P 1401 code…Help
Thread Starter
|
Member
Joined: Aug 2004
Posts: 49
Likes: 0
The EGR system is controlled directly by the PCM. EGR is not engaged when:
The engine is cold.
At very low ambient temperatures, sensed though the ECT and/or the IAT. Water vapour in the exhaust can freeze on the throttle plate if the EGR valve opens in these conditions.
he engine is at idle.
The engine is at WOT
In addition, EGR is reduced when:
the engine is under load, reducing further under greater load until EGR is zero.
as a function of BAROmetric air pressure - the higher the altitude the less pressure is available to operate the EGR valve.
The EGR is a pipe open between the exhaust manifold and an EGR valve mounted in the inlet manifold. The EGR valve is a poppet valve held closed by spring pressure. On command from the PCM, the poppet valve is lifted by vacuum pressure from the Electronic Vacuum Regulator (EVR) allowing exhaust gas to enter the inlet system by its own pressure, replacing some of the oxygen in the inlet manifold and lowering combustion temperatures. This EGR valve is a duty-cycled valve, meaning that it has a variable opening and closing, controlled by the EVR, to provide the required gas flow.
DPFE MONITOR
The method that OBD checks the DPFE system is as follows:
Circuit Checks
Fail?
Set DTCs P1400, P1401 or P1409
Pass, then Stuck Open Checks
Fail?
Set DTCs P0402
Pass, then Hose Test
Fail?
Set DTC P1405, P1406
Pass, then Flow Test
Fail?
Set DTC P1401 or P1408
Pass - Monitor Complete
Circuit Checks
This test is carried out constantly while the DPFE Monitor is running and takes a four second sample.
The DPFE sensor is tested for out of range values (typically >4.96 volts, <0.195 volts) and if this is detected the DTC P1400 or P1401 is set.
The EVR Output circuit is checked for opens and short using the internal smart driver in the PCM, and a failure records P1409.
Stuck Open Test
Next, whenever at idle, the PCM checks the voltage of the DPFE sensor and compares it with the voltage recorded by the PCM during the last Key On Engine Off state.
If the voltage is different this indicates a gas flow where none should exist, and the PCM stores the DTC P0402 EGR Flow Excessive Gas Detected. This can cause confusion: in this context excessive flow means there is a flow where none should be detected, ie, the EGR poppet valve has stuck open.
NOTE: When the EGR pipe is secure this is an effective test for the poppet valve in the EGR. Be aware however that if the EGR pipe is loose at the EGR end and exhaust gas can escape, then P0402 will be stored. The system has detected a gas flow but not through the EGR valve - gas is escaping from the pipe union with the EGR.
P1405 DPFE sensor Upstream hose off or plugged
P1406 DPFE sensor Downstream hose off or plugged.
NOTE: plugged in this context means blocked. This could either be an intentional plugging, blockage by foreign matter, kinking or melting which stops the gas flow. It is not difficult for work on the engine to knock off a sensor pipe either.
Not all applications use the P1406 code. In these vehicles the error code P1401 is recorded instead.
Flow Checks
Now the system checks the EGR for correct gas flow. During steady state driving with moderate loads and engine speeds the EVR duty cycle (operating rate) will keep increasing until the sufficient flow rate is produced. If the EVR duty cycle reaches 80% (ie 80% open) the PCM checks the DPFE sensor voltage with a table in memory to check that the gas flow is within parameters. If the voltage is too high it indicates that there is insufficient gas flow, and this stores the DTCs
P1401 EGR Insufficient Gas FLow detected.
P1408 EGR Flow out of self-test Range. (This is a KOER self test, rather than an EGR Monitor code.)
This is a functional test and will record a DTC for any flow restriction or incorrect DPFE signal.
Note: P0401 may also be generated for a hose off error, or if the DPFE sensor is failing because its voltage will not match the expected response stored in the PCM.
An open in the VREF wire also causes a P0401 since the voltage does not match the expected response.
SPECIAL CONDITIONS
The exhaust system contains a great deal of moisture as a result of the process of combustion. In very low ambient temperatures this moisture can freeze inside the EGR system hoses, pipe and the DPFE sensor and cause a DTC code. For this reason the following logic is used:
DRIVEABILITY CONCERNS
In normal operation the EGR system should be undetected by the owner. If the system fails with the EGR valve closed there will be no driveability concern. No MIL light means that the owner will remain unaware of it. Since emission testing is at idle (when the EGR does not operate) the vehicle will not fail the MOT.
The engine is cold.
At very low ambient temperatures, sensed though the ECT and/or the IAT. Water vapour in the exhaust can freeze on the throttle plate if the EGR valve opens in these conditions.
he engine is at idle.
The engine is at WOT
In addition, EGR is reduced when:
the engine is under load, reducing further under greater load until EGR is zero.
as a function of BAROmetric air pressure - the higher the altitude the less pressure is available to operate the EGR valve.
The EGR is a pipe open between the exhaust manifold and an EGR valve mounted in the inlet manifold. The EGR valve is a poppet valve held closed by spring pressure. On command from the PCM, the poppet valve is lifted by vacuum pressure from the Electronic Vacuum Regulator (EVR) allowing exhaust gas to enter the inlet system by its own pressure, replacing some of the oxygen in the inlet manifold and lowering combustion temperatures. This EGR valve is a duty-cycled valve, meaning that it has a variable opening and closing, controlled by the EVR, to provide the required gas flow.
DPFE MONITOR
The method that OBD checks the DPFE system is as follows:
Circuit Checks
Fail?
Set DTCs P1400, P1401 or P1409
Pass, then Stuck Open Checks
Fail?
Set DTCs P0402
Pass, then Hose Test
Fail?
Set DTC P1405, P1406
Pass, then Flow Test
Fail?
Set DTC P1401 or P1408
Pass - Monitor Complete
Circuit Checks
This test is carried out constantly while the DPFE Monitor is running and takes a four second sample.
The DPFE sensor is tested for out of range values (typically >4.96 volts, <0.195 volts) and if this is detected the DTC P1400 or P1401 is set.
The EVR Output circuit is checked for opens and short using the internal smart driver in the PCM, and a failure records P1409.
Stuck Open Test
Next, whenever at idle, the PCM checks the voltage of the DPFE sensor and compares it with the voltage recorded by the PCM during the last Key On Engine Off state.
If the voltage is different this indicates a gas flow where none should exist, and the PCM stores the DTC P0402 EGR Flow Excessive Gas Detected. This can cause confusion: in this context excessive flow means there is a flow where none should be detected, ie, the EGR poppet valve has stuck open.
NOTE: When the EGR pipe is secure this is an effective test for the poppet valve in the EGR. Be aware however that if the EGR pipe is loose at the EGR end and exhaust gas can escape, then P0402 will be stored. The system has detected a gas flow but not through the EGR valve - gas is escaping from the pipe union with the EGR.
P1405 DPFE sensor Upstream hose off or plugged
P1406 DPFE sensor Downstream hose off or plugged.
NOTE: plugged in this context means blocked. This could either be an intentional plugging, blockage by foreign matter, kinking or melting which stops the gas flow. It is not difficult for work on the engine to knock off a sensor pipe either.
Not all applications use the P1406 code. In these vehicles the error code P1401 is recorded instead.
Flow Checks
Now the system checks the EGR for correct gas flow. During steady state driving with moderate loads and engine speeds the EVR duty cycle (operating rate) will keep increasing until the sufficient flow rate is produced. If the EVR duty cycle reaches 80% (ie 80% open) the PCM checks the DPFE sensor voltage with a table in memory to check that the gas flow is within parameters. If the voltage is too high it indicates that there is insufficient gas flow, and this stores the DTCs
P1401 EGR Insufficient Gas FLow detected.
P1408 EGR Flow out of self-test Range. (This is a KOER self test, rather than an EGR Monitor code.)
This is a functional test and will record a DTC for any flow restriction or incorrect DPFE signal.
Note: P0401 may also be generated for a hose off error, or if the DPFE sensor is failing because its voltage will not match the expected response stored in the PCM.
An open in the VREF wire also causes a P0401 since the voltage does not match the expected response.
SPECIAL CONDITIONS
The exhaust system contains a great deal of moisture as a result of the process of combustion. In very low ambient temperatures this moisture can freeze inside the EGR system hoses, pipe and the DPFE sensor and cause a DTC code. For this reason the following logic is used:
DRIVEABILITY CONCERNS
In normal operation the EGR system should be undetected by the owner. If the system fails with the EGR valve closed there will be no driveability concern. No MIL light means that the owner will remain unaware of it. Since emission testing is at idle (when the EGR does not operate) the vehicle will not fail the MOT.
Thread Starter
|
Member
Joined: Aug 2004
Posts: 49
Likes: 0
Update...
Replaced the DPFE sensor and no longer throwing code P1401 Make sure you get Ford’s latest part (4U7Z-9J460-AA) for a 2001 F150 4.6L. Dealer gave me a discount $24.06, list $30.07.
The DPFE (Differential Pressure Feedback sensor controls the flow to the EGR valve.
The DPFE (Differential Pressure Feedback sensor controls the flow to the EGR valve.