E048

TEST CONDITIONS
1. Codes EO13, EO14, EO15, EO17, EO21, EO22,EO31, EO32, EO34, EO42, EO43, EO44, and EO45 not set;
2. Fuel control in closed loop operation;
3. No problems detected on the oxygen sensor circuits;
4. Coolant temp between 80°C and 110°C;
5. TPS between 10. and 22;
6. RPM between 1250 and 1650;
7. Right oxygen sensor toggling faster than 5 times per second.

FAILURE CONDITIONS
Integrator has not increased more than 14 counts when EGR was commanded off. Tested 5 times per ignition cycle - 3 failures will set the code.

ACTION TAKEN
1. ECM turns on "Engine Control System Fault" telltale;
2. ECM commands BCM to display "Service Soon" message on Driver Information Center (DIC);
3. EGR is disabled for entire ignition cycle.

DESCRIPTION
Code EO48 is designed to set if there is a EGR system fault in which the ECM can't control the rate of EGR flow to the engine. Possible causes of this are:
1. Electrical control system faults
2. Insufficient vacuum supply to the EVRV
3. E6R valve fault/improper EGR valve part number installed.
4. EGR intake manifold passages blocked.

Code EO43 is only tested under narrow engine performance conditions so that the test won't affect vehicle driveability or emissions. The code will not set unless the car is driven under the "Test Conditions" long enough for the ECM to perform three to five tests. Depending on the customer's driving habits, the code may not set even if an EGR system fault exists.

Notes on Fault Tree
1. Many other codes will disable both the EGR system and Code EO48. Diagnose and correct all other current ECM trouble codes before performing Code EO48 chart.
2. EGR system is providing EGR to the engine. Check for insufficient vacuum to the EGR valve. Also check for partially blocked intake manifold EGR passages.
5. Checking for power and ground to EVRV. System voltage should be present. If not, check the ground for opens or poor connection to engine.
6. Checking ECM's ability to cycle output. Voltage should cycle from 12 volts to 0 volts every 3 seconds.

Notes on Intermittents
At idle manipulate affected wiring and connectors. The EGR valve should stay closed (EVRV deenergized).

With engine off, attach a vacuum supply to EVRV. Select ECM output cycling EO04 "EGR Sol". EGR value should rise and fall every 3 seconds. Manipulate wiring to note any change in operation of valve during output cycling.

With a hot engine, idling, apply and release vacuum to the EGR valve and check for EGR valve binding in the up or down positions.

Check all vacuum hoses for pinched, cut, kinked, misrouted, or hoses blocked by foreign matter. Check for proper EGR valve part number. Remove the EGR valve and check for excessive carbon buildup that would restrict EGR flow or for foreign material holding the EGR valve open.