Does the CPU control the voltage level or anything concerning the charging system?

I still get "charg system fault" every so often and I have changed out the Alternator, new optima battery, fixed one bad ground and checked every ground I know of. The only thing I can think of that may still be effecting this is the cpu. When this happens, the voltage will go down to maybe 11 volts and then up to say 14..

Every time it starts this "charg system fault", if I shut the car off and re-start it, its gone. :confused: This is bugging me.... Here are the grounds I checked.



[Modified by SLICKMAN, 9:01 PM 8/18/2003]

 

TTT

 

I've the shop manual in front of me and it seems that the PCM controls the charging of the battery.
Since you already replaced the generator, the battery and checked for bad ground connections, I would now check the positive sides:
1) The output of the generator (big red cable) goes via a fusible link (looks like a wire but acts as a high amp fuse) to the starter and from there to the + side of the battery. Check for corrosion at starter.
2) From the same point at the starter, there is a grey cable going to another fusible link and from there back to the plug at the generator. (red wire) This is the DC sense line. Check for corrosion at starter. It also happens that this wire is crimped on its lug without properly stripping the insulation or the copper wire is broken in the insulation (due to vibration) which gives intermittent problems.
3) the other 2 wires on the generator connector go to the PCM. the grey one measures the fiels coil voltage and the other one (red) controls the charging rate. I'd check continuity for all thoe 3 wires with an Ohm meter.

I have a '99 vette so the wiring description is for that model year. I think there should be no difference with yours.
A shop manual would be very helpful in this case. In case you don't have one , let me know and I'll email you a copy of the generator page.

Hope this helps.

Roger

 

Don't really know the answer to your question, but your car looks sweet with the black/red interior :thumbs:

 

I did a visual on this when I installed the new optima and they looked clean and they were tight. I guess I should get under there and take them apart, clean and re-install. Sometimes looks can be deceiving. I should have done that when I was under there to eliminate the variable.

You know what I thought was strange, if I put a voltage meter on the battery side and then check the readings on both the DIC and the meter they are off by about 1 volt. If the DIC reads 13.2 the meter at the battery reads about 14.2… I know there’s a lose in wiring but, did not think that it was that high…

I’m not going to have the time this weekend to rip it apart but I will next weekend and post an update. One of the big questions I had were answered and that was the PCM controlling the charging rate. If the wiring is good, I think I have a PCM problem.

 

I'm going to quote from the service manual....

"Once the generator (alternator) is enabled by the PCM, the voltage regulator controls generator output independently of the PCM."

For a very long time GM has used an internal voltage regulator housed within the alternator and this hasn't changed. What has changed is that the PCM can turn the regulator on and off. Once the engine is up and running a turn on signal (5volts) is sent to the regulator and the charging starts. Under certain conditions the PCM can turn off the regulator when a too high a voltage is being generated (>16volts). This level could do some serious damage.

The PCM as well as three other control modules do monitor the generators output and can set DTC's. Voltages are monitored at the generator by the PCM (P0562, P0563, P1637). Voltages are monitored by the SCM, the seat control module, located under the drivers seat (B0846, B0851). Voltages are monitored by the LDCM, the left hand door control module, located inside the left hand door (B2282, B2284). Voltages are monitored by the RDCM, right hand door control module, located in the right hand door (B2283, B2285).

Depending on which DTC's are being set will determine what the problem might be. It might be as simple as a loose connector at one of the locations of a particular module.

Good luck

LEC

 

Now here is something I did not know... It could be one of four things causing this.. Looks like I'm in for a long haul finding this.

Thanks LEC (1964VETTE)

 

The only thing is, when this happens there are no codes set... other than a low voltage one I think. I have to check this out, I'll post what I find tonight..