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Injection Pump Failure Again

Code PO122 Low Voltage at the Accelerator Pedal! Looks like a NEW Accelerator Controller is in my future and a Re-Scan after the new part is installed! That sure beats the hell out of replacing ANOTHER IP! THANKS TO ALL WHO REPLIED AND THE CONVERSATION WITH TURBINE DOC!
 
Well if you have low voltage at sensor 1 that voltage comes from the PCM.

That could mean the sensor resistance was too high, or there may be nothing wrong with the APP, but with the wires from the PCM or the PCM itself.

Did you ohm out the sensors? The thing is, the PCM should do nothing if only 1 of the 3 sensors is not functional. It is fully functional on any 2 of the 3. So there must be more the story, like the 5V reference was shorting so it took out all 3 sensors and one 1 reported.
 
The sensors ohmed out at; Sensor 1 was over 6 and two and three at 3.5 with a digital ohm meter! Under acceleration with the key on and the scanner attached, it would not reach full voltage until the accelerator was fully depressed, then it would red full voltage. I recall that when the problem started, I was accelerating from about 15 mph to Interstate speed. It has done this once before, back in october of 09' in 4wd pulling a pop up camper up a muddy hill and as I pushed the pedal down, it just went to idle, so I shut it off, then restarted it and drove home!
 
APP sensor 1 should start at .5V and increase as throttle is opened.
APP sensors 2 & 3 should start at 4V -4.5V and decrease as throttle is opened.

You should be able to see this with your scanner. Voltage changes should be gradual with no sudden spikes or dips. Voltages are approximate and with engine idling.
 
The sensors should have the same resistance measurements when unplugged though, so if sesnor 1 is 6k ohms it may be faulty causing the voltage to drop a bit too much. All of mine measured about 4.5K.

Still one bad sensor should bring it to its knees like that.
 
Re scanned sensor and one was over 5 ohms and the other two over 7! I'd say it is worn out BUT the real problem is you can only buy the sensor as a unit! Everybody carries the round 3 pin version for Gassers but the rectangular 9 pin for Diesels comes only as a unit with the Accelerator Pedal/Bracket and only available from the Dealer! I called 1 800 AC DELCO to confirm this. Fortunately the Parts Man at my local Chev. Dealer said he would sell it to me Wholesale, cost, $350.00, OUCH! I didn't even ask how much it Retails for! I am going to do something I have never done before and that is buy an Electronic Part from a Salvage Yard unless anyone knows where I could buy one in the next 24 hrs. as Mowing Season is a week away and I need to get my trailer here to get Equipment ready! AGAIN, THANKS for all reply's, Keith
 
I think that is a relatively rare item to go bad... I think a clean used one would be okay.

If you are doing snow and lawn care perhaps yours sees more moisture/dirt than normal?
 
Pillow said:
I think that is a relatively rare item to go bad... I think a clean used one would be okay.

If you are doing snow and lawn care perhaps yours sees more moisture/dirt than normal?
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I agree 100% that is why tomorrow I am going to the local Pull & Pay Salvage Yard! I called them today and they have three trucks like mine to choose from! I see these trucks with the Original Owner still driving them with well over 250,000 Miles on them and never had to purchase this part. It is Highway Robbery from GM that you can only buy this New from them and it comes with the Pedal/Bracket and Sensor for over $ 350.00 Wholesale but if it was a Gas Engine I could buy it anywhere for around $ 40.00 to $50.00! Let's hope tomorrow's purchase is a good one!
 
I agree, robbery on some of these 6.5 specific parts!

Good Luck tomorrow. I need to go to the picker this week as well for a door lock. :(
 
buddy said:
Sometimes changing an IP can solve or temporarily relieve another problem, so best to figure out exactly what is happening. DB2s fail too.
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Care to expand on this? Except for a catastrophic mechanical failure, which could happen to a DS4 (or indeed any other component in the truck) what type of DB2 failure would leave you stranded?
 
My point is just that switching to mechanical injection isnt perfect. If I dont adequately lubricate my fuel with a DB2, or lift pump isn't funcitoning, the DB2 is going to die an early death too.
 
buddy said:
My point is just that switching to mechanical injection isnt perfect. If I dont adequately lubricate my fuel with a DB2, or lift pump isn't funcitoning, the DB2 is going to die an early death too.
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And this is different to a DS4 in what way? BTW, I do not add additional lubrication to my fuel and my DB2 has not died an early death. I don't think a DS4 does very well without a functioning lift pump. There are more DS4 "fixes" for sale and threads on how to keep one working on virtually every 6.5 website out there than I can count. How many places sell "fixes" for DB2s? How many threads on all of the failures of DB2s? Yes, like any mechanical component, they will eventually wear out. I wouldn't consider normal wear a failure.
 
There are more DS4 "fixes" for sale and threads on how to keep one working on virtually every 6.5 website out there than I can count. How many places sell "fixes" for DB2s?
Click to expand...

And for example C/K trucks was made with DB2 pump and 6.5 diesel 1992 and 1993, DS-4 came in 1994 and was used until they replaced 6.5 by duramax..
 
yeah,, but how long was the DB2 in use with 6.2? How long did the Military continue to use it after the DS4 came out? How long did Ford use the DB2 before they replaced the IDI with the powerchoke?

in most cases simple is best ('cept fuel injection vs carb which is irrelevant to a discussion on diesel)


I am sure the introduction of the DS4 had something to do with making it easier for the engine to control the 4L80e
 
Anubis said:
yeah,, but how long was the DB2 in use with 6.2? How long did the Military continue to use it after the DS4 came out? How long did Ford use the DB2 before they replaced the IDI with the powerchoke?
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Every 6.2 came with a DB2. GM continued using DB2s on 6.5NA engines until the end of production (2000?, not really sure). Only the turbo 6.5s after 1993 had DS4 pumps. The military 6.2/6.5 still uses DB2s, as do the marine engines. So from the first 6.2 engines to current production, DB2 injection pumps have been and are still used. No idea on the Fords. DB2 pumps came in all type configurations, and are used on lots of industrial 4, 6 & 8 cyl engines.
I am sure the introduction of the DS4 had something to do with making it easier for the engine to control the 4L80e
Click to expand...
No, they made plenty of vehicles with 4L80E transmissions and DB2 injection pumps. The DS4 was for emissions & driveability.
 
IMO,DB2 IP's fail just as fast as DS4's with a nonfunctioning LP.

DB2,s are known to last little beyond 125 k in my experience.I actually have/had more probs with the DB2.
I run 2 of each
 
My excursion to the Salvage Yard for a good used Throttle Position Sensor was not good except for the fact that the donor truck I looked at had all the wiring and all five cab marker lights so I my wind up there again with more tools to remove them and install them on my truck at a later date! Until then my quest goes on!
 
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