How JustAnswer Works:
  • Ask an Expert
    Experts are full of valuable knowledge and are ready to help with any question. Credentials confirmed by a Fortune 500 verification firm.
  • Get a Professional Answer
    Via email, text message, or notification as you wait on our site.
    Ask follow up questions if you need to.
  • 100% Satisfaction Guarantee
    Rate the answer you receive.
Ask kalamykid Your Own Question
kalamykid
kalamykid, Shop Owner/ Tech
Category: GM
Satisfied Customers: 3737
Experience:  I HAVE OWNED MY OWN SHOP FOR OVER THREE YEARS. I HAVE THE TOOLS AND SOFTWARE TO ANSWERE ALMOST ANY Q
5629372
Type Your GM Question Here...
kalamykid is online now
A new question is answered every 9 seconds

I have a 1995 gmc step van. The spedo bounces around. When

Customer Question

I have a 1995 gmc step van. The spedo bounces around. When driving the truck will shift itself into what feels like neutral the check engine light comes on. I have had it to 4 mechanics and they all have different ideas. I do know one of the check engine codes was a voltage issue from the fuel pump. Another was a break sensor
Submitted: 3 months ago.
Category: GM
Expert:  kalamykid replied 3 months ago.

If the speedometer is bouncing then most likely you have a bad connection at the vss " vehicle speed sensor " or the sped sensor itself is going bad. Do you have any transmission fluid leaking out around the plug for the vss?

Customer: replied 3 months ago.
I dont see any fluid leaking. It spent 2 weeks at the gmc dealer and all thru came up with was the drac mod. I replaced that and had no change. Would the vss effect the transmission shifting? While driving it goes in and out of neutral
Expert:  kalamykid replied 3 months ago.

Yes the vss can cause the transmission to change gears if the speed signal is lost. The vss tells the pcm how fast you are going and then tells the shift solenoids what to do and when to change gears. No vss signal and the pcm does not know what gear to tell the trans to be in.

Customer: replied 3 months ago.
What is the best way to troubleshoot the vss?
Customer: replied 3 months ago.
Also is this an obvious issue a gmc dealer should have caught after 2 weeks of diagnostics?
Customer: replied 3 months ago.
What is the best type of shop to bring the truck to for the vss replacement (transmission,electrical)?
Expert:  kalamykid replied 3 months ago.

It would have been the first place I would have gone to. To tell you the truth, the vss is not so easy to check. It is a magnet that picks up in the toner ring on the out put shaft. The teeth on the toner ring will cause a pulse when the teeth pass the tip of the sensor. The pcm picks up on the speed of the pulse to know how fast you are going. All magnets loose there strength over time and with heat. The vss cost about $30.00 and is very easy to replace, you have to jack up the driver side " more to the rear so you do not loose fluid" and then unplug the sensor. There is one bolt holding it in you have to remove. Then you have to use a screw driver to pop it out. Lube the new seal and pop the new one in bolt it down and plug it up. It should only take about 10 minutes to do the job.

Expert:  kalamykid replied 3 months ago.

You can do the job yourself, it is really not hard to do.

Customer: replied 3 months ago.
I just picked it up from the last mechanic that had it for 4 days and he said both sidesides of th3 vss are working. He said that 2 transmission codes came up 85 "no output signal and 58 no reply drop
Expert:  kalamykid replied 3 months ago.

Do you know what transmission you have in your truck? Is it a 4l60 ora 4l80 E?

Customer: replied 3 months ago.
I have no idea on the model tranny. Is there an easy way to figure it out?
Expert:  kalamykid replied 3 months ago.

Can you send me a pic of the transmission pan?

Customer: replied 3 months ago.
Attached is a pic of the tran pan
Expert:  kalamykid replied 3 months ago.

That is the 4l80 e transmission. Let me do a little more digging with the codes you have.

Expert:  kalamykid replied 3 months ago.

The first thing I would check would be to see if there is any trans fluid in the main plug on the passenger side of the transmission. It will be a round plug with about 15 wires in it. Unplug it and see if there is any fluid on the plug s bottom.

Customer: replied 3 months ago.
Thank you. After picking it up today and driving it. It seems the be not shifting as hard has it did when I brought it in. However, it's stalling when breaking. This is how the issue started last month. The mechanic claims to have nothe repaired anything. Did he maybe reset a computer?
Expert:  kalamykid replied 3 months ago.

He may have reset it. If the engine is stalling there may be a problem with a vacuum leak, or the idle control motor. Do you have the van with you and are you able to do some testing with me to see what is going on?

Customer: replied 3 months ago.
It's at my yard. I will be there first thing in the morning.
Expert:  kalamykid replied 3 months ago.

I work on here till about 6 am my time and then have to get some sleep, I get up around 12 noon eastern time. Can we work on it some where around there< or do I need to stay up so we can work on this in the morning? I do not mind just need to know how to plain my night tonight.

Customer: replied 3 months ago.
I will head down there now, give me about 30 min
Expert:  kalamykid replied 3 months ago.

We can work on this in the am if you would like, there is no reason for you to go now.

Customer: replied 3 months ago.
Ok lets plan on noon est?
Expert:  kalamykid replied 3 months ago.

That is good. Chat with you tomorrow.