P0251 & P0126 1998 GMC SAVANA G3500

Pete

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#1
Hi folks!
I'm trying to figure out what's going on with one of our school buses. I'm the tech (kinda) for our church school. If I can't figure it out then we send it to a REAL shop. There are things that I can fix to save them money so that's why I do this.
Anyhow, I'm trying to figure out if these two codes are related on this 1998 GMC SAVANA G3500, 6.5L Turbo Diesel, VIN 1GDHG31F9W1104567 w/81000 miles.
The one is the P0 Mod#10 Injection Pump Metering Control and the other is P0126 coolant temp insufficient stable operation. I haven't a clue what any of these mean.
The driver said the bus now stalls at idle or when coming to a stop. The CEL went on just before this happened.
Are they related and can anyone be so kind as to point me in the right direction?
Thanks sooo very much for all your help, past and present and may God also bless all!
 
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#2
"P0126 coolant temp insufficient stable operation" If you add the missing word "for" the meaning becomes more clear. P0126 coolant temp insufficient for stable operation. Check your engine temp. Is it low at highway speed, with poor heater output? Heater work better if you sit and idle for several minutes after driving several miles, but then cool down again when you hit the highway? These are symptoms of a thermostat problem.

P0251 may mean you need an injection pump. But maybe the pump code set because the engine was not reaching normal operating temperature. If you have any reason to condemn the T-stat as faulty, I suggest you replace that first.
 

Pete

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#3
THanks Danica!
The driver didn't mention any issues with heating or running cold although that doesn't mean it doesn't exist. I will have to check that myself. I will check back as soon as I found something out.
I reeeeeeeally appreciate you pointing me in the right direction.
Thanks so very much and may God bless you.
Pete
 

Pete

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#4
Well, it turns out that the thermostat was causing these codes and we don't need an injector pump like one shop said. Runs like a champ once again! I am truly grateful for the assistance that I've received here from all you folks. Danica and dabunk, thank you so very much!
Take care, God bless and keep doing what you guys do best with the gifts God has blessed you all with!