Subject: Models/Years Affected: Origination Date: Revision Date:

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Neil Allison
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1 Subject: Models/Years Affected: Origination Date: Revision Date: UI Bulletin #124f Intermittent Cluster, Radio and HVAC Display Resets on Snow Plow Trucks 2014 Chevrolet Silverado Chevrolet Silverado 2014 GMC Sierra GMC Sierra With Snow Plow Prep Package (RPO VYU) November 30, 2015 October 17, 2016 ADVISORY: Notice: GM Dealers refer to Service Information PIT#5387 for labor code/time information Condition/Concern: Trucks equipped with option VYU [Snow Plow Prep] and a snow plow, may exhibit occurrences in which the Instrument Panel Cluster (IPC), Radio and HVAC displays may blank out or reset after changing the snow plow position. This condition is caused by a system voltage over-shoot phenomenon called load dump. When the large electrical draw of the plow pump motor is suddenly removed the field energy that is built up in the alternator causes a system voltage overshoot that momentarily moves above the normal design operating levels for the module displays. As a result the displays will shut down or reset causing the momentary blank out condition. The modules are designed to do this and immediately recover. No modules should be replaced for this condition. Repair/Recommendation: Contact your local GM Dealer for an appointment to install PN VYU Snow Plow Jumper harness per GM Service Bulletin PIT#5387. Note: Your truck may already have the factory harness included as a loose part [in the glove box]. If not, the jumper harness and installation will be provided [one time] without charge. Installation charges will be waived only if the jumper is installed at your GM dealer. If your truck was delivered with the harness you have the option of having your snow plow dealer install it or you could do it yourself. These installation costs would not be covered by GM. Bulletin #124f P a g e 1 October 17, 2016

2 Installation Instructions: 1. Single alternator systems: a) Unplug the 2-way connector on the alternator. b) Identify the master alternator connector [at the very tip of the harness when it is fully extended.] Insert it in the alternator. c) Take the original alternator connector and plug it into the mating jumper harness connector. Note: In this case the second alternator connector will be unused and will remain capped and tied to the harness bundle. 2. Dual alternator systems: a) Unplug the control connectors on both alternators. Take the original master alternator connector and plug it into the mating jumper harness connector. b) Identify the master alternator connector [at the very tip of the harness when it is fully extended.] Insert it in the alternator on the RH side of the engine. c) Identify the slave alternator connector on the jumper harness and insert it in the LH alternator. Insert the removed LH alternator connector into the [unwired] cap on the jumper harness. 3. All systems: a) Route the snow plow jumper harness along the existing harness routing where possible and secure with tie straps as appropriate. Allow slack for engine roll. Bulletin #124f P a g e 2 October 17, 2016

3 b) Tie Strap the relay to the main harness bundle near the electrical center assuring an upright orientation to avoid water collection in the cap c) See detail 3 for updated relay mounting. d) Locate appropriate connection points for the fused [+] red/orange harness control wire and the black ground wire. Note [1] The appropriate plow control signal should be able illuminate a test lamp when the plow motor is running and the lamp should go out when the motor is not running. The jumper relay must be energized at the same time that the plow motor is. Note [2] If the connection point is the coil of the motor power solenoid and both terminals are hot [B+] when the motor is not running monitor them and discover which terminal goes to ground when the motor is running. The one that goes to ground is the connection point for the black wire the one that stays at [B+] is the connection point for the fused wire. The connection should work as described in note 1. e) For plows with all the control components mounted on the plow itself Route the relay coil wires [blunt cuts] out through the grille to the appropriate location to complete the required connections. See notes 1 and 2 in item d) above to correctly identify the connection points. Bulletin #124f P a g e 3 October 17, 2016

4 Note [3] A pair of capped and sealed 2-way connectors must be installed so the plow can be mounted and removed at will. M 2W = GM service kit F 2W = GM service kit sets would be required so caps can be fashioned from the extra parts. These parts can be included in the warranty repair/charges if needed. See Detail 4. Note [4] Manufacturers of plows [with controls mounted on the plow] often have an inexpensive jumper harnesses [with a set of sealed connectors] and installation instructions available to make this connection task easier. These custom jumpers can be included in the warranty repair/charges if needed. Install similar to example in Detail 4. f) For plows with the main hydraulic motor power solenoid mounted under hood Find the motor control solenoid and determine if one or both of the harness control wires can be attached to it. See notes [1] and [2] above to correctly identify the connection points you will use. g) Route all wiring away from heat sources and any conditions that could harm the wiring over time. Attach the jumper harness to existing wiring bundle [with tie straps and edge clips provided] as per drawings below. Allow slack for engine roll and vibration. Note: This change will reduce the potential for the cluster/radio reset issue. It is still possible if the battery is very cold and the alternator voltage is very high that the first time the plow is cycled you might still see the symptom. Adding more electrical loads and reducing RPMs when releasing the control will help. Bulletin #124f P a g e 4 October 17, 2016

5 Additional Reference Information UI Bulletin #124f Fig 1: Jumper harness wiring schematic Bulletin #124f P a g e 5 October 17, 2016

6 Fig: 2 Jumper Harness - Component Details Bulletin #124f P a g e 6 October 17, 2016

7 Fig: 3 Jumper Harness Layouts [see detail 3 for updated relay mounting] Bulletin #124f P a g e 7 October 17, 2016

8 Bulletin #124f P a g e 8 October 17, 2016

9 Layout Details UI Bulletin #124f 1. Primary Alternator 2. Slave Alternator 3. Relay [See Detail 3 for updated mounting] 4. Wires to plow [fused + & ground] Bulletin #124f P a g e 9 October 17, 2016

10 Detail 1 UI Bulletin #124f Bulletin #124f P a g e 10 October 17, 2016

11 Detail 2 UI Bulletin #124f Bulletin #124f P a g e 11 October 17, 2016

12 Detail 3 [updated] UI Bulletin #124f Add tie straps to relay Bulletin #124f P a g e 12 October 17, 2016

13 Detail 3 [updated] Single Battery Trucks Bulletin #124f P a g e 13 October 17, 2016

14 Detail 3 [updated] Dual Battery Trucks Bulletin #124f P a g e 14 October 17, 2016

15 Detail 4 2w connector shown use as required Bulletin #124f P a g e 15 October 17, 2016

Subject: Models/Years Affected: Origination Date: Revision Date:

Subject: Models/Years Affected: Origination Date: Revision Date: Intermittent Cluster, Radio and HVAC Display Resets on Snow Plow Trucks 2014 Chevrolet Silverado 1500 2015 and beyond Chevrolet Silverado