass valve does not operate properly. Possible causes are

  1. Defective vacuum cut valve by-pass valve.
  2. Defective vacuum cut valve.
  3. Blockage in by-pass hoses.
  4. Fault in EVAP Control System Pressure Sensor (EVAP-CSPS) or circuit.
  5. Defective EVAP Canister Vent Control Valve (EVAP-CVCV).
  6. Blockage in hose between fuel tank and vacuum cut valve.
  7. Blockage in hose between EVAP canister and vacuum cut valve.
  8. Defective EVAP canister.
  9. Blockage in fuel tank purge port.

To check overall function of vacuum cut valve by-pass valve, perform step 1 of PROCEDURE.

Malfunction is detected when ECM receives an incorrect signal from Transmission Control Module (TCM). Possible causes are

  1. Circuit between ECM and TCM is open or shorted.
  2. Weak battery.
  3. Defective TCM.

To set DTC, turn ignition on. Select DATA MONITOR with scan tool. Start engine and let it idle for at least 40 seconds.

Note. Use the following test to check overall function of PNP switch circuit. During this test, DTC may not be confirmed.

Malfunction is detected when PNP switch signal does not change between starting and driving. Possible causes are

  1. PNP switch circuit open or shorted.
  2. Defective PNP switch.

To check overall function of PNP switch circuit, turn ignition on. Measure voltage between body ground and ECM terminal No. 42 by backprobing. see scheme 1and see scheme 2. With A/T in Park or Neutral, or M/T in Neutral, voltage should be about zero volts. With transmission in any other position, battery voltage should exist.

More articles — Engine Controls - Self-Diagnostics - 2.0