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DTC 2-4-1

2-4-1 EGR SYSTEM




Trouble Code Conditions
Flow Malfunction:
If the Engine Control Module (ECM) sends out a control signal to the EGR vacuum controller and the Exhaust Gas Recirculation (EGR) temperature sensor signal is not changed, the ECM notes this as a fault, and Diagnostic Trouble Code (DTC) 2-4-1 is set.

Leakage:
If the Engine Control Module notes that the EGR temperature sensor has changed by more than 60 mV before the Engine Coolant Temperature (ECT) Sensor has reached 60°C (140°F), the ECM notes this as an EGR flow occurring when it should not, and Diagnostic Trouble Code 2-4-1 is set.

Substitute value(s)
- None.

Fault source(s)
Flow malfunction:
- Signal lead short circuit to live.
- Break in signal lead.
- Break in power lead.
- Bad contact or contact resistance in connectors.
- Defective vacuum hoses.
- Defective EGR vacuum controller.
- Defective EGR valve.

Leakage:
- Signal lead short circuit to ground.
- Defective vacuum hoses.
- Defective EGR vacuum controller.
- Defective EGR valve.
- Defective thermostat in engine coolant system.

NOTE: If engine does not reach working temperature within a given time, the engine compartment temperature can affect the EGR temperature sensor enough for the signal to the ECM to change by more than 60 mV.

Fault symptom(s)
Flow malfunction:
- None.

Leakage:
- Engine can idle unevenly.

TEST PROCEDURE

CHECK IDLE
- Start engine and listen to idle running.

If engine idles unevenly:
^ Check EGR-vacuum controller signal lead. Proceed to CHECK EGR VACUUM CONTROLLER SIGNAL LEAD section below.

If engine idles evenly:
^ Check engine coolant temperature. Proceed to CHECK ENGINE COOLANT TEMPERATURE section below.




CHECK ENGINE COOLANT TEMPERATURE
- Engine at idle.
- Enter DTC parameter list.
- Check if ECT rises and attains a normal level.

If ECT rises normally:
^ Check EGR vacuum controller function. Proceed to CHECK EGR VACUUM CONTROLLER FUNCTION section below.

If ECT does not rise sufficiently:
^ Test with new thermostat.




CHECK EGR VACUUM CONTROLLER FUNCTION
- Start and warm up engine.
- Enter DTC parameter list.
- Place hand on EGR vacuum controller.
- Rev engine and observe EGR flow on the Scan Tool (ST).
- If the ST shows an EGR flow, the EGR vacuum controller should be working (an impulse can be felt).

If impulses are felt in EGR vacuum controller (working):
^ Check vacuum to EGR vacuum controller. Proceed to CHECK VACUUM TO EGR VACUUM CONTROLLER section below.

If no impulses are felt in EGR vacuum controller (not working):
^ Check voltage to EGR vacuum controller. Proceed to CHECK VOLTAGE TO EGR VACUUM CONTROLLER section below.




CHECK VACUUM TO EGR VACUUM CONTROLLER
- Engine running.
- Disconnect white hose from EGR vacuum controller.
- Check for vacuum in hose.

If vacuum in hose:
^ Check vacuum from EGR vacuum controller. Proceed to CHECK VACUUM FROM EGR VACUUM CONTROLLER section below.

If no vacuum in hose:
^ Check white hose between EGR vacuum controller and intake manifold. Hose should not leak or be blocked.
^ Change hose if necessary.




CHECK VACUUM FROM EGR VACUUM CONTROLLER
- Engine running.
- Connect white hose to EGR vacuum controller.
- Carefully slack off yellow hose from EGR vacuum controller.
- Connect a vacuum gauge to EGR vacuum controller nipple.
- Rev engine so that EGR vacuum controller operates.
- Check that it transmits vacuum.
- Vacuum gauge indicator should oscillate rapidly.

If vacuum gauge indicator oscillates:
^ Check yellow hose. Proceed to CHECK YELLOW HOSE section below.

If vacuum gauge indicator does not oscillate:
^ Test with new EGR vacuum controller.




CHECK YELLOW HOSE
- Ignition off.
- Carefully slack off yellow hose from EGR valve.

WARNING: EGR valve can be hot.

- Check yellow hose between EGR vacuum controller and EGR valve. Hose must not leak or be blocked.

If hose OK:
^ Check EGR valve. Proceed to CHECK EGR VALVE section below.

If hose is blocked or leaks:
^ Test with new hose.




CHECK EGR VALVE
- Ignition off.
- Connect yellow hose to EGR valve.

Warning: EGR valve can be hot.

- Connect a vacuum pump to yellow hose at EGR vacuum controller.
- Start engine and allow to idle.
- Pump vacuum (max. vacuum 30 kPa (4.35 psi))
- Check if EGR valve retains vacuum. Engine should run unevenly when vacuum pump reads negative pressure.

If engine runs unevenly when vacuum pump reads negative pressure but vacuum pump loses vacuum:
^ Test with new EGR valve.

If engine idles evenly when vacuum pump reads negative pressure and vacuum pump retains vacuum:
^ Check that EGR pipe is not blocked. Clean pipe if necessary. If EGR pipe OK, test with new EGR valve.

If engine idles unevenly when vacuum pump reads negative pressure and vacuum pump retains vacuum:
^ Intermittent fault. Proceed to INTERMITTENT FAULT section below.

CHECK VOLTAGE TO EGR VACUUM CONTROLLER
- Ignition off.
- Disconnect EGR vacuum controller.
- Ignition on.



- Connect a voltmeter between EGR vacuum controller connector contact 2 and ground.

Voltmeter should read battery voltage.

If value OK:
^ Check EGR vacuum controller. Proceed to CHECK EGR VACUUM CONTROLLER section below.

If value differs:
^ Check lead between EGR vacuum controller contact 2 and main relay (2/12) connector 4 for break.

CHECK EGR VACUUM CONTROLLER
- Ignition off.
- Disconnect EGR vacuum controller.



- Connect an ohmmeter between EGR vacuum controller contacts 1 and 2.

Ohmmeter should read 75 - 95 ohms at + 20°C (68°F).

If value OK:
^ Test with new EGR vacuum controller.

If value differs:
^ Check signal lead. Proceed to CHECK SIGNAL LEAD section below.

CHECK SIGNAL LEAD
- Ignition on.
- EGR vacuum controller disconnected.



- Connect a voltmeter between EGR vacuum controller connector contact 1 and ground.

Voltmeter should read approx. 0 volts.

If value OK:
^ Check lead between EGR vacuum controller contact 1 and ECM # 33 for break.

If value over 5 volts:
^ Check lead between EGR vacuum controller contact 1 and ECM # 33 for short circuit to live.




CHECK EGR VACUUM CONTROLLER SIGNAL LEAD
- Engine at idle.
- Disconnect EGR vacuum controller.

If engine continues to idle unevenly:
^ Check EGR vacuum controller. Proceed to CHECK EGR VACUUM CONTROLLER section below.

If engine idles evenly:
^ Check lead between EGR vacuum controller contact 1 and ECM # 33 for short circuit to ground.




CHECK EGR VACUUM CONTROLLER
- Engine at idle.
- Carefully slack off yellow hose from EGR vacuum controller.

If engine continues to idle unevenly:
^ Check EGR valve. Proceed to CHECK EGR VALVE section below.

If engine idles evenly:
^ Test with new EGR vacuum controller.




CHECK EGR VALVE
- Engine at idle.
- Carefully slack off yellow hose from EGR valve.

Warning: EGR valve can be hot.

If engine continues to idle unevenly:
^ Test with new EGR valve.

If engine idles evenly:
^ Check if yellow hose blocked.
^ Change hose if necessary.




INTERMITTENT FAULT
Check leads and connectors
- Check EGR vacuum controller and ECM connector for bad contact, contact resistance and oxidation.
- Check lead between EGR vacuum controller contact 1 and ECM # 33 for intermittent break, intermittent short circuit to ground and intermittent short circuit to live.
- Check lead between EGR vacuum controller contact 2 and main relay (2/12) connector 4 for intermittent break.
- Check that EGR vacuum controller operates without interference using Diagnostic Test Mode (DTM) 3.
- Check that EGR valve does not bind, using a vacuum pump.
- Check 5-pin connector at left wheel-arch (C131) contacts 32 and 36 for contact resistance and oxidation.
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