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Valves use a butterfly style valve to restrict exhaust The majority of driving conditions will find the Exhaust Diverter Valves deactivated. During the mode, the butterfly valves in the Diverter Valves are open. During deactivation, exhaust flow is directed primarily through the side DIAGNOSIS AND TESTING - EXHAUST SYSTEM Exhaust system restriction can be checked by mea- suring back pressure using the DRB III t and PEP module pressure tester. WARNING: THE NORMAL OPERATING TEMPERA- TAKEN WHEN WORKING NEAR THE CATALYTIC (1) Disconnect and remove the upstream (before catalytic converter) oxygen sensor (Refer to 14 - (2) Install the Exhaust Back Pressure Fitting Adaptor CH8519. (3) Connect the Low Pressure Sensor (15 psi) CH7063 to the back pressure fitting. (4) Following the PEP module instruction manual, connect all required cables to the DRB III t and PEP module. Select the available menu options on the t display screen for using the digital pressure gauge function. (5) Apply the park brake and start the engine. speed to 2000 RPM. Monitor the pressure readings t. Back pressure should not exceed specified limit. Refer to specification in table below NOTE: Repeat test on opposite converter using the Fig. 1 VACUUM DIAGRAM ( DEACTIVATED ( 11 - 2 EXHAUST SYSTEM ZB EXHAUST SYSTEM (Continued) |