NEED HELP no speedometer, ABS & Brake lights on, not shifting

[John04TB]

All of a sudden one day I started my '04 TB LS 4WD (130K miles) and the speedometer was dead, the ABS and Parking Brake lights were steadily on and the car wouldn't shift. I read on the other forum how many people replaced the Vehicle Speed Sensor (VSS) and it fixed everything. I did that (after finally locating it) and it changed nothing. I didn't check for an O-ring b/c I saw it on the old VSS when I removed it.

Recently the heat shield(s) above the muffler came completely loose and were rubbing against the driveshaft, particularly on right turns. I realized that was in the vicinity of the VSS but I think (hope) the VSS was too far above the shield and shaft for the shield to hit it or its wires. (And I have already replaced the VSS.)

I also read it could be the EBCM ground wire (and I finally located the EBCM - or ABS Control Module as many call it), but I have no idea where the ground is. Nor how to check continuity, etc.

I also read it could be wheel speed sensors. Last fall I replaced the PS lines and dropped the rack. A couple months ago I replaced both front control arms and struts on both sides. I never disconnected the ABS lines,

At the same time I did the front brakes and replaced the driver side caliper - which I think required me to disconnect the wheel sensor from the hub? I only have a vague memory of that.

And I topped off the brake fluid. There was plenty in the reservoir but I'd read that something that simple could cause these symptoms.

I bought a (cheap) Innova 5210 OBD2/ABS scanner but it didn't find any ABS codes.

Any help would be greatly appreciated. If I do drive it I can only go 15 mph. I hope driving it won't make things worse. Thanks in advance.

 

[mrrsm]

This will sound like an Odd Diagnostic Approach... BUT... Take the time to Watch THIS Video produced by Will Robinson of Robinson's Auto ...Because your Bizarre Dash Lights situation sounds like a Class 2 Network Problem involving a Module on the Network Misbehaving and Bringing Down the Network via UXXXX Codes (U1000).

By following Will's Very Detailed Step By Steps and using a fairly inexpensive VXDIAG-NANO Tech 2 Emulation Scan Tool and conducting Bi-Directional Testing of ALL The Modules on that Network...You will be able to figure out which one is causing all of this trouble. Remember this.... any of the Modules having Comm Problems can make them ALL have problems:

 

[John04TB]

Wow @mrrsm! That is one educational video! And actually looks doable. Thank you!

I don't think this is my issue though as I'm not getting any network (U) codes. Though I'm not ruling out trying this as I have other electric issues.

 

[TJBaker57]

Personally, I would dismiss thoughts of the EBCM (ABS) system and concentrate on verifying the integrity of the Vehicle Speed Sensor wiring and signal between the VSS which you replaced and the PCM.

Stop Lamp Switch Signal and Vehicle Speed Sensor — 2004 Chevy Truck TrailBlazer 4WD L6-4.2L VIN S Service Manual | Operation CHARM

Detailed repair manual for the 2004 Chevy Truck TrailBlazer 4WD L6-4.2L VIN S.

charm.li

C310 — 2004 Chevy Truck TrailBlazer 4WD L6-4.2L VIN S Service Manual | Operation CHARM

Detailed repair manual for the 2004 Chevy Truck TrailBlazer 4WD L6-4.2L VIN S.

charm.li

 

[TJBaker57]

replaced the Vehicle Speed Sensor (VSS) and it fixed everything.

Are you CERTAIN that you replaced the Vehicle Speed Sensor and not the Rear Propshaft Speed Sensor? They are the same part number but serve different purposes.

 

[John04TB]

I replaced this part which I believe is the VSS,. Yes?

 

[Mooseman]

Merged both threads into one.

 

[TJBaker57]

I replaced this part which I believe is the VSS,. Yes?

View attachment 114458

As I mentioned, the part number is the same for both the Vehicle Speed Sensor and the Rear Propshaft Speed Sensor. The difference is the exact location of the sensor you replaced.

 

[John04TB]

As I mentioned, the part number is the same for both the Vehicle Speed Sensor and the Rear Propshaft Speed Sensor. The difference is the exact location of the sensor you replaced.

Thanks @Mooseman. I don't know how they got split (or did I post it twice?).

Now that I actually lifted the car I see there are two identical sensors at the cone end of the transfer case. I replaced the "passenger" side one. Is the VSS on the "driver's" side. Looking from behind, toward the front of the engine, one is at 11 o'clock (I call driver side), the other at 1:00. Are they the same part and so interchangeable?

 

[John04TB]

Assuming the driver side (11:00) is the VSS, I removed the new sensor from the other location, put back the original sensor there, and replaced the VSS sensor with the new one. No change in symptoms.

 

[Mooseman]

I know that the front and rear sensors are the same and some have switched the connectors causing issues with shifting and speedo readings staying at 0. Maybe try switching the connectors.

 

[John04TB]

Uh-oh. This last time under the car I noticed this hanging down. Green and purple wires. I have no idea if it was like that before I had these problems or not. Anyone know where this came from/goes?

 

[TJBaker57]

Uh-oh. This last time under the car I noticed this hanging down. Green and purple wires. I have no idea if it was like that before I had these problems or not. Anyone know where this came from/goes?

View attachment 114461View attachment 114462

Looks like the VSS wiring to me.

 

[TJBaker57]

Uh-oh. This last time under the car I noticed this hanging down. Green and purple wires. I have no idea if it was like that before I had these problems or not. Anyone know where this came from/goes?

View attachment 114461View attachment 114462

Also looks like those are maybe twisted too much? Should have 9 twists per foot. Remember this when making repairs.

 

[John04TB]

@TJBaker57 I never touched these wires so that's how they were always twisted. But thanks for the tip.

According to @Mooseman in another post (end of 2019), these are indeed the VSS wires. Now to figure out how to fix them.

"Looked up some schematics and found that the VSS is located at the rear of the TC and has LT GRN/BLK and PPL/WHT wires. "

 

[mrrsm]

VERY Good Catch!

This is Important...

The Number of Twists Per Inch is Critical for the VSS and the Wheel Hub ABS Circuits... Acting as the means to eliminate or reduce Ambient RF (Radio Frequency) Interference being carried by those circuits as the Alternating Current being generated by those Magnetic Induction Coils is VERY Minute. Just bear this in mind during your follow on Repair Procedures. :>)

EDIT:

Uh Oh... Missed @TJBaker57 Post...(Props... for Beating Me to The Punch on this idea...)

 

[John04TB]

Identifying the VSS wire colors confirms that the left/11:00 sensor is the VSS. Where do these broken wires go? (I also realized those wires were dangling in the pics I took of the sensors.)

All the sensors wires go into a plastic sheath that goes above the transmission so I'm not sure how to re-attach these wires.

 

[mrrsm]

Do these Views help to visualize the Harness Routing under your Vehicle...but ... "From 30,000' Above..." and Looking Down from the TOP?




Sometimes, having a Digital Bore-Scope to Poke Around on Top can be very revealing and give you a chance to take some Snap Shots of Where things ARE --vs-- Where Things SHOULD Be... and perhaps allow for the making of a Short Video as well.

Further, whenever conducting necessary Harness Repairs for installing Heat Shrink Insulating Tubes and when performing Solder Repairs afterwards, Disconnecting as MANY Harness Connectors as POSSIBLE will give you MORE Access and Room to Maneuver and conduct your Harness Wire Repairs. Using a Butane Soldering Kit works BEST under these very difficult conditions.

 

[John04TB]

Thanks @mrrsm. They're both helpful and add to my confusion. LOL.

I wonder if the lower pic is for a 2WD TB? The upper pic looks like my 4WD. From what I've been reading there are actually 3 sensors? Are they ALL the same part?

Based on what I saw, I concluded that 4 was the VSS b/c the connector wire colors are the same as the broken wire colors, Gr/Bl, Pu/Wh. So this diagram confuses me about exactly where the VSS is. A frustration I've had since starting this fix.

Maybe a scope is the way to go. The wires seem ripped off so I need to find where they go. Or find a way to connect them somewhere else.

 

[TJBaker57]

Do these Views help to visualize the Harness Routing under your Vehicle...but ... "From 30,000' Above..." and Looking Down from the TOP?

View attachment 114465

View attachment 114466
Sometimes, having a Digital Bore-Scope to Poke Around on Top can be very revealing and give you a chance to take some Snap Shots of Where things ARE --vs-- Where Things SHOULD Be... and perhaps allow for the making of a Short Video as well.

Further, whenever conducting necessary Harness Repairs for installing Heat Shrink Insulating Tubes and when performing Solder Repairs afterwards, Disconnecting as MANY Harness Connectors as POSSIBLE will give you MORE Access and Room to Maneuver and conduct your Harness Wire Repairs. Using a Butane Soldering Kit works BEST under these very difficult conditions.

That top image, the first one, does not appear to be a GMT360/370 transfer case. For one, the shift motor is on the wrong side. Secondly, the VSS and Rear Propshaft Speed sensors are also on the wrong sides. Trailblazer/Envoys VSS is on the left side closest to the shift motor.

 

[TJBaker57]

Top view, image from Ebay listing:

 

[TJBaker57]

Best SI graphic I could find. Note that number 1 is calling out the encoder motor harness connector, not the motor itself.

Take note of #5. That is where the VSS connects to the engine harness leading to the PCM.

 

[budwich]

you also consider what the root cause is for the wiring "dangling" just so your fix results in a permanent fix as opposed to "ongoing an event driven problem".

 

[Mooseman]

Maybe they were chewed by rodents. The wires are made of soy after all.