Pinpoint Test A: Poor Reception - AM/FM
Information and Entertainment System
Pinpoint Test A: Poor Reception - AM/FM
Normal Operation
The antenna receives AM and FM radio waves and sends them to the Audio Control Module (ACM) through the antenna cable. The ACM powers the antenna in order to amplify the AM signal.
- DTC B1A56:1D (Antenna: Circuit Current Out of Range) - sets continuously when the antenna enable circuit current is outside of limits. The current is checked once every 5 seconds.
- DTC B1A56:21 (Antenna: Signal Amplitude < Minimum) - sets on-demand when no signal is detected from the antenna.
This pinpoint test is intended to diagnose the following:
- Antenna
- Antenna cable
- Charging system
- Ignition system
- ACM
PINPOINT TEST A: POOR RECEPTION - AM/FM
NOTICE: Use the correct probe adapter(s) when making measurements. Failure to use the correct probe adapter(s) may damage the connector.
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A1 CHECK THE AUDIO SYSTEM RECEPTION
- Operate the audio system in radio tuner (AM/FM) mode.
- Check the reception with the engine running, and with the engine off.
- Does the poor reception only occur with the engine running?
Yes
GO to A2.
No
GO to A4.
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A2 CHECK THE GENERATOR
- Ignition OFF.
- Disconnect the wiring harness from the generator voltage regulator.
- Start the engine.
- Operate the audio system in radio tuner (AM/FM) mode.
- Is the reception OK?
Yes
INSTALL a new generator. REFER to Charging System Service and Repair. TEST the system for normal operation.
No
GO to A3.
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A3 CHECK THE IGNITION CIRCUITS
- Ignition OFF.
- Connect the wiring harness to the voltage regulator.
- Visually inspect the engine compartment and make sure all ignition coils are correctly and securely connected, and that there are no visible cracks in the coil housings.
- Inspect all the wiring harnesses and connectors for damaged insulation and loose or broken conditions.
- Are the ignition components OK?
Yes
USE a jumper cable to ground various parts of the vehicle to the frame (for example: engine, fenders, quarter panels, stone deflectors, air cleaner, body sheet metal). When the noise is eliminated, PROVIDE a permanent ground where necessary. TEST the system for normal operation.
No
REPAIR the ignition system as necessary. TEST the system for normal operation.
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A4 CHECK THE ANTENNA ENABLE CIRCUIT
- Ignition OFF.
- Disconnect: Antenna C9021.
- Operate the audio system in radio tuner (AM/FM) mode.
- Measure the voltage between the antenna C9021-1, circuit CME44 (BU), harness side and ground.
- Is the voltage greater than 10 volts?
Yes
GO to A6.
No
GO to A5.
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A5 CHECK THE ANTENNA ENABLE CIRCUIT FOR AN OPEN OR SHORT TO GROUND
- Ignition OFF.
- Disconnect: ACM C240A.
- Measure the resistance between the ACM C240A-2, circuit CME44 (BU), harness side and the antenna C9021-1, circuit CME44 (BU); and between the ACM C240A-2, circuit CME44 (BU), harness side and ground.
- Is the resistance less than 5 ohms between the ACM and the antenna, and greater than 10,000 ohms between the ACM and ground?
Yes
GO to A9.
No
REPAIR the circuit. TEST the system for normal operation.
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A6 CHECK THE AM/FM ANTENNA CABLE
- Ignition OFF.
- Disconnect: AM/FM Antenna In-Line Connection At RH Kick Panel.
- Disconnect: AM/FM Antenna Cable At ACM.
- Measure the resistance of the rear AM/FM antenna cable core between the antenna and the front AM/FM antenna cable in-line connection; and between the rear AM/FM antenna cable core and shield.
- Measure the resistance of the front AM/FM antenna cable core between the ACM and the rear AM/FM antenna cable in-line connection; and between the front AM/FM antenna cable core and shield.
- Is the resistance of each AM/FM antenna cable core less than 2 ohms, and the resistance between the core and shield of each AM/FM antenna cable greater than 10,000 ohms?
Yes
GO to A7.
No
INSTALL a new front or rear AM/FM antenna cable. REFER to Antenna Cable - AM/FM/Satellite Radio Service and Repair. TEST the system for normal operation.
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A7 ISOLATE THE ANTENNA
- Connect: AM/FM Antenna In-Line Connection At RH Kick Panel.
- Connect: AM/FM Antenna Cable At ACM.
- Install a new antenna. Refer to Antenna Service and Repair.
- Operate the audio system in radio tuner (AM/FM) mode.
- Is the reception OK?
Yes
The concern was caused by an inoperative AM/FM antenna. The system is now operating correctly.
No
GO to A8.
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A8 ISOLATE THE ANTENNA CABLE
- Ignition OFF.
- Substitute each antenna cable by routing a new component. Do not remove the original antenna cable at this time.
- Operate the audio system in radio tuner (AM/FM) mode.
- Is the reception OK?
Yes
INSTALL a new antenna cable for the inoperative cable. REFER to Antenna Cable - AM/FM/Satellite Radio Service and Repair. TEST the system for normal operation.
No
REMOVE the substitute antenna cable. GO to A9.
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A9 CHECK FOR CORRECT ACM OPERATION
- Disconnect all the ACM connectors.
- Check for:
- corrosion
- damaged pins
- pushed-out pins
- Connect all the ACM connectors and make sure they seat correctly.
- Operate the system and verify the concern is still present.
- Is the concern still present?
Yes
INSTALL a new ACM. REFER to Audio Control Module (ACM) Audio Control Module (ACM). TEST the system for normal operation.
No
The system is operating correctly at this time. The concern may have been caused by a loose or corroded connector.
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