OK, I have replaced the ignition switch, new battery on tender when parked, volts gauge on DIC read 13.1 -13.3. , all grounds and plugs cleaned and checked. IPC was new 5 K ago for same problem. Codes are all com codes . IPC fires up. Start car and sometimes the IPC, DIC go out. Then they come back on. All gauges 0 out. Tac and speedo bottom out
I have done all I know to do. Could this be the BCM. It is intermittent. It could go 100 miles or 10. Never know.
I do know I need to replace pass door lock/unlock relays. But even they work most of the time. Car starts and runs great with no other codes.
The only thing affected is the new IPC/DIC
Anyone got any more ideas?

 

BCM, Radio, HVAC, LDCM, RDCM and SDM are all 1096H

RFA is U1000H and U1096 H

SCM is No Comm

Thanks for the reply. I have been fighting this for 2 years. The previous owner had the IPC replaced. Car runs great.
CAR has only 19,000 miles on it and always garaged and babied.

 

had a similar problem or a direction to take based upon codes listed above? I really need some help on this.

It is a really nice 19,000 mile car , but I am not enjoying it with the IPC kicking in and out.

 

Has the car ever experienced water leaks or moisture/water backup inside the HVAC housing and dripping water on the BCM?
How about the two so-called "star" connectors next to the BCM? Have they been tampered with or look like they even remotely show any signs of corrosion? Just to be on the safe side, I would remove the tape on each one and remove the shorting bar and closely check the male pins as well as the female portion of the connectors for corrosion, or loose fit when plugged in. They are critical for serial data-bus functions.

Pics courtesy of Chief Curlee:

http://farm5.static.flickr.com/4068/...28632d20_b.jpg

http://farm5.static.flickr.com/4056/...055cb9f8_b.jpg

 

Thanks for the info. This makes perfect sense to me based upon the diagrams, symptoms and codes , but.......
1. The foot well area and BCM area show absolutely no signs whatsoever of any water intrusion. They are pristine.
2.On Bill's advice, before I replaced the ignition switch, I unclipped, un -taped and took apart those two connectors. I cleaned and checked them. I did the same with the accordion connectors and all grounds.

Based on your input, I am going to open up those connectors again and double check them again. The car is so clean and corrosion free, that every connector I have checked looked new. I am wondering if a wire to them may be loose or broken.

I am not so up on the use of a multi - meter and may need some guidance on checking whatever I need to with one. I am not about to give up and hope you guys will stick with me on this.

The car is so nice and this is my only issue so I want to stay on this.
Dealers are of no use. They charged the previous owner over a grand to replace the IPC. Poor diagnosis.
I'll let you know if another go at the connectors today does anything.
I am willing to go into the dash if nothing else works. Probably going to go part way there to install a new shift boot anyway. Had it partially apart to install new ignition switch.
This is a puzzler. It is like when you lose your car keys. You know they are laying somewhere laughing at you !!!!

Thanks again. Please stay tuned.
Dave

 

Hang with me. I do not plan to give up on this. I really appreciate your time and guidance on this , as well as Bill's input.
Dave

 

If you need help in how to remove a pin from a connector to provide for better testing of the wires you can PM me with your phone number. I can also help you with using an ohmmeter to check the integrity of wire. I have seen cases where the pin is not properly retained in the connector and causes problems. Easy to diagnosis and correct. Mr. Sam

 

for some reason your post doesn't come up here , but I got it on email.

I really appreciate your offer and will likely be in touch. I am going out right now to open up the foot well and look at the star connector. I will look closely for pin problems. I really appreciate all the input. Things like this drive me crazy, but solving them can be rewarding for sure. I am never to old to learn and would rather rely on you folks than all the bad advice I have received from dealers. Even Jamison Corvette here in Charleston had no idea. Together we will figure this out. That is the wonder of our Forums.
Dave

 

out, checked all the pins for alignment and visually inspected the wires. Wiggled them gently. Could not detect any problems visually.
Can't pull codes again as DIC and IPC are out.
It came on for 5 seconds several times , but then the DIC and IPC went dead with a little whistling sound as the gauges 0'd out. Twice the speedo pegged to 200. I checked all other accessories and they work fine; air, windows radio, lighter, antenna, all lights, etc.
The fact that it works sometimes , for as long as 100 miles then acts up is puzzling .
So I went back out restarted it after it had idled for 10 minutes it and all is working and codes were the same as above. Interesting that it does not set any IPC code. I cleared the codes. I am trying to discern a pattern here. Seems like it is better after the car runs awhile.
Puzzling. Well, even some beautiful women can be temperamental. I am in trouble now.

Flash: The wire colors on my BUSS's do not coincide with the above diagrams. WT heck ?

 

Have you checked for the shorted wire in the drivers door yet? Some of the symptoms seem to point to that.
http://forums.corvetteforum.com/c5-t...l-problem.html

I can't find the exact thread I'm looking for, but sometimes one of the wires on the backside of the connector is exposed and shorts to the door. affecting the IPC, drivers door switch, and other things.You need to pop out the accordian boot on the door and take a look. Sometimes just moving the boot around will temporarily "fix" the problem.

 

I had a spare tooth to check each door connector for tightness. Trying to figure out how to fab one. All plugs clean and visually cant see breaks or loose wires.
I am going to check G104 as mentioned in post you referred me to.
Star connectors look good.
Here is an observation: Once the car idles and gets hot and volts drop back to 12.7-7 on the DIC, the IPC goes out less often. And, if it goes out, restarting the car will sometimes bring it back up even when cold and volts read in the 13s. on the DIC.
Thanks for the input Stay with me. I am not giving up. Dadaroo says I can call him when I get ready to meter wires.

Hey Bill (Curlee) are u following along on this? Been at least a year since I started to track it down. You have given me a lot of good input. Just so far nothing has worked. It will be a real coup, if we can fix it. If not , I will sell or tradethe car as-is, though I love it and otherwise it is like new.. For sure the Corvette "experts" around Charleston don't have a clue. Their solution is to put in another new IPC. Never even mentioned checking grounds and plugs.

 

Have you also checked the primary power lead that comes inside the car for clean/tight (not to mention correct voltage)? It provides B+ (battery power)for all interior components. It is a separate, dedicated cable (red) that runs from the terminal on the under-hood FUSE box (under the small, square cover) to inside the car via a grommet on the firewall, and terminates to a stud on the inside fuse block.

This pic is of a typical C5 interior fuse panel and you can see the bare stud for the "B+" cable on the lower right corner in the photo (which would be oriented in the upper right-hand corner when actually installed in the car)




It's connections may not be faulty or poor, but it must be checked if for no other reason than to eliminate it as a problem source. Voltage drops anywhere in the circuitry due to loose or corroded connections can play havoc with things like IPCs, BCMs, etc that utilize low voltages (5 volts, etc) to function.

To me at least, your problem seems to be one of a basic "get power from point A to point B" and do so reliably. Intermittent open circuits, are some of the hardest to track and can be very time consuming. Connectors, of all types are the MOST likely culprits overall, with broken wires being the least likely overall. Of course nothing should be ignored in the search.

Btw, you should NOT be seeing 12.5 - 12.7 volts, etc on the DIC on a normally functioning electrical system. There will be SOME voltage drop from the battery itself, but not that much.

 

I will follow up on this one. The voltage displayed on DIC after startup is 13.1 to 13.2. After a 10 minute idle it was sitting at 12.7 What should it be? I assumed it dropped as battery was recharged after the idle period. I will check B+ term and the few grounds I missed like 104, 106,etc.

 

I'll double check both accordion plugs again. Will also look at a few grounds I missed under the hood and the fuse box B+ terminal as suggested elsewhere.
Thanks, Dave

 

IIRC, that bare wire is for the stereo speaker?...you might be chasing your tail checking that one...

IMO, the problem is on the serial data bus, as suggested by 8VETTE7. I would get the wiring diagram for that system, trace the wires and check them for continuity and proper resistance. Also, check all of the connections. The intermittent nature of this problem suggests something that can be affected by vibration, possibly. (ie, poor connection at a terminal)

I would suggest getting the factory service manuals for your specific MY. Or, a less-costly alternative would be a subscription to All Data. You can access the wiring diagrams and print them out.

I have both...

Hope this helps...

 

I have the 2001 FSM to help him. I suggested he call me to discuss. He is also near me.

 

You're correct about higher voltage readings immediately after start-up and then lowering a bit afterwards, but typically you should be seeing 14 (+/-), then dropping to approx 13.2 to 13.5 range. You should verify your voltage readings both directly at the battery, and also the alternator (B+ terminal to ground) and of course the B+ terminal at the fuse box as well. At least then you will have a base-line of sorts, to verify things are normal on the voltage "supply side".

Between all of us scratching our heads here, hopefully you will soon be able to put and end to your IPC headaches.

 

I called Dadaroo and we agreed that it is time to do exactly what you suggested. I am reading up on the use of meters and hope to get with him in the near future to run some tests on wiring. He has a plan of attack. I have gone about as far as I can without some experienced hands on oversight. Never ran continuity checks or used a multi-meter. He has solved a lot of such gremlins using a systematic run down process. I hope and feel we will eventually get it resolved. Will definitely post findings for all you great folks who have got me to this point. Sam has relatives here in Summerville, SC and he lives only an hour away. So we will be able to hook up fairly easily.
Dave
PS. Those lower voltage readings are off the DIC and I think they might reflect current draws. and not alternator output and battery condition? Possible?

 

You could be correct regarding that particular wire. I just assumed that was what Bill was trying to show in the picture. Having said that there have been numerous posts regarding bare wires on those connectors that should be covered with insulation shorting out, causing the door switch, IPC and other things to malfunction. so it should be looked at. If the OP moved those harnesses around to check them, the shorted wire would probably no longer be touching ground so the problem may be elsewhere.

 

sunchaser73 is 100% correct. That bare wire has NOTHING to do with your issue.

Brother,,,,,, You need a meter really bad.

With a DC Volt meter, read the following:

1. Battery voltage directly on the battery terminals engine running. If you want to read the same while you are driving down the road, measure the output of the Cigar lighter or the hot at all times AUX wire in the passengers foot well.
Battery voltage feeds the HOT AT ALL TIMES buss in each fuse box>

Both fuse boxes have a B+ stud. The battery RED positive has TWO wires. One goes to the starter and the other goes to the B+ stud on the fuse box in the engine compartment.

You will find TWO wires on the stud. The other wire feeds the passengers fuse box.

What ever battery voltage is RUNNING OR ENGINE OFF, you should read that voltage on the B+ fuse block feed.

2. Hot in ON and START or HOT in ON and RUN comes from the IGNITION SWITCH. It feeds all the modules that have dual power supplies. BCM, PCM, IPC, DCM SCM ect

These are the feeds off the ignition switch. This is from a 99 C5:



In you C5, The IPC is powered by TWO fuses from the I/P Fuse Box Fuse# 19 is the IGNITION SWITCH powered fuse and Fuse# 25 is the HOT at ALL times fuse.

On top of EACH fuse are two slots. Those are TEST points that you can read with a meter. Read fuse 19 to chassis ground when the issue happens. As long as the ignition switch is ON, you should read full BATTERY VOLTAGE on that fuse. If it is a lot lower or absent, that is a problem.



3. Serial data buss. If you pop the top off the the STAR Connector that has FOUR wires in it, you ISOLATE the LDCM, RDCM, and the Seat Module from the rest of the serial data wires.

Those three modules are or can be the cause of corrupt data on the serial data buss. Remove the shorting buss from that connector and see if the issue still happens. Post results. Yes you can drive the car with that disconnected.


4. Ignition switch HOT in ON and START feeds.

That switch gets its power from the HOT at ALL TIMES buss. Look carefully at the two connectors that the ignition switch connects to. Look for bent pins, corroded pins, melted pin sockets, There are some bent female pins in this ignition switch connector that caused a low voltage issue:



Test that stuff and see what you find.

Bill