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Engine Controls Self-Diagnostics - Tests - Pathfinder & QX4: Diagnosis Nissan Pathfinder II

Testing & Diagnostics 1 illustration ~6162 words

DIAGNOSTIC TESTS

Note. To identify circuits and wire colors referenced in testing, see appropriate diagram in WIRING DIAGRAMS article.

DTC Confirmation Test "A"

Malfunction is detected when MAF sensor voltage is too high when engine is not running. Depending on equipment available, use one of the following to set DTC

  1. Using Scan Tool Turn ignition on. Wait 6 seconds, then select MODE 7.
  2. Using MIL Turn ignition on. Wait 6 seconds and turn ignition off. Wait at least 5 seconds and turn ignition on. Retrieve DTCs using MIL. See SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - INTRODUCTION article.

DTC Confirmation Test "B"

Malfunction is detected when MAF sensor voltage is excessively low when engine is running. PCM will enter fail-safe mode. Depending on equipment available, use one of the following to set DTC

  1. Using Scan Tool Start engine and wait no more than 5 seconds. Select MODE 7.
  2. Using MIL Start engine and wait no more than 5 seconds. Turn ignition off and wait at least 5 seconds. Turn ignition on and retrieve DTCs using MIL. See SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - INTRODUCTION article.

DTC Confirmation Test "C"

Malfunction is detected when MAF sensor voltage is high under light-load driving conditions. Depending on equipment available, use one of the following to set DTC

  1. Using Scan Tool Start engine and warm to normal operating temperature. Run engine for at least 10 seconds at idle speed and select MODE 7.
  2. Using MIL Start engine and warm to normal operating temperature. Run engine for at least 10 seconds at idle speed. Turn ignition off and wait at least 5 seconds. Turn ignition on and retrieve DTCs using MIL. See SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - INTRODUCTION article.

DTC Confirmation Test "D" (Overall Function Check)

Malfunction is detected when MAF sensor voltage is low under heavy-load driving conditions. Depending on equipment available, use one of the following to set DTC

  1. Using Scan Tool Start engine and warm to normal operating temperature. Select MODE 1 and monitor mass airflow. Increase engine speed to 4000 RPM. Mass airflow output should increase as engine speed increases.
  2. Using MIL Start engine and warm to normal operating temperature. Measure voltage between ground and PCM terminal No. 54 by backprobing. see scheme 2 While monitoring voltage, increase engine speed to 4000 RPM. Voltage should increase as engine speed increases.

Malfunction "A" is detected when AP sensor voltage is too high or too low. Depending on equipment available, use one of the following to set DTC

  1. Using Scan Tool Turn ignition on. Wait at least 6 seconds then select MODE 7.
  2. Using MIL Turn ignition on. Wait at least 6 seconds and turn ignition off. Wait at least 5 seconds and turn ignition on. Retrieve DTCs using MIL. See SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - INTRODUCTION article.

Malfunction "B" is detected when AP sensor voltage is too high under light-load driving conditions. Depending on equipment available, use one of the following to set DTC

  1. Using Scan Tool Start engine and warm to normal operating temperature. Turn ignition off. Wait at least 5 seconds and restart engine. Run engine for at least 15 seconds at idle speed and select MODE 7.
  2. Using MIL Start engine and warm to normal operating temperature. Turn ignition off. Wait at least 5 seconds and restart engine. Run engine at idle speed for at least 15 seconds and turn ignition off. Wait at least 5 seconds and turn ignition on. Retrieve DTCs using MIL. See SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - INTRODUCTION article.

DTC Confirmation Test "C" (Overall Function Check)

Malfunction "C" is detected when AP sensor voltage is too low under heavy-load driving conditions. Depending on equipment available, use one of the following to check AP sensor circuit

  1. Using Scan Tool Turn ignition on. Select MODE 1 on scan tool. MAP reading should be more than 6.7 psi (46 kg/cm 2 ).
  2. Using MIL Turn ignition on. Measure voltage between PCM harness connector terminal No. 45 and ground by backprobing. see scheme 2 Voltage should be more than 1.74 volts.
Malfunction DetectedPossible CauseProcedure Required
"A"Open Or Short Circuit, AP Sensor"A"
"B"Vacuum Hose Leaking Or Plugged, Open Or Short Circuit, Intake Air Leaks, MAP/BARO Switch, AP Sensor"B"
"C"AP Sensor"A"

DTC CONFIRMATION IDENTIFICATION (DTC P0105)

Malfunction "A" is detected when IAT sensor voltage is too high or too low. Depending on equipment available, use one of the following to set DTC

  1. Using Scan Tool Turn ignition on. Wait 5 seconds then select MODE 7.
  2. Using MIL Turn ignition on. Wait 5 seconds and turn ignition off. Wait at least 5 seconds and turn ignition on. Retrieve DTCs using MIL. See SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - INTRODUCTION article.

Malfunction "B" is detected when IAT voltage is incorrect compared to Engine Coolant Temperature (ECT) sensor voltage. Depending on equipment available, use one of the following to set DTC

  1. Using Scan Tool Turn ignition on and select MODE 1. Ensure engine coolant temperature is less than 194°F (90°C) for entire procedure. Start engine and drive vehicle at 43 MPH for 100 consecutive seconds. Select MODE 7.
  2. Using MIL Turn ignition on. Measure voltage between PCM harness connector terminal No. 59 and ground by backprobing. see scheme 2 Voltage should be more than one volt. If voltage is not more than one volt, allow engine to cool until voltage is more than one volt. Ensure voltage does not decrease to less than one volt for entire procedure. Start engine and drive vehicle at 43 MPH for 100 consecutive seconds. Turn ignition off and wait at least 5 seconds. Turn ignition on and retrieve DTCs using MIL. See SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - INTRODUCTION article.

DTC Confirmation Test (DTC P0115)

Malfunction is detected when ECT voltage is too high or too low. PCM may enter fail-safe mode. Depending on equipment available, use one of the following to set DTC

  1. Using Scan Tool Turn ignition on. Wait at least 5 seconds, then select MODE 7.
  2. Using MIL Turn ignition on. Wait at least 5 seconds and turn ignition off. Wait at least 5 seconds and turn ignition on. Retrieve DTCs using MIL. See SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - INTRODUCTION article.

DTC Confirmation Test (DTC P0125)

Malfunction is detected when ECT voltage is incorrect, based on engine run time (engine coolant temperature too low). Depending on equipment available, use one of the following to set DTC

  1. Using Scan Tool Turn ignition on. Select MODE 1. Ensure coolant temperature is less than 50°F (10°C). Start engine and let idle for 65 minutes. Select MODE 7. DTC will set if coolant temperature does not increase to more than 59°F (15°C).
  2. Using MIL Turn ignition on. Measure voltage between ground and PCM harness connector terminal No. 59 by backprobing. see scheme 2 Ensure voltage is more than 3.8 volts. Start engine and let idle for 65 minutes. Voltage should be less than 3.8 volts. Turn ignition off and wait at least 5 seconds. Turn ignition on and retrieve DTCs using MIL. See SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - INTRODUCTION article. DTC will set if voltage does not decrease to less than 3.8 volts.

Malfunction "A" is detected when TP sensor voltage is too high or too low. PCM will enter fail-safe mode. Depending on equipment available, use one of the following to set DTC

  1. Using Scan Tool Start engine and drive vehicle for at least 5 seconds at 2 MPH or more. Ensure transmission is not in Park or Neutral. Select MODE 7.
  2. Using MIL Start engine and drive vehicle for at least 5 seconds at 2 MPH or more. Ensure transmission is not in Park or Neutral. Stop vehicle and turn ignition off. Wait at least 5 seconds and turn ignition on. Retrieve DTCs using MIL. See SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - INTRODUCTION article.

Malfunction "B" is detected when TP sensor voltage is high under light-load driving conditions. Depending on equipment available, use one of the following to set DTC

  1. Using Scan Tool Start engine and let idle for at least 10 seconds. Select MODE 7.
  2. Using MIL Start engine and let idle for at least 10 seconds. Turn ignition off and wait at least 5 seconds. Turn ignition on and retrieve DTCs using MIL. See SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - INTRODUCTION article.

Malfunction "C" is detected when TP sensor voltage is low under heavy-load driving conditions. Depending on equipment available, use one of the following to set DTC

  1. Using Scan Tool Start engine and warm to normal operating temperature. Measure voltage between ground and PCM harness connector terminal No. 101 by backprobing. see scheme 2 Select MODE 1 and monitor engine speed and MAF sensor voltage. Drive vehicle under a heavy-load condition (engine speed more than 2000 RPM and MAF voltage more than 3 volts) with voltage between ground and PCM terminal No. 101 more than 4 volts for at least 10 consecutive seconds. Select MODE 7.
  2. Using MIL Start engine and warm to normal operating temperature. Measure voltage between ground and PCM harness connector terminals No. 54 and 101 by backprobing. see scheme 2 Drive vehicle under a heavy-load condition with engine speed at 2000 RPM or more. Ensure voltage at PCM terminal No. 54 is more than 3 volts, and voltage at PCM terminal No. 101 is more than 4 volts. Maintain these conditions for at least 10 consecutive seconds. Stop vehicle and turn ignition off. Wait at least 5 seconds and turn ignition on. Retrieve DTCs using MIL. See SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - INTRODUCTION article.

DTC Confirmation Test (Overall Function Check)

Malfunction is detected when HO2S voltage is constantly.2-.4 volts. Start engine and warm to normal operating temperature. Measure voltage between ground and PCM harness connector terminal No. 50 (right bank) or No. 51 (left bank) by backprobing. see scheme 2 While monitoring voltmeter, increase engine speed to 2000 RPM under no load conditions. Voltage should continuously switch from less than.35 volt to more than.60 volt.

DTC P0131 or P0151 will set if HO2S voltage is constantly less than.6 volt. DTC P0132 or P0152 will set if HO2S voltage is constantly more than.35 volt. Start engine and warm to normal operating temperature. Measure voltage between PCM harness connector terminal No. 50 (right bank) or No. 51 (left bank) and ground by backprobing. see scheme 2 While monitoring voltmeter, increase engine speed to 2000 RPM under no load conditions. Voltage should be more than.6 volt at least one time. Voltage should be less than.3 volt at least one time.

Malfunction is detected when HO2S response time is too long. Start engine and warm to normal operating temperature. Measure voltage between PCM harness connector terminal No. 50 (right bank) or No. 51 (left bank) and ground by backprobing. see scheme 2 While monitoring voltmeter, increase engine speed to 2000 RPM under no load conditions. With PCM in Diagnostic Test Mode II, MIL should flash more than 5 times within 10 seconds.

DTC Confirmation Test

Malfunction is detected when HO2S voltage is too high. Depending on equipment available, use one of the following to set DTC

  1. Using Scan Tool Turn ignition on and wait at least 5 seconds. Turn ignition off and wait at least 5 seconds. Turn ignition on and wait at least 5 seconds. Select MODE 3.
  2. Using MIL Turn ignition on and wait at least 5 seconds. Turn ignition off and wait at least 5 seconds. Turn ignition on and retrieve DTCs using MIL. See SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - INTRODUCTION article.

Malfunction is detected when front HO2S heater circuit current is out of normal range. Depending on equipment available, use one of the following to set DTC

  1. Using Scan Tool Start engine and let idle for at least 6 seconds. Turn ignition off and wait at least 5 seconds. Start engine and let idle for at least 6 seconds. Select MODE 3 with scan tool.
  2. Using MIL Start engine and let idle for at least 6 seconds. Turn ignition off and wait at least 5 seconds. Turn ignition on and retrieve DTCs using MIL. See SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - INTRODUCTION article.

DTC P0137 or P0157 will set if rear HO2S minimum voltage is too high. DTC P0138 or P0158 will set if rear HO2S maximum voltage is too low. DTC P0139 or P0159 will set if rear HO2S response time is too long. DTC P0140 or P0160 will set if rear HO2S voltage is too high. Drive vehicle at a speed of more than 43 MPH for 2 consecutive minutes. Stop vehicle and leave engine running. Measure voltage between ground and PCM harness connector terminal No. 56 (right bank), or No. 57 (left bank) by backprobing. see scheme 2 While monitoring voltmeter, quickly increase engine speed to 4000 RPM under no load conditions and release accelerator pedal. Repeat 10 times.

  1. Voltage should be less than .54 volt at least once.
  2. Voltage should be more than .56 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 Overdrive off (A/T), or with transmission in 3rd gear (M/T), and recheck voltage.

Malfunction is detected when rear HO2S heater circuit current is out of normal range. Depending on equipment available, use one of the following to set DTC

  1. Using Scan Tool 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.
  2. Using MIL 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. Turn ignition on and retrieve DTCs using MIL. See SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - INTRODUCTION article.

Malfunction is detected when mixture ratio compensation amount is too large (mixture is too lean or too rich). Depending on equipment available, use one of the following to set DTC

  1. Using Scan Tool Start engine and warm to normal operating temperature. Turn ignition off and wait at least 5 seconds. Disconnect MAF sensor harness connector. see scheme 4 Start engine and let idle for at least 5 seconds. Turn ignition off and reconnect MAF sensor harness connector. Turn ignition on. Select MODE 7 and ensure DTC P0100 is set. Select MODE 4 and erase DTCs. Start engine and let idle for at least 10 minutes. Select MODE 7 and check for DTCs. If DTC P0171, P0172, P0174 or P0175 are present, go to «PROCEDURE»(ref-91142-S13838072972001030200000). If engine was difficult to start, fuel injection system has a malfunction. Attempt to start engine while depressing accelerator pedal. If engine does not start, check for intake or exhaust leaks or spark plug fouling.
  2. Using MIL Start engine and warm to normal operating temperature. Turn ignition off and wait at least 5 seconds. Disconnect MAF sensor harness connector. see scheme 4 Start engine and let idle for at least 5 seconds. Turn ignition off and reconnect MAF sensor harness connector. Turn ignition on and retrieve DTCs using MIL. See SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - INTRODUCTION article. Ensure DTC P0100 is set. Erase codes by switching PCM to Diagnostic Test Mode I. Start engine and let idle for at least 10 minutes. Retrieve DTCs using MIL. If DTC P0171, P0172, P0174 or P0175 are present, go to «PROCEDURE»(ref-91142-S13838072972001030200000). If engine was difficult to start, fuel injection system has a malfunction. Attempt to start engine while depressing accelerator pedal. If engine does not start, check for intake or exhaust leaks or spark plug fouling.

Malfunction is detected when TFT sensor voltage is too high or low, or when TFT voltage is rationally incorrect compared to ECT sensor and IAT sensor. Depending on equipment available, use one of the following to set DTC

  1. Using Scan Tool Turn ignition on. Wait at least 10 seconds then select MODE 7. If DTC is not set, select MODE 1 and monitor ECT sensor value. If engine temperature is more than 194°F (90°C), turn ignition off and allow engine to cool to less than 194°F (90°C). Turn ignition on. Wait at least 10 seconds then select MODE 7.
  2. Using MIL Turn ignition on. Wait at least 10 seconds then turn ignition off. Wait at least 5 seconds then turn ignition on. Retrieve DTCs using MIL. See SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - INTRODUCTION article. If DTC is not set, measure voltage between ground and PCM harness connector terminal No. 59 by backprobing. see scheme 2 If voltage is less than one volt, allow engine to cool until voltage is more than one volt. Turn ignition on and wait at least 10 seconds. Turn ignition off and wait at least 5 seconds. Turn ignition on. Retrieve DTCs using MIL.

Misfire is detected when crankshaft position sensor detects a fluctuation in engine speed. Depending on equipment available, use one of the following to set DTC

  1. Using Scan Tool Start engine and warm to normal operating temperature. Turn ignition off and wait at least 5 seconds. Start engine and drive vehicle at 1500-3000 RPM for at least 3 minutes. Hold accelerator pedal as steady as possible. Select MODE 7. Refer to freeze frame data for driving conditions in which DTC was set.
  2. Using MIL Start engine and warm to normal operating temperature. Turn ignition off and wait at least 5 seconds. Start engine and drive vehicle at 1500-3000 RPM for at least 3 minutes. Hold accelerator pedal as steady as possible. Turn ignition off and wait at least 5 seconds. Turn ignition on and retrieve DTCs using MIL. See SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - INTRODUCTION article.

Malfunction is detected when knock sensor voltage is too high or too low. Depending on equipment available, use one of the following to set DTC

  1. Using Scan Tool Start engine and let idle for at least 5 seconds. Select MODE 3 on scan tool.
  2. Using MIL Start engine and let idle for at least 5 seconds. Turn ignition off and wait at least 5 seconds. Turn ignition on and retrieve DTCs using MIL. See SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - INTRODUCTION article.

DTC P0335 will set if PCM does not receive proper pulse signal from CKP sensor while engine is running at a certain speed. DTC P1336 will set if chipping of flywheel teeth is detected by PCM. Depending on equipment available, use one of the following to set DTC

  1. Using Scan Tool Start engine and let idle for at least 15 seconds (for DTC P0335), or 2 minutes (for DTC P1336). Select MODE 7.
  2. Using MIL Start engine and let idle for at least 15 seconds (for DTC P0335), or 2 minutes (for DTC P1336). Turn ignition off and wait at least 5 seconds. Turn ignition on and retrieve DTCs using MIL. See SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - INTRODUCTION article.

Malfunction is detected when either one-degree signal or 120-degree signal is not sent to PCM during engine cranking. Depending on equipment available, use one of the following to set DTC

  1. Using Scan Tool Crank engine for at least 2 seconds. Select MODE 7.
  2. Using MIL Crank engine for at least 2 seconds. Turn ignition off and wait 5 seconds. Turn ignition on and retrieve DTCs using MIL. See SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - INTRODUCTION article.

DTC Confirmation Tests "B" & "C"

Malfunction "B" is detected when either one-degree signal or 120-degree signal is not sent to PCM often enough. Malfunction "C" is detected when the relationship between one-degree signal and 180-degree signal is out of normal range. Depending on equipment available, use one of the following to set DTC

  1. Using Scan Tool Start engine and idle for at least 2 seconds. Select MODE 7.
  2. Using MIL Start engine and idle for at least 2 seconds. Turn ignition off and wait 5 seconds. Turn ignition on and retrieve DTCs using MIL. See SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - INTRODUCTION article.

Malfunction is detected when EGR flow is not detected when EGR Control (EGRC) solenoid is energized by PCM. Start engine and warm to normal operating temperature. Check for EGR valve opening while quickly increasing engine speed to 3000 RPM. EGR valve should open and close without sticking. If operation is not as specified, go to PROCEDURE . If operation is as specified, diagnose EGR temperature sensor or circuit failure. See DTC P1401: EGR TEMPERATURE SENSOR .

Malfunction is detected when EGRC-BPT does not operate properly. Install vacuum gauge using a vacuum "T" to hose between EGRC-BPT and EGR valve. Raise drive wheels and support vehicle. Start engine and shift transmission into 1st gear. Observe vacuum gauge while keeping engine speed at 2000-2800 RPM. Vacuum should be 0-5.91 in. Hg. If vacuum is not as specified, go to PROCEDURE . If vacuum is as specified, check EGR system vacuum hoses for blockage, leaks or misconnection.

Malfunction is detected when 3-way catalyst does not operate properly. Start engine and drive vehicle at 43 MPH or more for 2 consecutive minutes. Stop vehicle and leave engine running. Measure voltage between ground and PCM harness connector terminals No. 50 (right front HO2S), or No. 51 (left front HO2S) and No. 56 (right rear HO2S), or No. 57 (left rear HO2S). Increase engine speed to 2000 RPM. Switching frequency of rear HO2S should be less than 75 percent of front HO2S switching frequency. If front HO2S does not switch more than 5 times within 10 seconds, diagnose front HO2S first. See DTC P0133 OR P0153: FRONT HEATED OXYGEN SENSOR .

Note. Fuel level should be low during this test.

Malfunction is detected when EVAP system has a leak or does not operate properly. Depending on equipment available, to set DTC, see USING SCAN TOOL or USING MIL .

Using Scan Tool

  1. Drive vehicle according to specified driving pattern to set System Readiness Test (SRT) codes. See SYSTEM READINESS TEST (SRT) CODES 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 under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - INTRODUCTION article. If EVAP system SRT is incomplete, turn ignition off, wait at least 5 seconds and go to next step.
  3. Perform driving pattern again. Stop vehicle and select MODE 3 on scan tool. If DTC P0440, P1440 or P1447 is set, perform appropriate diagnostic procedure. If DTC P0440, P1440 or P1447 is not set, go back to step 2 .

Malfunction is detected when improper voltage is sent to PCM through EVAP-CPVCV. Depending on equipment available, use one of the following to set DTC

  1. Using Scan Tool Start engine and let idle for at least 13 seconds. Select MODE 7.
  2. Using MIL Start engine and let idle for at least 13 seconds. Turn ignition off and wait at least 5 seconds. Turn ignition on and retrieve DTCs using MIL. See SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - INTRODUCTION article.

Malfunction is detected when improper voltage is sent to PCM through EVAP-CVCV. Depending on equipment available, use one of the following to set DTC

  1. Using Scan Tool Start engine and wait at least 8 seconds. Select MODE 7 on scan tool.
  2. Using MIL Start engine and wait at least 8 seconds. Turn ignition off and wait at least 5 seconds. Turn ignition on and retrieve DTCs using MIL. See SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - INTRODUCTION article.

Malfunction is detected when improper voltage is sent to PCM from EVAP-CSPS. Depending on equipment available, use one of the following to set DTC

  1. Using Scan Tool Start engine and warm to normal operating temperature. Measure voltage between ground and PCM harness connector terminal No. 60 (tank fuel temperature sensor) by backprobing. 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 on scan tool.
  2. Using MIL Start engine and warm to normal operating temperature. Measure voltage between ground and PCM harness connector terminal No. 60 (tank fuel temperature sensor) by backprobing. 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. Turn ignition off and wait at least 5 seconds. Turn ignition on and retrieve DTCs using MIL. See SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - INTRODUCTION article.

Malfunction is detected when zero MPH signal is sent to PCM while vehicle is moving. Depending on equipment available, use one of the following to check function of VSS circuit

  1. Using Scan Tool Raise drive wheels and support vehicle. Start engine. With transmission in a forward gear and wheels turning at 6 MPH, select MODE 1 and check VSS output signal. VSS output signal should be 6 MPH.
  2. Using MIL Raise drive wheels and support vehicle. Connect an oscilloscope between ground and PCM harness connector terminal No. 29 by backprobing. see scheme 2 Start engine. Shift transmission into a forward gear. Increase engine RPM until drive wheels are rotating at 25 MPH. VSS signal should be as shown. (Scheme 3)

Scheme 3

Scheme 3
Scheme 3

Malfunction is detected when IAC valve circuit is open. Depending on equipment available, use one of the following to set DTC

  1. Using Scan Tool Turn ignition on and wait at least 2 seconds. Select MODE 7.
  2. Using MIL Turn ignition on and wait at least 2 seconds. Turn ignition off and wait at least 5 seconds. Turn ignition on and retrieve DTCs using MIL. See SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - INTRODUCTION article.

Malfunction is detected when IAC valve circuit is shorted. Depending on equipment available, use one of the following to set DTC

  1. Using Scan Tool Start engine and warm to normal operating temperature. Turn ignition off and wait at least 5 seconds. Start engine and let idle for at least one minute. Select MODE 7 on scan tool.
  2. Using MIL Start engine and warm to normal operating temperature. Turn ignition off and wait at least 5 seconds. Start engine and let idle for at least one minute. Turn ignition off and wait at least 5 seconds. Turn ignition on and retrieve DTCs using MIL. See SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - INTRODUCTION article.

Malfunction is detected when voltage is sent to PCM from closed TP switch when throttle valve is opened. Start engine and warm to normal operating temperature. Measure voltage between ground and PCM harness connector terminal No. 28 by backprobing. see scheme 2 Battery voltage should exist at idle. At 2000 RPM, about zero volts should exist.

Malfunction is detected when PCM receives incorrect voltage from Transmission Control Module (TCM) continuously. Start engine. Measure voltage between ground and PCM harness connector terminals No. 26 and 27 by backprobing. see scheme 2 Voltage should be 6-8 volts.

Malfunction is detected when PCM calculation function is malfunctioning. Depending on equipment available, use one of the following to set DTC

  1. Using Scan Tool Start engine and let idle for at least 2 seconds. Select MODE 7.
  2. Using MIL Start engine and let idle for at least 2 seconds. Turn ignition off and wait at least 5 seconds. Turn ignition on and retrieve DTCs using MIL. See SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - INTRODUCTION article.

Malfunction is detected when MAP/BARO solenoid is energized when it has not been energized by PCM. Depending on equipment available, use one of the following to set DTC

  1. Using Scan Tool Turn ignition on and wait at least 10 seconds. Select MODE 7 on scan tool.
  2. Using MIL Turn ignition on and wait at least 10 seconds. Turn ignition off and wait at least 5 seconds. Turn ignition on and retrieve DTCs using MIL. See SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - INTRODUCTION article.

Malfunction is detected when there is little difference in Absolute Pressure (AP) sensor input voltage between ambient barometric pressure and intake manifold pressure. Depending on equipment available, use one of the following to set DTC

  1. Using Scan Tool Start engine and warm to normal operating temperature. Turn ignition off and wait at least 5 seconds. Turn ignition on and ensure Tank Fuel Temperature (TFT) is more than 32°F (0°C). TFT sensor voltage must be less than 4.2 volts. Start engine and let idle for at least 10 seconds. Select MODE 7 on scan tool.
  2. Using MIL Start engine and warm to normal operating temperature. Turn ignition off and wait at least 5 seconds. Turn ignition on. Measure voltage between ground and PCM harness connector terminal No. 60 by backprobing. see scheme 2 Ensure voltage is less than 4.2 volts. Start engine and let idle for at least 10 seconds. Turn ignition off and wait at least 5 seconds. Turn ignition on and retrieve DTCs using MIL. See SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - INTRODUCTION article.

Malfunction is detected when PCM does not operate in closed loop. Start engine and warm to normal operating temperature. Measure voltage between ground and PCM harness connector terminal No. 50 (right bank), or No. 51 (left bank) by backprobing. 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 PCM does not receive signal from ignition primary circuit. Depending on equipment available, use one of the following to set DTC

  1. Using Scan Tool Start engine. If engine will not start, crank engine for at least 5 seconds. Select MODE 7 on scan tool.
  2. Using MIL Start engine. If engine will not start, crank engine for at least 5 seconds. Turn ignition off and wait at least 5 seconds. Turn ignition on and retrieve DTCs using MIL. See SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - INTRODUCTION article.

Malfunction is detected when PCM receives improper voltage signal through EGRC solenoid. Depending on equipment available, use one of the following to set DTC

  1. Using Scan Tool Turn ignition on and wait at least 5 seconds. Select MODE 7.
  2. Using MIL Turn ignition on and wait at least 5 seconds. Turn ignition off and wait at least 5 seconds. Turn ignition on and retrieve DTCs using MIL. See SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - INTRODUCTION article.

Malfunction is detected when EGR temperature sensor voltage is low when engine coolant temperature is low. Depending on equipment available, use one of the following to set DTC

  1. Using Scan Tool Turn ignition on and select MODE 1 on scan tool. Ensure engine coolant temperature is less than 104°F (40°C). If engine temperature is more than specified, allow engine to cool. Start engine and let idle for at least 8 seconds. Select MODE 7 on scan tool.
  2. Using MIL Turn ignition on. Measure voltage between PCM harness connector terminal No. 59 and ground by backprobing. see scheme 2 If voltage is 1.5 volts or less, allow engine to cool. Start engine and idle for at least 8 seconds. Turn ignition off and wait at least 5 seconds. Turn ignition on and retrieve DTCs using MIL. See SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - INTRODUCTION article.

DTC Confirmation Test "B" (Overall Function Check)

Malfunction is detected when EGR temperature sensor voltage is high when engine coolant temperature is high. Start engine and warm to normal operating temperature. Let engine idle for at least 2 minutes. Ensure EGR valve is not open. If EGR valve is open, go to DTC P1402: EGR FUNCTION. If EGR valve is not open, measure voltage between ground and PCM harness connector terminal No. 63 by backprobing. see scheme 2 With engine speed increased to 1500 RPM, fully open EGR valve by hand. Voltage should decrease to less than 1.5 volts. If voltage is as specified, perform diagnosis for DTC P0400 and P1400. See DTC P0400: EGR FUNCTION and DTC P1400: EGR CONTROL (EGRC) SOLENOID. If voltage is not as specified, go to PROCEDURE.

Malfunction is detected when EGR flow is detected when EGRC solenoid is not actuated by PCM. Depending on equipment available, use one of the following to set DTC

  1. Using Scan Tool Turn ignition on and select MODE 1 on scan tool. Ensure engine coolant temperature is 14-104°F (-10-40°C) and EGR temperature sensor voltage is less than 4.8 volts. Start engine and let idle for at least 60 seconds. Turn ignition off. Repeat previous steps. Turn ignition on and select MODE 3 on scan tool.
  2. Using MIL Turn ignition on. Measure voltage between ground and PCM terminal No. 59 (engine coolant temperature) by backprobing. see scheme 2 Ensure voltage is 3.2-4.4 volts. Measure voltage between ground and PCM terminal No. 63 (EGR temperature sensor) by backprobing. Ensure voltage is less than 4.8 volts. Start engine and let idle for at least 60 seconds. Turn ignition off and wait at least 5 seconds. Turn ignition on and retrieve DTCs using MIL. See SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - INTRODUCTION article.

Malfunction is detected when canister purge flow is detected when EVAP-CPVCV is closed. Depending on equipment available, use one of the following to set DTC

  1. Using Scan Tool 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 2 seconds. Select MODE 7 on scan tool.
  2. Using MIL Start engine and warm to normal operating temperature. Turn ignition off and wait at least 5 seconds. Start engine and let idle for at least 2 seconds. Turn ignition off and wait at least 5 seconds. Turn ignition on and retrieve DTCs using MIL. See SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - INTRODUCTION article.

Malfunction is detected when EVAP-CVCV remains closed under certain driving conditions. Depending on equipment available, use one of the following to set DTC

  1. Using Scan Tool Start engine and drive vehicle at a speed of about 50 MPH for 15 minutes. Select MODE 7 on scan tool.
  2. Using MIL Start engine and drive vehicle at a speed of about 50 MPH for 15 minutes. Turn ignition off and wait at least 5 seconds. Turn ignition on and retrieve DTCs using MIL. See SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - INTRODUCTION article.

Malfunction is detected when EVAP system is not functioning properly or there is a leak in hose between EVAP Control System Pressure Sensor (EVAP-CSPS) and intake manifold. Raise drive wheels and support vehicle. Start engine and warm to normal operating temperature. Turn ignition off and wait at least 5 seconds. Start engine and wait at least 70 seconds. Measure and record voltage between PCM harness connector terminal No. 62 and ground by backprobing. see scheme 2 While monitoring voltage, maintain the following conditions for at least one minute

  1. A/C on.
  2. Steering wheel turned fully.
  3. Headlights on.
  4. Rear window defogger on.
  5. Engine speed at 3000 RPM.
  6. Transmission in any forward gear.

Ensure voltage remains .1 volt less than voltage measured at idle for at least one second. DTC may not be confirmed using this procedure.

Malfunction is detected when EVAP-CVCV remains open under certain driving conditions. Check EVAP-CVCV. See DTC P0446: EVAP CANISTER VENT CONTROL VALVE (EVAP-CVCV) . If EVAP-CVCV does not operate as specified, go to PROCEDURE . If EVAP-CVCV is okay, go to DTC P0440 OR P1440: EVAP CONTROL SYSTEM .

Malfunction is detected when an improper voltage signal is sent to PCM through vacuum cut valve by-pass valve. Depending on equipment available, use one of the following to set DTC

  1. Using Scan Tool Start engine and run for at least 5 seconds. Select MODE 7 on scan tool.
  2. Using MIL Start engine and run for at least 5 seconds. Turn ignition off and wait at least 5 seconds. Turn ignition on and retrieve DTCs using MIL. See SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - INTRODUCTION article.

Malfunction is detected when vacuum cut valve by-pass valve does not operate properly. Remove vacuum cut valve and vacuum cut valve by-pass valve as an assembly. see scheme 30 Check vacuum cut valve operation. Go to step 1 of PROCEDURE.

Malfunction is detected when PCM receives incorrect voltage from Transmission Control Module (TCM). Depending on equipment available, use one of the following to set DTC

  1. Using Scan Tool Start engine and let idle for at least 40 seconds. Select MODE 7.
  2. Using MIL Start engine and let idle for at least 40 seconds. Turn ignition off and wait at least 5 seconds. Turn ignition on and retrieve DTCs using MIL. See SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - INTRODUCTION article.

Malfunction is detected when PNP switch signal does not change between starting and driving. Turn ignition on. Measure voltage between PCM harness connector terminal No. 22 and ground by backprobing. see scheme 2 With transmission in Park or Neutral, voltage should be about zero volts. With transmission in any other gear, about 5 volt should exist. DTC may not be confirmed using this procedure.

More articles — Engine Controls Self-Diagnostics - Tests - Pathfinder & QX4