Pinpoint Test Ab: The Trailer Lamps Are On Continuously

WARNING: This page is about a different car, the 2006 Ford F550 Super Duty, 2006 Ford F450 Super Duty, and 2006 Ford Cab & Chassis. However, it is still accessible from the selected car via links, so may be relevant.

AB1 CHECK FOR VOLTAGE AT THE TRAILER TOW CONNECTOR

Key in OFF position.
Disconnect: Trailer Tow C4098 (4-Pin).
Disconnect: Trailer Tow C4099 (7-Pin).
Key in ON position.

Measure the voltage the between trailer tow (4-pin connector), harness side and ground; or between the trailer tow (7-pin connector), harness side and ground as follows:

CONNECTOR-PIN CIRCUIT

Connector	Connector-Pin	Circuit
4-pin connector	C4098-2	52 (YE)
7-pin connector	C4099-1
4-pin connector	C4098-1	64 (DG)
7-pin connector	C4099-4
4-pin connector	C4098-3	962 (BN/WH)
7-pin connector	C4099-6
7-pin connector	C4099-7	963 (BK/LG)

Fig 1: Checking Voltage At Trailer Tow Connector

Courtesy of FORD MOTOR CO.

Is any voltage present?

Yes : If the trailer parking lamps are on continuously, GO to AB2.

If the trailer LH or RH turn lamps are on continuously, GO to AB3.

No : The vehicle is operating correctly. SEND the trailer to an authorized camper/trailer repair facility.

AB2 CHECK THE CJB
- Key in OFF position.
- Disconnect: CJB C270J.
- Connect: Trailer Tow C4098 (4-pin).
- Connect: Trailer Tow C4099 (7-pin).
- Key in ON position.
- Do the trailer lamps continue to illuminate?
Yes : REPAIR circuit 962 (BN/WH). TEST the system for normal operation.

No : INSTALL a new CJB. TEST the system for normal operation.
AB3 CHECK THE SUSPECT RELAY
- Key in OFF position.
- Disconnect: Suspect Trailer Turn Relay.
- Carry out the component test for the trailer tow turn relay.
- Is the trailer tow relay OK?
Yes : REPAIR circuit 52 (YE) (LH turn) or 64 (DG) (RH turn) as necessary. TEST the system for normal operation.

No : INSTALL a new LH or RH turn trailer tow relay. TEST the system for normal operation.