Pinpoint Test A: Poor Reception - AM/FM
Information and Entertainment System
Pinpoint Test A: Poor Reception - AM/FM
Normal Operation
The AM/FM antenna grid, integral to the rear window, receives AM and FM radio waves. The antenna module sends the radio waves to the Audio Control Module (ACM) through the 2-piece antenna cable.
The ACM (Audio Control Module) powers the antenna to amplify the AM radio signal. If there is a concern on this circuit, only the AM radio reception is affected.
The noise suppression equipment reduces engine ignition and electrical systems interference transmitted through the speakers.
The RDS function allows the vehicle operator to choose which genre (category) of music to listen to. When the SCAN button is pressed, the ACM (Audio Control Module) only stops at channels falling within the selected category. If no channel in the selected category is found, the ACM (Audio Control Module) continues to scan without stopping. This may appear to be a reception issue, but it is actually due to the customer setting.
- DTC B1A56:21 (Antenna: Signal Amplitude 〈 Minimum)- sets when the signal strength is less than the pre-configured threshold value.
This pinpoint test is intended to diagnose the following:
- No channel found in the selected category
- Wiring, terminals or connectors
- Antenna grid
- AM/FM antenna cable
- Antenna module
- Charging system
- Ignition system
- Noise suppression equipment
- ACM (Audio Control Module)
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.
A1 CHECK THE RDS SETTING
- Turn the RDS function off. Refer to the Owner's Literature.
- Scan for a good channel.
Does the audio system find a good channel with normal reception?
Yes
The system is operating correctly at this time. The concern was a result of no channel being found in the selected category.
No
GO to A2.
A2 CHECK THE AUDIO SYSTEM RECEPTION
- Check the audio system reception with the engine running, and with the engine off.
Does the poor reception only occur with the engine running?
Yes
GO to A3.
No
If the concern is only with AM radio reception, GO to A7.
Otherwise, GO to A9.
A3 CHECK THE NOISE SUPPRESSION EQUIPMENT
- Check the engine ground strap for security, cleanliness, and metal-to-metal contact.
Are the connections clean, secure, and in metal-to-metal contact?
Yes
GO to A4.
No
CLEAN and SECURE the connections, or INSTALL a new engine ground strap as needed. TEST the system for normal operation.
A4 CHECK THE RADIO INTERFERENCE CAPACITOR
- Install a new radio interference capacitor.
- Start the vehicle.
- Operate the audio system in radio tuner (AM/FM) mode.
Is the reception OK?
Yes
The cause of the concern was an inoperative radio interference capacitor. The system is now operating correctly.
No
GO to A5.
A5 CHECK THE GENERATOR
- Ignition OFF.
- Disconnect: Generator C102A.
- Start the engine.
- Operate the audio system in radio tuner (AM/FM) mode.
Is the reception OK?
Yes
INSTALL a new generator. TEST the system for normal operation.
No
GO to A6.
A6 CHECK THE IGNITION CIRCUITS
- Ignition OFF.
- Connect: Generator C102A.
- Check the ignition circuits for correct routing, grounding, and integrity of the connections.
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.
A7 CHECK THE ANTENNA MODULE ENABLE CIRCUIT
- Ignition OFF.
- Disconnect: Antenna Module C9021.
- Operate the audio system in radio tuner (AM/FM) mode.
- Measure the voltage between the antenna module C9021-1, circuit VME49 (WH), harness side and ground.
Is the voltage greater than 10 volts?
Yes
GO to A9.
No
GO to A8.
A8 CHECK THE ANTENNA MODULE ENABLE CIRCUIT FOR AN OPEN OR SHORT TO GROUND
- Ignition OFF.
- Disconnect: ACM (Audio Control Module) C240A.
- Measure the resistance between the ACM (Audio Control Module) C240A-5, circuit VME49 (WH), harness side and the antenna module C9021-1, circuit VME49 (WH), harness side; and between the ACM (Audio Control Module) C240A-5, circuit VME49 (WH), harness side and ground.
Is the resistance less than 5 ohms between the ACM (Audio Control Module) and the antenna module, and greater than 10,000 ohms between the ACM (Audio Control Module) and ground?
Yes
GO to A12.
No
REPAIR the circuit. CLEAR any DTCs present. TEST the system for normal operation.
A9 CHECK THE ANTENNA GRID
- Ignition OFF.
- Inspect the antenna grid closely for signs of damage.
Is the antenna grid OK?
Yes
GO to A10.
No
REPAIR the antenna grid as necessary. TEST the system for normal operation.
A10 ISOLATE THE ANTENNA MODULE
- Ignition OFF.
- Install a new antenna module. Refer to Antenna Module .
- Operate the audio system in radio tuner (AM/FM) mode.
Is the reception OK?
Yes
The cause of the concern was an inoperative antenna module. The system is now operating correctly. CLEAR any DTCs. REPEAT the self-test.
No
GO to A11.
A11 ISOLATE THE AM/FM ANTENNA CABLE
- Ignition OFF.
- Substitute a known good AM/FM antenna cable by over-laying the body electrical harness.
- Operate the audio system in radio tuner (AM/FM) mode.
Is the reception OK?
Yes
INSTALL a new AM/FM antenna cable (part of the body electrical harness). CLEAR any DTCs present. TEST the system for normal operation.
No
GO to A12.
A12 CHECK FOR CORRECT ACM (Audio Control Module) OPERATION
- Ignition OFF.
- Connect: All Disconnected Connectors.
- Disconnect all the ACM (Audio Control Module) connectors.
- Check for:
- corrosion
- damaged pins
- pushed-out pins
- Connect all the ACM (Audio Control Module) connectors and make sure they seat correctly.
- Operate the system and determine if the concern is still present.
Is the concern still present?
Yes
INSTALL a new ACM (Audio Control Module). REFER to 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. CLEAR any DTCs. REPEAT the self-test.