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VSS code, no CEL, no speedo/odometer

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ddavisaf

15+ Year Contributor
2,588
81
Feb 12, 2005
Langley AFB, Virginia
Alright, the dread speedo question again.
There is not a CEL. Ran the diagnostic on it anyway and there's a VSS malfunction code there.
Replaced the VSS.
Replaced the instrument cluster.
Replaced the reed switch.

I'm looking at two possible options that I can think of.
ECU needs to be replaced
Transmission needs to be replaced.

Car is sold and I'd like to get a functional speedometer in this thing for them.
Where should I begin?
 
ddavisaf said:
I'm looking at two possible options that I can think of.
ECU needs to be replaced
Transmission needs to be replaced.

Where should I begin?

The ECU isn't directly involved in the function of the speedometer, it just reads the VSS signal like the AC, cruise and speedometer do. You should see a pulsing signal at 14 on the 2G DLC when the car is moving. Note if it seems to be stuck high or low. If you don't then I'd start running the diagnostic procedures in the FSM, first making sure that the VSS is good and checking that it gets power from the Ignition Switch.

Steve
 
My FSM is annoying me to death. I've been searching the procedure for about 2 hours now with no luck...

You should see a pulsing signal at 14 on the 2G DLC when the car is moving.
My tanslation skills don't work until Tuesday, help me out?

I'm going to continue my search for a schematic concerning the VSS power/signal path. You say it's tied into the Ignition switch, but any idea at what point? So maybe since my FSM seems to be incomplete I can start from a different location and try and track it down that way...
 
Alright... here's what I'm getting

From the harness...
Pin 3 - 4.5V
Pin 2 - OK: Continuity
Pin 1 - OK: Continuity

Testing the VSS
Looking at the top of the VSS w/ harnesses secure pin on top
1/2/3
Connect a 3-10kOhm resistance on pin 3 intercepting the power to pin 1?
Hook up a multimeter and test for voltage at pins 2 and 3. Applying power to pin 1 and ground pin 2.
1 Turn = 4 Pulses.
 
The speedometer is covered in the electrical section in the circuit diagrams 204 and 54-27 in the chassis electrical (at least on the Manual CD).

The VSS has three pins. Pin 1 (white) is 12v from the ignition switch IG1, pin 2 (black) is ground, pin 3 (yellow) is the output. The output goes to several places including pin 14 on the diagnostic connector.

The FSM says, to test it out of the car, you apply 12v to pin 1, ground to pin 2 and connect pin 3 to pin 1 using a 3k to 10k ohm resistor and measure between pins 2 and 3. If the VSS is good you will see 4 pulses/turn. In the car, they say to disconnect C-05 and C-06 and measure between pin 36 and ground. You should see 4.5v or more. Same if you measure the harness side at the transmission on pin 3 to ground. I assume this means the speedo is biasing pin 3 to 5v and the VSS pulls it to ground when it pulses.

Steve
 
I'm going to test everything while I'm at work tomorrow morning. I went and bought a new multimeter and some resistors. Thank you for the quick and easy. I'll post the results when I get them.
 
Have you tried hooking up a scanner to see if you are registering mph? This would at least tell you the vss is working and the PCM recognizes it. Other than that it seems you guys are covering it close. Good Luck
 
Tested both VSS I have in my possesion, both were good. Tested the harness, it's good. So, I'm hooking the scanner up to it tomorrow to see if I'm registering MPH. Assuming I'm not, this would indicate a lack of a "drive gear" in the transmission which would turn the VSS's gear, or a fault in the PCM? Or TCU, or whatever the hell it's called...
If it's the transmission, any idea how the gear that disappeared hasn't caused a single slip, grind, squeal, chirp, or any other indication that there would be a foreign object in the transmission?
 
I would think that if the actual vss, harness, etc had failed that there would be a failure code. The TCU can be a culprit but I would wait until I scanned to see if the PCM recognizes a signal. If you get a mph signal on your scanner you can rule out the vss and associated goodies. You may find then it's a wiring problem and may need to pin test to the speedo cluster. I use a Snap On Vantage so I can check wave forms. Not sure if it's a square wave or sine wave on this particular one but for sure it's a wave form.

Good Luck
 
I'm getting a failure code.... but I'm assuming it's a non-critical code because I don't have a CEL. I randomly ran the codes one days and I'm getting a Pxxxx whatever for a faulty VSS. However, when I tested the VSS And harness my readings were good. Which confuses the hell out of me.
 
Alrighty.
Good sensor
Harness tested good.
Hooked the scanner to the ECU and I'm not registering MPH. So this would mean I have a problem with either...?
a) The transmission lost it's drive gear for the VSS
b) The TCU isn't sending out a signal
c) The ECU isn't sending out the signal?
 
ddavisaf said:
b) The TCU isn't sending out a signal
c) The ECU isn't sending out the signal?
From what I can tell the VSS is the source and both the computers are users of it's output just like the gauge. They might have a problem and be pulling it low but that seems very unlikely.

Steve
 
So then the drive gear in the transmission must be the problem. It's either gone, or not responding. Any idea how this would not cause a problem with the operation of the rest of the transmission?
 
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