Schematic Reference: Cellular Telephone Schematics

Did you perform the Diagnostic System Check-Vehicle?

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Go to Step 2

Go to Diagnostic System Check - Vehicle

Verify the cellular phone is not operating properly.

Does the system operate normally?

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Go to Testing for Electrical Intermittents in Wiring Systems

Go to Step 3

1. Turn the ignition ON.
2. Switch the audio system ON.
3. Place the mobile phone in the vehicle kit and make a call.

Does the audio system switch to VOICE IN mode?

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Go to Step 12

Go to Step 4

1. Switch the audio system and ignition OFF.
2. Access the phone kit wiring.
3. Inspect all phone connections for terminal retention and that the connector is correctly located. Refer to Testing for Intermittent Conditions and Poor Connections and Wiring Repairs in Wiring Systems

Did you find and complete the repair?

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Go to Step 23

Go to Step 5

1. Turn the ignition ON.
2. Switch the audio system ON.
3. Connect a digital voltmeter between the mute line circuit of the cellular phone in-line connector and a known good ground.

Is the value as specified?

+10 V or greater

Go to Step 8

Go to Step 6

1. Disconnect the phone kit wiring.
2. Switch the audio system ON.
3. Connect a digital voltmeter between the mute line circuit of the cellular phone in-line connector and a known good ground.

Is the value as specified?

+10 V or greater

Go to Step 7

Go to Step 11

1. Verify that the mute line is correctly connected to the phone kit.
2. Verify that the voice signal and return lines are correctly connected to the phone kit. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and complete the repair?

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Go to Step 23

Go to Step 8

With the phone installed in the vehicle kit, make a phone call.

Is the value as specified?

Less than +1

Go to Step 18

Go to Step 9

1. Verify that the mute line is correctly connected to the phone kit.
2. Verify that the voice signal and return lines are correctly connected to the phone kit. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and complete the repair?

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Go to Step 23

Go to Step 10

Using a fused jumper, connect the mute line to a known good ground.

Does the audio system switch to VOICE IN mode?

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Go to Step 19

Go to Step 18

1. Remove the audio system head unit.
2. Using a digital ohmmeter, check the continuity of the mute line circuit between the radio connector and the mute line in-line connector for continuity. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you complete the repair

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Go to Step 23

Go to Step 18

Adjust the phone volume and audio system volume to approximately 50 percent while the call is in progress.

Does the caller's voice play through the audio system speakers?

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Go to Step 16

Go to Step 13

At the hands-free kit wiring, check that the positive speaker wire is connected to signal circuit and the negative wire is connected to ground circuit. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and complete the repair?

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Go to Step 23

Go to Step 14

1. Remove the audio system head unit.
2. Disconnect the phone kit wiring.
3. Using a digital ohmmeter, check the continuity of the voice signal line circuit, between radio connector and the inline connector . Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
4. Using a digital ohmmeter, check the continuity of the voice signal return line circuit, between radio connector and the inline connector. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and complete the repair?

Go to Step 23

Go to Step 15

Disconnect the signal circuit and ground circuit and connect a hands-free type speaker to the hands-free controller.

Does the speaker work?

Go to Step 21

Go to Step 19

Ensure that the phone volume and the audio system volume are set at approximately 50 percent. If either is set too high or too low, then the sound quality may be distorted or feedback may be heard.

Is the voice clear, with no distortion?

Go to Step 17

Go to Step 21

Can digital type noise be heard when a phone call is being made?

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Go to Step 22

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Replace the radio head unit. Refer to Radio Replacement in Entertainment.

Did you complete the replacement?

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Go to Step 23

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Refer out to cellular phone manufacturer.

Is the repair complete?

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Go to Step 23

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The permanently installed speaker. Audio system cannot accept this type of input.

Follow manufactures recommendations.

Is the repair complete?

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Go to Step 23

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Adjust phone and radio volume, radio bass and treble until clear sound is produced

Is the repair complete?

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Go to Step 23

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Ensure that an antenna system is connected to the phone kit and that all connections are tight

Is the repair complete?

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Go to Step 23

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Operate the system in order to verify the repair.

Did you correct the condition?

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System OK

Go to Step 3