Need help..No comm. w PCM/BCM/TCS etc.
04-28-2009, 01:04 AM
#21
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St. Jude Donor '08
No longer in Guam. Im in the air to TX. Call me tomorrow after 6PM Centeral time.
PM sent:
BC
04-28-2009, 01:12 PM
#22
Burning Brakes
Thread Starter
Ok I got this freakin thing going again thanks to you guys. I can't believe what it was either. I started this morning checking everything you guys told me to. Then I got really frustrated because nothing seemed to help. While I was in the car I was randomly playing with the seat controls.......and then it happend. The damn radio turned on, I moved the seat again and the volume changed. I am like whoa, WTF just happend. Then the wheels in my head start turning. What if the Seat control module has shorted to power through the star connector. I start pulling cables out of the SCM and low and behold all of my problems were solved. I guess some sort of residual power from the scm what shorting out the IPC and radio. I replaced the SCM and everything works great now. Chalk this one up to one of the craziest vette repairs of all time. I owe some of you guys a beer.
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05-07-2009, 08:28 PM
#24
Burning Brakes
Electrical gremlins..........
[QUOTE=lucky131969;1569872687]Ok. So you need to figure out why there is no communication over the serial data line. I don't know what year you are working on, but the serial data for year 99-04 is as below. I would check continutiy between the PCM pin 58 and the star connector(s) for starters. Make sure you disconnect the battery first before removing connectors.
Hi Lucky....I stumbled on this thread while looking for some info on a problem I've been having with the seat in my 99. Crazy symptoms..... What I saw was your schematic diagram and wondered if you had access to the schematic for the power seat switch. ( non-memory, basic power seat) The car sat in the rain one day and the seat starts moving by itself now!!! When it first happened, if you moved the seat all the way forward, as soon as you released the switch the seat would power all the way to the rear by itself....
I've checked all the plugs, fuses, harnass for bare wires, seat control module ( no apparent dampness) and the switch.
I now have the switch unplugged from the harnass and the seat has stopped it's dancing... I'n not sure as of yet that it is the switch, but if I can get the schematic to trace the internal wiring I think I can eliminate the rest of the components in the seat......
TIA
Hi Lucky....I stumbled on this thread while looking for some info on a problem I've been having with the seat in my 99. Crazy symptoms..... What I saw was your schematic diagram and wondered if you had access to the schematic for the power seat switch. ( non-memory, basic power seat) The car sat in the rain one day and the seat starts moving by itself now!!! When it first happened, if you moved the seat all the way forward, as soon as you released the switch the seat would power all the way to the rear by itself....
I've checked all the plugs, fuses, harnass for bare wires, seat control module ( no apparent dampness) and the switch.
I now have the switch unplugged from the harnass and the seat has stopped it's dancing... I'n not sure as of yet that it is the switch, but if I can get the schematic to trace the internal wiring I think I can eliminate the rest of the components in the seat......
TIA
05-07-2009, 08:52 PM
#25
Tech Contributor
[QUOTE=LT1vette;1570001203]
Ok. So you need to figure out why there is no communication over the serial data line. I don't know what year you are working on, but the serial data for year 99-04 is as below. I would check continutiy between the PCM pin 58 and the star connector(s) for starters. Make sure you disconnect the battery first before removing connectors.
Hi Lucky....I stumbled on this thread while looking for some info on a problem I've been having with the seat in my 99. Crazy symptoms..... What I saw was your schematic diagram and wondered if you had access to the schematic for the power seat switch. ( non-memory, basic power seat) The car sat in the rain one day and the seat starts moving by itself now!!! When it first happened, if you moved the seat all the way forward, as soon as you released the switch the seat would power all the way to the rear by itself....
I've checked all the plugs, fuses, harnass for bare wires, seat control module ( no apparent dampness) and the switch.
I now have the switch unplugged from the harnass and the seat has stopped it's dancing... I'n not sure as of yet that it is the switch, but if I can get the schematic to trace the internal wiring I think I can eliminate the rest of the components in the seat......
TIA
Hi Lucky....I stumbled on this thread while looking for some info on a problem I've been having with the seat in my 99. Crazy symptoms..... What I saw was your schematic diagram and wondered if you had access to the schematic for the power seat switch. ( non-memory, basic power seat) The car sat in the rain one day and the seat starts moving by itself now!!! When it first happened, if you moved the seat all the way forward, as soon as you released the switch the seat would power all the way to the rear by itself....
I've checked all the plugs, fuses, harnass for bare wires, seat control module ( no apparent dampness) and the switch.
I now have the switch unplugged from the harnass and the seat has stopped it's dancing... I'n not sure as of yet that it is the switch, but if I can get the schematic to trace the internal wiring I think I can eliminate the rest of the components in the seat......
TIA
05-07-2009, 08:59 PM
#26
Melting Slicks
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I had the same issue with the error codes. using the photos from Bill Curlee I found 2 bad connections in the connection pack in the passenger door. Fixed the connection and no more problems...
05-07-2009, 09:43 PM
#27
Le Mans Master
Not exactly true. You can replace a BCM and still drive the car. The security light will be on though and a code is set because of this. And the car will not start for three minutes every now and then...ask me how I know this.
Last edited by Goody; 05-07-2009 at 09:58 PM.
08-08-2010, 02:56 AM
#28
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pcm 10 no comm code
Digging up this thread is old news but maybe good news to me. My car is currently stuck at the mall no comm. issue.
I cant flash it or connect with HPTuners.
Reduced engine code
ABS code
TCS code
all came at once along with the no comm code.
The only odd thing is when i switch the car ON the speedo goes to 75mph and stays there.
I will be checking grounds in the doors and the one on the firewall (thanks to the pics)tomorrow when I get to the car, but that 75mph seems odd if anyone has any insight on this one please advise.
I cant flash it or connect with HPTuners.
Reduced engine code
ABS code
TCS code
all came at once along with the no comm code.
The only odd thing is when i switch the car ON the speedo goes to 75mph and stays there.
I will be checking grounds in the doors and the one on the firewall (thanks to the pics)tomorrow when I get to the car, but that 75mph seems odd if anyone has any insight on this one please advise.
08-08-2010, 08:56 AM
#29
Team Owner
Tagging for info!
Bill,
I will be calling you this week. 1998 Corvette, EBTCM mounted in the rear (Early C5)
I am still getting NO COMM with my EBTCM, even though I had done a few thing in the sticky thread.
I am going to start my thread next - I will be a bit busy today but I put your suggestions to use!
Thanks,Matt 661-406-7516
Bill,
I will be calling you this week. 1998 Corvette, EBTCM mounted in the rear (Early C5)
I am still getting NO COMM with my EBTCM, even though I had done a few thing in the sticky thread.
I am going to start my thread next - I will be a bit busy today but I put your suggestions to use!
Thanks,Matt 661-406-7516
This is interesting..
08-08-2010, 01:44 PM
#31
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Digging up this thread is old news but maybe good news to me. My car is currently stuck at the mall no comm. issue.
I cant flash it or connect with HPTuners.
Reduced engine code
ABS code
TCS code
all came at once along with the no comm code.
The only odd thing is when i switch the car ON the speedo goes to 75mph and stays there.
I will be checking grounds in the doors and the one on the firewall (thanks to the pics)tomorrow when I get to the car, but that 75mph seems odd if anyone has any insight on this one please advise.
I cant flash it or connect with HPTuners.
Reduced engine code
ABS code
TCS code
all came at once along with the no comm code.
The only odd thing is when i switch the car ON the speedo goes to 75mph and stays there.
I will be checking grounds in the doors and the one on the firewall (thanks to the pics)tomorrow when I get to the car, but that 75mph seems odd if anyone has any insight on this one please advise.
You BOTH have a corrupted Class II serial data buss. DISCONNECT the STARR 2 connector top (the one with FOUR wires) and see if that makes a difference.
BC
08-08-2010, 11:45 PM
#32
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Comm
OK Bill, first off thanks for saving me a lot of money on my last electrical issue. Your fix worked.
Now to this unexpected issue. When I take the cap off the star connectors should I reset the codes before trying anything or disconnect the battery afterwards?
When i switch the car on the guages cycle and the speedo guage stops at 75mph. Still wonderring WTDH is that all about. Also I noticed the wires in the pic below were cut. Yellow orange and black right above the star connectors. I dont see ANYTHING they could have gone to. The car has 6000 plus miles on it in the last few months and all was fine til the other day. From look of the wires i dont think they had just come lose they appear to have been lose. Looks like some hack alarm job. I dont think they were the culprit just wanted to know what they are. I attempted to add a pic of them.
Now to this unexpected issue. When I take the cap off the star connectors should I reset the codes before trying anything or disconnect the battery afterwards?
When i switch the car on the guages cycle and the speedo guage stops at 75mph. Still wonderring WTDH is that all about. Also I noticed the wires in the pic below were cut. Yellow orange and black right above the star connectors. I dont see ANYTHING they could have gone to. The car has 6000 plus miles on it in the last few months and all was fine til the other day. From look of the wires i dont think they had just come lose they appear to have been lose. Looks like some hack alarm job. I dont think they were the culprit just wanted to know what they are. I attempted to add a pic of them.
What price did Gene Culley give you??
Do you have all the power and proper grounds for the BCM?
In my 98 it is FOUR fuses that supply the BCM:
Instrument Panel Electrical Center
BCM & IPC, Mini fuse# 25
BCM2 Minifuse #23
BCM A Mini Fuse #9
BCM /1 Mini Fuse# 13
Theres also an Data Link Connector fuse that should be checked
C/ALDL , Mini Fuse# 29
The grounds for the BCM are at:
G-104 (On the frame next to the battery)
& G-202 in the cabin
The ground for the BCM goes through a SPLICE PACK (SP-208). Its located on the engine compartment fire wall on the main wiring harness behind the battery. It look like this:
If it gets corroded, it looks like this!!!
There are TWO small grey connectors next to the BCM (to the left of it) There the STAR connections. The connectors join all the serial data wires to each module. The cap on each connector is a shorting buss that connects all the wires together.
On Star connector#1 the BCM and PCM serial data wires are on:
BCM = Pin "M" (Light Green wire)
PCM = Pin "B" (Dark Green wire)
You can read the serial wire to ground and if memory serves me correctly, you should see around 750 ohms.
For a test, you can disconnect the STAR connector cap on STAR Connector # 2 and see if it changes symptoms. It connects the left and right door control modules and seat control module and ALDL OBDII terminal to the main STAR buss. That will take those modules serial data line out of the equasion. It wont harm anything!
Make sure that the STAR shorting caps are clean dry, free of corossion and on tight.
Hope this helps
Bill C
Do you have all the power and proper grounds for the BCM?
In my 98 it is FOUR fuses that supply the BCM:
Instrument Panel Electrical Center
BCM & IPC, Mini fuse# 25
BCM2 Minifuse #23
BCM A Mini Fuse #9
BCM /1 Mini Fuse# 13
Theres also an Data Link Connector fuse that should be checked
C/ALDL , Mini Fuse# 29
The grounds for the BCM are at:
G-104 (On the frame next to the battery)
& G-202 in the cabin
The ground for the BCM goes through a SPLICE PACK (SP-208). Its located on the engine compartment fire wall on the main wiring harness behind the battery. It look like this:
If it gets corroded, it looks like this!!!
There are TWO small grey connectors next to the BCM (to the left of it) There the STAR connections. The connectors join all the serial data wires to each module. The cap on each connector is a shorting buss that connects all the wires together.
On Star connector#1 the BCM and PCM serial data wires are on:
BCM = Pin "M" (Light Green wire)
PCM = Pin "B" (Dark Green wire)
You can read the serial wire to ground and if memory serves me correctly, you should see around 750 ohms.
For a test, you can disconnect the STAR connector cap on STAR Connector # 2 and see if it changes symptoms. It connects the left and right door control modules and seat control module and ALDL OBDII terminal to the main STAR buss. That will take those modules serial data line out of the equasion. It wont harm anything!
Make sure that the STAR shorting caps are clean dry, free of corossion and on tight.
Hope this helps
Bill C
08-09-2010, 12:02 AM
#33
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The wires that you found are the aux power wires. They are supplied to connect aftermarket stuff to. One is ground, one is hot at all times and one is switched hot. NORMAL.
Clear codes by the DIC reset. Disconnecting the battery generates random DTCs.
Did disconnecting STARR 2 make any difference?
Clear codes by the DIC reset. Disconnecting the battery generates random DTCs.
Did disconnecting STARR 2 make any difference?
08-09-2010, 10:47 AM
#34
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OK i tried that and yes i got a lot of comm errors. Reduced power still shows cant get past that. check tire pressure came back, check abs, check traction control, and 10-pcm no comm.
As soon as it came back the speedo went to 75mph.
I am having the car towed in a few minutes. I will check all the ground points from your other thread as its going to the shop with a lift. He is giving me a few hrs on the lift so i want to do everything i can before ordering another pcm and paying the dealership to flash it. That sounds like 600.00 plus after its all said and done.
I will try about anything before that as i do have time off to mess with this. I will post any progress or failures here for anyone else that may run into this issue.
Bill - Thanks for the piece of mind about the stray wires.
As soon as it came back the speedo went to 75mph.
I am having the car towed in a few minutes. I will check all the ground points from your other thread as its going to the shop with a lift. He is giving me a few hrs on the lift so i want to do everything i can before ordering another pcm and paying the dealership to flash it. That sounds like 600.00 plus after its all said and done.
I will try about anything before that as i do have time off to mess with this. I will post any progress or failures here for anyone else that may run into this issue.
Bill - Thanks for the piece of mind about the stray wires.
08-10-2010, 12:31 AM
#35
Racer
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Do you think someone with a tech 2 can repair this? If so I know someone just need to know what to tell them to do with the tech 2.
I think it connects thru the same connector wonderring if it will work since my hptuners will not connect. It just says that its not found.
I would have to tow the car to the dealership but if the flash wont work I dont want to waist the time.
Please advise...
I think it connects thru the same connector wonderring if it will work since my hptuners will not connect. It just says that its not found.
I would have to tow the car to the dealership but if the flash wont work I dont want to waist the time.
Please advise...
08-10-2010, 01:25 AM
#36
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St. Jude Donor '08
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08-10-2010, 10:19 PM
#37
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ok I have unplugged each module and the star connectors about everything I can. No change in the ECM still reads 75mph. I have checked all of the ground points I know of minus the ones behind the rear tires. They all look brand new. No snagged wires. Though the car is a 97 it was kept up pretty good from what I can see. I was actually hoping to find corrosion or something. The only time the guage relaxes is when you unplug either connector on the PCM. No scanner we connect will communicate with it.
Bill,
IF and I said IF i were to buy a PCM should/could I purchase a 2000 instead of the 97 and plug in add a lic to my HPTuners program the VATS and roll? Or should I just get another 97-98 PCM and program that.
I dont care about the vin registerring and all that I just want my car to RIDE again.
If there is anything else that anyone can think of for me to try I have nothing but time to try at this point. I surely dont want to buy a PCM just to find out that thats not the problem but im almost out of other options.
Finally I have an extra LS1 z28 PCM I want to know if I can plug this up JUST TO SEE IF IT COMMUNICATES period not to actually use in the car. Just want to use it to troubleshoot one step before purchasing one.
Thanks in advance.
Bill,
IF and I said IF i were to buy a PCM should/could I purchase a 2000 instead of the 97 and plug in add a lic to my HPTuners program the VATS and roll? Or should I just get another 97-98 PCM and program that.
I dont care about the vin registerring and all that I just want my car to RIDE again.
If there is anything else that anyone can think of for me to try I have nothing but time to try at this point. I surely dont want to buy a PCM just to find out that thats not the problem but im almost out of other options.
Finally I have an extra LS1 z28 PCM I want to know if I can plug this up JUST TO SEE IF IT COMMUNICATES period not to actually use in the car. Just want to use it to troubleshoot one step before purchasing one.
Thanks in advance.
08-10-2010, 10:45 PM
#38
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ok I have unplugged each module and the star connectors about everything I can. No change in the ECM still reads 75mph. I have checked all of the ground points I know of minus the ones behind the rear tires. They all look brand new. No snagged wires. Though the car is a 97 it was kept up pretty good from what I can see. I was actually hoping to find corrosion or something. The only time the guage relaxes is when you unplug either connector on the PCM. No scanner we connect will communicate with it.
Bill,
IF and I said IF i were to buy a PCM should/could I purchase a 2000 instead of the 97 and plug in add a lic to my HPTuners program the VATS and roll? Or should I just get another 97-98 PCM and program that.
I dont care about the vin registerring and all that I just want my car to RIDE again.
If there is anything else that anyone can think of for me to try I have nothing but time to try at this point. I surely dont want to buy a PCM just to find out that thats not the problem but im almost out of other options.
Finally I have an extra LS1 z28 PCM I want to know if I can plug this up JUST TO SEE IF IT COMMUNICATES period not to actually use in the car. Just want to use it to troubleshoot one step before purchasing one.
Thanks in advance.
Bill,
IF and I said IF i were to buy a PCM should/could I purchase a 2000 instead of the 97 and plug in add a lic to my HPTuners program the VATS and roll? Or should I just get another 97-98 PCM and program that.
I dont care about the vin registerring and all that I just want my car to RIDE again.
If there is anything else that anyone can think of for me to try I have nothing but time to try at this point. I surely dont want to buy a PCM just to find out that thats not the problem but im almost out of other options.
Finally I have an extra LS1 z28 PCM I want to know if I can plug this up JUST TO SEE IF IT COMMUNICATES period not to actually use in the car. Just want to use it to troubleshoot one step before purchasing one.
Thanks in advance.
Did you try this:
Disconnect the STARR 1 & STARR 2 connector tops. Jumper just the BCM & PCM serial data wires together and see if the issue goes away.
The car will/should start and run with just the BCM and PCM serial data connected.
Try that.
BC
08-10-2010, 10:58 PM
#39
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Use this post and find the BCM and PCM fuses. Check each fuse. Make sure that each one is good. Each module has mutiple power supplies.
Make sure that the ignition switch supplied voltages are the same voltage as the battery voltage:
- C5 ignition Switch repair - http://forums.corvetteforum.com/c5-t...ch-repair.html
Make sure that the ignition switch supplied voltages are the same voltage as the battery voltage:
- C5 ignition Switch repair - http://forums.corvetteforum.com/c5-t...ch-repair.html
08-10-2010, 11:17 PM
#40
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Use this post and find the BCM and PCM fuses. Check each fuse. Make sure that each one is good. Each module has mutiple power supplies.
Make sure that the ignition switch supplied voltages are the same voltage as the battery voltage:
- C5 ignition Switch repair - http://forums.corvetteforum.com/c5-t...ch-repair.html
Make sure that the ignition switch supplied voltages are the same voltage as the battery voltage:
- C5 ignition Switch repair - http://forums.corvetteforum.com/c5-t...ch-repair.html
