Speedometer not working
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Mountain Pass
Joined: Jan 2011
Posts: 126
Likes: 13
From: Buckley
Speedometer not working
Need help diagnosing my speedometer in my late 99
Odometer works
Vehicle speed can be seen through OBD. Does this rule out the VSS?
Is there a way to test the stepper motor?
cluster is currently out of truck and the circuitry looks great no cracks or corroded areas.
I have the stepper motors exposed with hopes to finding a way to test the speedometer one.
also when it was in the truck I removed the plastic on the front of it to see if it was just the needle.
My findings were with KEY OFF I could gently rotate the needle and it would slowly fall back to zero.
With KEY ON the needle would immediately drop back to zero as if there was power to it.
Is the VSS the only sensor that sends signal for speedometer?
Thanks in advance
Odometer works
Vehicle speed can be seen through OBD. Does this rule out the VSS?
Is there a way to test the stepper motor?
cluster is currently out of truck and the circuitry looks great no cracks or corroded areas.
I have the stepper motors exposed with hopes to finding a way to test the speedometer one.
also when it was in the truck I removed the plastic on the front of it to see if it was just the needle.
My findings were with KEY OFF I could gently rotate the needle and it would slowly fall back to zero.
With KEY ON the needle would immediately drop back to zero as if there was power to it.
Is the VSS the only sensor that sends signal for speedometer?
Thanks in advance
Lead Driver
Joined: Oct 2005
Posts: 6,129
Likes: 1,919
From: Ponca City, OK
I think I remember something about the 3rd brake light causing speedometer issues. Replacing the bulb was supposed to fix it, provided it's the cause. I'll see if I can find where I read it from for reference. Question though did the cruise control work with no speedo?
Butt-Head
Joined: Apr 2004
Posts: 9,405
Likes: 2,894
From: Reed Point, MT
If the cruise control works then the ABS module is seeing a vehicle speed sensor input. On the 99- up pickups, the analog AC VSS signal goes straight to the ABS module where it is converted to a digital signal that the PCM, speedometer, etc. can use. The cruise control is run through the PCM and is separate from the speedometer.
The caveat to this is that vehicles with 4 wheel ABS will use the front speed sensors to determine vehicle speed and output the signal to all of the other modules if the rear differential-mounted speed sensor is junk or the wires are torn off. The cruise control and speedometer will still function.
The caveat to this is that vehicles with 4 wheel ABS will use the front speed sensors to determine vehicle speed and output the signal to all of the other modules if the rear differential-mounted speed sensor is junk or the wires are torn off. The cruise control and speedometer will still function.
Thread Starter
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Mountain Pass
Joined: Jan 2011
Posts: 126
Likes: 13
From: Buckley
If the cruise control works then the ABS module is seeing a vehicle speed sensor input. On the 99- up pickups, the analog AC VSS signal goes straight to the ABS module where it is converted to a digital signal that the PCM, speedometer, etc. can use. The cruise control is run through the PCM and is separate from the speedometer.
The caveat to this is that vehicles with 4 wheel ABS will use the front speed sensors to determine vehicle speed and output the signal to all of the other modules if the rear differential-mounted speed sensor is junk or the wires are torn off. The cruise control and speedometer will still function.
The caveat to this is that vehicles with 4 wheel ABS will use the front speed sensors to determine vehicle speed and output the signal to all of the other modules if the rear differential-mounted speed sensor is junk or the wires are torn off. The cruise control and speedometer will still function.
So if I’m understand correctly it could be that the VSS is shot and the wheel speed sensors are sending the vehicle speed in its place?
or is it that the wheel speed sensors are shot? I thought they triggered a abs light?
I believe the vehicle speed wire behind cluster is gray/black. What kind of testing other than a continuity test is there if any?
Thread Starter
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Mountain Pass
Joined: Jan 2011
Posts: 126
Likes: 13
From: Buckley
well this will be a easy investigation. I will report any findings. Thanks
Thread Starter
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Mountain Pass
Joined: Jan 2011
Posts: 126
Likes: 13
From: Buckley
Update:
Third brake light was a burn out led board so I’ll grab new incandescent bulbs just to test then get a new oem housing.
I unplugged drivers abs sensor and ABS light cam on as expected. Still registered speed with edge cts2 monitor. Went and unplugged passenger side ( now both sides are unplugged). Truck still showed vehicle speed.
If I was to put a test lead on the signal wire from VSS what should I be seeing on multi meter?
is it possible bad grounds cause this?
one of the illumination bulbs is burnt out in cluster that lights up lower right hand side near Speedo. I will get this fixed just curious if this can cause no speed to register.
also reverse lights (08 style tail lights) are not illuminating and noticed the reverse bulbs are LED. I will be replacing with oem style bulb and testing for power.
Any other ideas would be great. I have multi meter and power probe if anyone has tips or thoughts. Thanks again
Third brake light was a burn out led board so I’ll grab new incandescent bulbs just to test then get a new oem housing.
I unplugged drivers abs sensor and ABS light cam on as expected. Still registered speed with edge cts2 monitor. Went and unplugged passenger side ( now both sides are unplugged). Truck still showed vehicle speed.
If I was to put a test lead on the signal wire from VSS what should I be seeing on multi meter?
is it possible bad grounds cause this?
one of the illumination bulbs is burnt out in cluster that lights up lower right hand side near Speedo. I will get this fixed just curious if this can cause no speed to register.
also reverse lights (08 style tail lights) are not illuminating and noticed the reverse bulbs are LED. I will be replacing with oem style bulb and testing for power.
Any other ideas would be great. I have multi meter and power probe if anyone has tips or thoughts. Thanks again
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Butt-Head
Joined: Apr 2004
Posts: 9,405
Likes: 2,894
From: Reed Point, MT
If you unplugged both front ABS sensors and you still have a vehicle speed showing on the CTS, then the VSS on the rear differential and its circuitry is not suspect.
Here's the rub (and I forgot to ask earlier) but is your ODOMETER working? It is run off of a separate motor not tied to the speedometer motor. If it's working and the speedo isn't then it's an easier diagnosis....something in the cluster is amiss. If the odometer doesn't work, then your issue is the gray/black wire either in the cab or near the splice in the harness under the hood because obviously the PCM is getting its input....which is shared from the ABS module.
Here's the rub (and I forgot to ask earlier) but is your ODOMETER working? It is run off of a separate motor not tied to the speedometer motor. If it's working and the speedo isn't then it's an easier diagnosis....something in the cluster is amiss. If the odometer doesn't work, then your issue is the gray/black wire either in the cab or near the splice in the harness under the hood because obviously the PCM is getting its input....which is shared from the ABS module.
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Thread Starter
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Mountain Pass
Joined: Jan 2011
Posts: 126
Likes: 13
From: Buckley
If you unplugged both front ABS sensors and you still have a vehicle speed showing on the CTS, then the VSS on the rear differential and its circuitry is not suspect.
Here's the rub (and I forgot to ask earlier) but is your ODOMETER working? It is run off of a separate motor not tied to the speedometer motor. If it's working and the speedo isn't then it's an easier diagnosis....something in the cluster is amiss. If the odometer doesn't work, then your issue is the gray/black wire either in the cab or near the splice in the harness under the hood because obviously the PCM is getting its input....which is shared from the ABS module.
Here's the rub (and I forgot to ask earlier) but is your ODOMETER working? It is run off of a separate motor not tied to the speedometer motor. If it's working and the speedo isn't then it's an easier diagnosis....something in the cluster is amiss. If the odometer doesn't work, then your issue is the gray/black wire either in the cab or near the splice in the harness under the hood because obviously the PCM is getting its input....which is shared from the ABS module.
trying not to spend 200$ for the gauge shop to repair it. I will be replacing the bulbs I mentioned above but have little hope it resolves the Speedo.
Wouldn’t expect the motor to be bad with 163k on it. But age could have taken it.
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