Hi,

This is what the service manual suggested

Event Code 853
Throttle mismatch
POT1 > 0 with FS and RS OFF or ON.
Note: Possible effects of this event code are:
* M1 is not operational.
* The line contactor is open.
* BRK is not releasing.
* POT is not operational.
* M2 is not operational.
Step 1: Check the condition of the control circuit fuse
(FU3). This provides power to the X10® Handle.
* If:FU3 is bad.
- Then repair or replace as necessary.
* If:FU3 is OK.
- Then continue to Step 2.
Step 2: Check the wiring from the positive signal to
CA205-3 and B-NEG to CA205-2 for opens or
shorts.
* If:The wiring is open or shorted.
- Then repair or replace as necessary.
* If:The wiring is OK.
- Then continue to Step 3.
Step 3: Using the handset, scroll down to the Monitor
menu. From there, scroll to the Tiller Throttle
menu and then to the Raw Tiller Throttle
menu. Check the value: the POT value is 0
with the POT in neutral and changes with
throttle movement.
* If:The event code continues.
- Then replace POT.
* If:The event code continues after replacing POT.
- Then continue to Step 4.
Step 4: Check the connections between CA205 and
CA410.
* If:The connections are bad.
- Then repair or replace as necessary.
* If:The connections are OK and the event code continues.
- Then continue to Step 5.
Step 5: Check the main PC board in the X10® Handle.
* If:The main PC board is bad.
- Then replace the main PC board.
* If:The main PC board is OK and the event code
continues.
- Then the issue exists within the X10® Handle.
Check the wiring and the operation of the X10®
Handle components and repair or replace as
necessary.
Event Code 854
Throttle POT out of range
POT voltage is outside of the expected range.
Note: Possible effects of this event code are:
* M1 is not operational.
* The line contactor is open.
* BRK is not releasing.
* POT is not operational.
* M2 is not operational.
Step 1: Check the condition of FU3 (this provides
power to the X10® Handle).
* If:FU3 is bad.
- Then repair or replace as necessary.
* If:FU3 is OK.
- Then continue to Step 2.
Step 2: Check the wiring from the positive signal to
CA205-3 and B-NEG to CA205-2 for opens or
shorts.
* If:The wiring is open or shorted.
- Then repair or replace as necessary.
* If:The wiring is OK.
- Then continue to Step 3.
Step 3: Using the handset, scroll down to the Monitor
menu. From there, scroll to the Tiller Throttle
menu and then to the Raw Tiller Throttle
menu. Check the value: the raw value should
go from 0-255.
* If:The event code continues.
- Then replace POT.
* If:The event code continues after replacing POT.
Fig. 21 (25918)

- Then continue to Step 4.
Step 4: Check the connections between CA205 and
CA410.
* If:The connections are bad.
- Then repair or replace as necessary.
* If:The connections are OK and the event code continues.
- Then continue to Step 5.
Step 5: Check the main PC board in the X10® Handle.
* If:The main PC board is bad.
- Then replace the main PC board.
* If:The main PC board is OK and the event code
continues.
- Then replace the X10® Handle switch cap