New Holland WorkMaster 50 Service Manual page 811

DTC 18F-03-Lambda sensor heater power stage short circuit to
battery
Control Module : ECU
NOTE: If the Lambda sensor B-9123 is replaced, it is necessary to perform the Replacement of the Lambda Sensor
- Reset ECU Data with the Electronic Service Tool (EST) before you return the machine to service. See Lambda
sensor - Configure - Reset ECU data (Lambda sensor) (55.989), if necessary.
Context:
The Lambda sensor B-9123 has a heating element encased in ceramic that heats the sensor tip. Whenever the
heater is operating, the heater low side driver power stage contained in the Engine Control Unit (ECU) A-9000 is
monitored for a short circuit to battery condition. If a short circuit to a power source condition exists in the heater
control circuit, this fault will occur. For information regarding the functional operation of the Lambda sensor B-9123
see Lambda sensor - Overview (55.989). For more information regarding the technical specifications of the lambda
sensor B-9123, see Lambda sensor - Technical Data (55.989).
Cause:
The Lambda sensor B-9123 low side driver heater control circuit is shorted to a voltage source.
Possible failure modes:
1. Faulty Lambda sensor B-9123 heater control circuit wiring, short to a voltage source.
2. Faulty Lambda sensor B-9123, internal failure.
3. Faulty ECU A-9000, software.
Solution:
1. Verify that the fault 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 5.
2. Check the Lambda sensor B-9123 heater control circuit wiring for a short to voltage source condition.
Disconnect the vehicle harness (VE) from the Lambda sensor B-9123 at connector X-9123.
With the key switch in the ON position, use a multimeter to perform the following voltage check on the vehicle
harness (VE) side :
From
X-9123 pin 3
A. If there is voltage, leave connector X-9123 disconnected and continue to Step 3.
B. If there is no voltage, leave connector X-9123 disconnected and continue to Step 4.
3. Locate the Lambda sensor B-9123 heater control circuit wiring short to voltage source condition.
Disconnect the vehicle harness (VE) from the ECU A-9000 at connector X-9102.
With the key in the OFF position, use a multimeter to perform the following continuity check on the vehicle harness
(VE) side :
From
X-9102 pin K07
Electrical systems - FAULT CODES
To
Chassis ground
To
to all other pins in connector X-9102 There should be no continuity.
47866583_ 02/12/2015
55.12 [55.DTC] / 90
Value
There should be no voltage.
Value