Possible Causes

WARNING: This page is about a different car, the 2003 Lincoln LS. However, it is still accessible from the selected car via links, so may be relevant.

An open in circuit 31-FB1 (BK/YE), 30-FA74 (RD/GN), 30S-FB1 (RD/YE) or 91S-FA76 (BN/BL).
A short to voltage in circuit 91S-FA76 (BN/BL).
Auxiliary coolant pump relay.
Auxiliary coolant pump motor.
DATC module.

Fig 1: Pinpoint Test I: Insufficient Heat During Engine Idle-3.9L Engine (Steps I1-I4)

Courtesy of FORD MOTOR CO.

Fig 2: Pinpoint Test I: Insufficient Heat During Engine Idle-3.9L Engine (Steps I4 Continued-I6)

Courtesy of FORD MOTOR CO.

Fig 3: Pinpoint Test I: Insufficient Heat During Engine Idle-3.9L Engine (Steps I7-I9)

Courtesy of FORD MOTOR CO.

Fig 4: Pinpoint Test I: Insufficient Heat During Engine Idle-3.9L Engine (Steps I10-I11)

Courtesy of FORD MOTOR CO.

Fig 5: Pinpoint Test I: Insufficient Heat During Engine Idle-3.9L Engine (Steps I12)

Courtesy of FORD MOTOR CO.