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Upfit FAQ for Chevrolet Police Vehicles, Part 2

This is the second in a series of answers to frequently asked questions (FAQ) concerning features, function and upfitting of the 2008 Chevrolet Impala (9C1 or 9C3) and Tahoe 2WD (PPV) police package vehicles and Tahoe 4WD (5W4) special service vehicle. For Part 1, which appeared in the March-April 2008 issue of Police Fleet Manager

, go to and check the “Article Archive” under the “Resources” drop-down.

Before beginning an upfit, detailed information can be found on two Web sites. First, try, linking to “Government” to find the GM Fleet and Commercial Law Enforcement Vehicles. Second, go to for “Dealer Direct Order” of useful non-OEM police vehicle wiring and equipment features. The information at these sites is also available on free CDs by calling GM Fleet and Commercial Sales at (800) 353-3867.

Each Impala and Tahoe emergency vehicle package is assembled and delivered to a Chevrolet dealer with an Owner’s Manual Supplement in the glove box or in the accessory package containing wheel trim. If the booklet is not found in the vehicle, we recommend that upfitters get a copy of it before starting an upfit. The standard and available options in GM law enforcement vehicles are designed to provide the same upfitting provision for the Impala and the Tahoe with certain exceptions.

Question 5:

How do I determine what the wires are for in the special upfitter harness found under the instrument panel in the Impala right front foot well and the Tahoe near the floor tunnel center?


First, look for the Owners Manual Supplement in the glove box. The harness is described as “Wiring Provisions for 12-volt Battery Power Supply.” Included in the harness are blunt-cut power source wires, control signal wires for controlling aftermarket equipment and connections for optional wiring features that may be ordered. The information that follows applies to the Impala and Tahoe police packages as well as the Tahoe special service package. Specific differences between Impala and Tahoe are noted where appropriate.

After laying the harness out on the vehicle floor and removing the factory protective bag and tape to expose the various wires, identify the following: One blunt-cut (red / white) 10 awg battery circuit. This circuit is breaker protected at 50 amps. Two blunt-cut (dark green and light green) 12 awg relay controlled circuits. These circuits are breaker protected at 30 amps. Two blunt-cut relay control wires: dark blue 18 awg (for dark green 30 amp) and light blue 18 awg (for light green 30 amp). One blunt-cut (black) 8 awg ground lead. Note: the Impala ground wire is part of the harness, and the Tahoe ground wire is located separately under the RH front door sill plate. One blunt-cut (yellow) 20 awg control lead. This wire is hot (12 volts) in “Ignition ACCESSORY” and “RUN.” One blunt-cut (pink) 20 awg control lead. This wire is hot (12 volts) in “Ignition START” and “RUN.” One blunt-cut (yellow / black) 20 awg park-enable signal wire. One blunt-cut (brown for Impala, dark green for Tahoe) 20 awg Vehicle Speed Signal wire. The signal is 4,000 pulses per mile.

Also included in the 12-Volt Battery Power Supply harness are connectors for the addition of optional wiring provisions. If the vehicle was ordered and assembled with these options, you will find the following wires in addition to the standard wires above. Alternately flashing grille lights and siren speaker wiring provision, Option Code 6J3. One blunt-cut (purple) 16 awg flasher unit control wire; 12 volts applied will cause the flasher to operate. Two blunt-cut (gray and tan) 16 awg power wires from the flasher unit are coiled in front of the radiator. Grille lamps are customer furnished. Two blunt-cut (light blue and light green) siren speaker wires. Two blunt-cut (light blue and light green) 16 awg wires are coiled in front of the radiator. Siren speaker and controls are customer furnished.

Exterior lamps emergency flashing system, Option Code 6J7. One blunt-cut (dark green / red) 18 awg control wire. A current of 12 volts applied will cause the headlamp high beams to flash alternately and the stop lamps and backup lamps to flash alternately to the rear. The headlamp flashing and rear lamp flashing functions can be separated. See the FAQ regarding separation of function.

Horn-siren control wiring provision, Option Code 6J4. A 5-foot continuous loop of (black) 22 awg wire with an in-line one-way connector permits connection to a controller to select vehicle horn or siren operation by the steering wheel horn control.

Radio front speaker connection wiring provision, Option Code WX7. Two blunt-cut wire pairs (gray and tan for left front speaker, dark green and light green for right front speaker) provide for connection to customer radio equipment. The vehicle radio front speakers audio is directed to the rear speakers. Warning sounds, i.e., key in ignition, are sent to the left rear speaker.

Published in Police Fleet Manager, May/Jun 2008

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