New Holland WorkMaster 50 Service Manual page 1021

DTC 78D-03-Throttle valve actuator control circuit over load
Control Module : ECU
Context:
The Engine Control Unit (ECU) A-9000 monitors the throttle valve actuator Z-9001 output 1 and output 2 h-bridge
circuits. The ECU A-9000 monitors both circuits for a short circuit condition. If the ECU A-9000 determines that the
output 1 circuit and output 2 circuits are shorted together, this fault will occur.
Cause:
The ECU A-9000 has detected a short circuit between the throttle valve actuator Z-9001 output 1 and output 2 h-bridge
circuits.
Possible failure modes:
1. Faulty throttle valve actuator Z-9001 h-bridge wiring short circuit.
2. Faulty throttle valve actuator Z-9001, internal failure.
3. Faulty ECU A-9000, software.
Solution:
1. Verify fault is present and active.
Use the Electronic Service Tool (EST) to check the status of this fault.
A. If the fault is present and active, continue with Step 2.
B. If the fault is no longer present or in an inactive state, the fault may be intermittent and not currently active.
Continue with Step 4.
2. Check the throttle valve actuator Z-9001 h-bridge circuit engine harness (EN) wiring for a short circuit.
Disconnect the engine harness (EN) from the throttle valve actuator Z-9001 at connector X-9011.
With the key in the OFF position, use a multimeter to perform the following continuity check on the engine harness
(EN) side :
From
X-9011 pin 2
A. If there is continuity, there is a short circuit in the throttle valve actuator Z-9001 h-bridge wiring. Locate and
repair the shorted conductor.
B. If there is no continuity, leave connector X-9011 disconnected and continue to Step 3.
3. Replace the throttle valve actuator Z-9001.
Use the Electronic Service Tool (EST) to check the status of this fault.
A. If the fault is no longer active, return the machine to service.
B. If the fault is still active, check the ECU A-9000 for the appropriate service manual and re-flash, if necessary.
4. Visually inspect the relevant harnesses and connectors for damage, bent or dislocated pins, corroded terminals,
or broken wires. Verify that the connectors are fully installed. Flex the harnesses involved to reveal intermittent
breaks or shorts in the wiring concerned. Operate the machine while you monitor the display.
A. If you find damage or the display indicates other than normal display readings, then repair the damage discov-
ered during the inspection or locate and repair the other than normal display condition and verify that the error
has been resolved.
B. If you do not find damage and the display indicates only normal readings, then erase the fault code and continue
operation.
Electrical systems - FAULT CODES
To
X-9011 pin 6
47866583_ 02/12/2015
55.12 [55.DTC] / 300
Value
There should be no continuity.