DTC 2-4-1

2-4-1 EGR SYSTEM, FLOW ERROR

Conditions for DTC
^ Engine hot (temperature above 65°C / 150°F) and running at part load with EGR signal unchanged.
^ The EGR temperature sensor signal should vary when the ICM transmits a control signal to the EGR controller. Absence of variation is interpreted as a flow error and the DTC is recorded.

Substitute value
^ None.

Fault sources
^ Open-circuit in signal lead.
^ No supply to EGR controller.
^ Faulty EGR controller.
^ Faulty vacuum hoses.
^ Faulty EGR valve (valve not opening).

Fault symptoms
^ None.


NOTE: Take care when removing the yellow and white hoses. Grip and twist hose rubber connector ends only, not the plastic hose itself. The hoses may break or crack if pulled from their connections.

TESTING PROCEDURE





Status message
^ Check current Status Message.

If Status message is: Flow error.
- Proceed with test procedure below.

^ The fault counter indicates the number of starts during which the ICM has detected a fault free signal after the DTC has been recorded.





Checking EGR controller operation
^ START and RUN engine up to working temperature.
^ Display DTC parameter list.





^ Read EGR flow.
^ Place hand on EGR controller.
^ Rev engine and observe EGR flow on Scan Tool.





^ EGR controller should operate when instrument indicates flow.

If controller clicks (operates):
- Check vacuum to controller.
If controller does not click (does not operate):
- Check controller supply.





Checking vacuum to EGR controller
^ RUN engine.
^ Carefully disconnect white hose from EGR controller and check if vacuum is present.

If vacuum is present:
- Check vacuum from EGR controller.
If vacuum is absent:
- Check white hose between controller and intake manifold.
- Hose must not be leaking or blocked.
- Replace hose as required.





Checking vacuum from EGR controller
^ IDLE engine.
^ Connect white hose to controller.
^ Carefully disconnect yellow hose from controller.
^ Connect vacuum gauge to controller.
^ Rev engine until controller operates.
^ Check that controller is passing vacuum.
^ Gauge needle should oscillate rapidly.

If needle oscillates rapidly:
- Check yellow hose.
If needle does not oscillate:
- Try with new EGR controller.





Checking yellow hose
^ Switch OFF ignition.
^ Carefully disconnect yellow hose at both ends.

WARNING! EGR valve may be HOT.

^ Ensure that yellow hose is not blocked or leaking.

If hose is clear:
- Check EGR valve.
If hose is blocked or leaking:
- Try with new hose.





Checking EGR valve
^ Switch OFF ignition.
^ Connect yellow hose to EGR valve.





^ Connect vacuum pump to yellow hose at EGR controller.
^ START engine.
^ Increase vacuum to maximum 30 kPa (4.5 lb/in).
^ Check that EGR valve maintains vacuum.
^ Engine should run unevenly when gauge indicates vacuum.
^ One of following three alternatives is possible:

Engine runs unevenly when gauge indicates vacuum but pump loses vacuum:
- Try with new EGR valve.
Engine idles evenly when gauge shows vacuum and vacuum pump maintains vacuum:
- Ensure that EGR pipe is not blocked.
- Clean as required.
- If pipe is not blocked, try with new EGR valve.
Engine idles unevenly when gauge shows vacuum and vacuum pump maintains vacuum:
- Intermittent fault.
- Check EGR controller connector for lose connections.
- Check lead between EGR controller terminal 1 and ICM terminal A27 for intermittent open-circuit, and for intermittent short-circuit to supply.





Checking supply voltage to EGR controller
^ Switch ON ignition.
^ Disconnect EGR controller.
^ Connect voltmeter between controller connector terminal 2 and ground.

Instrument should indicate battery voltage.

If reading is correct:
- Check signal lead.
If reading is incorrect (no voltage):
- Check lead between controller terminal 2 and main relay (2/32) terminal 3 for open-circuit.





Checking signal lead
^ Switch ON ignition.
^ Disconnect EGR controller.
^ Connect voltmeter across controller terminals 1 and 2.

Instrument should indicate battery voltage.

If reading is correct:
- Check controller resistance.
If reading is incorrect:
- Check lead between controller terminal 1 and ICM terminal A27 for open-circuit or short-circuit to supply.





Checking resistance of EGR controller
^ Switch OFF ignition.
^ Disconnect EGR controller.
^ Connect ohmmeter across controller terminals.

Instrument should indicate 75 - 95 Ohms at 20°C (68°F).

If reading is correct:
- DTC is due to poor connection in EGR controller connector.
- Check controller connections for signs of oxidation.
If reading is incorrect:
- Try with new controller.