C Engine Coolant Temperature Reads Inaccurately

Pinpoint Test C - Engine Coolant Temperature Reads Inaccurately

NOTE: Ford DOES NOT provide a procedure to perform the following pinpoint test without the Rotunda Instrument Gauge System Tester 014-R1063 or equivalent.

C1 - Check Power At Cluster Circuit 640 (R/Y)

- Turn ignition switch to the OFF position.
- Partially remove instrument cluster.
- Turn ignition switch to RUN position.
- Using a multimeter check for voltage at cluster connector pin C2-6, circuit 640 (R/Y).

Is B+ present?

YES GO to C2.
NO SERVICE Circuit 640 (R/Y) for open circuit. RESTORE vehicle. RETEST system.

C2 - Check Cluster Ground Circuit 676 (PK/O) For Open Circuit

- Using an ohmmeter connected to a known good ground, connect other end to ground pin C2-4, circuit 676 (PK/O).

Is resistance 5 ohms or less?

YES GO to C3.
NO SERVICE circuit 676 (PK/O) for open circuit. RESTORE vehicle. RETEST system.

C3 - Check Engine Coolant Temperature Sensor Circuit At Low

- Insert Rotunda Instrument Gauge System Tester 014-R1063 or equivalent. Disconnect connector at engine coolant temperature sensor and connect tester to instrument cluster side of connector. Set to 74 ohms.
- Turn ignition switch to RUN position.

Does gauge read cold?

YES GO to C4.
NO GO to C5.

C4 - Check Engine Coolant Temperature Sensor Circuit At High

- Set gauge system tester to 10 ohms.

Does gauge read hot?

YES REPLACE engine coolant temperature sensor. RESTORE vehicle. RETEST system.
NO G0 to C5.

C5 - Check Engine Coolant Temperature Input Circuit

- With ignition switch in the RUN position and using a voltmeter connected to known good ground, connect probe to engine coolant temperature sensor connector circuit 39 (R/W).

Is voltage 5 volts or more?

YES GO to C7.
NO GO to C6.

C6 Check Circuit 39 (R/W)

- Turn ignition switch to OFF position. Remove instrument cluster.
- Turn ignition switch to RUN position. Using an ohmmeter, measure resistance of circuit 39 (R/W) at instrument cluster connector pin C2-5 to engine coolant temperature sensor connector.

Is resistance 5 ohms or less?

YES GO to C7.
NO SERVICE circuit 39 (R/W) for open circuit. RESTORE vehicle. RETEST system.

C7 - Check Engine Coolant Temperature Gauge

- Turn ignition switch to OFF position.
- Disconnect cluster connectors.
- Using an ohmmeter, check gauge for continuity at contact clips.

Is there continuity at all clips?

YES GO to C8.
NO REPLACE engine coolant temperature gauge. RESTORE vehicle. RETEST system.

C8 - Check Printed Circuit

- Reconnect cluster connectors.
- Using an ohmmeter, check for continuity from gauge contact clips to cluster connectors per chart.

Connector Pin Circuit Circuit Function
C2-6 640 (R/Y) Ignition Voltage
C2-4 676 (PK/O) Gauge Ground
C2-5 39 (R/W) Engine Coolant Temperature Input

Is there continuity at all circuits?

YES REPLACE engine coolant temperature gauge. RESTORE vehicle. RETEST system.
NO REPLACE instrument cluster flex circuit. RESTORE vehicle. RETEST system.