ECM Code EO48 - EGR System Fault (1 Of 2): Action:

ECM turns on "ENGINE CONTROL SYSTEM" light. ECM commands BCM to display "SERVICE SOON" message on CCDIC panel. EGR is disabled for the entire key cycle.

To perform test, the ECM turns off EGR flow to engine and monitors 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 ECM assumes that either EGR was turned off before test started, or that EGR is flowing and ECM does not have ability to turn it off. The ECM tests EGR 6 times in a given key cycle. If EGR does not respond 3 or more times in 5 tests, code EO48 is set.

1. Many codes disable EGR and inhibit EO48 test. Repair other DFI codes before diagnosis of code EO48.
2. At idle, the EGR solenoid is electrically energized, blocking the flow of vacuum to the EGR valve.