GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2000 🢒 Yukon XL - 4WD 🢒 Body and Accessories 🢒 Cellular Communication 🢒 OnStar No or Poor Cellular Reception

Test Description

The following procedure is for improving reception performance. The vehicle must be in a area capable of transmitting and receiving cellular signals. The following numbers refer to the steps in the table.

  1. This step verifies that the phone is presently capable of placing a call.

    2.

  2. This step verifies that the phone is presently capable of placing a call.

    3.

  3. The vehicle needs to be in a area capable of transmitting and receiving cellular communications.

    4.

  4. This step tests the antenna for proper installation and condition.

Step

Action

Value(s)

Yes

No

1

Did you perform the OnStar® Diagnostic System Check?

--

Go to Step 2

Go to OnStar System Check

2

Turn ON the ignition, with the engine OFF. Activate the OnStar® Call Center button.

Is the connection made to the OnStar® Call Center?

--

Go to Step 3

Go to Step 9

3

Turn ON the ignition, with the engine OFF. Activate the emergency button.

Is the connection made to the OnStar® Call Center?

--

Go to Step 4

Go to Step 9

4

Was the connection to the OnStar® Call Center clear?

--

Go to Step 15

Go to Step 5

5

  1. Move the vehicle to a new area away from all buildings, high tension wires, and radio towers.
  2. Turn ON the ignition, with the engine OFF. Activate the OnStar® Center button.

Is the connection made to the OnStar® Center clear?

--

Go to Step 15

Go to Step 6

6

Check the following items:

  1. Coax the connections tight at the coupling box and the vehicle communication unit (VCU).
  2. Antenna not mounted over defogger grid lines
  3. No visible damage to the antenna coupling box
  4. Antenna not mounted over after market window tint
  5. Antenna pointing straight up and down
  6. Tip of antenna above the vehicle roofline

Did you find and correct the condition?

--

Go to Step 15

Go to Step 7

7

Is the area known for good cellular reception?

--

Go to Step 8

Go to Step 5

8

Replace the cellular antenna. Refer to Mobile Telephone Antenna Replacement .

Did you complete the replacement?

--

Go to Step 15

--

9

Test the XCVR RCV data circuit for a short to battery positive or an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the problem?

--

Go to Step 15

Go to Step 10

10

Test the XCVR CMP data circuit for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the problem?

--

Go to Step 15

Go to Step 11

11

Test the XCVR THRU data circuit . Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the problem?

--

Go to Step 15

Go to Step 12

12

Test the XCVR DIG return circuit for a short to ground or an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the problem?

--

Go to Step 15

Go to Step 13

13

Check the following items:

  1. Coax the connections tight at the coupling box and the VCU
  2. Antenna not mounted over defogger grid lines
  3. No visible damage to the antenna coupling box.
  4. Antenna not mounted over after market window tint.
  5. Antenna pointing straight up and down
  6. Tip of antenna above the vehicle roofline

Did you find and correct the condition?

--

Go to Step 15

Go to Step 14

14

Replace the vehicle interface unit (VIU). Refer to OnStar Vehicle Interface Unit Replacement .

Did you complete the replacement?

--

Go to Step 15

--

15

Operate the system in order to verify the repair.

Did you correct the condition?

--

System OK

Go to Step 2