Pinpoint Test U: The Steering Wheel Controls Are Inoperative/Do Not Operate Correctly (Early Build)
Information and Entertainment System
Pinpoint Test U: The Steering Wheel Controls Are Inoperative/Do Not Operate Correctly (Early Build)
Refer to Wiring Diagrams Set 130, Audio System for schematic and connector information. Electrical Diagrams
Normal Operation
The steering wheel controls contain the following switches: VOL-, VOL+, SEEK-, SEEK+, MODE, and VOICE. The VOICE switch is only active for vehicles with the Bluetooth Hands-Free System. The steering wheel controls are hardwired to the ACM (Audio Front Control Module).
For vehicles with the Bluetooth Hands-Free System, the ACM (Audio Front Control Module) broadcasts a message over the Medium Speed Controller Area Network (MS-CAN) to the Speech Recognition Module (SRM) when the VOICE switch is pressed. The SRM (Speech Recognition Module) then enters voice recognition mode and receives voice inputs from the microphone.
For all vehicles, a reference voltage is sent from the ACM (Audio Front Control Module) to the steering wheel controls. When a switch is pressed, the voltage is routed through a specific resistor value for each function. The ACM (Audio Front Control Module) provides the ground for the reference voltage. The ACM (Audio Front Control Module) uses this reference voltage to determine which control input function has been selected.
- DTC B2404 (Audio Steering Wheel Switch Circuit Fault)- set by the ACM (Audio Front Control Module) in continuous memory when the reference voltage to the steering wheel controls is out of range. This can be caused by any failure on the steering wheel controls circuit except for a stuck switch or a short to ground on the signal return circuit. This DTC will also be present on vehicles not equipped with steering wheel controls.
This pinpoint test is intended to diagnose the following:
- Wiring, terminals or connectors
- Steering wheel controls
- ACM (Audio Front Control Module)
PINPOINT TEST U : THE STEERING WHEEL CONTROLS ARE INOPERATIVE/DO NOT OPERATE CORRECTLY (EARLY BUILD)
NOTICE: Use the correct probe adapter(s) when making measurements. Failure to use the correct probe adapter(s) may damage the connector.
U1 MONITOR THE STEERING WHEEL CONTROLS PIDs
- Enter the following diagnostic mode on the scan tool: ACM (Audio Front Control Module) DataLogger.
- Monitor the steering wheel controls PIDs while pressing each steering wheel controls switch button as follows:
Steering Wheel Controls Switch PID VOL- SW_VOLDOWN VOL+ SW_VOLUP SEEK- SW_SEEKMINUS SEEK+ SW_SEEKPLUS MODE SW_MODE VOICE SW_PHONE
Do the PID values agree with the switch position?
Yes
GO to U4.
No
If only one PID value is incorrect or the PID value always reads one particular switch position, INSTALL new steering wheel controls. REFER to Steering Wheel Controls . CLEAR any DTCs present. TEST the system for normal operation.
If multiple PID values are incorrect or read incorrectly, GO to U2.
U2 CHECK THE REFERENCE VOLTAGE CIRCUIT TO THE STEERING WHEEL CONTROLS FOR A SHORT TO VOLTAGE
- Ignition OFF.
- Disconnect: Steering Wheel Controls C2264.
- Disconnect: ACM (Audio Front Control Module) C240D.
- Ignition ON.
- Measure the voltage between the ACM (Audio Front Control Module) C240D-6, circuit 8-MD26 (WH/BK), harness side and ground.
Is any voltage present?
Yes
REPAIR the circuit. CLEAR any DTCs present. TEST the system for normal operation.
No
GO to U3.
U3 CHECK THE CIRCUITS TO THE STEERING WHEEL CONTROLS FOR AN OPEN OR SHORT TO GROUND
- Ignition OFF.
- Measure the resistance between the ACM (Audio Front Control Module), harness side and the steering wheel controls, harness side; and between the ACM (Audio Front Control Module), harness side and ground as follows:
Positive Meter Lead Negative Meter Lead Circuit C240D-6 C2264-1, then ground 8-MD26 (WH/BK) C240D-8 C2264-2, then ground 9-MD26 (BN/YE)
Are the resistances less than 3 ohms between the ACM (Audio Front Control Module) and the steering wheel controls, and greater than 10,000 ohms between the ACM (Audio Front Control Module) and ground?
Yes
GO to U4.
No
REPAIR the circuit in question. CLEAR any DTCs present. TEST the system for normal operation.
U4 CHECK FOR CORRECT ACM (Audio Front Control Module) OPERATION
- Connect: All Disconnected Connectors.
- Disconnect all the ACM (Audio Front Control Module) connectors.
- Check for:
- corrosion
- damaged pins
- pushed-out pins
- Connect all the ACM (Audio Front 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 Front 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 present.