Pinpoint Test AC: The Trailer Battery Charging Is Inoperative/Does Not Operate Correctly
Trailer Lamps
Pinpoint Tests
Pinpoint Test AC: The Trailer Battery Charging Is Inoperative/Does Not Operate Correctly
Refer to Wiring Diagram Set 95, Trailer/Camper Adapter for schematic and connector information. Diagrams By Number
Normal Operation
The trailer battery charge relay coil receives voltage from the Smart Junction Box (SJB) fuse 12 (5A) through circuit CBP12 (GN/WH) when the ignition switch is in the RUN or ACC position. Ground for the trailer battery charge relay coil is supplied through circuit GD120 (BK/GN). The Battery Junction Box (BJB) fuse 13 (30A) supplies voltage to the trailer battery charge relay switch through circuit SSB13 (GY/RD). When the trailer battery charge relay is energized, the voltage is routed to the trailer tow connector through circuit CAT14 (OG).
This pinpoint test is intended to diagnose the following:
- Fuse
- Wiring, terminals or connectors
- Trailer battery charge relay
- Trailer tow connector
- Trailer
- SJB
PINPOINT TEST AC: THE TRAILER BATTERY CHARGING IS INOPERATIVE/DOES NOT OPERATE CORRECTLY
NOTICE: Use the correct probe adapter(s) when making measurements. Failure to use the correct probe adapter(s) may damage the connector.
NOTE: Before beginning diagnostics, visually inspect the trailer tow connector for signs of corrosion or damage. Repair or install a new trailer tow connector as required.
NOTE: Failure to disconnect the battery when instructed will result in false resistance readings. Refer to Battery.
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AC1 CHECK FOR VOLTAGE AT THE TRAILER TOW CONNECTION (BATTERY CHARGE INOPERATIVE)
- Ignition OFF.
- Disconnect the trailer from the vehicle.
- Ignition ON.
- Measure the voltage between the trailer tow connector pin 5, circuit CAT14 (OG), component side and ground.
- Is the voltage greater than 10 volts?
Yes
GO to AC8.
No
VERIFY the BJB fuse 13 (30A) is OK. If OK, GO to AC2. If not OK, REFER to the Wiring Diagrams to identify the possible causes of the circuit short.
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AC2 CHECK THE TRAILER BATTERY CHARGE RELAY (INOPERATIVE)
- Ignition OFF.
- Disconnect: Trailer Battery Charge Relay.
- Substitute the trailer battery charge relay with a known good relay.
- Ignition ON.
- Measure the voltage between the trailer tow connector pin 5, circuit CAT14 (OG), component side and ground.
- Is the voltage greater than 10 volts?
Yes
REMOVE the known good relay. INSTALL a new trailer battery charge relay. TEST the system for normal operation.
No
REMOVE the known good relay. INSTALL the original relay. GO to AC3.
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AC3 CHECK THE TRAILER TOW CONNECTOR
- Ignition OFF.
- Disconnect: Trailer Tow C473.
- Ignition ON.
- Measure the voltage between the trailer tow C473-5, circuit CAT14 (OG) and ground.
- Is the voltage greater than 10 volts?
Yes
INSTALL a new trailer tow connector. TEST the system for normal operation.
No
GO to AC4.
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AC4 CHECK FOR VOLTAGE TO THE TRAILER BATTERY CHARGE RELAY COIL
- Ignition OFF.
- Disconnect: Trailer Battery Charge Relay.
- Ignition ON.
- Measure the voltage between the trailer battery charge relay pin 86, circuit CBP12 (GN/WH), BJB face side and ground.
- Is the voltage greater than 10 volts?
Yes
GO to AC6.
No
VERIFY the SJB fuse 12 (5A) is OK. If OK, GO to AC5. If not OK, REFER to the Wiring Diagrams to identify the possible causes of the circuit short.
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AC5 CHECK CIRCUIT CBP12 (GN/WH) FOR AN OPEN
- Ignition OFF.
- Disconnect: SJB C2280e.
- Measure the resistance between trailer battery charge relay pin 86, circuit CBP12 (GN/WH), BJB face side and the SJB C2280e-6, circuit CBP12 (GN/WH), harness side.
- Is the resistance less than 5 ohms?
Yes
GO to AC12.
No
REPAIR the circuit. TEST the system for normal operation.
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AC6 CHECK CIRCUIT GD120 (BK/GN) FOR AN OPEN
- Ignition OFF.
- Disconnect: Negative Battery Cable.
- Measure the resistance between the trailer battery charge relay pin 85, circuit GD120 (BK/GN), BJB face side and ground.
- Is the resistance less than 5 ohms?
Yes
GO to AC7.
No
REPAIR the circuit. TEST the system for normal operation.
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AC7 CHECK FOR VOLTAGE TO THE TRAILER BATTERY CHARGE RELAY
- Measure the voltage between the trailer battery charge relay pin 30, circuit SSB13 (GY/RD), BJB face side and ground.
- Is the voltage greater than 10 volts?
Yes
REPAIR circuit CAT14 (OG) for an open. TEST the system for normal operation.
No
REPAIR circuit SSB13 (GY/RD) for an open. TEST the system for normal operation.
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AC8 CHECK FOR VOLTAGE AT THE TRAILER TOW CONNECTOR (BATTERY CHARGE ALWAYS ON)
- Ignition OFF.
- Measure the voltage between the trailer tow connector pin 5, circuit CAT14 (OG), component side and ground.
- Is any voltage present?
Yes
GO to AC9.
No
The vehicle is operating correctly. SEND the trailer to an authorized camper/trailer repair facility.
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AC9 CHECK CIRCUIT CAT14 (OG) FOR A SHORT TO VOLTAGE
- Disconnect: Trailer Battery Charge Relay.
- Measure the voltage between the trailer tow connector pin 5, circuit CAT14 (OG), component side and ground.
- Is any voltage present?
Yes
REPAIR the circuit. TEST the system for normal operation.
No
GO to AC10.
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AC10 CHECK THE TRAILER BATTERY CHARGE RELAY (ALWAYS ON)
- Measure the voltage between the trailer battery charge relay pin 86, circuit CBP12 (GN/WH), BJB face side and ground.
- Is any voltage present?
Yes
GO to AC11.
No
INSTALL a new trailer battery charge relay. TEST the system for normal operation.
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AC11 CHECK CIRCUIT CBP12 (GN/WH) FOR A SHORT TO VOLTAGE
- Disconnect: SJB C2280e.
- Measure the voltage between the trailer battery charge relay pin 86, circuit CBP12 (GN/WH), harness side and ground.
- Is any voltage present?
Yes
REPAIR the circuit. TEST the system for normal operation.
No
GO to AC12.
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AC12 CHECK FOR CORRECT SJB OPERATION
- Disconnect all the SJB connectors.
- Check for:
- corrosion
- damaged pins
- pushed-out pins
- Connect all the SJB connectors and make sure they seat correctly.
- Operate the system and verify the concern is still present.
- Is the concern still present?
Yes
INSTALL a new SJB. CLEAR any DTCs. REPEAT the self-test.
No
The system is operating correctly at this time. The concern may have been caused by a loose or corroded connector.
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