EGR System Malfunction

• P0401 indicates the Self Test has detected insufficient EGR flow.
• P1408 indicates EGR flow is less than required calibrated limited.

• Vacuum supply.
• EGR valve stuck closed.
• EGR valve leaks vacuum.
• EGR flow path restricted.
• EGRVR circuit shorted to PWR.
• VREF open to DPFEGR sensor.
• DPFEGR sensor downstream hose off or plugged.
• EGRVR circuit open to PCM.
• VPWR open to EGRVR solenoid.
• DPFEGR sensor hoses both off.
• DPFEGR sensor hoses reversed.
• Damaged EGR orifice tube.
• Damaged EGRVR solenoid.
• Damaged PCM.

• Receives signals from the engine coolant temperature (ECT) sensor, intake air temperature (IAT) sensor, throttle position (TP) sensor, mass air flow (MAF) sensor, and crankshaft position (CKP) sensor to provide information on engine operating conditions to the PCM.
• The engine must be warm, stable and running at a moderate load and rpm before the EGR system is activated. The PCM deactivates EGR during idle, extended wide open throttle or whenever a failure is detected in an EGR component or EGR required component.

• Receives a variable duty cycle signal (0 to 100%) from the PCM. The higher the duty cycle, the more vacuum the solenoid diverts to the EGR valve.

• An increase in vacuum acting on the EGR valve diaphragm overcomes the valve spring and begins to lift the EGR valve pintle off its seat, causing exhaust gas to flow into the intake manifold.

• One side of the tube is exposed to exhaust backpressure and the other side to the intake manifold, causing a pressure drop across the orifice whenever there is EGR flow. When the EGR valve closes, there is no longer any flow across the metering orifice and pressure on both sides of the orifice is the same.

• Measures the actual pressure drop across the metering orifice and relays a proportional voltage signal (0 to 5 V) to the PCM.

• Was PCM Quick Test performed? 

• Disconnect vacuum hose at EGR valve and connect hose to vacuum gauge.
  NOTE: Since EGR vacuum hose is disconnected, ignore DTCs during this KOER Self Test.
• Run Key ON, Engine Running (KOER) Self Test while monitoring gauge.
  • Approximately 30 seconds into test, EGR flow will be requested for a few seconds. The vacuum at this time should increase above 5.4 kPa (1.6 in-Hg) to open the valve.
• Did the vacuum increase to 10 kPa (3.0 in-Hg) or greater at any time during KOER Self Test? 

• Visually inspect both pressure hoses for reversed connection at DPFEGR sensor or at orifice tube assembly.
• Inspect both hoses for improper routing. Hoses should not be pinched or have dips where water could settle and freeze.
• Inspect both hoses for leaks and blockage.
• Inspect DPFEGR sensor and orifice tube assembly for blockage or damage at pick up tubes.
• Is there a fault detected? 

• Disconnect pressure hoses at DPFEGR sensor.
• Connect a hand vacuum pump to the downstream connection at sensor (intake manifold side of sensor or the smaller diameter pickup tube).
• Key ON, Engine OFF (KOEO).
• Access DPFEGR PID with a NGS Tester and note PID value.
• Apply 27-30 kPa (8-9 in-Hg) vacuum to the DPFEGR sensor and hold for a few seconds.
• Quickly release vacuum.
  • The DPFEGR PID voltage must be between 0.2 and 1.3 volt with the key on and no vacuum applied.
  • The DPFEGR PID voltage must increase to greater than 4.0 volts with the vacuum applied.
  • The DPFEGR PID must drop to less than 1.5 volts in less than 3 seconds when vacuum is released.
• Key OFF.
• Did the DPFEGR PID voltage indicate a fault in the DPFEGR sensor? 

• Disconnect vacuum hose at EGR valve and plug hose.
• Connect a hand vacuum pump to EGR valve.
• Start engine and bring to idle.
• Access DPFEGR and RPM PIDs with NGS Tester.
• Slowly apply 27--34 kPa (8--10 in-Hg) of vacuum to the EGR valve and hold it for 10 seconds. If engine wants to stall, increase rpm with throttle to maintain a minimum of 1000 rpm.
• Look for the following:
  • EGR valve starts opening at about 5.4 kPa (1.6 in-Hg) vacuum indicated by increasing DPFEGR PID voltage.
  • DPFEGR PID voltage increasing until EGR valve is fully open. DPFEGR PID should read 2.5 volts minimum with full vacuum applied.
  • DPFEGR PID voltage steady when vacuum is held. If voltage drops within a few seconds, the EGR valve or vacuum source could be leaking.
• Did the DPFEGR PID voltage indicate that the EGR valve is operating as described in this test? 

• Inspect vacuum lines between vacuum source and EGRVR solenoid and between EGRVR solenoid and EGR valve for leaks, kinks, disconnects, blockage, routing or any damage.
• Disconnect vacuum hoses at EGRVR solenoid.
• Connect EGRVR solenoid vacuum source hose to a vacuum gauge.
• With engine warm and at idle, take a vacuum reading.
• Was vacuum gauge reading a minimum of 51 kPa (15 in-Hg) at idle and vacuum lines OK? 

• Disconnect EGRVR solenoid.
• Key ON, Engine OFF (KOEO).
• Measure voltage of VPWR circuit between the EGRVR solenoid harness connector and chassis ground.
• Was EGRVR solenoid VPWR voltage greater than 10.5 V? 

• Measure resistance across EGRVR solenoid.
• Is solenoid resistance between 26 and 40 ohms? 

• Disconnect PCM.
• Install Breakout Box, leave PCM disconnected.
• Key ON, Engine OFF (KOEO).
• Measure voltage between PCM test pin 47 (EGRVR) and chassis ground.
• Key OFF.
• Was voltage greater than 1.0 V? 

• Measure resistance of EGRVR circuit between PCM test pin 47 and the EGRVR solenoid harness connector.
• Is resistance less than 5.0 ohms? 

• Remove Breakout Box.
• Reconnect PCM and EGRVR solenoid.
• Disconnect vacuum hose at the EGR valve and connect to a vacuum gauge.
• Key ON, Engine Running (KOER).
• With engine at idle, jumper PCM test pin 47 (EGRVR) to chassis ground.
• Is vacuum gauge reading 13.5 kPa (4.0 in-Hg) or greater? 

• Visually inspect the EGR system for signs of intermittent failure. 
• Is a fault found?

• Visually inspect both pressure hoses for reversed connection at DPFEGR sensor or at orifice tube assembly.
• Inspect both hoses for improper routing. Hoses should not be pinched or have dips where water could settle or freeze.
• Inspect both hoses for leaks and blockage.
• Inspect DPFEGR sensor and orifice tube assembly for blockage or damage at the pickup tubes.
• Is a fault detected? 

• Disconnect pressure hoses at DPFEGR sensor.
• Connect a hand vacuum pump to the downstream connection at sensor (intake manifold side of sensor or the smaller diameter pickup tube.)
• Key ON, Engine OFF (KOEO).
• Access DPFEGR PID with NGS Tester and note PID value.
• Apply 27--30 kPa (8--9 in-Hg) vacuum to the DPF EGR sensor and hold for a few seconds.
• Quickly release vacuum.
  • The DPFEGR PID voltage must be between 0.2 and 1.3 V with the key on and no vacuum applied.
  • The DPFEGR PID voltage must increase to greater than 4.0 V with the vacuum applied.
  • The DPFEGR PID must drop to less than 1.5 V in less than 3 seconds when vacuum is released.
• Does the DPFEGR PID voltage indicate a fault in the DPFEGR sensor? 

• Disconnect vacuum hose at EGR valve and plug hose.
• Connect a hand vacuum pump to EGR valve.
• Start engine and bring to idle.
• Access DPFEGR and RPM PIDs with NGS Tester.
• Slowly apply 17--34 kPa (5--10 in-Hg) of vacuum to the EGR valve and hold it for 10 seconds. If engine wants to stall, increase rpm with throttle to maintain a minimum of 800 rpm.
• Look for the following:
  • EGR valve starts opening at about 5.4 kPa (1.6 in-Hg) vacuum indicated by increasing DPFEGR PID voltage.
  • DPFEGR PID voltage increasing until EGR valve is fully open. DPFEGR PID should read 2.5 volts minimum with full vacuum applied.
  • DPFEGR PID voltage steady when vacuum is held. If voltage drops within a few seconds, the EGR valve or vacuum source could be leaking.
• Key OFF.
• Did the DPFEGR PID voltage indicate that the EGR valve is operating as described in this test? 

• Disconnect PCM.
• Install Breakout Box and connect PCM to Breakout Box.
• Disconnect plugged hose at EGR valve and connect to a vacuum gauge.
• Key ON, Engine Running (KOER).
• Jumper PCM test pin 47 (EGRVR) to chassis ground to activate the EGRVR solenoid to full ON. At idle, the vacuum gauge should read above 13.5 kPa (4.0 in-Hg).
• Observe vacuum gauge for an indication of a fault while performing the following:
  • Lightly tap the EGRVR solenoid and wiggle the EGRVR solenoid connector, vacuum lines and vehicle harness between the solenoid and PCM. A fault is indicated by a sudden drop in vacuum reading.
• Was a fault indicated? 

See TEST 4: INTERMITTENT

• Make sure to reconnect all disconnected connectors.
• Clear DTCs from PCM memory using NGS tester generic OBD-II function.
• Perform PCM Quick Test.
• Is same DTC present? 

• P0402 indicates Self Test has detected DPFEGR signal at idle is greater than at KOEO by a calibrated amount.

• Vacuum supply.
• EGR valve stuck closed.
• EGR valve leaks vacuum.
• EGR flow path restricted.
• EGRVR circuit shorted to PWR.
• VREF open to DPFEGR sensor.
• DPFEGR sensor downstream hose off or plugged.
• EGRVR circuit open to PCM.
• VPWR open to EGRVR solenoid.
• DPFEGR sensor hoses both off.
• DPFEGR sensor hoses reversed.
• Damaged EGR orifice tube.
• Damaged EGRVR solenoid.
• Damaged PCM.

• Receives signals from the engine coolant temperature (ECT) sensor, intake air temperature (IAT) sensor, throttle position (TP) sensor, mass air flow (MAF) sensor, and crankshaft position (CKP) sensor to provide information on engine operating conditions to the PCM.
• The engine must be warm, stable and running at a moderate load and rpm before the EGR system is activated. The PCM deactivates EGR during idle, extended wide open throttle or whenever a failure is detected in an EGR component or EGR required component.

• Receives a variable duty cycle signal (0 to 100%) from the PCM. The higher the duty cycle, the more vacuum the solenoid diverts to the EGR valve.

• An increase in vacuum acting on the EGR valve diaphragm overcomes the valve spring and begins to lift the EGR valve pintle off its seat, causing exhaust gas to flow into the intake manifold.

• One side of the tube is exposed to exhaust backpressure and the other side to the intake manifold, causing a pressure drop across the orifice whenever there is EGR flow. When the EGR valve closes, there is no longer any flow across the metering orifice and pressure on both sides of the orifice is the same.

• Measures the actual pressure drop across the metering orifice and relays a proportional voltage signal (0 to 5 V) to the PCM.

• Was PCM Quick Test performed? 

• Disconnect vacuum hose at EGR valve and plug hose.
• Perform Key ON, Engine Running (KOER) Self Test.
• Was KOER DTC P0402 output or unable to run KOER Self Test due to engine stall or no start? 

• Connect EGR vacuum hose.
• Perform KOER Self Test.
• Key OFF.
• Was KOER DTC P0402 output or unable to run KOER Self Test due to engine stall or no start? 

• Trace each vacuum hose from EGR vacuum regulator solenoid and verify that each hose is connected properly (Refer to vehicle vacuum diagram label).
• Verify that the EGR valve vacuum hose is not pinched or plugged and is routed properly.
• Are vacuum hoses OK? 

• Disconnect pressure hoses at DPFEGR sensor.
• Connect a hand vacuum pump to the downstream connection at sensor (intake manifold side of sensor or the smaller diameter pickup tube).
• Key ON, Engine OFF (KOEO).
• Access DPFEGR PID with a NGS Tester and note PID value.
• Apply 27-30 kPa (8-9 in-Hg) vacuum to the DPFEGR sensor and hold for a few seconds.
• Quickly release vacuum.
  • The DPFEGR PID voltage must be between 0.2 and 1.3 volt with the key on and no vacuum applied.
  • The DPFEGR PID voltage must increase to greater than 4.0 volts with vacuum applied.
  • The DPFEGR PID must drop to less than 1.5 volts in less than 3 seconds when vacuum is released.
• Does the DPFEGR PID voltage indicate a fault in the DPFEGR sensor? 

• Disconnect vacuum hose at EGR valve and connect hose to vacuum gauge.
• Start engine and bring to an idle.
• While monitoring vacuum gauge, disconnect the EGRVR solenoid harness connector.
  • The EGR valve requires vacuum greater than 5.4 kPa (1.6 in-Hg) to begin to open. If the vacuum reading remains greater than 5.4 kPa. (1.6 in-Hg) after EGRVR solenoid is electrically disconnected, this would indicate a mechanical fault in the EGRVR solenoid.
• Key OFF.
• Did the EGR vacuum remain greater than 5.4 kPa (1.6 in-Hg) at idle even after the EGRVR solenoid is disconnected electrically? 

• Disconnect EGRVR solenoid vacuum hoses.
• Remove EGRVR solenoid vent cap (if removable).
• Remove filter and inspect for blockage or icing in some cases.
• With a hand vacuum pump (and the EGR vacuum supply port plugged), apply 34--51 kPa (10--15 in-Hg) of vacuum directly to EGRVR solenoid at the vacuum source port. If the vacuum holds or is slow to release to atmosphere, the EGRVR solenoid vent could be plugged or restricted.
• Is the EGRVR solenoid vent or vent filter plugged or restricted? 

• Disconnect EGRVR
• Measure resistance across EGRVR solenoid.
• Is resistance between 26 and 40 ohms? 

• Disconnect PCM.
• Install Breakout Box, leave PCM disconnected.
• Measure resistance between PCM test pin 47 (EGRVR solenoid) and PCM test pins 51 and 103 (PWR GND).
• Is resistance greater than 10K ohms? 

• Measure resistance between PCM test pin 47 (EGRVR solenoid) and PCM test pin 90 (VREF).
• Is resistance greater than 10K ohms? 

• Disconnect pressure hoses at DPFEGR sensor.
• Connect a hand vacuum pump to the downstream connection at sensor (intake manifold side of sensor or the smaller diameter pickup tube).
• Key ON, Engine OFF (KOEO).
• Access DPFEGR PID with NGS Tester and note PID value.
• Apply 27--30 kPa (8--9 in-Hg) vacuum to the DPFEGR sensor and hold for a few seconds.
• Quickly release vacuum.
  • The DPFEGR PID voltage must be between 0.2 and 1.3 volts with the key on and no vacuum applied.
  • The DPFEGR PID voltage must increase to greater than 4.0 volts with vacuum applied.
  • The DPFEGR PID must drop to less than 1.5 volts in less than 3 seconds when vacuum is released.
  • Key OFF.
• Did the DPFEGR PID voltage indicate a fault in the DPFEGR sensor? 

• Key ON, Engine OFF (KOEO).
• View DPFEGR PID with NGS Tester and make note of voltage.
  NOTE: Typical DPFEGR sensor voltage with no EGR flow is between 0.2 and 1.3 V.
• Disconnect and plug vacuum hose at EGR valve.
• Connect a hand vacuum pump to EGR valve.
• Start engine and bring to idle.
• Observe DPFEGR PID at idle and compare to the KOEO voltage. A higher voltage at idle could be due to a non-seating EGR valve.
• Apply just enough vacuum (7-10 kPa (2-3 in-Hg)) to EGR valve to open it without stalling engine and release vacuum.
• Repeat several times while observing DPFEGR PID on NGS Tester.
• DPFEGR PID voltage should increase as valve begins to open and return to initial voltage as vacuum is released.
• A slow to return voltage could be an indication of a binding or slow-closing EGR valve.
• Key OFF.
• Did DPFEGR PID voltage indicate an open, binding or slow-closing EGR valve? 

• Disconnect vacuum hose at EGR valve from hand vacuum pump and connect hose to a vacuum gauge.
• Key ON, Engine Running (KOER).
• Observe vacuum gauge for an indication of a fault while performing the following:
  • Lightly tap on the EGRVR solenoid; wiggle the EGRVR solenoid connector and vehicle harness between solenoid and PCM. A fault is indicated by a sudden jump in vacuum reading.
• Key OFF.
• Was a fault indicated? 

• Remove EGRVR solenoid vent filter and inspect for contamination and excessive water absorption. In cold climate excessive water in filter could freeze and plug the EGRVR solenoid vent.
• Inspect EGR vacuum hose for possible blockage and pinching.
• Key OFF.
• Was EGRVR solenoid vent or filter contaminated or vacuum hose plugged? 

• Make sure to reconnect all disconnected connectors.
• Clear DTCs from PCM memory using NGS tester generic OBD-II function.
• Perform PCM Quick Test.
• Is same DTC present?