2007 C6Z...7800 miles....analog guage and DIC show 14.5 volts...Lights nice and bright...battery tests fine...car starts and runs fine...Everything seems normal other than the message I keep getting on DIC...No codes when tested with OBDII...I use a Battery Tender ANYTIME Im not driving the car....Car is out of warranty so I dont want to take it to the dealership unless absolutely necessary...Anyone experience this before on a C6???

 

Go to an auto parts store and use a code reader to see what is up. You can then make a decision.

Could be a glitch in the computer. My C6 had an erroneous gage reading while under warranty, but when it was taken into the dealer all was well and the reading later returned to normal.

The rate of charge is actually controlled by the car's computer.

 

I have an OBDII code reader....As stated in my original post there were/are no codes...the guage (analog) and DIC shows a normal charging rate...It doesnt make any sense to me...

 

When I went into the dealer to explore my problem they started with a code reader then went to a lap top computer. Might need a deeper analysis of the problem.

 

I get that same message. There's nothing wrong with my charging system. My alternator/battery are working as intended. I clear it with a code reader. Takes about 30 seconds. Sometimes it comes back a couple weeks later. I clear it again.

Some of these messages on the DIC are *soft* codes and can be removed safely with a code reader. Even the cheapest code reader should work fine for removing soft codes.

The one I use is the Actron CP9550 Pocket Scan Plus OBD II and CAN Code Reader. It has most code definitions right on the screen.

However, it may be a genuine issue that needs attention, so best to consult your local speed shop for verification.

 

Do you have aftermarket spark plugs?

They are known to cause RF interference and give you these symptoms.

 

No...the car only has 7800 miles...all stock with the exception of Corsas..

 

That's the code reader I have....Thing is...there are NO codes...The only message I get is "service charging system" on the DIC

 

Sounds like I may have to break down, bite the bullet and take it to the dealer for a diagnostic check with more test equipment than what I have..

 

What is the volt reading when the message appears?

Does it stay on or just flicker on and off intermittently?

 

The analog guage shows normal at all times.....The message stays displayed on the DIC until I hit the reset button...Usually comes back on within a few miles

 

Found the problem....There is a 15 amp fuse for the horn...it also has something to do with the alternator...The fuse is fuse #2 in the underhood fuse block....It's labeled horn/alt sense...Seems the horn wasnt working either...I replaced the fuse...it blew the second I tried honking the horn...I replaced it again, but didnt try the horn....Took it for a drive and it never set the "service charging system" message again....I tried the horn again, which immediately blew the fuse, then I started getting a "service charging system" message again.....Now I just gotta figure out where the short in the horn is...

 

What made you check the horn fuse? Or were you just checking the fuse boxes and noticed that one was blown? You must have saved a lot of $ by finding it yourself rather than taking it to a dealer. Good luck to you searching for the short in the horn.

 

Actually, I posted this same question on the C6Z side of the CF...someone there had experienced the same problem and suggested I check it...I had noticed the horn didnt work the other day but never thought it would affect the charging system

 

Had the same DIC issue...was aftermarket plugs for me. Though I'd been told to check the horn fuse and alt->starter connections.

The horn shares a circuit with the charging system...sounds like a potential bad connection at the alt.

 

I am glad you found out what was wrong. Good luck making the repairs.

Brent
GM Customer Service

 

Thanks...So far Im not having any luck finding the source of the short in the horn..

 

Some of this from the service manual may be helpful. It states the horn may have gotten water in it and shorted. Are there 2 horns on the vette? I would disconnect one horn at a time and if it honks with one and blows the fuse with the other then I would replaced the bad horn. In old days they were 2 different tones so you have to know which one if there are 2 different part numbers.

EDIT: Looked again... looks like the horn assembly is one unit in the right front wheelhouse so there may not be a way to test the individual horns as it appears they are together in one unit.

The horn system consists of the following components:

• HORN fuse

• Horn relay

• Horn slip ring

• Horn switch (The horn switch is part of the inflatable restraint steering wheel module.)

• Horns

• Body Control Module (BCM.)

System Operation
The vehicle horn system is activated under the following conditions:

• Either of the horn switches is depressed.

• The body control module (BCM) commands the horns on. The BCM commands the horns on under any of the following conditions:

- When the content theft deterrent system detects a vehicle intrusion. For further information refer to Content Theft Deterrent (CTD) Description and Operation .

- When the panic button is depressed on the remote control door lock transmitter. For further information refer to Keyless Entry System Description and Operation .

- When the keyless entry system is used to lock the vehicle, a horn chirp may sound to notify the driver that the vehicle has been locked. The notification feature may be enabled or disabled through personalization. For further information refer to Keyless Entry System Description and Operation .

Circuit Operation
Battery positive voltage is applied at all times to the horn relay coil and the horn relay switch. Pressing either of the horn switches applies ground to the horn relay control circuit. The BCM may also apply ground to the horn relay control circuit as described above. When the horn relay control circuit is grounded, the horn relay is energized and battery positive voltage is applied to the horns through the horn control circuit. The horns sound as long as ground is applied to the horn relay control circuit.

The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.
Condition/Concern:
Some customers may comment that the Service Charging System message displays on the DIC. Using the Tech2, DTC P0621 is stored. This may be a result of aftermarket spark plugs or an open in circuit number 2540.

Recommendation/Instructions:
1. Check for aftermarket spark plugs. Plugs that are designed with a "Pulse" technology may interfere with this circuit and cause the Service Charging System message to illuminate on the IP and/or P0621 DTC store in the ECM. If aftermarket plugs are installed, replace plugs with OEM parts. This is not considered a warranty repair and all cost associated with this repair will be the customers responsibility.

2. Circuit 2540 is supplied voltage from the Horn fuse, position #2 in the UBEC. Apply the horn to see if it works. If the horn does not work, suspect an open fuse. This fuse may open if the horn is shorted due to water intrusion. If the horn is functional, check the integrity of circuit 2540 between the UBEC and the generator. Refer to SI document 1481125 for the schematic. Repair circuit 2540 as needed and re-evaluate the customers concern.

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.


HORN INOPERATIVE
The numbers below refer to the step numbers on the diagnostic table.

Verifies that the body control module (BCM) is providing ground to the horn relay.

Tests for voltage at the battery positive voltage terminal of the horn relay coil.

Tests for voltage at the battery positive voltage terminal of the horn relay switch.

The horns need maximum current flow to operate properly. A high resistance, greater than 0.5 ohm in the horn control circuit or the horn ground circuit could cause operating problems with the horns. Check the circuits for faults that would restrict current flow.

The horn relay control circuit includes the horn slip ring and the horn switch. The horn slip ring and the horn switch must be tested for a high resistance, an open or a short to voltage when testing the relay control circuit. Refer to Circuit Testing and Wiring Repairs .

 

Did you disconnect the horn and then try the horn again with a new fuse in the fuse holder? I believe a dead short in the horn wiring will blow the fuse. If the fuse does not blow the horn would be the culprit.

 

My guess it the horn may have gotten water in it. It's bolted to the right side of the lower radiator support.