New Holland WorkMaster 50 Service Manual page 809

DTC 18F-02-Lambda sensor heater power stage open circuit
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 an open circuit condition. If an open circuit condition exists in the heater control circuit, this fault will occur. For in-
formation 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 - Tech-
nical Data (55.989).
Cause:
The Lambda sensor B-9123 low side driver heater control circuit is open.
Possible failure modes:
1. Faulty Lambda sensor B-9123 heater control circuit wiring, open circuit.
2. Faulty Lambda sensor B-9123 battery voltage supply wiring, open circuit.
3. Faulty Lambda sensor B-9123, failed internally.
4. 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 4.
2. Check the Lambda sensor B-9123 heater circuit wiring for an open circuit 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 4
A. If there is no voltage, there is an failure in the battery voltage supply wiring to the lambda sensor B-9123. Use
the appropriate vehicle service manual, if necessary, to locate and repair the failed conductor.
B. If there is voltage, leave connector X-9123 disconnected and continue with Step 3.
3. Check the Lambda sensor B-9123 low side driver wiring for an open circuit.
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 for an open circuit on
the vehicle harness (VE) side :
From
X-9123 pin 3
Electrical systems - FAULT CODES
To
chassis ground
To
X-9102 pin K07
47866583_ 02/12/2015
55.12 [55.DTC] / 88
Value
There should be approximately
12.0 V.
Value
There should be continuity.