Troubles with cruise

[befarrer]

I am trying to install the later model GM electronic cruise in my 86 Fiero, which never had cruise to start with, but I cannot get it to do anything. I am running a Quad 4 HO with a 5-speed getrac (with optical VSS), and a 1990 Grand AM Quad 4 HO ECM last 3 digits on the ECM are 404.

Everything is wired up right at the cruise plug, everything gets voltage at the right times. The only things I dont know about are the cruise disable wire that goes to the PCM, according to Sinister Fiero's instructions, it gets grounded or left open depending on model, and I have tried both. I am also confused as to why he uses a relay, I initially wired it up according to a factory wirirng diagram, which has one of the wires hooked into the brake light cruise switch (live with brakes not on and dead with them on), but using his relay, it grounds the wire with the brakes off, and is live with the brakes on?? Also according to his wiring chart, the relay is always on unless the brakes are applied.

Sinister's wiring is here:

http://www.gmtuners.com/files/index.htm

A wiring diagram and instructions on how to install in a non-gm motorhome are here, nowhere do they list a relay, and I see no grounds going to the cruise module other than the ground wire.

I dont think any of this is my problem though, I have been reading that the cruise module wants a 0-5V 4000PPM VSS signal, the speedometer needs a 0-9V 4000PPM signal, and that is the only VSS output on my ECM, I am thinking that my VSS signal is too high of a voltage for my cruise module to read. Is this possible? I have confirmed I am getting a VSS signal at the module, and with the key on, and engine off, it reads 9.2V.

IF you can access this site, there is a link to a wiring diagram for my ECM here, it is in the 2nd post down XXXX707:
http://www.quad4forums.com/forums/showt ... m+diagrams

[Sinister Fiero]

First off, just want to be clear on a couple of things. NO GM transmission ever made use of an "optical" VSS type speed sensor. It is either a reed switch type (as in the case of stock Fiero) or a permanent magnet type (as in the case of later-than-fiero model transmissions).

AFAIK, the only optical type VSS speed sensor GM ever used was in early 80's GM cars where it was mounted to the back of the speedometer.

Concerning the VSS input signal, I think the module is simply looking for a Hi/Lo input that pulses 4000 times per mile. I don't think it cares much if it is 0-9 volts (I could be wrong?) or 0-5 volts; as long as it is at least 5 volts (Hi) but not more than battery voltage; and the Lo is GROUND. It is very important that the "pull down" (Lo) pulse is ground; as it has been explained to me what these circuits need in order to operate properly.

Do you have anything else running off the ECM's VSS 4000 ppm output such as the Fiero's speedometer? If so, do you have this cruise module wired/spliced directly up to the output from the ECM before that output goes thru a conditioner/buffer circuit for the Fiero speedo? You could always try disconnecting everything from the ECM VSS output except for the cruise module and see if it works. That might tell you if something else you have hooked up to the VSS circuit is interfering with the cruise unit.

Concerning the brake relay, the electronic stand-alone cruise control modules need two brake switch inputs in order to work. One input (ppl wire) needs to see 12v + voltage with the ign key on and no brakes applied and needs to see that signal drop to GROUND when brakes are applied; and the other (wht wire) expects to see the opposite. The relay wiring method in my instructions was put in there to simplify wiring and avoid certain potential Fiero wiring issues, especially in manual transmission applications. If you do not install and wire up the relay as instructed in my wiring directions, the cruise unit will probably not work at all.

If all the above checks out but your cruise still doesn’t work, you may want to perform the following checks with the cruise module unplugged…

1) Do you have 12v + voltage coming into pin F at all times the key is on regardless of if the brakes are applied or not and what position the cruise switch is in?

2) Do you have 12v + voltage coming into pin A with the cruise switch in the ON, RES/ACC, and SET/COAST positions with the key on? (NOTE: when cruise switches start to fail, they may drop voltage on this circuit when you press the RES/ACC and SET/COAST buttons and this will cause the cruise control to become inoperable).

3) Do you have 12v + voltage coming into pin B ONLY when you press the Set/Coast button with the key on?

4) Do you have 12v + voltage coming into pin C ONLY when you press the RES/ACC button with the key on?

5) Do you have 12v + voltage coming into pin D any time the key is on except when the brakes are applied and/or when you step on the clutch pedal; and does this signal drop to ground when you apply the brakes and/or step on the clutch pedal? (Test this circuit using a test light hooked to POS battery voltage so you can verify a good ground with brakes applied and/or clutch pedal depressed – test light should light up brightly NOT dim when it comes on)

6) Do you have good grounds going to pins E and H?

7) Do you have GROUND coming into pin G any time except when you apply the brakes and/or step on the clutch pedal? (Test this circuit using a test light hooked to POS battery voltage so you can verify a good ground with brakes NOT applied and clutch pedal not depressed). Then does this circuit show 12v + voltage with brakes applied and/or when the clutch pedal is depressed?



NOTE: These electronic cruise control modules need to see both brake inputs switch state at the same time (oppositely to each other) when the brakes are applied. They also need to see that the brakes are applied at least once per key cycle before they will start working. This means you simply cannot start the car and take off down the road without touching the brakes and expect the cruise control to work. It needs to see that the brakes were applied at least once after turning the key on / starting the engine before it will enable cruise operation.

These electronic cruise control modules will only work above a certain vehicle speed (usually 35mph). If you try setting the cruise at slower speeds, the unit will not function.

The tension/slop on the cruise control cable hookup to the throttle body must be properly set or the cruise control may not function. There can be some but very little slop with closed throttle, but there should not be tension on the cable with closed throttle that could prevent the throttle from closing all of the way. Excessive slop can result in the system being inoperable.

Let me know if you have any other problems.

-ryan

[befarrer]

The only thing I have hooked up to my ECM VSS signal is my speedometer, I am using no buffer as I am using a Pontiac Sunbird instrument cluster which has a 1 wire speedo in it. My VSS is the magnet one used on later models, I knew it was different from the Fiero style, just couldnt remember what type lol.

[Sinister Fiero]

The only thing I have hooked up to my ECM VSS signal is my speedometer, I am using no buffer as I am using a Pontiac Sunbird instrument cluster which has a 1 wire speedo in it. My VSS is the magnet one used on later models, I knew it was different from the Fiero style, just couldnt remember what type lol.

Ok, well that speedo should be able to share the VSS output signal from the ECM with the electronic cruise module, no problem. If your speedo is registering speed correctly, then that signal should be ok for the electronic cruise to use and your problem is most likely elsewhere.

Let me know what you come up with.

-ryan

[befarrer]

Concerning the brake relay, the electronic stand-alone cruise control modules need two brake switch inputs in order to work. One input (ppl wire) needs to see 12v + voltage with the ign key on and no brakes applied and needs to see that signal drop to GROUND when brakes are applied; and the other (wht wire) expects to see the opposite. The relay wiring method in my instructions was put in there to simplify wiring and avoid certain potential Fiero wiring issues, especially in manual transmission applications. If you do not install and wire up the relay as instructed in my wiring directions, the cruise unit will probably not work at all.

-ryan

Stupid question, but I have to make both wires have a ground when they are not live? I just have the brake light wire spliced into my brake light wire at the brake switch, I dont know if that one drops to ground with the brakes off or not, I dont think so. The other one, I have running to the other connector on the brake switch, so that one does not. I will add your relay tonight and see if it works.

Thanks,

[Sinister Fiero]

Concerning the brake relay, the electronic stand-alone cruise control modules need two brake switch inputs in order to work. One input (ppl wire) needs to see 12v + voltage with the ign key on and no brakes applied and needs to see that signal drop to GROUND when brakes are applied; and the other (wht wire) expects to see the opposite. The relay wiring method in my instructions was put in there to simplify wiring and avoid certain potential Fiero wiring issues, especially in manual transmission applications. If you do not install and wire up the relay as instructed in my wiring directions, the cruise unit will probably not work at all.

-ryan

I have to make both wires have a ground when they are not live?

Yes. I had an instance on a Fiero swap I did in the past where I hooked up to an existing Fiero brake switch wire that output the 12v + signal when I needed it to but didn't quite drop to ground when it was off. And this caused the cruise not to work. Apparently the module wants to see a good ground on these circuits when they are not "hot".

I just have the brake light wire spliced into my brake light wire at the brake switch, I dont know if that one drops to ground with the brakes off or not, I dont think so. The other one, I have running to the other connector on the brake switch, so that one does not. I will add your relay tonight and see if it works.

Thanks,

I highly recommend just wiring the cruise up using the relay method and not trying to use both brake switch outputs.

[befarrer]

Ok, I have everything wired up as per the instructions, and all wires check out fine at the cruise connector, and still I got no workie, so either the module is no good, or ms VSS signal has to be reduced to a 5V signal.

I had way less troubles doing the wiring on my engine swap than this. lol

[Sinister Fiero]

Ok, I have everything wired up as per the instructions, and all wires check out fine at the cruise connector, and still I got no workie, so either the module is no good, or ms VSS signal has to be reduced to a 5V signal.

I had way less troubles doing the wiring on my engine swap than this. lol

If all you have hooked up to the PCM 4k ppm VSS output is your Sunbird speedo and this cruise module, I don't see why it isn't working. The Speedo is probably putting the 12v in there, but even if it was, the cruise should still work since all GM speedos of that era work the same (pretty much). Where did you get the cruise module? If you got it from me, I tested it before I shipped it out so I know it works. But if you got it from another car, it could be bad. I have come across a couple that were bad in the last few months.

[befarrer]

I am thinking it is bad, I got mine from the junkyard a few months ago, cant even remember what vehicle, just that it was a FWD GM. I got another one from a 99 Grand Am. How do you test them? My GF has a 99 Grand Am V6 with cruise, I was thinking of just plugging into that. I may do that with the new module before I put it in my Fiero since it was from the same car.

[Sinister Fiero]

I am thinking it is bad, I got mine from the junkyard a few months ago, cant even remember what vehicle, just that it was a FWD GM. I got another one from a 99 Grand Am. How do you test them? My GF has a 99 Grand Am V6 with cruise, I was thinking of just plugging into that. I may do that with the new module before I put it in my Fiero since it was from the same car.

What I do to test them is plug them into a car that uses the same type of module (might have to swap cables tho).