P0405
DTC P0405 EGR Pintle Position Circuit Low Voltage
Circuit Description
An Exhaust Gas Recirculation (EGR) system is used to lower Oxides of Nitrogen (NOx) emission levels caused by high combustion temperatures. It accomplishes this by feeding small amounts of exhaust gases back into the combustion chamber. When the air/fuel mixture is diluted with the exhaust gases, combustion temperatures are reduced.
A linear EGR valve is used on this system. The linear EGR valve is designed to accurately supply exhaust gases to the engine without the use of intake manifold vacuum. The valve controls exhaust flow going into the intake manifold from the exhaust manifold through an orifice with a VCM controlled pintle valve. The VCM commands EGR by applying a 12 volt duty cycle to the EGR valve feed control circuit. This can be monitored on a scan tool as Desired EGR position.
The VCM can monitor the pintle position with the EGR pintle position signal. This sensor uses a variable resistor with a 5 volt reference, a signal circuit and a ground. The signal circuit monitors changes in voltage on the variable resistor as the pintle moves.
The VCM will set a DTC P0405 if an unusually low pintle position signal voltage is detected for a calibrated period of time.
Conditions for Running the DTC
- No active MAP sensor DTCs
- No active IAT sensor DTCs
- No active ECT sensor DTCs
- No active TP sensor DTCs
- No active EVAP system DTCs
- No active IAC DTCs
- DTC P0300, P1336, P1404, or P1441 are not active
- The system voltage is greater than 11.7 volts
- The desired EGR position is greater than 0%
Conditions for Setting the DTC
The EGR feedback signal voltage is less than 0.14 volts for more than 10 seconds.
Action Taken When the DTC Sets
- The VCM illuminates the MIL (Malfunction Indicator Lamp) if a failure is detected during 2 consecutive key cycles.
- The VCM will set the DTC and records the operating conditions at the time the diagnostic fails. The VCM stores the failure information in the scan tools Freeze Frame and/or the Failure Records.
Conditions for Clearing the MIL/DTC
- The VCM turns OFF the MIL after 3 consecutive drive trips when the test has Run and Passed.
- A history DTC will clear if no fault conditions have been detected for 40 warm-up cycles (coolant temperature has risen 22 °C (40 °F) from the startup coolant temperature and the engine coolant temperature is more than 70 °C (158 °F) during the same ignition cycle).
- Use the scan tool Clear Information function.
Diagnostic Aids
Due to the moisture associated with exhaust systems, the EGR valve may freeze and stick in colder weather at times. By watching the ACTUAL EGR and DESIRED EGR POSITION on a cold vehicle with a scan tool, the fault can be verified easily. Check the freeze frame data to determine if the DTC set when the vehicle was cold by viewing the Engine Coolant Temperature (ECT).
Excessive carbon deposits may cause a restriction of movement in the EGR pintle. This problem may be compounded in cold weather with moisture freezing in the valve. Check for full range operation in the EGR system with the scan tool.
Check for excessive exhaust back pressure. Refer to Restricted Exhaust System Check. An intermittent may be caused by any of the following conditions:
- A poor connection
- Rubbed through wire insulation
- A broken wire inside the insulation
Thoroughly check any circuitry that is suspected of causing the intermittent complaint. Refer to Intermittents and Poor Connections Diagnosis.
If a repair is necessary, then refer to Wiring Repairs or Connector Repairs.
Steps 1 - 5:
Steps 6 - 10:
Steps 11 - 15:
Steps 16 - 19:
Steps 20 - 23:
Steps 24 - 30:
Steps 31 - 38:
Steps 39 - 41:
Test Description
Numbers below refer to the step numbers on the diagnostic table.
2. Commanding the EGR valve open determines whether the EGR system can control the EGR valve accurately and if the condition is present.
4. Jumping the 5 volt reference circuit to the signal circuit checks the signal circuit and VCM.
13. Check the terminals for being backed out, improperly formed, damaged, and for poor tension.
14. The replacement VCM must be programmed and the Crankshaft Position System Variation Learn Procedure must be performed. Refer to the latest Techline procedures for VCM programming.
15. Clearing the DTCs is a very important step for this diagnostic. The clearing function allows the EGR valve to relearn a new minimum pintle position.