Circuit Description

Output Driver Modules (ODM) are used by ECM to turn on many of the current driven devices that are needed to control various engine and transmission functions. Each ODM is capable of controlling up to 7 separate outputs by applying ground to device which ECM is commanding ON. Unlike ODMs used in prior years, ODMs have capability each output circuit individually. When DTC P1640 is stored, it indicates an improper voltage level has been detected on an ODM output. Since A/C is an option, no A/C will cause air conditioning clutch relay output to always fail. If a fault is seen on air conditioning clutch relay output, it will not be logged as a fault until A/C request input interrupts a high voltage, indicating A/C has been installed.

When DTC sets, ECM will not illuminate MIL. ECM will store conditions present when DTC was set as FAILURE RECORDS data only.

A history DTC will clear after 40 consecutive trip cycles during which diagnostic runs and fault is no longer recognized. DTC can be cleared with scan tool, or by disconnecting battery voltage feed to ECM.