Diesel Data: Automotive Repair

O/D Main Switch & O/D OFF Indicator Light Circuit




CIRCUIT DESCRIPTION
The O/D main switch contacts go off when the switch is pushed in and comes on when it is pushed out.
In O/D main switch OFF position, the O/D OFF indicator lights up, and the Engine Control Module (ECM) prohibits shifting to overdrive. The ECM also causes the O/D OFF indicator light to blink when a malfunction is detected.
In this case, connecting the terminals in the DLC2 or DLC1 can display the malfunction code.




WIRING DIAGRAM
(*) O/D Main Switch
Contacts go off with switch pushed in.
Contacts go on with switch pushed out.




DIAGNOSTIC CHART
O/D OFF indicator light does not light up.




O/D OFF indicator light remains ON.













INSPECTION PROCEDURE