Pinpoint Test D: The Differential Cooler Pump Never Runs Or Runs Continuously

WARNING: This page is about a different car, the 2013 Ford Mustang. However, it is still accessible from the selected car via links, so may be relevant.

D1 CHECK THE DIFFERENTIAL OIL PUMP OPERATION
- Ignition ON.
- Listen for differential oil pump operation.
- Is the differential oil pump operating?
- Yes : GO to D2.
- No : GO to D3.
D2 CHECK THE DIFFERENTIAL OIL PUMP RELAY
- Disconnect: Differential Oil Pump Relay.
- Is the differential oil pump still operating?
- Yes : REPAIR circuit CYT14 (VT/OG) for a short to voltage.
- No : INSTALL a new relay.

D3 CHECK THE VOLTAGE TO THE DIFFERENTIAL OIL PUMP RELAY

Ignition OFF.
Disconnect: Differential Oil Pump Relay.

Measure the voltage between:

Positive Lead		Negative Lead
Pin	Circuit	Pin	Circuit
Relay Cavity 1	CBB46 (WH/BU)	-	Ground
Relay Cavity 3	SBB12 (GN/RD)	-	Ground

Fig 1: Checking Voltage To Differential Oil Pump Relay

Courtesy of FORD MOTOR CO.

Are the voltages greater than 11 volts?

Yes : GO to D4.
No : VERIFY BJB fuse 46 (5A) is OK.
If OK, REPAIR circuit CBB46 (WH/BU).

VERIFY BJB fuse 12 (20A) is OK.

If OK, REPAIR circuit SBB12 (GN/RD).

If either fuse is not OK, REFER to the SYSTEM WIRING DIAGRAMS to identify the possible causes of the circuit short.

D4 CHECK THE DIFFERENTIAL PUMP VOLTAGE SUPPLY CIRCUIT FOR A SHORT TO GROUND

Measure the resistance between:

Positive Lead		Negative Lead
Pin	Circuit	Pin	Circuit
C3427-1	CYT14 (VT/OG)	-	Ground
C3427-2	CYT14 (VT/OG)	-	Ground

Fig 2: Identifying Differential Pump Connector Terminals

Courtesy of FORD MOTOR CO.

Is the resistance greater than 10, 000 ohms?

Yes : GO to D5.
No : REPAIR the circuit.

D5 CHECK THE DIFFERENTIAL PUMP VOLTAGE SUPPLY CIRCUIT FOR AN OPEN

Measure the resistance between:

Positive Lead		Negative Lead
Pin	Circuit	Pin	Circuit
Relay Cavity 5	CYT14 (VT/OG)	C3427-1	CYT14 (VT/OG)
Relay Cavity 5	CYT14 (VT/OG)	C3427-2	CYT14 (VT/OG)

Fig 3: Identifying Differential Pump Relay Cavity 5 Connector Terminals

Courtesy of FORD MOTOR CO.

Is the resistance less than 3 ohms?

Yes : GO to D6.
No : INSPECT in-line connector C237 for corrosion, bent pins and pushed-out terminals. VERIFY in-line connector C237 is fully seated and connected. REPAIR or INSTALL new as necessary.
If in-line connector C237 is OK, REPAIR the circuit.

D6 CHECK THE DIFFERENTIAL PUMP GROUND CIRCUIT FOR AN OPEN

Measure the resistance between:

Positive Lead		Negative Lead
Pin	Circuit	Pin	Circuit
C3427-3	GD171 (BK/GY)	-	Ground

Fig 4: Identifying Differential Pump Connector Terminals

Courtesy of FORD MOTOR CO.

Is the resistance less than 3 ohms?

Yes : INSTALL a new differential cooler fluid pump. REFER to REAR DRIVE AXLE/DIFFERENTIAL - FORD 8.8-INCH RING GEAR .
No : REPAIR the circuit.