Chevrolet Trax: DTC B125A: Antenna signal circuit

Diagnostic Instructions

• Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
• Review Strategy Based Diagnosis for an overview of the diagnostic approach.
• Diagnostic Procedure Instructions provides an overview of each diagnostic category.

DTC Descriptors

DTC B125A 02

Antenna Signal Circuit Short to Ground

DTC B125A 04

Antenna Signal Circuit Open Circuit

Diagnostic Fault Information

Circuit/System Description

The multi-band antenna is located on the roof of the vehicle. The radio antenna is enabled when the radio is turned on. The radio provides battery voltage to the antenna using the center conductor of the antenna coaxial cable. When a 12 V signal is seen on the center conductor of the antenna coax, both AM and FM signals are amplified.

Conditions for Running the DTC

• Ignition ON.
• Battery voltage must be between 9-16 V.

Conditions for Setting the DTC

B125A 02

The radio detects a short to ground in the antenna signal circuit center conductor.

B125A 04

The radio detects an open in the antenna signal circuit center conductor.

Action Taken When the DTC Sets

Radio reception may be poor or not available.

Conditions for Clearing the DTC

• The condition responsible for setting the DTC no longer exists.
• A history DTC will clears after 50 consecutive malfunction-free ignition cycles have occurred.

Reference Information

Schematic Reference

Radio/Navigation System Schematics (Encore), Radio/Navigation System Schematics (Trax)

Connector End View Reference

WIRING SYSTEMS AND POWER MANAGEMENT - COMPONENT CONNECTOR END VIEWS - INDEX - ENCORE WIRING SYSTEMS AND POWER MANAGEMENT - COMPONENT CONNECTOR END VIEWS - INDEX - TRAX

Description and Operation

Radio/Audio System Description and Operation (with Monochrome Display), Radio/Audio System Description and Operation (with Color Display)

Electrical Information Reference

• Circuit Testing
• Connector Repairs
• Testing for Intermittent Conditions and Poor Connections
• Wiring Repairs

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Verification

1. Ignition ON, A11 Radio ON.
2. Verify station reception is normal when tuned to several known good AM and FM stations.

If AM or FM reception is poor.

Refer to Circuit/System Testing

If reception is normal

3. All OK.

Circuit/System Testing

1. Ignition OFF, disconnect the radio antenna coax cable from the A11 Radio and from the T4M Radio Antenna.
2. Verify the antenna coax cable passes the coax cable component test. Refer to Component Testing

If the coax cable does not pass the test

Replace the antenna coax cable

If the coax cable passes the test

3. Connect the radio antenna coax cable to the A11 Radio.
4. Ignition ON, A11 Radio ON.
5. Verify a test lamp illuminates between the antenna coax cable center terminal at the T4M Radio Antenna and chassis ground.

If the test lamp does not illuminate

Replace the A11 Radio.

If the test lamp illuminates

6. Test or replace the T4M Radio Antenna.

Component Testing

CAUTION: Refer to Test Probe Caution .

NOTE: Before testing the coax cable, check the cable exterior for being pinched, cut, damaged, or having loose connections at the components, which can cause reception issues.

To prevent false reading when testing the center coax terminals, use care not to ground the test probe on the outer housing/shield.

Coax Cable Test

1. Ignition OFF, disconnect the coax cable at both components.
2. Test for less than 5 ohms between coax cable center terminal end to end.

If 5 ohms or greater

Replace the coax cable

If less than 5 ohms

3. Test for less than 5 ohms between the coax cable outer shield end to end.

If 5 ohms or greater

Replace the coax cable

If less than 5 ohms

4. Test for infinite resistance between the coax cable center terminal and the coax cable outer shield.

If less than infinite resistance

Replace the coax cable

If infinite resistance

5. All OK.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the repair.

• Radio Antenna Base Replacement
• Control Module References for radio replacement, programming, and setup.

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