E048 Part 1 of 2

Code E048 (Part 1 of 2):

Emission Wiring Circuit:

DESCRIPTION:

Code E048 is designed to set if there is an EGR system fault. The test for code E048 is performed under conditions where the EGR is normally enabled (allowing exhaust gas to flow into the intake). To perform the test, the PCM/ECM (turns off EGR flow to the engine and monitors the oxygen sensor (closed loop) integrator. With EGR turned off, the integrator should swing to a higher value reflecting leaner air/fuel mixtures. If not, the PCM/ECM assumes that either EGR was turned off before the test started or that EGR is flowing and the PCM/ECM doesn't have the ability to turn it off.

TEST CONDITIONS:

1. Codes EO13, EO14, EO15, E021, E022, E031, E032, E034, E044, E045 clear.
2. Coolant temp between 85° and 110°C.
3. TPS between 7° and 14°.
4. Engine speed between 1450 and 1650 RPM.
5. Oxygen sensor swinging (closed loop operation).
6. Vehicle speed greater than 35 MPH.
7. 10 minute timer after start-up expired.
8. Steady throttle.

TEST:

In the test conditions, the PCM/ECM will turn off EGR and look for the oxygen sensor integrator to indicate a leaner mixture. The PCM/ECM will perform the test up to six times in a given key cycle.

FAILURE CONDITIONS:

If the oxygen sensor fails to indicate a leaner mixture in at least 3 of the 5 tests, code E048 is set.

ACTION TAKEN:

1. PCM/ECM turns on "SERVICE ENGINE SOON" telltale.
2. EGR is disabled for the entire key cycle.

NOTES ON FAULT TREE:

1. Checking for EGR operation using PCM/ECM override.

2. Checking for EGR gases to enter the intake manifold by raising the EGR valve off of its seat.

3. Checking for EGR solenoid able to pass vacuum.

VACUUM TEST:

1. Connect a vacuum gauge to the source side of the EGR solenoid. Start the engine, manifold vacuum should be present. If it is not, repair leaks or obstruction between the EGR solenoid and throttle body.

2. Connect a vacuum gauge to the EGR valve vacuum supply. There should be no vacuum with the engine idling. If there is, follow chart E048 part 2 of 2.

3. With the gauge hooked to the EGR valve vacuum supply, disconnect the EGR solenoid connector. There should be more than 8 inches of vacuum available. If not, repair leak or obstruction in EGR valve vacuum hose.