PINPOINT TEST C: DTC B1255 OR DTC B1257 — AMBIENT TEMPERATURE SENSOR OPEN CIRCUIT OR SHORT TO GROUND
Test Step
Result / Action to Take
C1 CHECK THE AMBIENT TEMPERATURE SENSOR RESISTANCE
Ignition OFF.
Disconnect: Ambient Temperature Sensor C198.
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?
Yes
GO to
C2
.
No
INSTALL a new ambient air temperature sensor
and bracket. TEST the system for normal
operation.
C2 CHECK THE REMOTE CLIMATE CONTROL MODULE OUTPUT VOLTAGE
Ignition ON.
Press the AUTOMATIC button.
Measure the voltage between the ambient temperature sensor C198, circuit 788 (RD/OG) and circuit 470 (PK/BK).
Is the voltage between 4.7 and 5.1 volts?
Yes
INSTALL a new RCC module. TEST the system
for normal operation.
No
If diagnosing DTC 1255, GO to
C3
. If diagnosing
DTC 1257, GO to
C5
.
C3 CHECK CIRCUIT 788 (RD/OG) FOR AN OPEN
Ignition OFF.
Disconnect: RCC Module C228.
Measure the resistance between the RCC module C228 pin 7, circuit 788 (RD/OG) and the ambient temperature sensor
C198, circuit 788 (RD/OG).
Is the resistance less than 5 ohms?
Yes
GO to
C4
.
No
REPAIR circuit 788 (RD/OG) for an open. TEST
the system for normal operation.
C4 CHECK CIRCUIT 470 (PK/BK) FOR AN OPEN
Measure the resistance between the RCC module C228 pin 15, circuit 470 (PK/BK) and the ambient temperature sensor
C198, circuit 470 (PK/BK).
Is the resistance less than 5 ohms?
Yes
INSTALL a new RCC module. TEST the system
for normal operation.
No
REPAIR circuit 470 (PK/BK) for an open. TEST
the system for normal operation.
C5 CHECK CIRCUIT 788 (RD/OG) FOR A SHORT TO CIRCUIT 470 (PK/BK)
Ignition OFF.
Disconnect: RCC Module C228.
Measure the resistance between the ambient temperature sensor C198, circuit 788 (RD/OG) and circuit 470 (PK/BK).
Yes
GO to
C6
.
No
REPAIR circuit 788 (RD/OG) for a short to circuit
470 (PK/BK). TEST the system for normal
operation.
Page 14 of 47
2003 Taurus/Sable Workshop Manual
11/22/2011
http://www.fordtechservice.dealerconnection.com/pubs/content/~WS3H/~MUS~LEN/19/...
