Erratic speedo at Idle
Erratic speedo at Idle
My 424 is showing a fluctuating and erratic speed anywhere from 0 to 40 kmh when stationary at idle even when disconnected from my dakota digital gps speed sender. When I'm moving it shows correct speed.
There are 2 speed signal wires:
B5 "Vehicle Speed Sensor Signal High"
B6 "Vehicle Speed Sensor Signal Low"
The problem still occurs when both wires are disconnected.
If I ground the Blue/White B5 "Vehicle Speed Sensor Signal High" wire it goes straight to 0 km/h.
What is causing this problem?
There are 2 speed signal wires:
B5 "Vehicle Speed Sensor Signal High"
B6 "Vehicle Speed Sensor Signal Low"
The problem still occurs when both wires are disconnected.
If I ground the Blue/White B5 "Vehicle Speed Sensor Signal High" wire it goes straight to 0 km/h.
What is causing this problem?
- vlad01
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Re: Erratic speedo at Idle
Probably RFI noise, Sounds like a simple pull-up/pull-down resistor should fix the issue.
I'm the director of VSH (Vlad's Spec Holden), because HSV were doing it ass about.
Re: Erratic speedo at Idle
Thanks.
I tested it again this time by pulling the "B5 "Vehicle Speed Sensor Signal High" wire from the back of the ECU itself. Every time I disconnected the wire the fluctuating stops.
I assume I need to make a pull down resistor. Do I just add a resistor to the speed sensor wire and ground?
I tested it again this time by pulling the "B5 "Vehicle Speed Sensor Signal High" wire from the back of the ECU itself. Every time I disconnected the wire the fluctuating stops.
I assume I need to make a pull down resistor. Do I just add a resistor to the speed sensor wire and ground?
Last edited by h4x0r on Tue Sep 17, 2019 9:44 am, edited 1 time in total.
- vlad01
- Posts: 7803
- Joined: Mon Oct 08, 2012 6:41 pm
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VP I executive
VP II executive
VP II executive #2
VR II executive - Location: Kyneton, Vic
Re: Erratic speedo at Idle
How do you have the wiring configured? Sounds like something isn't wired right. Even though a resistor should in theory patch the issue there must be a cause to it.
I'm the director of VSH (Vlad's Spec Holden), because HSV were doing it ass about.
Re: Erratic speedo at Idle
This is my plug: download/file.php?id=15460&mode=view
I have 2 VSS wires:
B5 "Vehicle Speed Sensor Signal High" is connected to the output of my GPS Dakota Digital.
B6 "Vehicle Speed Sensor Signal Low" is not connected to anything.
Correct speed works while driving but when I stop at Idle I can get fluctuating speeds.
I have 2 VSS wires:
B5 "Vehicle Speed Sensor Signal High" is connected to the output of my GPS Dakota Digital.
B6 "Vehicle Speed Sensor Signal Low" is not connected to anything.
Correct speed works while driving but when I stop at Idle I can get fluctuating speeds.
- delcowizzid
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Re: Erratic speedo at Idle
Plug an old gearbox reluctor sensor on the wires and see if it goes away at idle .You might just have issues cause there isn't a resistance over the wires so the wires turned into an antenna and picking up electrical noise
If Its Got Gas Or Ass Count Me In.if it cant be fixed with a hammer you have an electrical problem
Re: Erratic speedo at Idle
Maybe B6 needs to connect to the output ground of your GPS?h4x0r wrote:This is my plug: download/file.php?id=15460&mode=view
I have 2 VSS wires:
B5 "Vehicle Speed Sensor Signal High" is connected to the output of my GPS Dakota Digital.
B6 "Vehicle Speed Sensor Signal Low" is not connected to anything.
Correct speed works while driving but when I stop at Idle I can get fluctuating speeds.
Joe.
Re: Erratic speedo at Idle
The dakota digital GPS speed sender only has a ground for its own power supply: http://www.dakotadigital.com/pdf/GPS-50-2.pdfj_ds_au wrote: Maybe B6 needs to connect to the output ground of your GPS?
Grounding B6 showed no effect when I tested it.
I have done some DIY test shielding of the B5 wire with aluminum foil Seems to be happening less.
Anyone know how to shield it properly or put a resistance on it to eliminate interference? Other online posts say its common for VSS to pickup interference from injector pulses etc.
Re: Erratic speedo at Idle
I think you might be right.delcowizzid wrote:Plug an old gearbox reluctor sensor on the wires and see if it goes away at idle .You might just have issues cause there isn't a resistance over the wires so the wires turned into an antenna and picking up electrical noise
Any idea how to shield or fix the resistance?
- delcowizzid
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Re: Erratic speedo at Idle
You could get some shielded single core wire and earth the shield at one end its how a lot of tps signal wires are sheilded
If Its Got Gas Or Ass Count Me In.if it cant be fixed with a hammer you have an electrical problem