K 2500 Truck 4WD V8-379 6.2L DSL VIN C FI (1989)
Radio/Stereo: All Technical Service Bulletins
Audio - Information on Radio Diagnosis
CHEVROLET
921399A
RADIO SYSTEM DIAGNOSIS INFORMATION
Issued: 03/11/92
Subject:
RADIO DIAGNOSIS
Model and Year:
1988-92 C/K TRUCKS
Radio conditions may be more accurately diagnosed on C/K vehicles by using a Tech 1 or CAMS T-100. Radio system diagnosis with the Tech 1
requires body cartridge TK03040B and the T-100 requires the use of ALDL E&C (Entertainment and Comfort) adapter, part number 56746.
On the aforementioned vehicles, the radio system consists of a radio control head, radio receiver, cassette deck, and graphic equalizer. The Tech 1 or
T-100 when used can override and simulate the radio control head.
The Tech 1 or T-100 allows you to monitor or transmit messages to and from any radio system component.
This makes testing of the receiver, balance controls, volume, fader, individual speakers, clock, station select and other features possible. The technician
can then accurately attribute a given condition to a specific component rather than remove each of the separate units for diagnosis and repair.
Cassette tape player functions cannot be tested with this system, however, a more accurate diagnosis can still be made by verifying correct operation of
the other system components.
Please refer to the Tech 1 or T-100 handbook for more detailed entertainment system diagnosis information.
To apply Tech 1 or CAMS T-100 diagnostics to C/K vehicles, a jumper wire between ALDL connector terminal "J" and the radio receiver must first be
installed (Figure 1).
SERVICE PROCEDURE
1.
Remove lower steering trim panel.
2.
Locate the six wire connector going into the bottom of the radio receiver at location C247. Please refer to the 1992 ELECTRICAL DIAGRAM
AND DIAGNOSIS MANUAL page 196 (Figures 2 and 3).
3.
Locate the white wire (pin 6) in this six wire connector. Also locate the unused pin in the seventh position on the radio receiver. Both the white
wire in the sixth position and the open unused seventh pin are serial data terminals. The open pin on the radio receiver in position seven is not
shown on the electrical wiring diagram. The six wire connector is visible from under the dash and is quite accessible (Figure 3).
4.
Using a 16 inch place of 0.8 GA wire make a jumper wire to install between ALDL terminal J and the open seventh position pin of the radio
receiver. Use a wire with white insulation to indicate a serial data line.
The connection at the ALDL location can be made with terminal part number 12077411. The connection at the radio receiver can be made with
terminal part number 12047767. These terminals are included in Packard Electric terminal repair kit J38125.
5.
After the jumper wire is made, remove the six wire connector from the radio receiver. Plug in the jumper wire on pin seven. Reinstall the six wire
connector. Note that the terminal connection to pin seven is a friction fit to the pin. The terminal does not clip into place.
6.
Connect the opposite end of the jumper wire to ALDL terminal J (Figure 4).
7.
Using wire ties, secure the jumper wire to the existing instrument panel harness (leave the wire in place after diagnosis).
8.
Proceed with normal diagnosis using either the Tech 1 or CAMS T-100.
SERVICE PARTS INFORMATION
Part Number
Description
Quantity
12077411
Terminal
1
