Challenge, figure this one out [Archive] - Diesel Place : Chevrolet and GMC Diesel Truck Forums

: Challenge, figure this one out


byrdman73
08-29-2005, 08:24 PM
Engine codes P0236, P0238, P0251, P0238. What is causing the codes and why does it run like crap half the time?

1996 GMC K3500 Crew cab dually 4x4 automatic 270k miles

Sometimes it runs REAL good, sometimes it runs like Star Jones in the NYC marathon. Vacuum at the actuator stays bewteen 23 and 15 in-hg. the actuator is good, holds vacuum. I replaced the turbo waste gate solenoid because the old one was working about as hard as Britney Spears works on her singing. Turbo boost fluctuates between 1 and 17ish (gauge only goes to 15). I'm getting about 12.5 mpg unloaded. I replaced the fuel filter within the past 500 miles. The SES light comes on occasionally, but doesn't stay on constantly. The cat has been gutted by the previous owner, exhaust is otherwise stock. I replaced the IP about 1000 miles ago due to a failed optical sensor (P0187,P0251,P0370). The ECM isn't in limp mode, the cruise control works reguardless of performance. The "Water in fuel" light comes intermitently with no real pattern. I've run three full tanks of fuel and two bottles of Dry Gas with no real effect on the light. Seems to come and go as it pleases with no rhyme or reason, kinda like my cat (feline, not gutted).The ECM may have been programmed by the previous owner but I've never driven another 6.5TD so I have no real reference.

When it runs good, I love it. When it runs bad I want to sell it, but who would buy a malfunctioning POS (besides me).

I think it was Prof. Plum in the study with a candle stick.

byrdman73
08-29-2005, 08:47 PM
Correction- I'm getting 13.5 mpg
The tire size is larger than stock (again, previous owner) 225/75-16 to 235/85-16. Calculating the tread width, aspect ratio yadda yadda.... 12.5 mpg measured - 13.5 actual

thefermanator
08-29-2005, 10:15 PM
Sounds like bad connections at the batteries. Have you checked all your battery cables, ground connections?

knkreb
08-29-2005, 10:21 PM
Winning numbers are:

236 - Turbo system
238 - Turbo system - hi voltage
251 - Injection pump Cam system

Your boost is too high. Over 12 will set off SES light.

Say NO to Dry Gas. No alcohol additives please. If WIF light is on, get water out of system. Open water drain valve - t-handle on thermostat housing. Drain into something and check to see if you have water mixed in your fuel, or if you are getting a bad electrical signal.

If you have water in system, go to great lengths to get it out. You don't want to wipe out that new IP.

byrdman73
08-30-2005, 09:59 AM
What would cause the boost to be to high? How do I reduce it?

Has there ever been a problem with the fuel tank developing condensate on the inside? Is that a source for WIF? If it is a bad electrical signal, what is the likely source?