C5 gauges going wild

[Eddiek]

Hi!,I'm looking for Bill Curlee,he seems to be the expert with the C5s. My name is Eddie. I bought my 2002 vette coupe brand new & presently only have 29000 miles on it. For a number of years the turn signals would work & not work. About a couple of months ago,the digital display in the gauge cluster started to display to service the traction system,then service vehicle soon, soon after that. Then about a month ago,the gauges start going wild,water temp gauge would peg out,oil pressure & water pressure gauges would go to 0 but the battery voltage gauge would be the only constant gauge that would work. The clock would go on & off,the ac would go on sometimes by itself. My brother looked on corvette forum & one of the posts recommended turning the ignition key to on & off position,repeating it for about 15 minutes. I tried & it worked. I only drive the car on the weekends,so the following weekend it was fine but the 2nd weekend it returned back to the craziness. My brother saw a post where the ignition switch was the solution but was not in my case. My brother checked other posts & we checked many grounds & connections. We checked a 4 wire jump connector where the passenger side floor is. When disconnected,the symptoms disappeared. The post suggested that either the drivers seat module or the LDCM or RDCM had a bad connection or was bad. We took the fuse off for the driver's seat but that didn't solve the problem. We didn't know where the LDCM or RDCM were located so we checked all 4 connections going to both doors assuming that LD & RD stands for left & right door.. That didn't work either. After putting everything back together,the fuses for the door controls on both side blew. This is really getting frustrating. Can someone HELP!!! Thanks

 

[Rob]

Moving out of the Site Help and Feedback forum....

 

[Bill Curlee]

I love Corvette Action Center.. Its an excellent Knowledge base However,, I spens most of my time in Corvette Forum C5 section. Some time in the C6 Section. Register for Corvette Forum and Im there daily. My wife says it HOURLY

Now Back to you post and the Issue at hand.. Most all the main C5 modules, are digitaly connected via a SERIAL DATA BUSS. The Body Control Module (BCM) acts like a router and controls data messages.
IF,,, that data Bus is corrupt,, things get crazy. You see it in the IPC because those gages are visual.but other module are having the same issues.

Things that cause the MADDNESS:

If the BCM is wet or bamp, it can corrupt the data buss

If another module has a power or data issue, it can seand out BAD DATA and corrupt the data buss.

After YEARS of C5 ownership,, and expierencing this issue,, I have tracked it down to a couple issues.

,,, Wet or Damp BCM.. If the BCM is wet or damp, it can and will cause this issue. Check under the carpet for dampness and report your findings.. The cure is another complete post..



TWO,,,, POWER TO THREE MODULES: The LDCM, RDCM and Seat Control Module can cause this issue. If the power connectors for those module have bent , corrroded or deformed female pins,, it will cause the issue. The loose fitting pins MALE to FEMALE, cause the module to turn ON & OFF rapidly and that corrupts the serial data buss.

Solution: In the PASSENGERS FOOT WELL,, to the left of the BCM (big silver box) are two THIN connectors.. Those are STAR Data connectors.. Find the one with FOUR WIRES. Pop the top off the four wire connector and see if that resolve the weird issues. If it does, , post the results.


Let me know what you find and the fix is easy...




BC

 

[c4c5specialist]

Hi there,

Along those lines, lets think more simply. Control modules, when they lose ground sourcing create all sorts of issues.

On C5, this is even MORE of a problem. Seat control or door control can create your condition. Seat control modules have been shorted due to the wire support for the cushion sagging to the wiring for the seat control module. This bridges 2 circuits and the module shuts down. This can short the module without ruining it. I usually recommend people start the vehicle WITHOUT SITTING IN THE SEAT, this can sometimes eliminate the problem, showing the cause is under the seat.

Normally, and more prevelant, if you look at the connections from the body to the DOORS, you may find your issue also.

The BLACK connector, with the 6 pins may have terminals that are burned or spread apart. When this occurs, the communications lines are now the ground source.

I disagree with Curlee on the pulling the star connector. Here is why. When you do that, you are shutting down the entire communications line to both seats and doors, so you do not know if it is the seat or which actual door control modules. These 4 wires are seat control module, left door control and right door control module and the line going back to the class 2 system.

So, if you remove the hush panels and pull the connectors out and look at the FEMALE side of the connection, you may see whats in the picture attached.

Allthebest, Paul

 

[Eddiek]

C5 gauges go wild

Hi there,

Along those lines, lets think more simply. Control modules, when they lose ground sourcing create all sorts of issues.

On C5, this is even MORE of a problem. Seat control or door control can create your condition. Seat control modules have been shorted due to the wire support for the cushion sagging to the wiring for the seat control module. This bridges 2 circuits and the module shuts down. This can short the module without ruining it. I usually recommend people start the vehicle WITHOUT SITTING IN THE SEAT, this can sometimes eliminate the problem, showing the cause is under the seat.

Normally, and more prevelant, if you look at the connections from the body to the DOORS, you may find your issue also.

The BLACK connector, with the 6 pins may have terminals that are burned or spread apart. When this occurs, the communications lines are now the ground source.

I disagree with Curlee on the pulling the star connector. Here is why. When you do that, you are shutting down the entire communications line to both seats and doors, so you do not know if it is the seat or which actual door control modules. These 4 wires are seat control module, left door control and right door control module and the line going back to the class 2 system.

So, if you remove the hush panels and pull the connectors out and look at the FEMALE side of the connection, you may see whats in the picture attached.

Allthebest, Paul

Hi paul

Thanks for getting back to me & giving me your input to the problems I am encountering.

My brother & I did check these connectors in the door jamb area. They seem to be pretty clean & the females looked pretty good as well. Is there any way to isolate the left side from the right side?

I will try to start the car without sitting in the seat as you suggested. After we tried solving the problem on Saturday,the front driver's seat was brought up forward. My brother must have moved it forward. I sat in the seat & notice that the right rear portion of the seat seemed like it was sagging. So maybe it could be a seat related problem as you have suggested. I'll check it as soon as I can(pretty busy) & will get back to you with results.

Thanks again,

Eddiek

 

[Eddiek]

C5 gauges go wild

Hi paul

Thanks for getting back to me & giving me your input to the problems I am encountering.

My brother & I did check these connectors in the door jamb area. They seem to be pretty clean & the females looked pretty good as well. Is there any way to isolate the left side from the right side?

I will try to start the car without sitting in the seat as you suggested. After we tried solving the problem on Saturday,the front driver's seat was brought up forward. My brother must have moved it forward. I sat in the seat & notice that the right rear portion of the seat seemed like it was sagging. So maybe it could be a seat related problem as you have suggested. I'll check it as soon as I can(pretty busy) & will get back to you with results.

Thanks again,

Eddiek

Hi again Paul, Will this seat issue still occur with fuse #4 removed? Thanks

 

[Eddiek]

Hi again Paul, Will this seat issue still occur with fuse #4 removed? Thanks

Also,how can you isolate LDCM from RDCM?

 

[Bill Curlee]

Power to the SCM does not necessarily cause the issue. You need to isolate the serial data wire in the connector/wiring harness. If the serial data wire in that connection or wiring harness is grounded or shorted to another wire, it can cause the issues that you have.

Here is a schematic for the serial data circuit.

Examine the seat connector and the wire in BOTH connectors. Make sure that they are not damaged or the connectors are crushed.

Ive also seen wet carpets under the seat cause the same issue

If you pop the top off the serial Dita STAR connector with four wires, it completely isolates the LDCM RDCM and SCM from ALL the other serial data circuits. When the top is removed, does the symptoms change?

Using a single solid piece of bell wire, you can jumper any serial data circuit to the feed wire (PIN A ) in the four wire connector.

BC

 

[Eddiek]

Power to the SCM does not necessarily cause the issue. You need to isolate the serial data wire in the connector/wiring harness. If the serial data wire in that connection or wiring harness is grounded or shorted to another wire, it can cause the issues that you have.

Here is a schematic for the serial data circuit.

Examine the seat connector and the wire in BOTH connectors. Make sure that they are not damaged or the connectors are crushed.

Ive also seen wet carpets under the seat cause the same issue

If you pop the top off the serial Dita STAR connector with four wires, it completely isolates the LDCM RDCM and SCM from ALL the other serial data circuits. When the top is removed, does the symptoms change?

Using a single solid piece of bell wire, you can jumper any serial data circuit to the feed wire (PIN A ) in the four wire connector.

BC

Hi Bill, when removing the top off the 4 wire data star connector,symptoms disappeared. To try the other suggestions that you have suggested,I'm going to have to wait till my brother to help me. I t may take some time,as he is a very person. I will let you know what results, thank you so much Eddiek

 

[c4c5specialist]

HI there,

Yes, you remove the comb, and therefore remove the communications line for all 3 modules. When jumping the star connector, it is critical NOT to spread apart the terminals and create further issues.

Yes, you can remove the #4 fuse, however this is ONLY for the seat control module, not for the doors.

Now, to Curlees point, another way to go about this when the condition occurs is to determine what works, does the switch on the drivers door work but the passenger side does NOT ??? I mean to test from both doors, NOT JUST THE MASTER SWITCH.

Remember, the door switch on the door working does NOT NEED TO COMMUNICATE with the other door to make the window work.

So, if one doesnt work, thats usually the suspect door.

Allthebest, paul

 

[David Shiel]

Hi Paul, I am new here. Hush panels?

Hi there,

Along those lines, lets think more simply. Control modules, when they lose ground sourcing create all sorts of issues.

On C5, this is even MORE of a problem. Seat control or door control can create your condition. Seat control modules have been shorted due to the wire support for the cushion sagging to the wiring for the seat control module. This bridges 2 circuits and the module shuts down. This can short the module without ruining it. I usually recommend people start the vehicle WITHOUT SITTING IN THE SEAT, this can sometimes eliminate the problem, showing the cause is under the seat.

Normally, and more prevelant, if you look at the connections from the body to the DOORS, you may find your issue also.

The BLACK connector, with the 6 pins may have terminals that are burned or spread apart. When this occurs, the communications lines are now the ground source.

I disagree with Curlee on the pulling the star connector. Here is why. When you do that, you are shutting down the entire communications line to both seats and doors, so you do not know if it is the seat or which actual door control modules. These 4 wires are seat control module, left door control and right door control module and the line going back to the class 2 system.

So, if you remove the hush panels and pull the connectors out and look at the FEMALE side of the connection, you may see whats in the picture attached.

Allthebest, Paul

Are they the side panels in the foot wells, and is that where the black plugs are? I never checked those. Everything else though. I like the idea of testing the door switches when the gauges go out. Bill, Sam and I fought this issue on my 2001 for a long while and I ended up with a new BCM and two rubbed through wires at 19,000 miles under the dash. Also the RDCM lok relays replaced