Service engine soon
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Joined: Oct 2002
Posts: 7,295
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From: St. Louis (Out in the woods)
P0402 Diagnostic
HE20 DTC P0402: CHECK FOR EGR FLOW AT IDLE WITH EGR VACUUM HOSE DISCONNECTED
Diagnostic Trouble Code (DTC) P0402 indicates that Self-Test has detected EGR flow at idle.
NOTE:
If DTC P1405 is in Continuous Memory, diagnose that first starting with HE50.
Possible causes:
-- EGR valve stuck open.
-- EGR vacuum regulator solenoid vent plugged or iced.
-- EVR circuit shorted to GND.
-- EVR circuit shorted to VREF.
-- Improper vacuum hose connection.
-- Plugged/pinched EGR Vacuum Regulator Solenoid vacuum hose.
-- Plugged EGR tube.
-- Damaged EGR Vacuum Regulator Solenoid solenoid.
-- Pinched/iced pressure hoses.
-- Damaged Differential Pressure Feedback EGR (D.P.F. EGR) sensor.
-- Damaged PCM.
l Key off.
l Disconnect vacuum hose at EGR valve and plug hose.
l Run Key On Engine Running (KOER) Self-Test.
l Is KOER DTC P0402 output or unable to run KOER Self-Test due to engine stall or no start?
Yes
There is possible EGR flow at idle. INSPECT pressure hoses first for pinching and icing. If OK, REMOVE and INSPECT the EGR valve and EGR tube for signs of contamination, unusual wear, carbon deposits, binding and other damage. SERVICE as necessary (use Rotunda EGR Valve Cleaner 021-00056 or equivalent, if needed). RECONNECT all components. COMPLETE PCM Reset to clear DTCs. RERUN «Quick Test».
No
RECONNECT vacuum hose to EGR valve. GO to «HE21».
HE21 CHECK FOR EGR FLOW AT IDLE WITH EGR VACUUM HOSE CONNECTED
l Key off.
l EGR vacuum hose connected.
l Run KOER Self-Test.
l Is KOER DTC P0402 output or unable to run KOER Self-Test due to engine stall or no start?
Yes
There is possible EGR flow at idle. GO to «HE22».
No
The fault that produced DTC P0402 is intermittent. INSPECT pressure hoses for pinching and icing. SERVICE as necessary. If OK, GO to «HE30».
HE22 CHECK EGR SYSTEM VACUUM HOSES FOR INTEGRITY AND CONNECTION
NOTE:
A pinched or plugged EGR vacuum hose can trap vacuum between the EGR Vacuum Regulator solenoid and EGR valve not allowing the EGR valve to close.
l Key off.
l Trace each vacuum hose from EGR Vacuum Regulator solenoid and verify that each hose is connected correctly. (Refer to vehicle vacuum diagram label.)
l Verify that the EGR valve vacuum hose is not pinched or plugged and routed properly.
l Are vacuum hoses OK?
Yes
RECONNECT vacuum hoses. GO to «HE23».
No
SERVICE vacuum hoses as necessary. RECONNECT all components. COMPLETE PCM Reset to clear DTCs. RERUN «Quick Test».
HE23 CHECK D.P.F. EGR SENSOR OUTPUT BY APPLYING VACUUM WITH HAND PUMP
l Key off.
l Disconnect pressure hoses at D.P.F. EGR sensor.
l Connect a hand vacuum pump to the downstream connection at sensor (intake manifold side of sensor or the smaller diameter pickup tube).
l Key on, engine off.
l Access DPFEGR PID with a Scan Tool and note PID value.
l Apply 27-30 kPa (8-9 in-Hg) vacuum to the D.P.F. EGR sensor and hold for a few seconds.
l 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.
l Does the DPFEGR PID voltage indicate a fault in the D.P.F. EGR sensor?
Yes
REPLACE damaged D.P.F. EGR sensor. RECONNECT all components. COMPLETE PCM Reset to clear DTCs. RERUN «Quick Test».
No
RECONNECT D.P.F. EGR sensor. GO to «HE24».
HE24 CHECK FOR EGR FLOW AT IDLE WITH EGR VACUUM REGULATOR SOLENOID CONNECTOR OFF
l Key off.
l Disconnect vacuum hose at EGR valve and connect hose to vacuum gauge.
l Start engine and bring to an idle.
l While monitoring vacuum gauge, disconnect the EGR Vacuum Regulator solenoid vehicle 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 the EGR Vacuum Regulator solenoid is electrically disconnected, this would indicate a mechanical fault in the EGR Vacuum Regulator solenoid.
l Does the EGR vacuum remain greater than 5.4 kPa (1.6 in-Hg) at idle even after EGR Vacuum Regulator solenoid is electrically disconnected?
Yes
This indicates a fault in the EGR Vacuum Regulator solenoid. GO to «HE25».
No
GO to «HE26».
HE25 INSPECT EGR VACUUM REGULATOR SOLENOID VENT FOR PLUGGING
NOTE:
A plugged EGR Vacuum Regulator solenoid vent will not allow EGR vacuum to vent to atmosphere.
l Key off.
l Disconnect EGR Vacuum Regulator solenoid vacuum hoses.
l Remove EGR Vacuum Regulator solenoid vent cap (if removable).
l Remove filter and inspect for blockage or icing in some cases.
l With the EGR vacuum supply port plugged, apply 34-51 kPa (10-15 in-Hg) of vacuum directly to EGR Vacuum Regulator solenoid vacuum source port with a hand vacuum pump. If the vacuum holds or is slow to release to atmosphere, the EGR Vacuum Regulator solenoid vent could be plugged or restricted.
l Is the EGR Vacuum Regulator solenoid vent or vent filter plugged or restricted?
Yes
SERVICE EGR Vacuum Regulator solenoid as necessary. If unable to service, REPLACE EGR Vacuum Regulator solenoid. RECONNECT all components. COMPLETE PCM Reset to clear DTCs. RERUN «Quick Test».
No
REPLACE damaged EGR Vacuum Regulator solenoid. RECONNECT all components. COMPLETE PCM Reset to clear DTCs. RERUN «Quick Test».
HE26 MEASURE EGR VACUUM REGULATOR SOLENOID COIL RESISTANCE
l Key off.
l EGR Vacuum Regulator solenoid disconnected.
l Measure resistance across EGR Vacuum Regulator solenoid.
l Is resistance between 26 and 40 ohms?
Yes
GO to «HE27».
No
REPLACE damaged EGR Vacuum Regulator solenoid. RECONNECT all components. COMPLETE PCM Reset to clear DTCs. RERUN «Quick Test».
HE27 CHECK EVR CIRCUIT FOR SHORT TO GROUND IN HARNESS
l Key off.
l Disconnect Scan Tool from DLC.
l EGR Vacuum Regulator solenoid disconnected.
l Disconnect PCM. Inspect for damaged or pushed out pins, corrosion, loose wires. Service as necessary.
l Install breakout box, leave PCM disconnected.
l Measure resistance between Test Pin 47 (EVR) and Test Pins 51 and 103 (PWR GND) at the breakout box.
l Is resistance greater than 10,000 ohms?
Yes
GO to «HE28».
No
SERVICE short between EVR circuit and ground. REMOVE breakout box. RECONNECT all components. RERUN «Quick Test».
HE28 CHECK EVR CIRCUIT FOR SHORT TO VREF
l Key off.
l Breakout box installed, PCM disconnected.
l Measure resistance between Test Pin 47 (EVR) and Test Pin 90 (VREF) at the breakout box.
l Is resistance greater than 10,000 ohms?
Yes
REPLACE damaged PCM. REMOVE breakout box. RECONNECT all components. RERUN «Quick Test».
No
SERVICE short between EVR circuit and VREF. REMOVE breakout box. RECONNECT all components. RERUN «Quick Test».
If you need a test routine that is not posted, let me know and I will add it.
My guess (that's all it is right now) is that either the EGR valve is stuck partially open or the DPFE sensor is bad.
Steve
Diagnostic Trouble Code (DTC) P0402 indicates that Self-Test has detected EGR flow at idle.
NOTE:
If DTC P1405 is in Continuous Memory, diagnose that first starting with HE50.
Possible causes:
-- EGR valve stuck open.
-- EGR vacuum regulator solenoid vent plugged or iced.
-- EVR circuit shorted to GND.
-- EVR circuit shorted to VREF.
-- Improper vacuum hose connection.
-- Plugged/pinched EGR Vacuum Regulator Solenoid vacuum hose.
-- Plugged EGR tube.
-- Damaged EGR Vacuum Regulator Solenoid solenoid.
-- Pinched/iced pressure hoses.
-- Damaged Differential Pressure Feedback EGR (D.P.F. EGR) sensor.
-- Damaged PCM.
l Key off.
l Disconnect vacuum hose at EGR valve and plug hose.
l Run Key On Engine Running (KOER) Self-Test.
l Is KOER DTC P0402 output or unable to run KOER Self-Test due to engine stall or no start?
Yes
There is possible EGR flow at idle. INSPECT pressure hoses first for pinching and icing. If OK, REMOVE and INSPECT the EGR valve and EGR tube for signs of contamination, unusual wear, carbon deposits, binding and other damage. SERVICE as necessary (use Rotunda EGR Valve Cleaner 021-00056 or equivalent, if needed). RECONNECT all components. COMPLETE PCM Reset to clear DTCs. RERUN «Quick Test».
No
RECONNECT vacuum hose to EGR valve. GO to «HE21».
HE21 CHECK FOR EGR FLOW AT IDLE WITH EGR VACUUM HOSE CONNECTED
l Key off.
l EGR vacuum hose connected.
l Run KOER Self-Test.
l Is KOER DTC P0402 output or unable to run KOER Self-Test due to engine stall or no start?
Yes
There is possible EGR flow at idle. GO to «HE22».
No
The fault that produced DTC P0402 is intermittent. INSPECT pressure hoses for pinching and icing. SERVICE as necessary. If OK, GO to «HE30».
HE22 CHECK EGR SYSTEM VACUUM HOSES FOR INTEGRITY AND CONNECTION
NOTE:
A pinched or plugged EGR vacuum hose can trap vacuum between the EGR Vacuum Regulator solenoid and EGR valve not allowing the EGR valve to close.
l Key off.
l Trace each vacuum hose from EGR Vacuum Regulator solenoid and verify that each hose is connected correctly. (Refer to vehicle vacuum diagram label.)
l Verify that the EGR valve vacuum hose is not pinched or plugged and routed properly.
l Are vacuum hoses OK?
Yes
RECONNECT vacuum hoses. GO to «HE23».
No
SERVICE vacuum hoses as necessary. RECONNECT all components. COMPLETE PCM Reset to clear DTCs. RERUN «Quick Test».
HE23 CHECK D.P.F. EGR SENSOR OUTPUT BY APPLYING VACUUM WITH HAND PUMP
l Key off.
l Disconnect pressure hoses at D.P.F. EGR sensor.
l Connect a hand vacuum pump to the downstream connection at sensor (intake manifold side of sensor or the smaller diameter pickup tube).
l Key on, engine off.
l Access DPFEGR PID with a Scan Tool and note PID value.
l Apply 27-30 kPa (8-9 in-Hg) vacuum to the D.P.F. EGR sensor and hold for a few seconds.
l 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.
l Does the DPFEGR PID voltage indicate a fault in the D.P.F. EGR sensor?
Yes
REPLACE damaged D.P.F. EGR sensor. RECONNECT all components. COMPLETE PCM Reset to clear DTCs. RERUN «Quick Test».
No
RECONNECT D.P.F. EGR sensor. GO to «HE24».
HE24 CHECK FOR EGR FLOW AT IDLE WITH EGR VACUUM REGULATOR SOLENOID CONNECTOR OFF
l Key off.
l Disconnect vacuum hose at EGR valve and connect hose to vacuum gauge.
l Start engine and bring to an idle.
l While monitoring vacuum gauge, disconnect the EGR Vacuum Regulator solenoid vehicle 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 the EGR Vacuum Regulator solenoid is electrically disconnected, this would indicate a mechanical fault in the EGR Vacuum Regulator solenoid.
l Does the EGR vacuum remain greater than 5.4 kPa (1.6 in-Hg) at idle even after EGR Vacuum Regulator solenoid is electrically disconnected?
Yes
This indicates a fault in the EGR Vacuum Regulator solenoid. GO to «HE25».
No
GO to «HE26».
HE25 INSPECT EGR VACUUM REGULATOR SOLENOID VENT FOR PLUGGING
NOTE:
A plugged EGR Vacuum Regulator solenoid vent will not allow EGR vacuum to vent to atmosphere.
l Key off.
l Disconnect EGR Vacuum Regulator solenoid vacuum hoses.
l Remove EGR Vacuum Regulator solenoid vent cap (if removable).
l Remove filter and inspect for blockage or icing in some cases.
l With the EGR vacuum supply port plugged, apply 34-51 kPa (10-15 in-Hg) of vacuum directly to EGR Vacuum Regulator solenoid vacuum source port with a hand vacuum pump. If the vacuum holds or is slow to release to atmosphere, the EGR Vacuum Regulator solenoid vent could be plugged or restricted.
l Is the EGR Vacuum Regulator solenoid vent or vent filter plugged or restricted?
Yes
SERVICE EGR Vacuum Regulator solenoid as necessary. If unable to service, REPLACE EGR Vacuum Regulator solenoid. RECONNECT all components. COMPLETE PCM Reset to clear DTCs. RERUN «Quick Test».
No
REPLACE damaged EGR Vacuum Regulator solenoid. RECONNECT all components. COMPLETE PCM Reset to clear DTCs. RERUN «Quick Test».
HE26 MEASURE EGR VACUUM REGULATOR SOLENOID COIL RESISTANCE
l Key off.
l EGR Vacuum Regulator solenoid disconnected.
l Measure resistance across EGR Vacuum Regulator solenoid.
l Is resistance between 26 and 40 ohms?
Yes
GO to «HE27».
No
REPLACE damaged EGR Vacuum Regulator solenoid. RECONNECT all components. COMPLETE PCM Reset to clear DTCs. RERUN «Quick Test».
HE27 CHECK EVR CIRCUIT FOR SHORT TO GROUND IN HARNESS
l Key off.
l Disconnect Scan Tool from DLC.
l EGR Vacuum Regulator solenoid disconnected.
l Disconnect PCM. Inspect for damaged or pushed out pins, corrosion, loose wires. Service as necessary.
l Install breakout box, leave PCM disconnected.
l Measure resistance between Test Pin 47 (EVR) and Test Pins 51 and 103 (PWR GND) at the breakout box.
l Is resistance greater than 10,000 ohms?
Yes
GO to «HE28».
No
SERVICE short between EVR circuit and ground. REMOVE breakout box. RECONNECT all components. RERUN «Quick Test».
HE28 CHECK EVR CIRCUIT FOR SHORT TO VREF
l Key off.
l Breakout box installed, PCM disconnected.
l Measure resistance between Test Pin 47 (EVR) and Test Pin 90 (VREF) at the breakout box.
l Is resistance greater than 10,000 ohms?
Yes
REPLACE damaged PCM. REMOVE breakout box. RECONNECT all components. RERUN «Quick Test».
No
SERVICE short between EVR circuit and VREF. REMOVE breakout box. RECONNECT all components. RERUN «Quick Test».
If you need a test routine that is not posted, let me know and I will add it.
My guess (that's all it is right now) is that either the EGR valve is stuck partially open or the DPFE sensor is bad.
Steve
