Cruise control on jacks
Thread Starter
Teching In
Joined: Aug 2019
Posts: 36
Likes: 5
From: So Fla
Cruise control on jacks Doing a 454 to 8.1/ 4L80 swap in a 1986 motor home with the Howell EFI harness and ECU - everything starts up fine and am waiting on the driveshaft and in the mean time and trying to ops check the cruise control and it will not engage.
Is it possible to engage it in a no load situation (with no driveshaft) ?
I am using Torque Pro and am monitoring VISS and VOSS etc and get it up to 50 mph on speedo output , have 20 ohms from switch to TAC ground pin and everything rings out properly from stalk to TAC connector. No fault code thrown either
Only thing i can think of is maybe the ECU is looking at manifold pressure ??
Is it possible to engage it in a no load situation (with no driveshaft) ?
I am using Torque Pro and am monitoring VISS and VOSS etc and get it up to 50 mph on speedo output , have 20 ohms from switch to TAC ground pin and everything rings out properly from stalk to TAC connector. No fault code thrown either
Only thing i can think of is maybe the ECU is looking at manifold pressure ??
You CANNOT test cruise control on jackstands. If it does set, it will immediately go past the set limit and won't be able to compensate in time. It doesn't look for manifold pressure in any way for cruise control to work. It looks for the brake light switch to be functional, so you have to have both sets of contacts on the switch hooked up, the normally closed to the PCM and the normally open to the TAC. Also, you will need the brake lights hooked up, and if you have LED brake lights, you will need some sort of a load resistor because the LEDs don't have enough resistance, and the PCM will think the brake lights/switch are not working. One last thing, you MUST press the brake pedal at least once during any ignition cycle for it to set, if you don't, and I am thinking you probably didn't since there would be no need with no driveshaft, the PCM will again think the brake switch isn't working and will inhibit the cruise. So basically it would be easier to just try it when you get it out on the road.
Thread Starter
Teching In
Joined: Aug 2019
Posts: 36
Likes: 5
From: So Fla
Ahh yes the brake actuation thing and you nailed it - I didn't need to hit the brakes at all.
I have the brake switches wired properly and have like 20 ohms from light circuit to the low pin on the TAC connector ( there was an existing resistance wire that was left over from the 200 year old vacuum CC system so I retained that leg in the circuit.
Got the call that the driveshaft is ready today so hopefully this weekend all goes good.
Thanks for the explanation on that, there is a really good detailed cruise control explanation Avalanchefanclub but the pedal actuation per ignition cycle wasn't mentioned.
I have the brake switches wired properly and have like 20 ohms from light circuit to the low pin on the TAC connector ( there was an existing resistance wire that was left over from the 200 year old vacuum CC system so I retained that leg in the circuit.
Got the call that the driveshaft is ready today so hopefully this weekend all goes good.
Thanks for the explanation on that, there is a really good detailed cruise control explanation Avalanchefanclub but the pedal actuation per ignition cycle wasn't mentioned.
