DTC 2-4-1
2-4-1 EXHAUST GAS RECIRCULATION SYSTEM, FLOW MALFUNCTIONPrecondition for DTC
^ In order for the Exhaust Gas Recirculation (EGR) diagnosis to be active, it is necessary for (a) the car to be started at an Engine Coolant Temperature (ECT) higher than -1O°C (14°F), (b) the ECT to be higher than +80°C (176°F) when the engine was switched off the previous time, (c) battery voltage to be above 12 Volts and (d) the ECT sensor to be undamaged. If voltage across the EGR temperature sensor is not reduced when the ECM sends out a control signal to the EGR controller, the ECM interprets this as system blockage and DTC 2-4-1 is set.
Substitute values
^ Long term fuel trim inhibited.
^ Idle air trim inhibited.
^ Only initial charge pressure is permitted.
Fault sources
^ Signal lead short circuited to voltage.
^ Break in signal or voltage lead.
^ Loose connection or contact resistance in connectors.
^ Defective vacuum hoses.
^ Defective EGR controller.
^ Clogged EGR pipe.
^ Defective EGR valve.
Fault symptoms
^ Poorer performance from initial charge pressure limit.
TESTING PROCEDURE
Checking the EGR Controller
^ Switch Ignition ON.
^ Use Diagnostic Test Mode 3 to check that the EGR controller functions.
^ Refer to: Output Device Test - Diagnostic Test Mode 3 if needed.
If the EGR controller operates:
- Check EGR flow.
If the EGR controller does not operate:
- Check the voltage to the EGR controller.
Checking the EGR Flow
^ Switch Ignition OFF.
^ Remove a lead which is coupled to connector 2 on the EGR controller.
^ Connect a free lead to connector 2 on the EGR controller.
^ START the engine and let it run at idling speed.
^ Connect the free lead to ground (engine block).
The engine should now run at an uneven idling speed.
If the engine runs unevenly at idling speed:
- The fault is intermittent. Proceed to: INTERMITTENT FAULT section below.
If the engine does not run unevenly at idling speed:
- Check the vacuum at the EGR controller.
Checking the Vacuum TO the EGR Controller
^ Switch Ignition OFF.
^ Carefully withdraw the white hose from the EGR controller.
^ Connect a vacuum meter to the white hose.
^ START the engine and let it run at idling speed.
The vacuum meter should give a reading.
If the vacuum meter gives a reading:
- Check the vacuum from the EGR controller.
If the vacuum meter does not give a reading:
- Check that the white vacuum hose and connection to the intake manifold are not blocked.
Checking the Vacuum FROM the EGR Controller
^ Engine at idling speed.
^ Connect the white hose to the EGR controller.
^ Carefully disconnect the yellow hose from the EGR controller.
^ Connect a vacuum meter to the EGR controller's connector.
^ Connect the free lead to ground so as to open the EGR controller.
The vacuum meter should give a reading.
If the vacuum meter gives a reading:
- Check the yellow hose.
If the vacuum meter does not give a reading:
- Test with a new EGR controller.
Checking the Yellow Hose
^ Switch Ignition OFF.
^ Carefully disconnect the yellow hose from the EGR valve.
Caution: The EGR valve can get very hot.
^ Check the yellow hose between the EGR controller and the EGR valve.
The hose must not leak or be clogged.
If the hose is OK:
- Check the EGR valve.
If the hose is clogged or leaks:
- Test with a new hose.
Checking the EGR Valve
^ Switch Ignition OFF.
^ Connect the yellow hose to the EGR valve.
Caution!The EGR valve can get very hot.
^ Connect a vacuum pump to the yellow hose at the EGR controller.
^ Start the engine and let it run at idling speed.
^ Pump up vacuum to max. 30 kPa (4.35 psi).
^ Check that the EGR valve retains its vacuum pressure.
The engine should run unevenly when the Vacuum pump shows negative pressure.
If the engine runs unevenly when the vacuum pump shows negative pressure but the vacuum pump loses vacuum:
- Test with a new EGR valve.
If the engine runs smoothly at idling speed when the vacuum pump shows negative pressure and the vacuum pump retains vacuum:
- Check that the EGR pipe is not clogged. Clean the pipe if necessary.
If the EGR pipe is OK:
- Test with a new EGR valve.
Checking the Voltage to the EGR Controller
^ Switch Ignition OFF.
^ Disconnect the EGR controller and return the connection.
^ Switch Ignition ON.
^ Connect a voltmeter between the EGR controller's connector 1 and ground.
The voltmeter should show battery voltage.
If value is OK:
- Check the EGR controller.
If value is incorrect:
- Check the lead between EGR controller connector 1 and the main relay (2/32) connector 3 for signs of a break.
Checking the Signal Lead
^ Switch Ignition OFF.
^ EGR controller disconnected.
^ Connect the measuring box and check the ground connections.
^ Connect the control module.
^ Connect an ohmmeter between connector #40 (ECM A40) on the measuring box and connector 2 on the EGR controller's connector.
The ohmmeter should show about 0 ohms.
If the reading is OK:
- Check the signal lead for short circuiting to voltage supply.
If the reading differs:
- Check the lead between the EGR controller's connection 2 and ECM A40 for signs of a break.
Checking the Signal Lead for Short Circuiting to Voltage Supply
^ Switch Ignition ON.
^ EGR controller disconnected.
^ Connect a voltmeter between connectors #40 (ECM A40) and #42 (ECM A42) on the measuring box.
The voltmeter should show less than 1 Volt.
If the reading is OK:
- Check the EGR controller.
If the reading differs:
- Check the lead between the EGR controller's connector 2 and ECM A40 for signs of short circuiting to voltage supply.
Checking the EGR Controller
^ Switch Ignition OFF.
^ Connect the EGR controller.
^ Switch Ignition ON.
^ Use Diagnostic Test Mode 3 to check that the EGR controller functions.
^ Refer to: Output Device Test - Diagnostic Test Mode 3 if needed.
If the EGR controller functions:
- The DTC was caused by poor contact in the control module's and/or EGR controller's connector.
- Rectify with regard to contact resistance and oxidation.
If the EGR controller does not function:
- Test with a new EGR controller.
INTERMITTENT FAULT
Checking the Leads and Connectors
^ Check the EGR controller's and ECM's connectors for signs of loose connection and contact resistance and oxidation.
^ Check the lead between the EGR controller's connector 2 and ECM A4O for signs of an intermittent disruption and intermittent short circuiting to ground.
^ Check the lead between the EGR controller's connector 1 and the main relay (2/32) connector 3 for signs of intermittent disruption.