DTC P0405 Exhaust Gas Recirculation
(EGR) Position Sensor Circuit Low Voltage
An Exhaust Gas
Recirculation (EGR) system is used in order to lower Oxides of Nitrogen (NOx) emission levels. The EGR system accomplishes this by
feeding small amounts of exhaust gas back into the combustion chamber. High combustion
temperatures cause NOx. Combustion temperatures are
reduced when the air/fuel mixture is diluted with the exhaust gases.
The EGR valve is
designed to accurately supply exhaust gases to the engine without the use of
intake manifold vacuum. The EGR valve controls the exhaust flow into the intake
manifold from the exhaust manifold through an orifice with a PCM controlled pintle. The PCM controls the pintle
position using inputs from the Throttle Position (TP) sensor, the Manifold
Absolute Pressure (MAP) sensor and, the Engine Coolant Temperature sensor. The
PCM commands the EGR valve in order to supply the correct amount of exhaust gas
recirculation for the current engine operating conditions. This can be
monitored on a scan tool as the Desired EGR Position.
The PCM monitors the
position of the EGR valve through a feedback signal. The PCM supplies a 5.0
volt reference and a ground to the EGR valve. A voltage signal representing the
EGR valve pintle position is sent to the PCM from the
EGR valve. This feedback signal can also be monitored on a scan tool and is the
actual position of the EGR pintle. The Actual EGR
Position should always be near the commanded or Desired EGR Position.
Conditions
for Running the DTC
The ignition voltage is
greater than 11.7 V.
Conditions
for Setting the DTC
- The EGR feedback signal voltage is
less than 0.14 volts.
- All conditions present for 10
seconds.
Action
Taken When the DTC Sets
- The PCM illuminates the malfunction
indicator lamp (MIL) on the second consecutive ignition cycle that the
diagnostic runs and fails.
- The PCM records the operating
conditions at the time the diagnostic fails. The first time the diagnostic
fails, the PCM stores this information in the Failure Records. If the
diagnostic reports a failure on the second consecutive ignition cycle, the
PCM records the operating conditions at the time of the failure. The PCM
writes the conditions to the Freeze Frame and updates the Failure Records.
Conditions
for Clearing the MIL/DTC
- The PCM turns OFF the malfunction
indicator lamp (MIL) after 3 consecutive ignition cycles that the
diagnostic runs and does not fail.
- A last test failed, or current DTC,
clears when the diagnostic runs and does not fail.
- A history DTC clears after
40 consecutive warm-up cycles, if no failures are reported by this or
any other emission related diagnostic.
- Use a scan tool in order to clear
the MIL and the DTC.
Due to the moisture
associated with exhaust systems, the EGR valve may freeze and stick in colder
weather at times. After the vehicle is brought into a warm shop for repairs,
the valve warms and the condition disappears. By monitoring the Actual EGR and
the Desired EGR Positions on a cold engine with a scan tool, the fault can be
verified easily. Review the freeze frame data to determine if the DTC set when
the vehicle was cold by viewing the Engine Coolant Temperature (ECT).
The numbers below refer
to the step numbers on the diagnostic table.
- If the scan tool
displays 5.0 volts, the EGR pintle
position signal, 5.0 volt reference circuit, and the PCM are OK. For
any test that requires probing the PCM or component harness connectors,
use the Connector Test Adapter Kit J 35616-A .
Using this kit will prevent any damage to the harness connector terminals.
- If the scan tool
displays 5.0 volts, the EGR pintle
position signal circuit and the PCM are OK. For any test that requires
probing the PCM or component harness connectors, use the Connector Test
Adapter Kit J 35616-A .
Using this kit will prevent any damage to the harness connector terminals.
- Disconnecting the
PCM allows using the DMM J 39200 in
order to test the continuity of the circuits. This aids in locating an
open or a shorted circuit.
|
Step |
Action |
Value(s) |
Yes |
No |
|
Did
you perform the Powertrain On-Board Diagnostic
(OBD) System Check? |
-- |
|||
Did
DTC P1635 fail this ignition cycle? |
-- |
|||
|
Monitor
the EGR pintle position voltage on Engine 1 Data
List on the scan tool. Is the EGR pintle position voltage
below the specified value? |
0.14V |
|||
Does
the scan tool indicate that this diagnostic failed this ignition? |
-- |
Go to Diagnostic Aids |
||
Is
the EGR pintle position voltage near the specified
value? |
5.0V |
|||
Is
the voltage near the specified value? |
5.0V |
|||
Did
you find the 5.0 volt reference circuit open or shorted? |
-- |
|||
Did
you find and correct the condition? |
-- |
|||
Did
you find the EGR pintle position signal circuit
open or shorted to a ground? |
-- |
|||
Did
you find and correct the condition? |
-- |
|||
Did
you find and correct the condition? |
-- |
|||
|
Replace
the EGR valve. Refer to EGR
Valve Replacement . Is the action complete? |
-- |
-- |
||
|
Important: Program the replacement
PCM. Refer to PCM
Replacement/Programming . Replace
the PCM. Is the action complete? |
-- |
-- |
||
Does
the scan tool indicate that this test ran and passed? |
-- |
|||
|
Select
the Capture Info option and the Review Info option using the scan tool. Does
the scan tool display any DTCs that you have not diagnosed? |
-- |
Go to the applicable
DTC table |
System OK |