When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
I'm wondering what to check next. This car and this engine are both new to me. I'll give all the info I can think of - please let me know what you think I should do/check next!
Symptoms:
The car will intermittently stall/die, and seems to do it more frequently when cold - especially likes to stall either when idling, or as I'm pulling into a parking place, leaving me to "coast" in. RPM's will seem to dip too low ("normal" is 850-950, but if it drops to 500-600 there's a strong chance it will die), like the idle valve is having trouble compensating. When the car is in motion (at road speed), there are no issues, other than an occasional perceived loss of power (I could be making this up, but it doesn't seem to feel as peppy as it did).
What happened prior to these symptoms:
1) Car was fine when last driven, had 0 issues. Was parked outside in heavy rain for the last few days. Interior apparently has a leak. Driver's floor carpet was very wet. Driveway is sloped so the nose is pointed up...not sure if the pass. side kick panel got wet or not. Before driving again, I did the following...
2) I removed the stock C6 air bridge with K&N, and installed a 4" round intake with a similarly-sized K&N. Didn't touch the MAF. MAF is mounted the same distance from the TB as it was previously.
3) I removed my group 78 battery and installed a small Deka (ETX20L) in it's place.
4) I removed the driver seat to test fit a bucket seat.
5) I installed an axle-back exhaust.
6) Test driving after all the above is when I first noticed these sumptoms.
7) I have driven appx 20 miles so far since all of this started.
DIC codes:
28-TCS C1295 H (brake lamp switch circuit open
99-HVAC B0363 H (left air temperature actuator
A0-LDCM U1064 H (loss of comm w/ BCM
A1-RDCM B2265 H (horizontal position sensor fault
A1-RDCM U1064 H (loss of comm w/ BCM)
A6-SCM U1255 H (loss of comm)
What I've done so far:
1) Checked all air intake clamps, all were snug
2) Removed TB (car has an LS2 92mm TB w/ built-in idle control), cleaned, reinstalled
3) Removed MAP sensor, cleaned, reinstalled
4) Currently cleaning both the round intake and C6 K&N's I had on the car.
...I think the rain might be a coincidence, as I'd lean toward something that I touched being the problem - but as you can see, I didn't really touch anything complicated, and there don't seem to be any codes related to what I touched since the last time I drove it. I'm really not sure where to look next, as there's no CEL. Any ideas?! TIA!
Anytime I see any issues like stalling with a cold engine I think of a bad or failing ECT sensor...also, there is no "idle valve" on the C5. May also be a failing crankshaft sensor but without a scan tool to look at some data PIDS and or a scope you will only be GUESSING and that can get a little expensive. You may have clogged rain ducts (udders) which may be the cause of your wet carpeting...if your passenger side floor is wet your BCM may have some water intrusion issues...the BCM "loss of comm" with the door control modules. You cleaned and reinstalled the MAP sensor but without a scan tool or some electrical testing you don't really know if it's operating correctly...Without smoke testing for vacuum leaks you are also guessing there too...you can however spray some Brake Kleen around the PCV system or downstream of the MAF sensor and see if you notice a change in RPM...at least with a scan tool you could check your fuel trims to diagnose correctly for a vacuum leak !!
Anytime I see any issues like stalling with a cold engine I think of a bad or failing ECT sensor...also, there is no "idle valve" on the C5. May also be a failing crankshaft sensor but without a scan tool to look at some data PIDS and or a scope you will only be GUESSING and that can get a little expensive. You may have clogged rain ducts (udders) which may be the cause of your wet carpeting...if your passenger side floor is wet your BCM may have some water intrusion issues...the BCM "loss of comm" with the door control modules. You cleaned and reinstalled the MAP sensor but without a scan tool or some electrical testing you don't really know if it's operating correctly...Without smoke testing for vacuum leaks you are also guessing there too...you can however spray some Brake Kleen around the PCV system or downstream of the MAF sensor and see if you notice a change in RPM...at least with a scan tool you could check your fuel trims to diagnose correctly for a vacuum leak !!
TY. For some reason I can't get my scan tool to communicate via OBD. Works fine in other cars.
If you have 'No Comm" when hooking up your scan tool you may have issues with your serial data line...if you know where the 2 splice packs (Star Connectors) are to the left of the BCM pull the bus bar (shown in pic)off the top of the one with 4 wires and see if you can now communicate...if still no good pull the other bus bar off the top of the other one with 9 wires I believe...see if you can now communicate !!
Seems to be getting a little better over time as far as the stalling (only did it once yesterday) - but now my part-throttle cruising is wonky. Feels like I'm running into constant gusts of wind...not quite a misfire, but you can feel the power isn't smooth at part throttle and there's a slight, consistent fluctuation. Gonna have a look at plugs today just for due diligence though I'm pretty sure that's not the cause.
i would go over the grounding points on the car, these cars are known to do all sorts of weird things when they get corroded and have weak contacts
If possible, could you link me to a diagram of the ground points? Not sure where they are on this car and it's definitely worth a look. Thanks so much!
Did a couple of WOT pulls and the car felt good, but I don't trust it to be consistent yet. One of those "wish I would have never touched anything and left well enough alone" moments. LOL! Pull seems more linear with the intake and exhaust change - it used to feel like it was coming on VTEC @ over 4000, it was a distinct kick. Now it pulls just as hard if not harder, but it's a smoother transition from mid to high RPM's.
If only I can get these driveability issues sorted, I'll be happy as a clam!
Heading out for plugs, fuel filter, and injector O-rings...may as well rule out basic maintenance stuff. Haven't done these since I bought the car.
If you have 'No Comm" when hooking up your scan tool you may have issues with your serial data line...if you know where the 2 splice packs (Star Connectors) are to the left of the BCM pull the bus bar (shown in pic)off the top of the one with 4 wires and see if you can now communicate...if still no good pull the other bus bar off the top of the other one with 9 wires I believe...see if you can now communicate !!
Oh boy...what a bummer. Looks like I've got another can of worms!
I tried pulling the first bus bar - no change. Still no comms.
Then, I pulled the second one. Again, no comms - BUT - I got the "8 chimes of death" along with the DIC reading "service engine soon," "reduced engine power," and "low fuel." Was I supposed to plug the first one (4 wire) back in before pulling the second one, or leave them both out?
What would be the next step in the troubleshooting process for no comms with the OBD port? It has power, because I can see the red and green LED's in my scanner lighting up.
Also...what is this plug above the DIC for? A PO tapped into the yellow power wire (I think it was to hard wire to the cigarette lighter USB charger, because it goes into the center console), and the orange wire is not connected to anything.
Even though you have a new battery.
I would check it. Sounds you are not
drawing enough amps at idle.
Good luck
Thank you for reminding me of this! I have my full size battery here - I charged them both up overnight, and I'm doing voltage checks about every 90 minutes. Later today I'll load test both batteries. If the larger battery fares better, I'll put it back in and see if that solves it.
I had the small battery here from another (4 cylinder) car, and it was enough for that car. And the Vette starts up instantly with it. But, I do notice my voltage slowly drop on the DIC - it shows ~14.2 when I first start the car, but within a short drive, it will be down to the low 13's.
Bummer if I have to put the 41 lb battery back in - that was an easy way to shed 22 lbs.
I'm about to run out and check the OBD stuff - gonna verify 12v on pin 16, verify fuse 29, and check grounds...then reinstall the bus bars and see what happens. I *DID* see threads where people were able to get SOME devices to communicate, but OTHER devices would not - I have a feeling this could be my issue, but I don't have another OBD device to test with. Just my generic ELM327 unit and Torque Pro on my phone.
Both are new-ish and tendered. Both start the car instantly. But, the low speed stalling and light stumbling problem DID begin after putting the small battery in (as well as installing a different intake).
Oh boy...what a bummer. Looks like I've got another can of worms!
I tried pulling the first bus bar - no change. Still no comms.
Then, I pulled the second one. Again, no comms - BUT - I got the "8 chimes of death" along with the DIC reading "service engine soon," "reduced engine power," and "low fuel." Was I supposed to plug the first one (4 wire) back in before pulling the second one, or leave them both out?
What would be the next step in the troubleshooting process for no comms with the OBD port? It has power, because I can see the red and green LED's in my scanner lighting up.
Also...what is this plug above the DIC for? A PO tapped into the yellow power wire (I think it was to hard wire to the cigarette lighter USB charger, because it goes into the center console), and the orange wire is not connected to anything.
Hard to tell where you're at in the picture...Is that the BCM in that pic ??...I can tell by the 87D number... I will look at that connector when I get home...so the connector has 3 wires ??...orange, yellow and black ??...is that black tape on the yellow wire a butt joint and does it change color ??...looking at wiring it looks like the radio circuits have a lot of orange wires. It is OK to pull both combs out but I don't see how everything is going crazy now....all the modules should be isolated from the data line...is the fuel gauge is going to E and the water temp is maxed out along with the DIC warning ???...when you start splicing into the radio circuit you can run into a lot of electrical issues ...try pulling fuses 5 (radio/cd), 28 (bose) and 24(radio/ant) and see what happens...even try pulling that connector shown in your pic and see what happens too !!...is there an aftermarket radio installed ???
p.s. If you have a multimeter probe all of the wires on the Star Connectors with the combs removed and see if you are showing 12 volts on any of them with key on...the radio data wire is on Star Connector 1 is colored ORANGE BTW...LOL !!!
also watch the video at 55:50 !!
it almost sounds like you messed up the MAF when you cleaned it? did anything touch the wire inside the MAF?
since the car can be driven id run it over to a local parts house that checks codes for free and see if there scanner works on your obdll port, it might just be yours dont and all this is for nothing
Oh boy...what a bummer. Looks like I've got another can of worms!
I tried pulling the first bus bar - no change. Still no comms.
Then, I pulled the second one. Again, no comms - BUT - I got the "8 chimes of death" along with the DIC reading "service engine soon," "reduced engine power," and "low fuel." Was I supposed to plug the first one (4 wire) back in before pulling the second one, or leave them both out?
What would be the next step in the troubleshooting process for no comms with the OBD port? It has power, because I can see the red and green LED's in my scanner lighting up.
Also...what is this plug above the DIC for? A PO tapped into the yellow power wire (I think it was to hard wire to the cigarette lighter USB charger, because it goes into the center console), and the orange wire is not connected to anything.
Those 3 wires are taped or stowed...yellow wire is hot with ignition switch and orange is hot at all times...it is listed as C206 !!...looks like orange wire feeds the cigar lighter.
it almost sounds like you messed up the MAF when you cleaned it? did anything touch the wire inside the MAF?
since the car can be driven id run it over to a local parts house that checks codes for free and see if there scanner works on your obdll port, it might just be yours dont and all this is for nothing
Yeah, I know Autozone stopped doing that a long time ago...I'll see if anyone still does. I sure hope that finds the issue, because it's just not making any sense. Didn't touch the MAF at all...after the issue started, I took it out and cleaned it with contact cleaner to no avail.
Today I put my old (big) battery back in...pulled out...it stalled at the first stop sign. Battery wasn't the issue.
Went back home, installed the LMC5 that came today. Then, I drove 20 mins to the store. It ran perfect! I figured maybe that was it. Then I come out of the store, and it stalled TWICE before I even put it in gear to back out. Cleared codes, drove home. Tomorrow I'll see if I can get a different OBD scanner on it. I have a new fuel filter to install as well.
After that...I'm gonna have to get it to a shop, bend over, and take what they give me.
'03 C5Z - intermittent stalling...ideas?
