- Jul 21, 2017
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Hey, I’ve been having some issues with my cruise and I think it has something to do with the VSS wiring. Does anybody know how to check to see if the cruise control system is receiving a signal from the VSS?
Electrical Cruise control
- Thread starter Brad Hanks
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On a 1990, the signal from the cruise control is relayed to the ECU and cruise control amplifier together. The ECU uses it to prevent stalling when coming to a stop. If there is an issue with the VSS, you can dump the codes and will get a code 28 from the ECU. If no code, then the ECU is receiving a proper signal, and you would assume the speed control module is as well.
www.stangnet.com
If you assume your system should work, I would start at the wiring off the column. The horn/cruise button contacts tend to corrode and make a bad connection. You can just remove the column trim, located the cruise/horn wiring, and test for the proper resistance values received on the wiring. If that checks out, you'll want to verify the vacuum dump switch on the brake pedal seals when the pedal is at rest, and you'll want to test the clutch deactivation switch and made sure the state changes as you press and release the clutch.
Short of that, there are specific cruise testers you can find on ebay to help troublshoot. Info is in the link above.
Foxbody Cruise Control information, location, wiring diagrams
Done a little research into this and figured what I learned should be put into a thread and added to the tech sticky. As you can imagine, nobody really gives much thought to cruise control on these cars, so many searched threads had dead ends. So many this will help someone out down the road...
www.stangnet.com
If you assume your system should work, I would start at the wiring off the column. The horn/cruise button contacts tend to corrode and make a bad connection. You can just remove the column trim, located the cruise/horn wiring, and test for the proper resistance values received on the wiring. If that checks out, you'll want to verify the vacuum dump switch on the brake pedal seals when the pedal is at rest, and you'll want to test the clutch deactivation switch and made sure the state changes as you press and release the clutch.
Short of that, there are specific cruise testers you can find on ebay to help troublshoot. Info is in the link above.
- Jul 21, 2017
- 92
- 6
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Hey thanks for the reply. So I won’t have codes anymore I’m running an aftermarket ecu, but I was told by them the cruise is separate and still should work. I know the horn still works so not sure of that makes a difference. How do you check the clutch switch and brake dump valve?
You’ll have to use a multimeter on the clutch switch. It’s in the right side near the gas pedal and depresses against the clutch quadrant. Set your meter on continuity and press and release the clutch. You should see it open and close.
for the brake vac switch, you could remove the vac line and install another vac line and use tgar to blow into the line. You should not be able to blow with your foot off the brake, but if you press the pedal it should open and allow you to blow thru.
The cruise is standalone from the ECU, but the vss wiring is shared. Did you remove any wires?
for the brake vac switch, you could remove the vac line and install another vac line and use tgar to blow into the line. You should not be able to blow with your foot off the brake, but if you press the pedal it should open and allow you to blow thru.
The cruise is standalone from the ECU, but the vss wiring is shared. Did you remove any wires?
- Jul 21, 2017
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- Jul 21, 2017
- 92
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I have the dash out right now due to some other repairs so they should be pretty easily found and tested while I’m there.
- Jul 21, 2017
- 92
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I don't think the Megasquirt PnP units come with a VR conditioner in them. Otherwise you could pull up the speedo guage on tuner studio and verify it's receiving a signal. Is that right @a91what ?
- Jul 21, 2017
- 92
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To clarify it DOES have 2 vr conditioning units in it... but the MS2 firmware does not support VSS inputs. It can be done with some programming magic but I would need to know the bus HZ that the CPU uses on those inputs and a few other things to make it work but again the firmware does not support it.
If you have a multimeter with a HZ input you can place it across those leads to the VR sensor and watch the pulses.
Or with a multimeter set to AC voltage across the two VR wires you should notice an increasing AC voltage with speed
If you have a multimeter with a HZ input you can place it across those leads to the VR sensor and watch the pulses.
Or with a multimeter set to AC voltage across the two VR wires you should notice an increasing AC voltage with speed
I guess bowing that, you can pull the harness off the cruise amplifier and hook your multimeter to the VSS wiring. It will be in the wiring diagrams in the link above.
then you’ll need to spin the VSS. You can put the rear axle on jackstands and just drive the car, or pull the VSS and manually spin it. Then you can verify if you have a signal at the cruise amplifier
then you’ll need to spin the VSS. You can put the rear axle on jackstands and just drive the car, or pull the VSS and manually spin it. Then you can verify if you have a signal at the cruise amplifier
- Jul 21, 2017
- 92
- 6
- 8
- Jul 21, 2017
- 92
- 6
- 8
- Jul 21, 2017
- 92
- 6
- 8
In case you were curious the clock spring contacts were pretty rough.On a 1990, the signal from the cruise control is relayed to the ECU and cruise control amplifier together. The ECU uses it to prevent stalling when coming to a stop. If there is an issue with the VSS, you can dump the codes and will get a code 28 from the ECU. If no code, then the ECU is receiving a proper signal, and you would assume the speed control module is as well.
Foxbody Cruise Control information, location, wiring diagrams
Done a little research into this and figured what I learned should be put into a thread and added to the tech sticky. As you can imagine, nobody really gives much thought to cruise control on these cars, so many searched threads had dead ends. So many this will help someone out down the road...
If you assume your system should work, I would start at the wiring off the column. The horn/cruise button contacts tend to corrode and make a bad connection. You can just remove the column trim, located the cruise/horn wiring, and test for the proper resistance values received on the wiring. If that checks out, you'll want to verify the vacuum dump switch on the brake pedal seals when the pedal is at rest, and you'll want to test the clutch deactivation switch and made sure the state changes as you press and release the clutch.
Short of that, there are specific cruise testers you can find on ebay to help troublshoot. Info is in the link above.
Attachments
not at the CC unit.. I know where they are down at the ECU. you can just google A9L ecu pinout and look on veryuseful.com
- Jul 21, 2017
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It's pin 3 and 6 at the ECU.
Looks like at the cruise amplifier it's a Dark Green/white wire and Orange/Yellow wire.
Looks like at the cruise amplifier it's a Dark Green/white wire and Orange/Yellow wire.
- Jul 21, 2017
- 92
- 6
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