Ford Galaxy / Ford S-MAX. Manual — part 789

LOCATE and RECTIFY the break in the circuit
between the TRM and the trailer socket with the aid
of the Wiring Diagrams. CHECK system operates
correctly If necessary RENEW the trailer socket.
CHECK system operates correctly

A9: CHECK CIRCUIT CAT19A (VT) BETWEEN THE TRAILER MODULE (TRM) AND THE
TRAILER SOCKET FOR SHORT TO GROUND

Measure the resistance between the trailer socket,
connector C4AT23-D, pin 6, circuit CAT19A (VT),

wiring harness side and ground.

1

Is a resistance of more than 10,000 Ohm measured?
Yes

GO to A10

.

No

LOCATE and RECTIFY the short to ground in the
circuit between the TRM and the trailer socket with
the aid of the wiring diagrams. CHECK system
operates correctly If necessary RENEW the trailer
socket. CHECK system operates correctly

A10: CHECK THE CIRCUIT BETWEEN THE SMART JUNCTION BOX AND THE TRAILER
MODULE (TRM) FOR OPEN CIRCUIT

NOTE: Keep the brake pedal depressed during the following measurement.

Disconnect TRM from connector C4AT23-C.

1

Ignition switch in position II.

2

APPLY the brakes.

3

Measure the voltage between the TRM, connector
C4AT23-C, pin 3, circuit CLS44E (VT/BN), wiring

harness side and ground.

4

Does the meter display battery voltage?
Yes

INSTALL A NEW TRM. CHECK system operates
correctly

No

LOCATE and RECTIFY the break in the circuit
between soldered connection SP451 and the TRM
with the aid of the Wiring Diagrams. CHECK system
operates correctly

A11: CHECK THE VOLTAGE AT THE TRAILER SOCKET WITH THE REAR FOG LAMPS
SWITCHED ON

Ignition switch in position II.

1

Switch on the REAR FOG LAMPS.

2

Switch on the dipped beam.

3

Measure the voltage between the trailer socket,

4

connector C4AT23-D, pin 2, circuit CAT07A (RD/YE)
and ground.

Does the meter display battery voltage?
Yes

Continue fault finding on the trailer.

No

GO to A12

.

A12: CHECK CIRCUIT CAT07A (RD/YE) BETWEEN THE TRAILER MODULE (TRM) AND
THE TRAILER SOCKET FOR OPEN CIRCUIT

Ignition switch in position 0.

1

Disconnect TRM from connector C4AT23-A.

2

Measure the resistance between the TRM,
connector C4AT23-A, pin 8, circuit CAT07A

(RD/YE), wiring harness side and the trailer socket,
connector C4AT23-D, pin 2, circuit CAT07A
(RD/YE), wiring harness side.

3

Is a resistance of less than 2 Ohms registered?
Yes

GO to A13

.

No

LOCATE and RECTIFY the break in the circuit
between the TRM and the trailer socket with the aid
of the Wiring Diagrams. CHECK system operates
correctly If necessary RENEW the trailer socket.
CHECK system operates correctly

A13: CHECK CIRCUIT CAT07A (RD/YE) BETWEEN THE TRAILER MODULE (TRM) AND
THE TRAILER SOCKET FOR SHORT TO GROUND

Measure the resistance between the trailer socket,
connector C4AT23-D, pin 2, circuit CAT07A

(RD/YE), wiring harness side and ground.

1

Is a resistance of more than 10,000 Ohm measured?
Yes

INSTALL A NEW TRM. CHECK system operates
correctly

No

LOCATE and RECTIFY the short to ground in the
circuit between the TRM and the trailer socket with
the aid of the wiring diagrams. CHECK system

operates correctly If necessary RENEW the trailer
socket. CHECK system operates correctly

A14: CHECK THE VOLTAGE AT THE TRAILER SOCKET WITH THE REVERSING LAMPS
SWITCHED ON

Ignition switch in position II.

1

ENGAGE the reverse gear.

2

Measure the voltage between the trailer socket
C4AT23-D, pin 8, circuit CAT03A (VT/OG) and

ground.

3

Does the meter display battery voltage?
Yes

Continue fault finding on the trailer.

No

GO to A15

.

A15: CHECK CIRCUIT CAT03A (VT/OG) BETWEEN THE TRAILER MODULE (TRM) AND
THE TRAILER SOCKET FOR OPEN CIRCUIT

Ignition switch in position 0.

1

Disconnect TRM from connector C4AT23-A.

2

Measure the resistance between the TRM,
connector C4AT23-A, pin 6, circuit CAT03A

(VT/OG), wiring harness side and the trailer socket,
connector C4AT23-D, pin 8, circuit CAT03A
(VT/OG), wiring harness side.

3

Is a resistance of less than 2 Ohms registered?
Yes

GO to A16

.

No

LOCATE and RECTIFY the break in the circuit
between the TRM and the trailer socket with the aid
of the Wiring Diagrams. CHECK system operates
correctly If necessary RENEW the trailer socket.
CHECK system operates correctly

A16: CHECK CIRCUIT CAT03A (VT/OG) BETWEEN THE TRAILER MODULE (TRM) AND
THE TRAILER SOCKET FOR SHORT TO GROUND

Measure the resistance between the trailer socket,
connector C4AT23-D, pin 8, circuit CAT03A

(VT/OG), wiring harness side and ground.

1

Is a resistance of more than 10,000 Ohm measured?
Yes

INSTALL A NEW TRM. CHECK system operates
correctly

No

LOCATE and RECTIFY the short to ground in the
circuit between the TRM and the trailer socket with
the aid of the wiring diagrams. CHECK system
operates correctly If necessary RENEW the trailer
socket. CHECK system operates correctly

A17: CHECK CIRCUITS CAT11A/B (OG) BETWEEN THE TRAILER MODULE (TRM) AND
THE TRAILER SOCKET FOR SHORT TO GROUND

Ignition switch in position 0.

1

Disconnect TRM from connector C4AT23-A.

2

Measure the resistance between the TRM,
connector C4AT23-A, pin 12, circuit CAT11A/B

(OG), wiring harness side and ground.

3

Is a resistance of more than 10,000 Ohm measured?
Yes

INSTALL A NEW TRM. CHECK system operates
correctly

No

LOCATE and RECTIFY the short to ground in the
circuits connected to the TRM, connector C4AT23-
A, pin 12 with the aid of the Wiring Diagrams.
CHECK system operates correctly If necessary
RENEW the trailer socket. CHECK system operates
correctly

PINPOINT TEST B : INDIVIDUAL TRAILER LAMPS INOPERATIVE, LAMPS
ON VEHICLE OK

TEST CONDITIONS

DETAILS/RESULTS/ACTIONS

B1: DETERMINE THE CAUSE OF THE FAULT

Ignition switch in position II.

1

CHECK the trailer lamps after every step.

2

APPLY the brakes.

3

SWITCH ON the left-hand turn signal.

4

SWITCH ON the right-hand turn signal.

5

SWITCH ON the dipped beam.

6

Is the left-hand turn signal lamp on the trailer
inoperative?
Yes

GO to B2

.

No

- One trailer stoplamp inoperative: LOCATE and
RECTIFY the break in the circuits on the trailer with
the aid of the wiring diagrams. CHECK system
operates correctly
- Right-hand trailer turn signal lamp inoperative:

GO to B5

.

- Left-hand rear trailer rear lamp inoperative:

GO

to B8

.

- Right-hand rear trailer lamp inoperative:

GO to

B9

.

B2: CHECK THE VOLTAGE AT THE TRAILER SOCKET WITH THE LEFT-HAND TURN