Normal Operation

WARNING: This page is about a different car, the 2005 Mercury Mountaineer and 2005 Ford Explorer. However, it is still accessible from the selected car via links, so may be relevant.

The PCM communicates with the diagnostic tool through the controller area network (CAN) circuits 3125 (RD/YE) and 3126 (TN/YE). If one of the bus wires becomes shorted to ground or voltage, or if some but not all termination resistors are lost, communications can continue. Check circuits 3125 (RD/YE) and 3126 (TN/YE) between the PCM C175b and the data link connector (DLC) C251. The total resistance values must not be more than 5 ohms. If the resistance is more than 5 ohms there is an open in circuit 3125 (RD/YE) and 3126 (TN/YE), damage to the DLC C251, damage to the PCM C175b, or a problem in the in-line connectors.

Voltage is supplied to the PCM on circuits 729 (RD/WH) and 994 (WH). The PCM is grounded through circuits 570 (BK/WH) and 1205 (BK).