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

ECM turns on SERVICE ENGINE SOON light for the entire key cycle and 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 5 times in a given key cycle. If EGR does not respond 3 or more times during a key cycle, Code EO48 is set.

NOTE: Test numbers refer to test numbers on diagnostic chart.

Test Number 1) Checks for EGR operation using ECM override.

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

Test Number 3) Checking for EGR solenoid able to pass vacuum.