PIT5058C

Bulletin No.: PIT5058C
Date: 19-Oct-2015
Subject:
Diagnostic Tip - School Bus Brake Warning System RPO UJ1 Functional Test And Diagnostics
Models:
2008 - 2016 Chevrolet Express Cutaway or Cargo Chassis With RPO UJ1
2008 - 2016 GMC Savana Cutaway or Cargo Chassis With RPO UJ1
This PI was superseded to update Model Years. Please discard PIT5058B.
The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.
Condition/Concern
Some dealers may need information on the operation and diagnostics of the UJ1 brake warning pressure warning system.
Recommendation/Instructions
To test for the proper function and operation of the UJ1 brake warning system:
1.
Turn key to on position (Do not start engine) Park brake not applied.
2.
Wait approximately 2 seconds.
3.
Brake symbol will come on and chime will sound.
4.
Start engine, light should go out and chime should stop.
If the warning system does not function correctly, then follow the below diagnostics:
1.
Disconnect X141 (left rear of the engine compartment near the cowl) and the brake light and chime should be off. If the light and chime are still on then
check circuit 33 for a short to ground between X141 and the IPC terminal 14.
2.
Ground terminal A on the female side with the engine on and park brake released and the brake light and chime should come on. If the light and chime
does not come on then check circuit 33 for an open between X141 and the IPC terminal 14.
3.
Check male side of X141 circuit 33 with an ohm meter to ground and should be close to 0 ohms with engine off and key on. Start engine and circuit
should go OL indicating that the flow switch opened. Then, turn the steering to the stop in pressure relief (do not hold for more than 5 seconds)and
verify that the circuit stays OL to check the operation of the pressure switch.
Warranty Information
The correction for this concern may be one of several repairs described in the diagnostic tips above. For vehicles repaired under warranty, please use the
appropriate warranty labor operation based on the actual cause and repair.
Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the
remaining steps do not need to be performed.
GM bulletins are intended for use by professional technicians, NOT a "do-it-yourselfer". They are written to inform these technicians of conditions that may
occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools,
safety instructions, and know-how to do a job properly and safely. If a condition is described, DO NOT assume that the bulletin applies to your vehicle, or that
your vehicle will have that condition. See your GM dealer for information on whether your vehicle may benefit from the information.
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