Pinpoint Test B: DTC B1251 Or DTC B1253 — A/C In-Vehicle Temperature Sensor Open Circuit Or Short To Ground
Refer to Wiring Diagrams Cell
55
, Automatic Climate Control System for schematic and connector information.
Normal Operation
Under normal operation, the in-vehicle air temperature sensor receives a ground from the electronic automatic temperature control (EATC) module through circuit 3059 (YE/LG). A 5-volt
reference voltage is supplied to the in-vehicle air temperature sensor from the EATC module through circuit 3058 (LG/RD).
Possible Causes
An open in circuit 3059 (YE/LG) or 3058 (LG/RD)
A short together in circuit 3059 (YE/LG) and 3058 (LG/RD)
A short to ground in circuit 3058 (LG/RD)
In-vehicle air temperature sensor
Electronic automatic temperature control (EATC) module
PINPOINT TEST B: DTC B1251 OR DTC B1253 — A/C IN-VEHICLE TEMPERATURE SENSOR OPEN CIRCUIT OR SHORT TO GROUND
NOTE:
For
DTC B2267
only.
Measure the resistance between HVAC module C228a-11, circuit 1124 (WH), harness side and
the RH temperature blend door actuator C2092-1, circuit 1124 (WH), harness side.
Is the resistance less than 5 ohms?
A9 CHECK HVAC MODULE CONNECTION
Carry out the HVAC Module Cold Boot Process.
Carry out the HVAC Module On-Demand Self Test.
Operate the system.
Does the concern return?
Yes
INSTALL a new HVAC module. REFER to
Section 412-01
. TEST the
system for normal operation.
No
The system is operating correctly at this time. The concern may have
been caused by a loose or corroded connector. CLEAR the DTCs.
REPEAT the self-test. TEST the system for normal operation.
Test Step
Result / Action to Take
B1 CHECK THE SENSOR RESISTANCE
Ignition OFF.
Disconnect: In-Vehicle Temperature Sensor C233.
Measure the resistance between the in-vehicle temperature sensor pins, component
side.
Note the ambient temperature and compare the in-vehicle temperature sensor resistance
with the table below.
Is the resistance within the specified values for the temperature range?
Temperature
Resistance
10-20°C (50-68°F) 37,000-58,000 ohms
20-30°C (68-86°F) 24,000-37,000 ohms
30-40°C (86-104°F) 16,000-24,000 ohms
Yes
GO to
B2
.
No
INSTALL a new in-vehicle temperature sensor. CLEAR the DTCs. REPEAT the
self-test. TEST the system for normal operation.
B2 CHECK THE EATC MODULE OUTPUT VOLTAGE
Ignition ON.
Press the AUTO button on the EATC module.
Measure the voltage between in-vehicle temperature sensor C233-1, circuit 3058
(LG/RD) and C233-2, circuit 3059 (YE/LG).
Yes
INSTALL a new in-vehicle temperature sensor. TEST the system for normal
operation. If the code returns, INSTALL a new EATC module. TEST the system
for normal operation.
No
If diagnosing DTC B1251, GO to
B3
. If diagnosing DTC B1253, GO to
B5
.
Page 9 of 45
2006 Town Car Workshop Manual
12/30/2011
http://www.fordtechservice.dealerconnection.com/pubs/content/~WS6G/~MUS~LEN/19/...
