Pinpoint Test C: The Message Center Displays Wiring Fault On Trailer

Refer to TRAILER/CAMPER ADAPTER for schematic and connector information.
Normal Operation and Fault Conditions

The braking energy provided to the trailer is modulated with a PWM signal that varies between 0 volts and battery voltage, the higher the duty cycle the more braking power available. The TBM varies the PWM signal based on various inputs such as vehicle speed, the manual slider switch and the gain buttons. With the vehicle stationary and with the manual slider switch fully to the left with a gain of 10, there should be more than 10-12 volts supplied to pin 3 of the 7-pin trailer tow connector C4099.

When a trailer is connected to the vehicle the message center should display TRAILER CONNECTED. If the WIRING FAULT ON TRAILER message is only displayed when the trailer is connected the fault is with the trailer wiring.

The trailer brake system only works with electric-magnet actuated drum type brakes and electric over hydraulic brakes. If the trailer is equipped with a different style of brakes or if the trailer is not equipped with brakes, the system does not function.

DTC Fault Trigger Conditions
- DTC Fault Trigger Conditions
- TBM C2806 -- Trailer Brake Output Circuit Short to Vbatt
  - This DTC sets in continuous memory if the PWM output is greater than 9 volts when vehicle speed is greater than 3 km/h (2 mph). The TBM disables the trailer brake output and shuts down.
- TBM C2807 -- Trailer Brakes Wiring Circuit Short to Ground
  - This DTC sets in continuous memory and on-demand if battery voltage drops by more than 20 percent during a braking event or the trailer brakes draw more than 28 Amps. The TBM disables the trailer brake output and shuts down.
Possible Sources
- Wiring, terminals or connectors
- TBM
- Trailer
NOTE: Use the correct probe adapter(s) when making measurements. Failure to use the correct probe adapter(s) may cause damage to the connector.

C1 VERIFY TBM (TRAILER BRAKE CONTROL MODULE) DIAGNOSTIC TROUBLE CODES (DTCS)

Verify a trailer is not connected to the trailer tow connector.

Ignition ON.

Using a diagnostic scan tool, carry out the TBM self-test.

Clear the Diagnostic Trouble Codes (DTCs).

Test drive the vehicle in the following manner:
- maintain a speed greater than 5 km/h (3 mph)
- turn the headlights ON
- lightly apply the brakes for more than 5 seconds
- activate the left and right turn signals

Ignition OFF.

Ignition ON.

Wait at least 10 seconds for all modules to wake up and prove out.

Using a diagnostic scan tool, carry out the TBM self-test.

Is DTC C2806 or C2807 present?

Yes

GO to C2

For all other TBM Diagnostic Trouble Codes (DTCs), GO to DTC Chart: TBM . If no Diagnostic Trouble Codes (DTCs) return, the system is operating correctly at this time. INSPECT the 7-pin trailer tow connector C4099 for water intrusion, corrosion, pushed-out pins and spread terminals. REPAIR or INSTALL new as necessary.

C2 CHECK THE TRAILER TOW CONNECTOR
- Ignition OFF.
- Disconnect in-line connector C211.
- Using a diagnostic scan tool, carry out the TBM self-test.
- Clear the Diagnostic Trouble Codes (DTCs).
- Test drive the vehicle in the following manner:
  - maintain a speed greater than 5 km/h (3 mph)
  - turn the headlights ON
  - lightly apply the brakes for more than 5 seconds
  - activate the left and right turn signals
- Ignition OFF.
- Ignition ON.
- Wait at least 10 seconds for all modules to wake up and prove out.
- Using a diagnostic scan tool, carry out the TBM self-test.
Is DTC C2806 or C2807 present?

Yes For DTC C2806, GO to C4 For DTC C2807, GO to C3

No INSTALL a new 7-pin trailer tow connector.

C3 CHECK THE TBM (TRAILER BRAKE CONTROL MODULE) PWM (PULSE WIDTH MODULATION) OUTPUT CIRCUIT FOR A SHORT TO GROUND

Ignition OFF.

Connect in-line connector C211.

Disconnect TBM C307.

Measure:

Positive Lead	Measurement / Action	Negative Lead
C4099-3	Courtesy of FORD MOTOR COMPANY	Ground

Is the resistance greater than 10, 000 ohms?

Yes

GO to C4

No	REPAIR the circuit.

C4 CHECK THE TBM (TRAILER BRAKE CONTROL MODULE) PWM (PULSE WIDTH MODULATION) OUTPUT CIRCUIT FOR A SHORT TO VOLTAGE

Ignition OFF.

Connect in-line connector C211.

Disconnect TBM C307.

Ignition ON.

Operate the park lamps and measure:

Positive Lead	Measurement / Action	Negative Lead
C4099-3	Courtesy of FORD MOTOR COMPANY	Ground

Operate the stoplamps and measure:

Positive Lead	Measurement / Action	Negative Lead
C4099-3	Courtesy of FORD MOTOR COMPANY	Ground

Operate the reversing and measure:

Positive Lead	Measurement / Action	Negative Lead
C4099-3	Courtesy of FORD MOTOR COMPANY	Ground

At anytime, was any voltage present?

Yes	REPAIR the circuit. REFER to the OEM Electrical Wiring Diagram Introduction to identify the possible causes of the circuit short.

GO to C5

C5 CHECK FOR CORRECT TBM (TRAILER BRAKE CONTROL MODULE) OPERATION

Inspect TBM C307.

Repair:
- corrosion (install new connector or terminal - clean module pins)
- damaged or bent pins - install new terminals or pins
- pushed-out pins - install new pins as necessary

Connect TBM C307 and make sure that it seats correctly.

Test drive the vehicle in the following manner:
- maintain a speed greater than 5 km/h (3 mph)
- turn the headlights ON
- lightly apply the brakes for more than 5 seconds
- activate the left and right turn signals

Ignition OFF.

Ignition ON.

Wait at least 10 seconds for all modules to wake up and prove out.

Using a diagnostic scan tool, carry out the TBM self-test.

Is DTC C2806 or C2807 present?

Yes	CHECK OASIS for any applicable Technical Service Bulletins (TSBs). If a TSB exists for this concern, DISCONTINUE this test and FOLLOW the TSB instructions. If no Technical Service Bulletins (TSBs) address this concern, INSTALL a new TBM. REFER to: Trailer Brake Control Module (TBM) .

No	The system is operating correctly at this time. The concern may have been caused by a loose or corroded connector. ADDRESS the root cause of any connector or pin issues.