New Holland WorkMaster 50 Service Manual page 813

DTC 18F-04-Lambda sensor heater power stage short circuit to
ground
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 ground condition. If a short to ground 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 ground.
Possible failure modes:
1. Faulty Lambda sensor B-9123 heater control circuit wiring, shorted to ground.
2. Faulty Lambda sensor B-9123, failed internally.
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 ground condition.
Disconnect the vehicle harness (VE) from the Lambda sensor B-9123 at connector X-9123.
Use a multimeter to check for continuity on the vehicle harness (VE) side :
From
X-9123 pin 3
A. If there is continuity, continue with Step 3.
B. If there is no continuity, continue with Step 4.
3. Locate the Lambda sensor B-9123 heater control circuit wiring short to ground condition.
Carefully disconnect the vehicle harness (VE) from the ECU A-9000 at connector X-9102.
Use a multimeter to check for continuity on the vehicle harness (VE) side :
From
X-9102 pin K07
A. If there is continuity, there is a short to ground condition in the vehicle harness (VE) between connector X-9123
pin 3 and X-9102 pin K07.Use the appropriate vehicle service manual, if necessary, to locate and repair the
grounded conductor.
Electrical systems - FAULT CODES
To
chassis ground
To
chassis ground
47866583_ 02/12/2015
55.12 [55.DTC] / 92
Result
There should be no continuity.
Result
There should be no continuity.