| Subject: | Monsoon Audio System Diagnostics |
| Models: | 2005-2007 Pontiac G6 |
This PI was superseded to update the model years. Please discard PIC3313.
The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.
Condition/Concern:
This information applies only to vehicles with the Monsoon system RPO U85. One or more speakers are inoperative, have distorted sound, or a repeat speaker failure.
Recommendation/Instructions:
The Monsoon radio system is an 8-channel 200-Watt system. The front door tweeters and rear midrange speakers are coupled together inside the amplifier (i.e., on the same bridge). Similarly, the front door lower speakers and the rear subwoofers are coupled
together within the amplifier. It is important to know this as it can be possible to have a concern with one of the channels, wires, or speakers that affect the operation of one or all of the channels that use the same bridge. This can confuse diagnoses.
Example: The wiring for the left tweeter is shorted to ground. This is causing the rear midrange speakers to sound distorted. The distortion is more perceivable in the midrange as they are dominant which could draw your attention away from the loss of
audio from the left tweeter.
Likely Locations for Wiring Damage:
| • | The upper door trim panel pull handle screw could damage the right tweeter jumper harness. |
| • | The instrument panel carrier near C206, on the right side kick panel, could damage the main body harness. |
| • | The main wire harness could be damaged at the right package shelf pass through. |
Useful Facts When Diagnosing Monsoon (U85) Audio Concerns:
| • | The amplifier is turned on through the use of a 12v, discreet, pull up signal, identified as circuit 5165. SI documents 1483147 and 1483148 do not show this. Circuit 5165 is a pink wire located in amp C2 A3, and radio C1 B6. This circuit also turns
on the Antenna Amplifier Module. SI document 1483147 does not show that the circuit splits at C206 where two wires are crimped into terminal B5. One branch is going to the Amplifier and one branch is going to the Antenna Amplifier Module. |
| • | SI document 1483147 incorrectly show the presence of a mute line (circuit 5748). The line was eliminated before production. |
| • | When measured with an ohm meter, the tweeters should be 4 ohms (use impedance meter for tweeter as it has a capacitor filter inline located at the tweeter body), low level door speakers 2 ohms, rear midrange 4 ohms, and the rear subwoofers 2 ohms. |
| • | Roughly 2 - 7v AC should be detected at the speaker connector when testing a normally operating system. Voltage will rise and fall with volume. |
| • | Less than 1v DC should be detected at the speaker connector. 1v or more is a possible indication of a damaged quad bridge output device in the Amplifier. REPLACE the Amplifier, if the wiring between a speaker and the Amplifier is proven to be NOT
shorted to voltage. Prolonged exposure to DC voltage can cause a speaker coil to short. This condition is first signaled by distortion/noise, eventually leading to failure. If this condition is present and not identified it can cause repeat speaker failures.
Lower than expected resistance readings when testing the speakers can be a tell tale sign of this condition. |
| • | The low level audio signals from the radio to the amp will register about 100mv. If greater than 500mv, the radio is not "setup" for the amp. This will cause distortion in all speakers because the signal is being amplified twice. |
| • | If the low level signals are shorted to ground, circuit protection in the radio will kick in causing no audio from any speaker. |
| • | If the low level signal wires are broken or damaged and in close proximity to other circuits, noise could couple onto the low-level signal wires and the noise will be amplified. Examples: A whine noise heard through the speaker(s) when the fuel
pump is running or faint ticking noise heard when the IP backlighting is in use. |
Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.
