Pinpoint Test C: Dtc B1255 Or Dtc B1257 - A/C Ambient Termp Sensor - Lincoln 2006 Town Car Workshop Manual

2006 Town Car Workshop Manual
B7 CHECK MODULE CONNECTION
Carry out the Electronic Automatic Temperature Control (EATC) Module Cold Boot
Process.
Carry out the EATC on-demand self test.
Operate the system.
Does the concern return?
Pinpoint Test C: DTC B1255 Or DTC B1257 — A/C Ambient 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 A/C ambient 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 A/C ambient temperature sensor from the EATC module through circuit 3061 (LB/OG).
Possible Causes
An open in circuit 3059 (YE/LG) or 3061 (LB/OG)
A short together in circuit 3059 (YE/LG) and 3061 (LB/OG)
A short to ground in circuit 3061 (LB/OG)
A/C ambient temperature sensor
Electronic automatic temperature control (EATC) module
PINPOINT TEST C: DTC B1255 OR DTC B1257 — A/C AMBIENT TEMPERATURE SENSOR OPEN CIRCUIT OR SHORT TO GROUND
C1 CHECK THE AMBIENT TEMPERATURE SENSOR RESISTANCE
Ignition OFF.
Disconnect: Ambient Temperature Sensor C132.
Measure the resistance between the ambient temperature sensor terminals.
Is the resistance within the specified values for these temperature ranges: 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?
C2 CHECK THE EATC MODULE OUTPUT VOLTAGE
Ignition ON.
Press the AUTOMATIC button.
Measure the voltage between ambient temperature sensor C132-1, circuit 3061 (LB/OG) and C132-2,
circuit 3059 (YE/LG).
Is the voltage between 4.7 and 5.1 volts?
C3 CHECK CIRCUIT 3061 (LB/OG) FOR AN OPEN
Ignition OFF.
Disconnect: EATC Module C228a.
Measure the resistance between EATC module C228b-17, circuit 3061 (LB/OG) and ambient
temperature sensor C132-1, circuit 3061 (LB/OG).
http://www.fordtechservice.dealerconnection.com/pubs/content/~WS6G/~MUS~LEN/19/...
Test Step
Yes
INSTALL a new EATC module. REFER to Section
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.
Result / Action to Take
Yes
GO to C2.
No
INSTALL a new ambient air temperature sensor and bracket.
CLEAR the DTCs. REPEAT the self-test. TEST the system for
normal operation.
Yes
INSTALL a new ambient air temperature sensor. TEST the system
for normal operation. If the code returns, GO to
No
If diagnosing DTC 1255, GO to C3
C5 .
Yes
GO to C4.
No
REPAIR circuit 3061 (LB/OG) for an open. CLEAR the DTCs.
REPEAT the self-test. TEST the system for normal operation.
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412-01. TEST the system for
C7 .
. If diagnosing DTC 1257, GO to
12/30/2011