Yes, I'm still driving my old 96 Silverado with 6.5 Diesel.Mechanically it's very sound and reliable. Several years ago I replaced the PMD (Fuel Solenoid Driver)with an after market unit that was advertised to cure the problems so many 6.5 owners had with their injection pumps. My PMD is located away from the engine in the front bumper and working great. Recently I've been getting a yellow flashing light on the dash that says "Service Throttle Soon". It's not the check engine light. When the light comes on I loose cruise control and sometimes (not always) the engine de-powers itself. Cycling the key three times cures it and it runs fine until the next episode, which can be two minutes or two hundred miles. This truck is the first year GM was drive by wire for the injector pump. I'm wondering if the control unit attached to gas pedal is going bad? I've been told this component is around $500.00 these days. I'm not getting any codes, and the truck runs great pulling hard even though it's only 190 horsepower. Diesel's have come a long way haven't they. Thanks for your input, Hans

I Believe the "gas" pedal has 2 sensors, and it causes that error when they don't agree with each-other for any reason. I think a good place to start is leaning the connectors at the throttle, and reassembling with dielectric grease.

HJGyswyt wrote:Yes, I'm still driving my old 96 Silverado with 6.5 Diesel.Mechanically it's very sound and reliable. Several years ago I replaced the PMD (Fuel Solenoid Driver)with an after market unit that was advertised to cure the problems so many 6.5 owners had with their injection pumps. My PMD is located away from the engine in the front bumper and working great. Recently I've been getting a yellow flashing light on the dash that says "Service Throttle Soon". It's not the check engine light. When the light comes on I loose cruise control and sometimes (not always) the engine de-powers itself. Cycling the key three times cures it and it runs fine until the next episode, which can be two minutes or two hundred miles. This truck is the first year GM was drive by wire for the injector pump. I'm wondering if the control unit attached to gas pedal is going bad? I've been told this component is around $500.00 these days. I'm not getting any codes, and the truck runs great pulling hard even though it's only 190 horsepower. Diesel's have come a long way haven't they. Thanks for your input, HansAlright, first things first.How do you know it has no codes? Did you check or just because it has no CEL? It could be 2 things:#1 Accelerator Position Sensor or TPS. (most likely the problem)#2 The pedal itself. I would check both with a VOM. Bet it's #1 but I have been wrong before. :BBTW, 96 was not the first year of TBW for the 6.5. 94 was.Yes diesels have come a long way but I still like my 6.5 for a daily driver better than my Duramax. :)In fact after reading your post again I will bet you a dinner it's the TPS. And that is 4x'x as cheap as the pedal. :)Let us know what you find out.

I test drove a new 6.5 in 94. It's still the only stock diesel I've ever seen that could lay rubber from a stand still.

Actually, the accelerator pedal has 3 sensors and it seems that one of the sensors on the accelerator pedal has gone out. Check for any codes with a reader and take care of them first. Then, as suggested, clean the terminals on the accelerator pedal, both the male and female side. For more information on the throttle light, go to The Truck Stop. The people there are great in lending a hand on the 6.2 and 6.5 diesels. Someone there may also have a used accelerator pedal.I had the same issue with my 99 Chevy and it did turn out to be the accelerator pedal position sensor. Good luck on finding the issue.

Turtle n Peeps wrote:How do you know it has no codes? Did you check or just because it has no CEL? It could be 2 things:#1 Accelerator Position Sensor or TPS. (most likely the problem)#2 The pedal itself. I would check both with a VOM. Bet it's #1 but I have been wrong before. :BIn fact after reading your post again I will bet you a dinner it's the TPS. And that is 4x'x as cheap as the pedal. :)Let us know what you find out.I don't know what CEL stands for, but I do have a code reader. Recently with the service throttle light on it has not thrown any codes, but last year a couple times I did get the "check engine light" on and it did indicate throttle position sensor when I looked up the codes online. After clearing them I'd secretly hoped the truck had healed itself and I went on some long trips with my camper without a problem. But recently I've been asking my truck to work hard, more than it probably should, hauling my big cab-over camper and pulling a four horse trailer at the same time. Then last weekend towing my (over 10,000lb) travel trailer. Seems it only happens when it's working very hard, because my empty commutes to and from work never causes anything to go wrong. Where is the Throttle Position Sensor? On the injector pump? I haven't a clue. Thanks everyone for your replies, and I did locate a brand new pedal assembly for $320 at Accurate Diesel on line if I have to go that route. Hope to replace the TPS switch first though. Hans

Any GM exclusive mechanics? 6.5 Diesel ? | Good Sam Community

21 Replies

imadtchmn
Explorer
Jul 22, 2013
Sure does look like it's a pin issue with all that corrosion on it. I had the same type of issue on mine, but it was where the extension went into the main harness, so I hardwired it and no more issues at all. Love my truck.
MARK_VANDERBENT
Explorer
Jul 22, 2013
good to hear!! sold my 95 suburban 6.5 diesel 4 months ago with 526,000 miles on her and man do I miss that truck!!!!!!!!! I try not to think about it.
HJGyswyt
Explorer
Jul 21, 2013
This is a follow up for anyone who subscribed to this thread. My truck has been giving me issue still, I went shopping for newer used trucks with a maximum $20,000 budget and came home discouraged by what I found in that price range. I know I'm anal retentive when it comes to maintenance and cleanliness, but there are a whole lot of people out there who don't appreciate their rolling stock and abuse them.

Anyway, I keep wanting to find my problem, and I hope I'm one step closer now. Appears the PMD I installed two years ago didn't have a weather proof plug on it, which is OK if you remote it to the interior as some have done, but where I went with it in the front bumper the electrical contacts have taken a beating from weather and all the crappy de-icer they love to spray on our roads here in Washington State.

So I cleaned things up, weather proofed the plug, use massive amounts of electrical grease to protect the contacts and installed a new Fuel Solenoid Driver on the heat sink in the bumper. Time will tell if I have re-curing issues again or not. Hope this is the fix I've been looking for.

Made the back of the plug in weather proof here where the wires enter.

My new Fuel Solenoid Driver mounted away from engine heat inside front bumper.

The PMD cooler mounted in the bumper as seen from the front.
nremtp143
Explorer
Jun 18, 2013
I'm glad someone got good GM 6.5s in the '90s. I had a 2500 4x4 Suburban with the 6.5L Turbo that had 7 injector pumps, 4 lift pumps and 2 sets of injectors in 122k miles. I loved the truck, the engine stunk! Stayed on the skid truck more than it did the road for a while.
As far is the OP, like stated above , you may have gotten a bad part. If you can, ohm it out and see if you have a bad one, or return it if it still has a warranty.
Sorry you are having problems, hopefully it will be a very simple fix when it is found.
Jarlaxle
Explorer II
Jun 18, 2013
Try posting on The Diesel Page...they have lots of guys there who know 6.5 Detroits.
imadtchmn
Explorer
Jun 18, 2013
imadtchmn wrote:
From what you have stated, it sounds like an intermittent open in the circuit. Chevys are famous for them. Check and maybe crimp the connections at the pedal so the connection is tight. Also check the circuit with an ohm meter from the pedal to the injector pump and ecm.

I know it's a lot of work, but like you, I love my truck. It has to be something that is common with 3 pedal circuits. That is how many circuits the pedal has in it. If I can find one, I'll send you the wiring diagram..

Sent you a PM with links to the wiring diagrams.
mythree
Explorer
Jun 18, 2013
I also had a 94 with the same problem never ever found it. I ended up blowing the motor like a moron and parted the truck out. It had worked hard its whole life. Farming and rv hauling, I wasn't to mad she had 423,000 thousand miles on her.BEST TRICK I EVER OWNED.
_40Fan
Explorer
Jun 18, 2013
Also new means, Never Ever Worked. Might just be a bad part.
_40Fan
Explorer
Jun 18, 2013
Heck, he was going "up" the freeway!

I'd file a claim with NTSB just because of the issue it could have caused.

I'll do some more digging and see if I can come up with anything.
45Ricochet
Explorer
Jun 18, 2013
Sorry OP, I subscribed just to see who had the best guess.
You got more stones than me though in shutting her down going down the freeway :E
Good Luck
Rick