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Discussion Starter #1
Hi all, I'm having a problem and want to see if anyone has ideas before I just start tearing into this thing.


Car: 2007 Lumina SS (basically G8 gt with a few differences)
6.0l L76, 4 speed auto (4l60 i think, but haven't figured it out yet)

Single Zone Manual Climate control
Base radio (not touch screen)
152xxx KM



Issue: generally when cold, but occasionally when its warmed up also, I'll get a "Stability Control Off" message in the dic, this is always accompanied by harsh shifting. It'll stay off for anywhere between 10 seconds and three minutes and then go away. Normally its on the first start after it sits a while (IF it is going to act up) and then works normal by the time I'm 2km up the road or so. It doesn't seem to be triggered by any particular event. bumps, turns, accelleration, or braking dont' seem to have an effect either way. Sometimes it'll give me the message before I can even get it out of park leaving the house, other times it does nothing the entire day.



Also related, occasionally the ac blower will stop, when it does the a/c light and the recirc lights will turn off. Moving any setting on the HVAC will bring it back online. When this happens it completely resets the climate control and the blend air and mode door actuators have to move before the desired operation is restored.



WHAT I KNOW so far:
using a tech2 emulator I have come up with the following items:
EBCM module no communication
BCM no communication
U0214 CAN-Bus No Communication with RFA (Remote Function Actuator)
U0184 CAN-Bus No Communication with Audio System IRC (Integrated Radio Chassis)
U0164 CAN-Bus No Communication with HVAC (Heating Ventilation and Cooling)
U0155 CAN-Bus No Communication with IPC (Instrument Panel Cluster)



Now the obvious answer is there is likely a communications issue somewhere that will resolve the entire set of issues I'm having. In full disclosure, its hotter than hell here and I haven't done any actual diagnostics yet outside of re-seating the ebcm connector which didn't make any difference. When Its acting up there is no communication from the scan tool to any modules on the low speed bus.



I don't have any good wiring diagrams for this car but if its like most gm cars of the era, the only place that both the low and high speed bus meet up is the body control module so that is my number one suspect currently. Is anyone aware of any common wiring splices that give issues on these cars or places where wiring gets rubbed through that may be shorting out something and causing the bcm to go offline? This weekend I'll pull the under dash panel out and check all the bcm wiring I can find and the connectors but I'm not real hopeful it'll be that easy. Do these cars have known issues with body control modules failing in weird ways like this?





I'm good at diagnostics and great with electrical, just hoping for some direction to go in before I start ripping stuff out to test. Thanks for reading this far!
 

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As best as I can understand from reading the G8 service manual (considering this type of stuff is way over my head), is that the low speed data bus is loosing its communication with various modules for short periods of time. Figuring everything was normal up until this started >>>> How long ago did this crop up ? Did you have some type of problem that may have forced you to mess with any connector(s) that might contain the low speed data bus wire ? They say some of the modules are very sensitive to a specific amount of voltage loss, which causes it/them to loose communication on the bus loop during that time frame. You know for sure that the cars voltage is up there around the 12.0 an above range at all times ? If it sounds like I'm not making sense, I can understand (cause "I" don't even know if I'm making any sense when I read it myself). May have to wait for the really sharp members (who know this stuff), to post up some thoughts for a possible solution.
 

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Discussion Starter #4
Goperit, GREAT questions. As far as a when did it start, I have no idea. I purchased the car about a month ago now and its done it from day one. I have monitored the voltage and there are a few times when the watching it through the engineering mode in the instrument panel that it'll dip down to 11.7 or 11.9 very very briefly. A multimeter confirms this to be true. HOWEVER, I've watched it like a hawk and the voltage is stable well above 12.0 volts moving and it'll do it then but not at the times when the voltage dips briefly. I have debated possible ground or power issues because it is a bit sluggish when starting but only at rapid (within 10 minutes or so) restarts, basically just long enough for the starter to heat soak thoroughly. I've mostly written that off as normal operation because the temperature here is punishing. a few days ago the heat index was 117 at 9pm. i'd have problems starting then too.

The battery is new as of about two months ago per the previous owner. Looking the car over I think its had some mods done that have been removed so I don't know whats been done to it. The manifolds have locking bolts like you'd use with headers and it seems to have a very mild, but more aggressive than stock cam. It still has the HSV brakes and clubsport wheels. I doubt someone would put that kind of money into stopping unless there were good reasons for it to go that well at some point. Nothing so far sticks out to me as an issue though.

I really don't think its a voltage issue or at least if it is the issue isn't obvious.

It does appear that its a low speed bus issue but i also wonder if its the actual bcm? I'll be digging into it more this afternoon.


well, sorry for kinda rambling but it helps me to get my thoughts together a bit. I'm off to yank the underdash panel and check the bcm and wiring.

Does anyone have a wiring diagram they can send me by chance?
 

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Discussion Starter #5
Well ****. I broke down today. First time I've had to come home on a tow truck in 15 years :-(

I've got all new hoses and belts and fluids on the way to baseline it but I guess they didn't get here fast enough.

My car has an aftermarket transmission cooler and one of the hoses for it popped. I made a turn and was being a bit aggressive with the throttle and suddenly I noticed a lot of smoke behind me. Wondered who the hell was smoking so bad and then realized it was me. Got it off the side of the road and shut down quickly. The transmission felt fine it was just the smoke that tipped me off so I don't think I ran the clutches dry. Almost two hours for the tow truck because the first driver got in a wreck on the way to me. Got it home and torn apart. Went to about 15 different auto shops trying to find one with the right size hose that was oil rated. Finally found a shop that also did hydraulic hoses and bought a few meters of way overrated stuff but it should hold up.

Started putting it back together but ran out of daylight. Tomorrow morning early I'll knock it out and see if the transmission is hurt. Here's hoping at least.

My new maf sensor, radiator hoses, and brake fluid came in today though so I'll take this as a good chance to do a coolant flush and replace the maf while its all torn apart.
 

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Hopefully, you'll get the issues resolved and the car will be back on the road soon. Regarding the initial query, have not even the slightest clue and subscribed for updates.
 

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Discussion Starter #7
Today on as the world turns:

Got up really early before the sun got hot and attacked it. New transmission cooler lines fitted and started putting it back together. Had a bunch of stuff that needed to be installed. Vacuum line from the valley cover to the intake was shot and I taped it up the day I bought the car waiting on a replacement. pulled the throttle body off and replaced the hose which crumbled to pieces rather than be removed whole. Replaced the MAF and MAP sensors (all factory ac delco parts) and installed the new upper and lower radiator hoses. Used a bottle of water wetter, gallon of green coolant, and topped the rest off with good bottled water (no pure steam distilled or de-ionized water available here) All new clamps to boot as well.

Put a liter (no quarts here, only liters) of atf in to start and had a bit of a pump growl in reverse, put another in and it quieted down completely. Wound up needing a little less than 3 liters of trans fluid to top it off. Put it on an incline to burp the cooling system and monitored the data stream while it heated up. Thermostat opened up and it seems fine temperature wise. I drove it around for about 25 minutes and it felt fine. Took it to work and back this evening with no issue (around 20 miles round trip). It did set the check engine light again for a p0172 and p0175 (system too rich bank 1 AND 2). Probably the VCM otr intake? It runs great and the new maf was definitely an improvement in the off idle response.

I don't think the alternator is charging right though. It does charge but at idle it is often 12.2 or less and watching the bcm data with the tech 2 the battery info shows almost a 40 amp discharge at idle in traffic and the battery charge state depleting. It picks up going down the road but the highest I saw was 13.7 volts and the regulator was set at over 75% so I'm thinking it may be weak, thoughts?

I've also got a small spot on the radiator that looks like a weeping leak. No liquid visible but a stain for sure and crystallized residue so I guess I'll be ordering a new radiator for it.


On the alternator, is it worth it to spend the extra on the ss/ppv alternator? I see amazon has the original for 177 shipped while the ss/ppv alternator is almost 360.
 

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Presume if the alternator were failing there should be some sort of indication on the instrument cluster. Nevertheless, an alternator lasting eleven years is decent and would install an identical replacement unit for less than half the price of the ss/ppv alternator. The lone exception would be if additional accessories or upgrades were added subsequently placing higher electrical demands on the unit. Good luck
 

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From the peanut gallery, go with an AC Delco alternator, aftermarket units seem to give our cars fits.
Board member Les recently swapped out his failed battery and tried to go to a higher amperage alternator if that is what the ss/ppv unit is, it caused engine serge's on his V6.
Swapping back to the old alternator solved the serge problem.
He got his alternator thru Rock Auto.
All I got, good luck.
 

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Discussion Starter #10
Update for today,

New Delco alternator ordered, should take about a week and a half to get here. Thanks BAS G8 for the tip on going with the delco unit. I'm wondering if the firmware im my bcm/cluster doesn't have an error message programmed like the g8's do because I think I should be getting an error with the idle voltage output sometimes. Hopefully its just the alternator and not the bcm fried and this will fix it completely.

i've driven it a good bit and so far the transmission still feel fine so here's hoping.

I also took it and had it detailed and waxed. When the transmission cooler line popped the other day it atomized trans fluid and coated the entire car. Figured I'd finally throw a few decent pictures up!
 

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If the Chevrolet Lumina SS didn't come with an owner's manual, then one might be available online for download since they are almost an indispensable resource. Gosh, that's certainly an interesting looking factory spoiler a division of General Motors installed on the assembly line.
 

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If the Chevrolet Lumina SS didn't come with an owner's manual, then one might be available online for download since they are almost an indispensable resource.

A BILLION THANKS for this idea!


My car didn't have a manual with it sadly and I haven't been able to find one through any means so far. BUT your idea did prod me to look again for one and I stumbled across a full download of the factory service manual for the Australian cars for 2007 so I downloaded it (its over 10000 pages) I've been reading through the conditions to set the stability control light and it looks like it only needs to see low voltage for 100 milliseconds to turn it off. This is way faster than my Fluke or the scan tool would ever show. I do have an oscilloscope so I took it down stairs this morning and hooked it up and the trace does show the voltage taking a dump for short periods of time while its cold, coinciding with the error messages. I'm still not sure, but very optimistic the new alternator will fix it. Update on this in a week or so when it comes in!




Gosh, that's certainly an interesting looking factory spoiler a division of General Motors installed on the assembly line.

It is an interesting looking spoiler and quite aggressive, especially for original equipment! It cuts the rear visibility a tad; I'm used to it now but the first few days I drove it when I'd look in the rear view I thought someone was riding my butt.




Man I wish the inspections here weren't so strict, I'd love to throw heads and a cam on this thing with some long tubes and a raucous exhaust.
 

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Good deal and most certainly backup the download to an alternate location such as a flash drive.
 

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Discussion Starter #14
Sorry its taken so long to update this, but things got busy and life got in the way, and then I went back to the states for several weeks. Here again and gettting settled in so wanted to post an update.



The new alternator came in and didn't really change much but as I was installing it I found out that the main charging wire that goes to it was shot, like insulation gone and copper a different color from the heat of bad connection shot. Evidently this harness is discontinued or just completely not listed in the parts manuals because noone seemed to be able to find it. I wound up ordering a roll of 4awg cable, correct ends, adhesive heat shrink and a really nifty high temperature wire guard product and just building my own. This made a HUGE difference in most everything about the car. it starts better hot now and charges much better as well.
 

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Since then the stability control light does still come on but less often. Sometimes it'll go a week or so without showing up. A big part of the problem is that I believe the car has an underdrive pulley setup installed since the replacement belt I ordered is too long. I think this is causing a slight dip in voltage when it comes back down to idle sometimes and tripping the traction system. I'm working through a thunk in the left front of the car when I brake suddenly that I think is control arm related. I've got a low mileage set of used ones I just purchased and hopefully it'll fix it. I ordered oil and a filter a few weeks ago and it finally arrived this afternoon. Was going to change it myself but found a shop with a pit so I had them do it and was able to get under it and check things out at the same time. I'm impressed at how nice this car is for being out here almost 12 years. The guys at the oil change shop really liked it too. They were all over it and one of them spent about 15 minutes cleaning the engine bay up!

Thats about it for now. Planning a track day on saturday so hopefully I'll have some pictures to put up soon
 

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Seems like the culprit was located, but definitely try to determine what caused the insulation to burn off in the first place.
 
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