Okay so installed new batt and alternator but still have this annoying message on the display. i have checked and cleaned batt connections and wires at the alternator. Still getting the message. Any ideas of what the problem could be???!!

 

Could be any number of issues. I just recently got done fighting this same thing myself. Its worth cleaning the grounds under the battery tray on the frame rail. There are 3 ground cables that connect to a stud on the rail. They may also be loose and messing w/ the battery cables might have broke their contact.

Additionally there is one ground on each of the front frame rails slightly behind the headlight door near where the headlight motors plug into their power source.

There are also some connections to your starter motor that if dirty or loose will cause the charge system message.

A dirty ignition switch is also a source of many problems I have been told.

 

lets start here Where did you buy the alternator?

 

Oreillys

 

That is what I figured. I bet the msg was still there as soon as you installed it. It is a Generic replacement it bolts up and plugs in but is missing an internal circuit that the C5
needs GO get your old one back if you can

 

Shoot me a text message if ya don't mind 8105135831

Thanks

 

From member Evil Twin
because this car is 11 years old and as many who have Pm'd me have found that the local parts guy just put a GM alternator in there, Now while the alternator may check out , there are no generic specific test for the discreet circuit that is found ONLY in the original Alt/gen found in these three specific years.. they speak directly to the PCM, and have locked in parameters for spooling up in DC voltage and in AC voltage, anything reported outside of these very specific parameters will post a Charging system fault... the biggest culprit is putting anything other than the specific French made Valeo 110 amp alt/gen. The way around this is putting an upgraded alt/gen and the PCM has to be re flashed at the dealer to accept the higher amperage and the algorithms specific to the 140 alt/gen. The PCM does not like anything other than the original... or a rebuilt original.. not just a cross references one..Ive told hundreds of people over the last 10 years to make sure they do not give up their original Valeo 110. Some have gone back to get theirs and have it rebuilt to find that their charging system fault was all of a sudden gone.. and for anyone who thinks getting a charging system fault is a natural thing.. let me tell you it isnt..most is a communications problem and a DIC code display, which is a pain in the ***...

here is how this communications link works.. Ive posted this hundreds of time when I did this write up:

The PCM monitors the alternator through the red and grey wires The L-terminal circuit from the generator is a discrete circuit (a discrete circuit has no splices and only one source and destination) into the PCM. The PCM applies ignition voltage to the generator L-terminal circuit. A small amount of current flows from this circuit through the generator windings to ground to create a magnetic field which starts the generator process. When the generator is at operating speed and producing voltage, a solid state switch for the L-terminal circuit in the generator opens and the PCM detects that the initial startup current flow has stopped.

The PCM expects to detect low voltage on the L-terminal circuit prior to the generator rotating at operating speed and conversely expects the circuit to be at ignition voltage potential when the generator is operational. When the PCM detects a fault (circuit shorted to ground, or circuit shorted to voltage), the Driver Information Center will display Charging System Fault.

The generator has an input to the PCM called the F Terminal to indicate the percentage of total capacity ( 110 amps- not 140 amps )that the generator is producing. This signal is detected by the PCM as a duty cycle from the generator and displayed on the scan tool as a percentage. The PCM can monitor the generators output under all conditions to determine if it is functioning normally.

When there is low demand from the electrical system on the generator, a low duty cycle percentage will be displayed. As more accessory load is placed on the generator, the duty cycle output detected by the PCM will approach 100 percent. A normally functioning generating system will never reach 100 percent as indicated on the scan tool.

The L and F terminals are the red and grey

 

Will the "Charge system fault" message display intermittently or every time ? I get it if I haven't driven the car for a few days. I've had the car for 4 years, so I don't know if the alternator was ever changed.

 

I had the same message on my car. The alternator was so bad it couldn't be rebuilt. As soon as I installed a new correct GM alternator the code went away. Not a cheap fix but it took car of all of my problems.

 

I had a similar issue on my 02 c5z. It would throw the charge system code intermittently and eventually I had to replace the alt with one from autozone. Problem solved 6 months go by now it's throwing the charge system fault code again. Alt checked good, replaced the battery, and the volts still won't charge past 12 volts when it normally stayed just over 13volts. I've checked all the wires I know to but haven't found any bad or bad connections. Not sure what to do next to try and solve the issue.

 

Had the same issue last year, ended up being a bad connection at the starter. The plastic broke that holds the stud in and cause a failing connection. Went through a few alternators and a lot of long nights trying to find the problem. Hope this helps

 

Any leads on possible issues causin the problem is much appreciated.

 

I chased this too. After a new battery and alternator, it ended up being the connection at the starter. The positive side bolt backed out. Might check that.