DTC 18, 35, 54 on 6.5 ltr. Turbo Diesel in 1995 C-3500

[Lance1030]

On a recent trip, my truck started missing. The SES light would occasionally come on and the truck would run rough. The frequency of this seemed to increase. I found an auto parts store and checked the codes and came up with the following: 17,18, 35. In an effort to fix this, I Changed the PCM to a SS Diesel unit which consists of a Standyne PCM mounted on a heat sink mounted to the upper intake bolts. After installing this on a test drive the SES light returned. I then changed the fuel filter. Still the SES light came on.

Currently, when I start it seems to run fine for a while. After about 10-15 minutes of driving and usually under part throttle acceleration, it will miss and set the SES light. When I read the codes I seem to consistently get 18, 35, and 54. I have taken the following steps to try and address the issue 1. Changed fuel filter again. 2. Changed out the lift pump with a NAPA unit. 3. Checked battery connections. 4. Removed the upper intake and removed the black filter unit and checked the wiring as best I could. 5. Re did the ground from the wiring block on the firewall to the engine. 6. Re seated the connectors going to the ECM behind the glove box. None of these seemed to have any effect on the problem.

Any comments or suggestions as to where to go from here would be much appreciated!

[rjwest]

Link to codes. http://www.troublecodes.net/GM/

[Lance1030]

>Link to codes. http://www.troublecodes.net/GM/

RJwest, Thanks for the link that's a neat site.

[tom.mcinerney]

Lance -

The harness grounds esp at rear psgr side engine, and the battery-block grounds are problemmatic, particularly if your codes are not for obviously related issues.
The ignition switch on this year is oft worth replacing [unless renewed all ready], it powers lots critical items/circuits...and is known to fail.
Good luck, keep updating.

[Lance1030]

Tom Mac

Thanks for the reply. I went out this evening and decided to see if I could induce a failure by moving the ignition switch. I don't know if the switch caused this or not, but now when I try to start the truck, the starter grinds for about 2-3 times as long as usual, then when the truck starts it makes a very loud clatter followed by an immediate setting of the SES light and a code 18. The truck doesn't always start, but always seems to set the code 18. Code 18 is listed as - Pump Cam Reference Pulse Error. This happened five times or so in sequence while I was in my driveway. I would clear the code and repeat the process. I also seem to notice a fuel smell as if the truck were trying to run rich. It was dark, so I couldn't tell if it was smoking due to too much fuel. I also tried using my wife's key to see if I could cause some change due to the ignition switch but didn't notice any difference.

I guess the "good" news is that now that the problem is getting worse it should be easier to find

[rjwest]

There are many more experienced Injector members
than myself. Usually GM would replace the pump
for this problem under warrenty. If less than 120 k miles.

Also, may be the sensor is dirty ( have you been running colored fuel / ) was told that will disclor sensor.

Anyway, you may be ablt to clean/replace semsor.
on truck, not sure.

[Kennedy]

The simple answer= Time for a pump.

[DmaxMaverick]

Also, may be the sensor is dirty ( have you been running colored fuel / ) was told that will disclor sensor.

I've heard of this a few times, and don't believe a word of it. It's my experience that this is an excuse some dealers will use to deny warranty coverage. I know of several (about a dozen) 6.5's of all years that have been using dyed fuel (legally) from day one, and they don't behave any different than those that use on-road fuel. One pump failed and the dealer tried this excuse. Didn't fly with this farmer. A letter from Stanadyne to the dealer got the pump replaced under warranty.

Don't believe everything the dealer tells you.


Lance
JK is probably right. Sounds like the pump has gone south.

[Lance1030]

Thanks for the replies. I have not been using dyed fuel, and unfortunately I now have 126,000 miles on the truck, so I guess a pump is in order.

[ucdavis]

Hate to say it but that was precisely the sequence when my pump bought it. Grounds is your only hope for a reprieve, and you should probably go thru grounds w/126K on rig anyway (undo, brighten & snug down all grounds; maybe add some No-Ox grease to prevent corrosion from messing up electrical signal in future). If the grounds are not at fault, pump it.

[Lance1030]

UCDavis,

Thanks for the reply. Actually that's helpful. I don't mind spending the money on the pump, but I'd hate to unnecessarily.

[tom.mcinerney]

Yeah, Lance, it doesn't hurt to do some maintenance about now. Many of these trucks do fine for 100K, then get a sad syndrome repetitive failures. Electric engine controls need good alt+batt+cables+harness grounds. All diesels need clean, lubricating fuel. The cooling system needs good air and coolant flow to work.

[Lance1030]

Tom Mac

Thanks for the info. I've checked most of the grounds and I plan to check the rest soon. I'm waiting for my mechanic to have a chance to replace the IP. I'll post again after the IP is replaced. One additional thing we found is that the coolant temp sensor (the one which feeds the computer, not the one which feed the gage on the dash) was bad. I plan to have this replaced as well. I suspect this may have contributed to less than ideal running.