Truck is a 1996 3500 Chev. Has the 6.5L TD. We have some pretty bad driveabity probs. It came to us with low power and excessive smoke on rolling accelerations. We traced the issue to a vacuum sensor line to the waste gait. Line had melted...we replaced and rerouted. Waste gait seemed to work ok. NOW i am getting some weird codes....im a 24V Cummins man, so i am used to Injection Pumps going out...and i am getting codes that look unhealthy! Here they are....


P0251 Pump cam somthing......


p0370 Timing something


P1216 Fuel pressure something....cant remember the definitions!


Any suggestions?

pump cam system, timing reference high resolution, injection timing control. sounds bad


PM dieseldan or gmctd, they should have something to say about it.

P0251 is the lo resolution - 1 pulse per crank pulse, and P0370 is hi resolution - 64 per crank pulse, signals out of the Optical Sensor, which is in the inj pump.


P1216 is Fuel Solenoid response time short - also in the inj pump.


These could be caused by dirty fuel and\or air bubbles in the fuel.


Inspect and change the fuel filter first, checking quality\clarity of remaining fuel in filter bowl.


Make sure you have more than a quarter-tank fuel.


Could also be poor grounding and\or faulty connections from the PCM harness to the main engine harness, and the engine harness to the inj pump harness.


I won't even say it could also be inj pump..........

We just changed the fuel filter the day before and cleaned the IAT sensor. Then this stuff started to happen. (Codes and such) BUT the driveability probs were always present. Bad smoke and low power.


Any points of intrest as far as grounds go that are bad about connections? The positive terminal on one of the batterys is got some junk on it....might pull em all and clean them.....ill loosen all the grounds i can find and retighten them....The truck wouldnt even start this morn....so.....got some checking to do!


Thanks all.....if come pump R&R....i might need some tips....

Good start would be to clean (+) and (-) battery posts.


Check for corrosion at either end of cables - if so, replace.


Check battery terminations at starter, check battery grounds to engine block.


Check grounds at rear of passenger-side head - this is main PCM and engine sensor ground.


Unplug and check all wire harness connectors for oxidation\corrosion, starting with those behind fuel filter, then at inj pump.


Black smoke\no power is vacuum\wastegate failure - plastic lines, solenoid, vac pump, wastegate actuator, in that order.


If occured over long period, wastegate may be sticking - just remove vac line, work lever back and forth till free.


You've probaly fixed that one, but check vac pump for ~25" at idle.


Check vac at wastegate for ~15" at idle - PCM sets this value by pulsing the wastegate solenoid.


Low battery voltage can cause strange codes, can be caused by low alternator output.


Alternator pulley is specific to the 6.5 - odd diameter gives correct tachometer reading.


What is vehicle mileage, for reference?Edited by: gmctd