DTC Codes

[de_lok]

Hi, my name is Dewayne, and Im a Dieselholic....................... ;)

I recently bought a very nice 96 1500 Chevy 6.5l knowing it had some issues. SES light is on. A mechanic had replaced the IP and PMD and relocated it to the fenderwell. There was no resistor in the old PMD. Within 2k miles it started to "hickup". I replaced the PMD with a new one and a PMD heatsink/cooler. Now I am getting DTC codes 251
ans 406. SES light still on. 251 - Injection Pump Cam System and 406 - EGR Sensor Circuit High Voltage . Can anyone explain in more detail what these codes mean and what I should do/replace next?

I should also mention before I replaced the PMD (only have about 50 miles on new one) I would get 16 mpg at best and that was tender-footin the pedal. From what I can tell I have a 3:42 gear and should get at least 20 mpg?

PS: Did anyone besides me notice the (tiny) article on page 24 of Diesel Power magazine of a possible v-6 Duramax ? ! ! ? ! ! ! ! Got my fingers crossed ! ! smile.gif :eek: :D

[redsuburban]

I also get code P0251 on a regular basis. The GM dealer was insistant that it was the pump and PMD until they realized that both were still under warranty and it would be their buck. They could care less now but will be happy to "read" the codes for $70.00!! My local corner garage (they won't touch a diesel) researched the 251 code on their handy-dandy shop computer which indicated that a 251 code could also be attributed to one of the following:

1)air in the fuel line
2)low/no fuel/restricted fuel during hard cornering
3)low fuel level in tank.

This code only shows up for me during start-up or shut down. It has never stumbled or failed to start when P0251 shows up.
Apparently P0251 is a soft code and does nothing to the drivability of your truck (I hope).
Good luck!

[de_lok]

Thanks redsuburban, maybe it is a soft code and nothing to worry about. The truck starts and runs very good.

Now if I could find out something about the EGR 406 code..........

[jspringator]

Do some poking around on the forum about eliminating the egr. From what I hear it makes a huge difference.

[de_lok]

I had recently installed a new FSD/cooler and #9 resistor. Only had approx 20 miles on new parts when 251 and 406 were scanned. I should have cleared the codes first(SES was on before new parts were intsalled). I have cleared them and took a test drive. Within 2 miles SES light came back on. Still have code 406 but code 251 is gone! I also have been told that alternator interference can cause a code 251. I was also told if code 251 is scanned with no
noticable engine problems :stalling, cutting off, etc.. to clear it and not to worry about it much. But if code 251 is scanned and the classis 6.5 syptoms do show up get prepaired to replace the IP.
So far my truck starts and runs great, got my fingers crossed..............

Now if I could only find out a little more detail about code 406..... Help Guys ! !

[redsuburban]

I've never heard of 251 being connected to an alternator problem but then I need to replace alternators faithfully every 2 years or so anyway. My scanner code book lists P0251 as 'Injection Pump Metering Control A'. There's all sorts of IP Metering Contol DTC's but I've never had any others. When my IP went south the last time in July of 2003, I got no SES or DTC's.

Don't know about 406 but you've got me curious.

Now if I could just figure out why this thing suddenly sounds like a jar of marbles.... :confused:
I'm waiting on my spiffy new TDP 6.5 Trouble Shooting Manual before I tear into this thing.

[de_lok]

Just a note to let you guys know I have everything fixed. I started another thread on the DTC 406 and it got noticed by someone who knew exactly how to diagnose it. Turned out to be a bad vacuum pump, easy to replace and not too expensive.

The previous owner's mechanic had just replaced the IP (200 miles before I bought it) and had the owner send it to the dealer to set the IP timing. (the day after he picked it up from his mechanic the mechanic was killed in a motorcycle accident)The dealer printed out a long list of things he needed including a new IP ! ! Go figure ! ! Not having his trusted mechanic to go too he decided to sell as is, he sure didnt trust the dealer, so I got it at a deal! I believe the code 251 was due to the IP being replaced and not in correct time.

With all codes gone and SES light out I plan to get someone with a TECH 2 to set IP timing and then I will moniter fuel milage.

Thanks everybody for there help ! smile.gif