COUPLING 6L2939 - Caterpillar

Illustration 1 g01116579
PWM Buffer For The Left Conveyor Ratio DialNote: If the CID 021 FMI F00 diagnostic code is only present under certain extreme operating conditions such as dial full clockwise or dial full counterclockwise, the PWM buffer is probably out of specification. Replace the PWM buffer.This diagnostic code is recorded when the ECM reads the signal from PWM buffer for the left conveyor ratio dial as above normal or shorted to +V. This procedure checks the PWM buffer. This procedure does not does not check the conveyor ratio dial.The possible causes of this diagnostic code are:
+V circuit supply from the ECM to the buffer is open.
Return circuit is open.
Signal circuit is open or the buffer is disconnected.
Signal circuit is shorted to +V.
The buffer is malfunctioning.
The ECM has failed. This is unlikely.System Response:The results of this diagnostic code are:
Conveyor diagnostic lamp on the machine operator's station will be ON.
The auger or conveyor for the left side will either be ON all of the time or OFF all of the time.Note: Ensure that the diagnostic code CID 021 FMI F00 for the buffer is on hold and that the diagnostic code present indicator on the ECM display is ON. This procedure can cause new diagnostic codes to be recorded. Ignore these created codes. When the procedure is completed, clear the created codes.Test Step 1. Check Return Circuit
Turn the key start switch to the OFF position.
Disconnect the machine harness connector from the PWM buffer.
At the machine harness connector for the buffer, measure the resistance between return contact "B" (wire P201-GN) and the frame ground.Expected Result:The resistance should measure 5 ohms or less.Results:
OK - The resistance measures 5 ohms or less. The return circuit is correct. Proceed to Test Step 2.
NOT OK - The resistance measurement is greater than 5 ohms. Repair: The return circuit is open. Wire P201-GN is open between the buffer connector contact "B" and ECM connector contact 39. Repair the wiring harness or replace the wiring harness. Stop.Test Step 2. Check +V Circuit Supply To BufferThe machine harness remains disconnected from the buffer.
Turn the key start switch to the ON position.
At the machine harness connector for the buffer, measure