I need help please on abs- **SOLVED**

[Num12005]

I have a little code reader that i bought from oreillys, it didnt have any codes at all. When i first started it the abs/brake lights went out, and i thought it was fixed. Soon as i went for a drive it got to about 15mph and bam, they all came back on.. You think i need a real scanner? Thanks for the help.

 

[corvette744]

I think it would be nice to see your front wheel speed sensor reading at different speeds and rear input as well.Your at a point now were you need to take it to a reputable mechanic or start with the scanner and watching sensors to verify their good.If it was me i would pay to get it diagnosed and if easy fix it myself.If it is a wiring issue you said its not your strong point so might be a good option before you ruin the trans or just waste more money at it.

 

[Num12005]

Yep, i agree. I usually do .y own mechanic work but this ones very frustrating. I have one more thing to check and then ill take it to my mechanic friend. Im at a point where i may just sell it, it has 220k but has been an excellent truck, it hasnt ever left me stranded.

 

[Num12005]

Ok, i took front sensor readings and heres what they are, i tested on mv and ohm..
Lf- on 200 mv setting--- highest was 2.4 flucuates alot
Lf- on 2k ohm-- 1.1

Rf-on 200mv- 5.1 highest flucuates to zero also
Rf-on 2k ohm-- also put a real scanner on and its saying c0236, and it will not show mph, so wiring issue..has to be

 

[exp500]

Stay on the VSS, that is your code.Not Front. Check both sides of connectors closely, look for corrosion,bent pins,loose females,Damaged wires, all the way to/from speed sensor to abs. Check interior grounds, grounds at ABS,engine grounds/tcase grounds.
A subscrption to AlldataDIY and a little laptop/tablet with this helps alot.Vxdiag VCX Nano for GM/Opel Diagnostic/ECU Programming Tool

 

[Num12005]

Well, i pulled the green connector at the pcm, tested both speed signal wires from connector all the way to pcm and its good on continuity.. i took all trans connectors loose , checked for loose/bent pins and applied dielectric grease, abs plugs also. Cleaned and checked grounds again on the frame, checked passenger side ground (to back of block)and it looks new. I havent pulled the loom back off the ground wires, on drivers side frame(under driver) yet, and i havent checked the grounds under the divers side pillar..

 

[Num12005]

Do the grounds in the upper left of dash under pillar go to gauges, etc?

 

[corvette744]

Well, i pulled the green connector at the pcm, tested both speed signal wires from connector all the way to pcm and its good on continuity.. i took all trans connectors loose , checked for loose/bent pins and applied dielectric grease, abs plugs also. Cleaned and checked grounds again on the frame, checked passenger side ground (to back of block)and it looks new. I havent pulled the loom back off the ground wires, on drivers side frame(under driver) yet, and i havent checked the grounds under the divers side pillar..

Question does your speedo work or no.Were the vss goes into the trans is the mounting surface really rusty.Did you check continuity at that connector-i think it goes to the ebcm.

 

[Num12005]

Speedo does not work at all, on my friends scanner it was stuck on 3mph, on the scanner..
The surface at the tail end of trans was pretty clean, no rust. Also, i pulled the loom as far forward as i could and the vss wires look like they route inside the group of wires that come up behind the intake, across the intake.. After that i have no idea. I just tested for continuity from the vss connector to pcm.. which showed good. Now do they route elsewhere from harness under hood to somewhere else i have no clue.. ill check the schematics and see right quick..

 

[exp500]

3 MPH on a drive around? According to print on post 24 the VSS wires straight to pcm. I wish you had a VSS plug so you could jack rear wheels and see if you have AC output from VSS.
PCM Ground tests good? EBC Ground Known problem.


Cause of ABS light on, C0265, C0201, U1041

GM has determined that a poor ground connection at the A poor connection at the EBCM is causing unnecessary replacement of brake modules. The EBCM ground is different for each application. Do not replace the brake module to correct this condition.
Clean the ground connection to fix to ABS light on, C0265, C0201, U1041

• Remove and clean the EBCM Ground. It is located on the frame beneath the driver’s side door. You may find multiple grounds at that location, but the EBCM ground is the heavy (12-gauge) wire.

• The ground point may have a fastener with a welded-on nut. Do NOT reuse the old fastener. New part numbers are listed below.

• Remove the fastener and ground wires and clean the area, front and back, using a tool such as a *3M(TM) Scotch-Brite Roloc disc or equivalent.

• Install the grounds, then the new washer and new bolt to the frame. You may have to enlarge the hole

• IMPORTANT: USE the NEW bolts, washers and nuts specified in this bulletin. These parts have been identified due to their conductive finish.

• Tighten the nut to 79 lb in.

• Spray the ground connection front and back side of the repair area using Rubberized Undercoating.

• Check to ensure a good connection for the negative battery cable to frame ground. It is possible for this ground to cause similar symptoms with the ABS as described above.

New part numbers:

For full size trucks

11588564 Bolt

11609679 Washer

11609746 Nut

Midsize SUVs

11588337 Nut

11610367 Washer

11503749 Nut

 

[corvette744]

Yes thats the key to see if you have ac voltage coming out of the vss that would answer alot and save a bunch of chasing around time.Yes ground is a cause i have seen that bulletin before.At least your in the right area its not in the fronts.

 

[Num12005]

I appreciate your help man, i fugured it was just a bad vss but nope.. So how would i test it for output? Put it on jack stands and run it in gear(which is dangerous) but i will do it if needed.

 

[Num12005]

Yes sir, 3mph on the scanner on a test drive. He cleared all the codes and tried again, lights came back at about 15mph. No speedo at all. This has to be moisture related because the 1st time it happened last year, i had been driving in the rain. Then it went haywire for good this time, after 3 hour drive in heavy rain..

 

[corvette744]

Sounding more like a wiring issue-i would think you need a scanner to see the ac or voltage when driving.Try this and let us know what you get.http://blog.buyanycarparts.com/how-to-check-the-speed-sensor-on-a-99-chevy-silverado/

 

[exp500]

You can use a multimeter to see fluctuating voltage output (or frequency) depending on meter. This ones cheap.

More Information for SKP SKTX3A

 

[Num12005]

I cut the wires to the vss and hooked up mulitmeter, ac voltage increases with wheel speed, highest it would go was 5.8 but i only spun it so fast as im on jack stands.

 

[Num12005]

I may have found the issue, i took the vatozone vss out and put the original back in as the connector surface was shaped different, making me think maybe the plug was lnt fully seating on the pins. I squeezed the pins together a little and plugged it inyo the original, now the speedo works and it seems to be shifting again but yhats on jack stands. Abs light is still on but it may go out once the vss is working. I have my fingers crossed that it was this simple‍

 

[exp500]

Forward progress! Check ground underneath if it's still in the air.
Thats why I don't like parts cannon. Usually get lucky, but never truly find cause. It really raises hell when ya don't get lucky. Good Job!

 

[Num12005]

I think its fixed. What i think happened was, the 2 wires coming out of vss were showing the wire as if someone had messed with it at some point, i think moisture was getting in the plug and grounding it out. So initially i checked the continuity and it was good so i used liquid electric tape to seal it up, and i installed the new vss, which didnt work. So after

much head scratching and test i noticed the new vss had this plug in shape, which did not match my factory plug in. So i installed the old vss, pinched the female pins in a little and installed it with dielectric grease, and now it works.. So my initial find and fix probably worked but the plug in didnt match.. i also changed the ground wire from floor to frame below the drivers side floor, it was almost completely severed on one end, only 5 or 6 strands holding it on. Also i think the abs module probably had the bad relay as described before. Im not 100% sure which thing fixed it.. Just letting yall know, i really appreciate all the help..

 

[Num12005]

I appreciate the help very much