(see also [url=https://www.corvetteforum.com/forums/c5-tech/3668889-the-electrical-issues-of-my-1998-convertible.html#post1589875338here[/url])

The power seat, driver side, works perfectly. Passenger seat doesn't do anything.

Today I hooked up a Tech 2 scanner and when checking the SCM (Seat Control Module) it only shows functions / diagnostics for the driver seat. It doesn't seem to detect the passenger power seat at all. They are sports seats.

When I purchased the car 2 weeks ago, it had the following SCM history codes:

B0851 H Battery 1 Out of Range
B0856 H Battery 2 Out of Range
U1255 H Serial Data Line Malfunction
U1064 H Loss of Communication with BCM
U1016 H (code wordt 2x gegeven) Loss of Communication with PCM

Clearing the codes, about a week later the following code returned:

B0856 H Battery 2 Out of Range

That is the only code that has come up thus far.

My question is, is it normal that the Tech 2 doesn't detect the passenger power seat? Or is it an error in my Tech 2? How should I start treating this problem? Any ideas are welcome...

 

The passenger seat is not on the serial bus so it will not show on the Tech 2. We'll just need to do some old school diagnostics.

I assume the Lumbar does not work either?

Test Circuit Breaker 36 (seat motors) and Fuse 3 (lumbar) to make sure they are not "open or blown". Both in the I/P fuse box.

Thanks for opening up separate Threads for each issue. I will try to help on each one. Just add a "new" Post on the original Thread for every new Thread so I will get an email update so I know you created another one. I will be looking at the BPMV issue next.

 

It makes things much clearer indeed, that was some good advice you gave. And thank you for your help!

Wasn't aware of this differentiation, good to know...

The lumbar, passenger side, doesn't work; driver side lumbar does work. Neither driver nor passenger side lumbars will show up in the Tech 2 -> same reason (not on serial bus)?

Had already tested that the day I bought the car. All fuses and circuit breakers are intact.

So I peeked underneath the seat and saw this interesting spectacle (minus the arrows):



Ha! A couple of unconnected connectors. Serving as proof that 17 years ago the GM-mechanics forgot to properly install the passenger seat. Solving this issue will be super easy, simply by joining the connectors...

... but MAYBE I should wait before removing the seat -JUST in case- until the shop manual will have arrived....

 

Correct, the Lumbar is not on the Serial Bus either. I have all the schematics also to work with you. Let us know when you hook things up. 8VETTE7 is probably right so expect a drain.

I have a write up for checking for drain if you have it. Here it is:


Suggest you remove the hood light bulb first so it does not provide a drain.

For measuring battery drain I would hook up an ammeter to the negative side of the battery by removing the negative cable and measure between the cable and the negative battery post.

When you connect the ammeter the car should draw several amps until it goes into "sleep" mode which can take several minutes. Normal sleep mode drain should be 30 milliamps or less by GM standards. You will need an ammeter that can transition from whatever the drain is down into the sleep mode. If you have a drain I suggest the following:

Once you determine you have a drain with an ammeter what I recommend first is to listen to each fuse box and see if you hear any relays operating. If not, then place your hand on each relay to see if any of them feel hot. That can be the start if you find something like that is happening.

If nothing shows up you can hear or feel then I recommend you separate the two fuse boxes from each other. This is easy and done by removing the Red cable from the engine fuse box that feeds the passenger fuse box. It is on the right rear side of the engine fuse box. There is a stud there where the large Red wire from the battery connects. Just remove the nut and disconnect the large Red wire feeding the passenger fuse box and reattach the Red battery cable. NOTE: I would recommend disconnecting the negative ammeter hookup when working on the positive side doing this.

What you will be doing is measuring the drain with an ammeter to see if disconnecting the passenger fuse box causes the drain to go away or not. By depowering the passenger fuse box you will depower the BCM which controls the sleep mode so do not expect the sleep mode to happen.

If removing the feed to the passenger fuse box you then see you have eliminated the drain then you know it is something related to those circuits. If it does not reduce the drain then you know it is related to the engine fuse box. It could be a rare case where you have some drain via both fuse boxes and we can deal with that if you think it is the case.

Just so you know, even though it may appear to be a problem in the engine or interior area the fuse boxes do feed circuits to each other that are not affected by separating the boxes. So, separating the fuses boxes can tell you how to narrow down your search but still not where the issue may be. That is where the schematics come into play to track down the “real” culprit. Hope that makes sense.

Once you basically know where it is then you can remove fuses and relays to see where the drain is coming from.

PS: There are cases where the alternator causes a drain so it can be disconnected and see if the drain drops.

 

Splendid information Dadaroo, I will take this up after my holiday. I expect to have the workshop manual at hand then also.

Good method for testing if there's a drain, I will definitely try that.

 

The PASSENGERS SEAT DOES NOT connect to the serial buss.

Its just connected to POWER and you must move and adjust it by moving the seat multifunction switch until the seat is at the desired position.

The TECH 2 will NOT se it or control it.