DIAGNOSTIC TROUBLE CODE
P0404 ELECTRIC EXHAUST GAS RECIRCULATION OPENED
Features of the Circuit
- By any chance if high combustion temperatures are created by oxides of nitrogen then an Exhaust Gas Re-circulation EGR system which is the chief feature of this system will be boosted to counter this.
- This is done by supplying small amounts of exhaust gases back into the combustion chamber.
- Combustion temperatures are minimized as soon as the air/ fuel mixture dilutes the exhaust gases.
- The EGR valve has been specially designed to generate exhaust gases to the engine without using intake manifold vacuum.
- This valve regulates exhaust flow entering the intake manifold from the exhaust manifold through an orifice with an ECM controlled pintle.
- The pintle position is monitored by the ECM using inputs from the Throttle Position (TP) and the Manifold Absolute Pressure (MAP) sensor.
- This task over, the ECM then directs the EGR valve to operate as necessary by controlling an ignition signal through the ECM.
- The ECM further monitors the results of its command through a feedback signal.
- The desired EGR position can be checked with the help of a scan tool.
- A voltage signal representing the EGR valve pintle position is sent to the ECM by a 5 volt reference and a ground to the EGR valve.
- The scan tool can also be used here to note the feedback signal which is the actual position of the EGR pintle.
- The correct EGR position should always be close to the commanded or Desired EGR position.
- This Diagnostic Trouble Code (DTC) is capable of identifying an open or short circuit.
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Time for setting the DTC |
Task boosted after DTC sets |
When will DTC clear? |
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1) When EGR circuit is in a short to ground or in open condition.
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1) The Malfunction Indicator Lamp (MIL) will glow after three successive trips with a fail. |
1) The MIL will turn off after four consecutive ignition cycles in which the diagnostic runs without a fault. |
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2) The ECM will begin to store conditions which were present when the DTC failed.
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2) Disconnecting the ECM battery feed for 10 seconds |
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3) This information will be recorded in the Freeze Frame buffering Failure Records.
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3) The scan tool can be used to remove all existing DTCs.
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4) A history DTC will be stored.
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4) A history DTC will clear after 40 consecutive warm-up cycles without a fault. |
DIAGNOSTICS TOOLS
- Moisture related with exhaust systems might result in the EGR valve to freeze and malfunction in cold weather occasionally.
- This problem will be solved when the vehicle is taken to any warm shop for repairs and the affected part duly repaired.
- The error in can be easily noted by comparing the Actual EGR and the desired EGR positions on a cold vehicle with a scan tool.
- Note the Engine Coolant Temperature (ECT) and then check the Freeze Frame data to ensure that the DTC was set when the vehicle was cold.