File in Section:

Service Bulletin

Bulletin No.:
Date:

PIT5359
December, 2014

PRELIMINARY INFORMATION
Subject:

Radio Back Lighting Stays On After Key Off / Dead Battery / TCCM Repeat Failure

Models:

2014 Chevrolet Silverado 1500
2015 Chevrolet Silverado
2014 GMC Sierra 1500
2015 GMC Sierra
With Transfer Case (RPO NQF or NQH)

The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.

Condition/Concern
Some owners many comment that their radio backlighting will stay on even after the ignition has been turned off and
the key has been removed for several minutes. Eventually, the battery will go dead. While diagnosing the concern,
voltage may be present at the following fuses with the ignition key in the off position: F23DL F22DL F30DL F31DL
F32DL (reference SI Doc ID 3819053). These fuses are all on the same Run/Crank Ignition Buss Bar, in the Left I/P
Fuse Block, and should not have any power with the ignition off. In some cases, there may only be 2 or 3 volts
present, so a voltmeter must be used to check for voltage
This could be caused by the TCCM back feeding voltage into the fuse block with the ignition off. If the TCCM is
disconnected, the voltage at the fuses will be gone. If the TCCM is replaced, the issue may only be corrected for a
short time. The internal circuitry of the TCCM may have been permanently damaged by a voltage spike, causing the
back feed.
In most cases, the voltage spike is caused by an aftermarket accessory, which utilizes a solenoid or relay, that is
wired onto the F30DL fuse or to the X61A I/P Junction Block connector X7 terminal 11 or connector X5 terminal 35. If
these solenoids or relays are not properly suppressed, they will produce a voltage spike. The voltage spike can be
transmitted onto the Run/Crank Ignition Buss Bar and permanently damage the TCCM.

Recommendation/Instructions
Important: DO NOT replace the TCCM until the root cause of the condition has been narrowed to the solenoid/relay
voltage spikes.
To prevent damage to any of the sensitive electronic components on the bussed circuit, the solenoid/relay MUST
have the control circuit suppressed with a diode. The diode will prevent the voltage spikes from being transmitted
onto the Run/Crank circuit.

2150773

Install a diode, P/N 12112422, across the coil of the solenoid. It is important that the striped end of the diode be
connected to the positive terminal of the coil and the other end of the diode be connected to ground.

2150775

Important: Be sure to insulate the diode with heat shrink tubing before installing as shown in the picture above.
Notice: Some solenoids/relays may only have a positive post and will get their ground through their mounting
bracket. In this case, the striped end of the diode is to be connected to the positive terminal and other end should be
connected to the ground of the solenoid/relay.

2226201

Install a diode, P/N 12112422, across the coil of the relay. It is important that the striped end of the diode be
connected to the positive terminal of the coil and the other end of the diode be connected to ground. Be sure to
insulate the diode with heat shrink tubing before installing.

Parts Information
Part Number

Description

Qty

12112422

Diode

1

Warranty Information
This repair will not be covered under warranty due to the failure being caused by an aftermarket accessory.
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.