Thread: Speedometer stops working in Neutral...

Is that all it feeds? Seems like a pretty heavy AWG wire for only a 10 amp fuse.

it feeds a whole wack of circuits

It's all back together, and short of the BTSI all working right, it's the exact same. Now I can't shift the car when I should be able to (key out of ignition, etc.) and the car gives me the key without the use of a paper towel, lol. Oh well, at least I know it's fixed and I learned a **** ton about the circuitry of the car itself. As far as the neutral issue, it's looking more and more like it's a cluster issue, I have a spare cluster I'll try, but for now it's going to a back burner. I'm going to concentrate on the ABS\TCS problem I have now.

Looking at the schematic for the PCM\instrument cluster, it doesn't look like it could be a cluster issue. It might be a VSS issue. The VSS ouput (Connector 2 Pin 55. DK green wire) comes out of the PCM, then get's split off to the cruise, DIC, cluster, HUD, and ABS. This tells me that the VSS signal simply stops when the car is in neutral, it's not the cluster. Could it be my VSS? When the speedo is working, it is accurate. I've been researching the VSS and it looks like it has 2 wires, a VSS High ans VSS Low. Can anyone tell me what the High and Low is and how to test it? Maybe the Low side is bad or something along those line.

This is what I have been following:

The two things I would look into would be the neutral safety switch, since its the only thing I can think of that activates in neutral, or the VSS.

VSS on this year is not a serial data line. Most W body didn't get it until 2004 IIRC although I would need to check FSM to be sure of that. Being a seperate green wire to the cluster tells me this one is analog. Should get 4000 pulses per mile.

I beginning to think that there is a break in one of the 4 wires that goes from the range switch to the PCM itself. When I shift into neutral, the VSS signal simply stops. When I get time, I'm going to check continuity between the wires on the range switch and the PCM connection.

Okay checked all 4 wires, all are fine, then short to ground when they should, they have good connections, everything. I'm pretty much at a loss here...I'll look into the VSS wiring my next day off, but other than that, I have no clue.

Do you have a scanner?

If so.. I'd look at the vehicle speed in the pcm while you shift into N. The pcm should still be reading the pulses and sending it to the cluster/cruise etc etc as it needs to.

I have Torque Pro and it has both GPS and OBD settings for speed, on the OBD setting, 0 MPH in neutral. In D\3\2\1, normal speedometer readings on everything. Haven't tried in Reverse, lol...

My bad, I went out and tested it again, the OBD setting in Torque Pro DOES keep speedometer readings in Neutral. The VSS wire doesn't connect directly to the OBD2 port though, it's carried through the data stream, isn't it?

I found an older thread where someone said the EBTCM was the cause, but I don't see how it could be. My ABS and TCS OFF lights are on, and a local mechanic used a Genisys scanner to pull codes and there are none...Anyone have any clue on where to go from here?

Bump?

It's an oddball problem for sure. From many angles.

Most of us wouldn't worry about no mph reading in N. Kinda like I bought my car w/o a working highbeam switch. 70k later..I still haven't fixed it due to lack of care and projectors.

Seems like you've traced most of this back. The pcm isn't dropping out the reading on N, only the cluster. Can you please link that EBTCM thread. According to the schematic above. There are three feeds going into the cabin. One for HUD, one for IP and one for BCM. When you shift to N, I am thinking the wiring harness is shifting slightly or something silly. Check the connections at the back of the fuse box. Make sure they have good connection etc.

http://www.grandprixforums.net/showthread.php?t=84446

That's a good idea, I wonder if I should check for continuity between the VSS wire at the PCM and the cluster? Then shift into neutral and see if it's still connected?

Thank you so much for your input, it's greatly appreciated

The pcm feeds the fuse box and the fuse box feeds into the car. You could probably wiggle the harness while checking continutiy

So there is a fuse on the VSS line? Or is the VSS wire just run in the same harness as all the other wires that run to the fuse box? We are talking about the under hood fuse box, correct? I don't see a fuse for the VSS on here:

Sorry for all the questions, I'll be performing all these tests over the weekend and I want to make sure that I'm testing the right stuff. I don't know why, but I keep thinking the EBTCM might be playing a role in this, or is affected by this. I pulled codes on my ABS with a Genisys scanner and it showed no faults. I'm sure you saw my other thread where I have replaced all 4 bearings, and the harness on the front passenger side, and verified their connection to the EBTCM, along with all the powers, grounds, etc going to the EBTCM.

Take a look at the schematic you posted. It references the green vss wire going into Connector 1 cavity E5 then coming out on Connector 2 cavity C8 and E8 if I'm reading it right. All dark green. C8 and E8 would have two wires coming from each. If that's what you see, then those are the wires. IIRC they called it a relay center because it has fuses, relays and it relays other wires from the engine harness to the harness that heads into the cabin. To see those wires, you need to remove the fuse box off the strut, pop the back off it and look at the big three connectors that are bolted to the back of the fuseblock.

Oh okay, so the "Underhood accessory wiring junction block" is the relay center. I thought it was an actual connector on the firewall or something of the sort. I have been in there before, when I ran a new wire for my fuel pump (10 AWG). I'll take a look at that area this weekend. Thanks again for all your help, I'll be updating the thread with my findings.