Erik_Hagglund

Hello!

So I have a 2003 conv. and the driver seat won't move.
Well, that's not entirely true: the seat moves, but only when ignition is off and only for about 1/10 of an inch. Only forward, and only one time for every time I turn on the ignition.

I have a DTC B0856 (5 volt reference out of range) and have started searching for what's causing it. I've purchased a shop service manual from Corvette Central (part #115222) and I have a Tech2 as well...

Since I couldn't operate the seat I couldn't fit a spanner between the seat and that wall behind the seat and the floor. So I had to go through the seat, removing the cushion and separate the actual seat from the "sleigh". Now I can access the SCM and the electric motors, as well as the sensors. But I can't find anything wrong. I've cleaned the connetors and now the seat is moving every axis except "entire seat rearward"... something wrong with the seat control switch.
The shop service manual suggests looking for broken cables, and if none is found it suggests replacing the module.
So I guess that's what I'm going to do next... I'm going to buy a used one, because $500 is too much money for trial and error.

But, and here's my question: What module do I need? The one I currently have is labelled "10435193", but apparently there's also a "09360841" and allegedly even a third one, "10342158"??
I have the sport seats, with memory and steering column telescope... which module do I need??? I've googled quite extensively on this but I only get more confused... now I'm imagining that the "10435193" module is for the passenger seat, I don't know anything anymore... I need some help. Both with what might cause my problems (i.e. why the seat won't move when ignition is on, but DOES move when it's off. Also not moving as soon as I connect the Tech 2 tool, independent whether ignition is on or off) and also about the module... will my problems be over if I buy a new one? I found a thread about repairing it, I might try that too...

Okay, that's it, I'm sorry if it's incoherent or for any bad grammar, english is not my native language.

Oh, one more thing... the shop service manual I got from Corvette Central has some pages that are... I guess "out of focus" is the best way to describe it, I get nauseous when reading it, it's like reading a text with your eyes crossed.... is there an electronic copy that can be downloaded or purchased from somewhere, or will GM send replacement pages if I contact them?

Thank you in advance for any help

dadaroo

I am not aware of any differences in the SCMs from 97 to 04. GM does alter P/Ns from different vendors. The passenger seats do not use SCMs, they use a relay control unit.

DTC B0856 is NOT a 5 volt reference issue. It is saying the SCM main motor power feed is low or high but Out of Range. I assume low is the issue.

Have you made sure your battery is good? You need at least 12.5 volts before you start the car. May want to load test it if not sure.

If you want another SCM or seat switch contact Marc at VetteNuts.net who is a great Forum vendor here.


May want to do this while you are working on the seat to clean up the motor control rods.



I would try jumpering the SCM for the reverse movement to see if it works.

Keep us informed.

Mr. Sam

PS: OEM GM service manuals should have NO bad pages.

NealB

Both my 2003 Z06 and the 2002 convertible I bought Sport Seats from have the same PN driver side seat control module 10435193

Marc@Vettenuts.net

Here is a link to our seat modules: http://www.vettenuts.net/index.php?l=product_list&c=25

Erik_Hagglund

Hello again, and thank you for your reply. The battery is a spanking new optima red top that has a ctex mxs 5.0 charger for maintenance charging. When writing this post it reads 12.72 volts from my digital multimeter, so voltage shouldn't be an issue, but looking at the tech2 it says voltage at battery 2 is 0.21 volts... It also says DTC B0856 is present... And now also DTC B2860 (column position sensor failure) that wasn't there 2 days ago... Starting to suspect I'm having short to ground issues :'(
Anyhow, according to tech2, B0856 IS 5 Volt reference out of range:



But it seems to also be an issue with the voltage to the scm.... Haven't got a DTC for it though... But it looks weird:



Any thoughts? Wires connecting the SCM, Seat Switch, sensors and motors has been taped with electrical-tape, does it come like that from Bowling Green or has someone been tampering with this prior to me....?

Thanks for the tip about changing the seat brackets and stuff, I will definitely look in to that, like you said...while I still have the chair disassembled I'm a fat guy too and 102571 mi on my odometer... So it's just a matter of time

dadaroo

Got it and I will look at this issue again. You may want to unplug the Black connector to the seat and measure what voltages you have going to it from the Orange wires.

I would also make sure there is a good ground continuity on the Black ground wire there also.


Mr. Sam

dadaroo

You are correct about B0856. Not sure how I messed that up but I did. Don't have time to post the SCM diagnostics on that right now but will later today.

I need to find out where Battery 2 voltage is coming from. Maybe the BCM and is related to your CL issue.


I'll be back later.


Mr. Sam

dadaroo

I was correct in what I said before as it is not discussed as a reference volt issue in my 2003 FSM. Take a look as it discusses Battery 2 voltage. That appears to be your issue.

Let me know if you need any schematics.

https://www.dropbox.com/s/mpa60cvo76...B0856.pdf?dl=0


Mr. Sam

Erik_Hagglund

Hello Mr. Sam!

I get more and more confused. Spent all day testing circuits back and forth, reading the schematics that I have, trying to trace where all the cables are coming from but I can not for the life of me understand which pin in the SCM connector is suppose to be battery 1 and battery 2. According to my schematics (or connector description, think the connector is called "C1"), I have "Battery positive voltage" in pin number 7 I believe (I don't have the book with me at the moment).
I agree that the Battery 2 voltage appears to be the issue... I will look in to this tomorrow. Just have to find out which pin is the battery 2 pin...

dadaroo

C1 Pin 3 is Battery 1 and the other is C3 Pin A Battery 2. Both are Orange wires.

Check Fuse 4 for Battery 1 and Circuit Breaker 35 for Battery 2 in the I/P fuse box.

Keep us updated. Most likely the SCM or the Circuit Breaker.


Mr. Sam

Erik_Hagglund

Okay, I've tested the pins mentioned above and both of them has the same voltage as the car battery so I guess the conclusion must be that my SCM is toast?
I also checked all pins on all connections for short to ground, but only the pin that should have ground, had ground. But I also tested the pins on the SCM, while everything was unplugged, and found that there was ground on quite a few pins... Not sure that should be the case....
https://youtu.be/LlFfdAZOKHo

dadaroo

Yes, it sounds like the SCM is a problem.


Mr. Sam