Cruise Control Not Working

[knh208]

I've owned my 6.5 for a shade over 5 years now. Last year in February, I moved my PMD from the pump to a heatsink in the bumper. I used a chitty EDAM cable that worked poorly at best. Cost me a $50 tow, a week of diagnostics in the driveway, and eventually a new cable.

Even with all of the troubles that I had with that cable, the cruise control always worked until the truck stalled. The truck was stalling because the cable was garbage, and would lose connection. All I had to do was open the hood and bend the cable around a bit, and it would start right up again. Still a major PITA!

After the new cable arrived, I drove for a couple weeks without any issues. Then, while driving along one day, cruise control would not engage. I started by checking for voltage to and from the multifunction switch. If you ever decide to perform this type of check, be careful with the hazard light switch sticking out of the top of it. Ask me how I know... Long story short, voltage was good in all positions.

The next thing that I did was check voltage to the PCM while swapping in my Heath GL4. I get voltage to on, resume and set pins on the PCM.

The check engine light was always on with the stock PCM, due to a dead MAF sensor. Heath set me up with an F program, so I have the MAF disconnected. Since installing, the check engine light has not come on, other than at startup to show that the bulb is good.

I recently picked up an Autel MaxiTrip TP100 from Princess Auto. It seems to work well. It shows me quite a few parameters while the engine is running and will check DTC's. It tells me there are no codes. Typically, I have used a SnapOn scanner or TechII for checking codes, but my mechanic friend has been hard to meet up with.

I can think of a few things that could be causing the cruise control to not work:
1) Bad PCM - when I installed the Heath GL4, I assume this ruled out the possibility, because its unlikely two of them would be bad.
2) Bad wiring in cruise circuit - voltage at the PCM suggests this is not the case
3) Bad PMD - I am not getting any codes. The only times the truck has ever stalled were due to bad lift pump shortly after purchase and due to bad EDAM cable. All of these events were prior to cruise control quitting.
4) Bad brake switch - Again, I am not getting any codes, my brake lights work, and when I tap the brakes while moving, the idle speed decreases. This tells me that the PCM is seeing the brake switch signal as it should.
5) Bad APP - No codes. Never had any issues that would suggest this is the problem.
6) Bad PMD cable - The only thing that really changed between 100% cruise operation and cruise control failure was the cable, and with the other one being so poor, I have been hesitant to swap it back in for testing.

So, now that I have prepared a novel on the subject, I'm going to call on you guys to help me diagnose this. I am going to scan with the TechII as soon as I can to see if there are any codes that the Autel scanner will not read. The only other things that I can think to try now are switching the old PMD cable back in, and getting a good known PMD to try.

Am I missing anything? :mad2:

Thanks in advance!!!

 

[ak diesel driver]

I believe the brake pedal switch is or has 2 parts one for brakes and one for cruise. That's where I would start. I would also get Car Code as a scanner it will let you do TDCO also.

 

[ak diesel driver]

Did you do a KOKO like in the instructions? Just wondering if that might affect cruise capability.

 

[Slim Shady]

You need a wiring schematic to check your cruise out. You are probably not getting the vss input you need to the cruise unit. I don't know whether the unit is a stand alone or built into the PCM.

The basics of a cruise unit are vss input, power and brake cut out switch.

 

[WarWagon]

Don't rule out any parts because of no codes or that they were replaced.

I would check the cable connectors for corrosion or other damage left over from the 1st cable. Then suspect the 'used' PMD that was moved. They die without a code.

 

[matuva]

Is your cruise switched on ? I mean may be you pushed lfet this little button on the signal switch and now your cruise ids off ?

 

[Crankme69]

My cruise control on my 95 was giving me fits after I relocated the my FSD cooler & PMD to the bumper.

This all started after I purchased & installed a new Dtech PMD with the original #9 stanadyne resister. I noticed upon installation that the old resister did not want to set completely flush in the new Dtech PMD but I was able to get the plug on & locked. The truck started fine but after that my cruise would work like every so often like it was possessed...So I purchased a new #9 resister from Dtech & installed it along with the new Dtech PMD. The new Dtech resister fit flush deep into the Dtech PMD the plug fit perfect no fighting with the cable plug to get it locked and my cruise has worked flawlessly ever since I replaced the resister.

Interesting enough, before I purchased the new resister I called & talked with what I thought were tech's at both Dtech & Stanadyne & neither of these so called techs had ever heard of the PMD having any effect on the cruise control...

That didn't exactly make me feel warm & fuzzy some tech service that is

 

[Dave01]

I had trouble with my cruise a few months ago, turned out it was caused by a failing battery. The cruise would drop out, or not engage at all, at what seemed like random times. Then I realized it was OK when I wasn't using a lot of electric accessories, but would fail when I was drawing a lot of power. It turned out I had a bad battery, had punched my battery mod bolt through and was leaking acid, voltage was very low. New set of batteries and the cruise has worked perfectly ever since.

 

[knh208]

I believe the brake pedal switch is or has 2 parts one for brakes and one for cruise. That's where I would start. I would also get Car Code as a scanner it will let you do TDCO also.

As far as I know, its one part for brakes, and one part for PCM. PCM = idle speed while coasting / braking as well as cruise cut-out. Am I correct, or is there a third part?

 

[knh208]

Did you do a KOKO like in the instructions? Just wondering if that might affect cruise capability.

Instructions for what procedure?

 

[knh208]

You need a wiring schematic to check your cruise out. You are probably not getting the vss input you need to the cruise unit. I don't know whether the unit is a stand alone or built into the PCM.

The basics of a cruise unit are vss input, power and brake cut out switch.

I do have the wiring schematic for the truck. Cruise control is built into the PCM.

 

[knh208]

Don't rule out any parts because of no codes or that they were replaced.

I would check the cable connectors for corrosion or other damage left over from the 1st cable. Then suspect the 'used' PMD that was moved. They die without a code.

I've hit the connectors with dielectric grease a couple times to makes sure the connection is good. I certainly do suspect the PMD, and would like to get a known good one from someone in the Saskatoon area.

 

[knh208]

My cruise control on my 95 was giving me fits after I relocated the my FSD cooler & PMD to the bumper.

This all started after I purchased & installed a new Dtech PMD with the original #9 stanadyne resister. I noticed upon installation that the old resister did not want to set completely flush in the new Dtech PMD but I was able to get the plug on & locked. The truck started fine but after that my cruise would work like every so often like it was possessed...So I purchased a new #9 resister from Dtech & installed it along with the new Dtech PMD. The new Dtech resister fit flush deep into the Dtech PMD the plug fit perfect no fighting with the cable plug to get it locked and my cruise has worked flawlessly ever since I replaced the resister.

Interesting enough, before I purchased the new resister I called & talked with what I thought were tech's at both Dtech & Stanadyne & neither of these so called techs had ever heard of the PMD having any effect on the cruise control...

That didn't exactly make me feel warm & fuzzy some tech service that is

Interesting. I'll have to dig the resistor our and check it out. Still a dealer installed Stanadyne unit that I moved to the bumper. Again, anyone in Saskatchewan that has an easily accessible known good PMD that I can try, I would REALLY appreciate it!

 

[knh208]

I had trouble with my cruise a few months ago, turned out it was caused by a failing battery. The cruise would drop out, or not engage at all, at what seemed like random times. Then I realized it was OK when I wasn't using a lot of electric accessories, but would fail when I was drawing a lot of power. It turned out I had a bad battery, had punched my battery mod bolt through and was leaking acid, voltage was very low. New set of batteries and the cruise has worked perfectly ever since.

Batteries are definitely weak, and I plan to change them within a week. We'll see what that yields.

 

[ak diesel driver]

Instructions for what procedure?

When you installed your GL4 it should have come with instructions on how to do a KOKO. key on key off It let's the pcm select a TDCO. Don't know if that would matter or not for your cruise. If you don't have it get Car Code to set your TDCO where you want it. -1.94 is supposed to be optimal performance. Some are using -1.5 so it's not so rattly when it's cold.

 

[knh208]

When you installed your GL4 it should have come with instructions on how to do a KOKO. key on key off It let's the pcm select a TDCO. Don't know if that would matter or not for your cruise. If you don't have it get Car Code to set your TDCO where you want it. -1.94 is supposed to be optimal performance. Some are using -1.5 so it's not so rattly when it's cold.

Yes, I followed the instructions that came with the GL4. Autoenginuity is on my list of things to buy with Christmas money. Don't really need it when I know there is a TechII available, but I would love the convenience!

 

[knh208]

I just thought of one more thing that I am curious about before I start tearing out parts. My high idle still works, and switches off with the brake pedal. Does that verify that the brake switch is good, or is there a 3rd circuit that I need to check that is for cruise only?

 

[knh208]

Had some time...

I finally had some time to work on my truck while the ol' lady is out of town. In my original post, I made a checklist of all the items that I thought could make my cruise control fail:

I can think of a few things that could be causing the cruise control to not work:
1) Bad PCM - when I installed the Heath GL4, I assume this ruled out the possibility, because its unlikely two of them would be bad.
2) Bad wiring in cruise circuit - voltage at the PCM suggests this is not the case
3) Bad PMD - I am not getting any codes. The only times the truck has ever stalled were due to bad lift pump shortly after purchase and due to bad EDAM cable. All of these events were prior to cruise control quitting.
4) Bad brake switch - Again, I am not getting any codes, my brake lights work, and when I tap the brakes while moving, the idle speed decreases. This tells me that the PCM is seeing the brake switch signal as it should.
5) Bad APP - No codes. Never had any issues that would suggest this is the problem.
6) Bad PMD cable - The only thing that really changed between 100% cruise operation and cruise control failure was the cable, and with the other one being so poor, I have been hesitant to swap it back in for testing.

I replaced my brake switch. Stupid $6 part is more work to replace than its worth! Make sure you have atleast two new clips when you tackle this job. They break easily on the way off, and also on the way back on! For all this work, the cruise control issue is still not resolved.

The second thing I did was swap in my old PMD cable that caused stalling issues due to a broken wire. I replaced the old cable originally because of a stalling issue. Cruise control worked 100% with the old cable before I took it out. This test was also a failure. Cruise control is still not functioning. I have switched back to the new cable because it is far more reliable.

This leaves me with two possible options: PMD, or APP. Still need to get to a proper scan tool for a test.

Still open to any advice!

Cheers,

Kevin

 

[Dave01]

Batteries are definitely weak, and I plan to change them within a week. We'll see what that yields.

Did you every get new batteries? What does your voltage read at key on, and at idle?

 

[knh208]

Did you every get new batteries? What does your voltage read at key on, and at idle?

Sure did! Two shiny new ones from Costco! Their warranty is essentially a "batteries for life" program. If you walk in with a battery purchased within the previous 36 months, they give you a cash refund. This allows you to go buy new ones off the shelf with a new warranty. The employees in customer service here have no interest in testing anything. They take your word for it.

As for voltage, it reads 13V with key on, and 14V at idle.

The old batteries were so bad that on the day I replaced them it was -23°C (-10F), block heater and oil pan heater were plugged in for 3 hours, and it didn't turn over fast enough to fire once.

The new batteries have enough snap to start the truck at -20°C (-4F) without being plugged in.... and even with my dead injectors. At that temperature, it is near 2 minutes before all cylinders catch and the cloud of white smoke clears.