Upfitter Relay Box
Upfitter Relay Box
Pinpoint Tests
Pinpoint Test I: The Upfitter Switch Controlled Component is Inoperative
Refer to Wiring Diagram Set 140, Customer Access for schematic and connector information. Diagrams By Number
Normal Operations
With the ignition is in run or accessory, voltage is supplied to the upfitter switches from the Body Control Module (BCM). When an upfitter switch is activated (moved to the on position), voltage is routed to the coil side of the corresponding upfitter relay.
Each of the upfitter relays (switch side) are supplied voltage at all times from the Battery Junction Box (BJB). When the upfitter relay is switched activated, the relay energizes and supplies voltage to the customer supplied accessory.
All of the upfitter relays share the same ground circuit.
This pinpoint is intended to diagnose the following:
- Fuse
- Wiring, terminals or connectors
- Customer installed accessory
- Upfitter relay
- Upfitter switch
- BCM
PINPOINT TEST I: THE UPFITTER SWITCH CONTROLLED COMPONENT IS INOPERATIVE
NOTICE: Use the correct probe adapter(s) when making measurements. Failure to use the correct probe adapter(s) may damage the connector.
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I1 CHECK THE UPFITTER SYSTEM
- Ignition ON.
- Operate all the upfitter accessories.
- Are all the upfitter accessories inoperative?
Yes
VERIFY the BCM fuse 41 (7.5A) is OK. If OK, GO to I2. If not OK, REFER to the Wiring Diagrams to identify the possible causes of the short circuit. Diagrams By Number
No
GO to I5.
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I2 CHECK THE UPFITTER SWITCH ON INDICATORS
- Place the upfitter switches to the ON position.
- Do the on indicators illuminate?
Yes
REPAIR circuit GD138 (BK/WH) between the relays and ground for an open. TEST the system for normal operation.
No
GO to I3.
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I3 CHECK FOR VOLTAGE TO THE UPFITTER SWITCH
- Ignition OFF.
- Disconnect: Upfitter Switch C3389.
- Ignition ON.
- Measure the voltage between the upfitter switch C3389-8, circuit CBP41 (BU), harness side and ground.
- Is the voltage greater than 10 volts?
Yes
INSTALL a new upfitter switch. REFER to Upfitter Switch Service and Repair. TEST the system for normal operation.
No
GO to I4.
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I4 CHECK THE UPFITTER SWITCH VOLTAGE SUPPLY CIRCUIT FOR AN OPEN
- Ignition OFF.
- Disconnect: BCM C2280B.
- Measure the resistance between the upfitter switch C3389-8, circuit CBP41 (BU), harness side and the BCM C2280B-3, circuit CBP41 (BU), harness side.
- Is the resistance less than 5 ohms?
Yes
GO to I11.
No
REPAIR circuit CBP41 (BU) for an open. TEST the system for normal operation.
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I5 BYPASS THE UPFITTER SWITCH
- Ignition OFF.
- Disconnect: Upfitter Switch C3389.
- Ignition ON.
- Connect a fused jumper wire between the upfitter switch connector, harness side as follows:
- Does the upfitter accessory operate?
Yes
REMOVE the jumper wire. INSTALL a new upfitter switch. REFER to Upfitter Switch Service and Repair. TEST the system for normal operation.
No
REMOVE the jumper wire. VERIFY the BJB fuse 18 (30A) (relay 1), fuse 19 (30A) (relay 2), fuse 44 (15A) (relay 3) or fuse 28 (10A) (relay 4) is OK. If OK, GO to I6. If not OK, REFER to the Wiring Diagrams to identify the possible causes of the short circuit. Diagrams By Number
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I6 CHECK THE UPFITTER RELAY
- Ignition OFF.
- Connect: Upfitter Switch C3389.
- Disconnect: Suspect Upfitter Relay.
- Substitute a known good relay.
- Ignition ON.
- Place the upfitter switch in question to the ON position.
- Does the upfitter accessory operate?
Yes
REMOVE the known good relay. INSTALL a new upfitter relay. TEST the system for normal operation.
No
REMOVE the known good relay. GO to I7.
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I7 CHECK FOR VOLTAGE TO THE UPFITTER RELAY COIL
NOTE: Make sure the upfitter switch and the ignition are on.
- Measure the voltage between the suspect upfitter relay, relay box face side and ground as follows:
- Is the voltage greater than 10 volts?
Yes
GO to I8.
No
REPAIR the circuit in question for an open. TEST the system for normal operation.
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I8 CHECK THE UPFITTER RELAY VOLTAGE SUPPLY CIRCUIT FOR VOLTAGE
- Ignition OFF.
- Measure the voltage between the suspect upfitter relay, relay box face side and ground as follows:
- Is the voltage greater than 10 volts?
Yes
GO to I9.
No
REPAIR the voltage supply circuit in question for an open. TEST the system for normal operation.
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I9 CHECK THE UPFITTER RELAY GROUND CIRCUIT FOR AN OPEN
- Measure the voltage between the suspect upfitter relay, relay box face side and ground as follows:
- Is the voltage greater than 10 volts?
Yes
GO to I10.
No
REPAIR the upfitter relay ground circuit in question for an open. TEST the system for normal operation.
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I10 CHECK THE UPFITTER RELAY OUTPUT CIRCUIT
- Measure the resistance between the upfitter relay in question and the customer access point as follows:
- Is the resistance less than 5 ohms?
Yes
The vehicle is operating correctly. REPAIR or INSTALL a new customer installed accessory.
No
REPAIR the upfitter relay output circuit in question for an open. TEST the system for normal operation.
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I11 CHECK FOR CORRECT BCM OPERATION
- Disconnect all the BCM connectors.
- Check for:
- corrosion
- damaged pins
- pushed-out pins
- Connect all the BCM 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 BCM. REFER to Body Control Module (BCM) Service and Repair. TEST the system for normal operation.
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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