View Full Version : Codes P0236 ;P0251 ;P0370
I finally purchased a code reader and this what I got P0236, P0251,and P0370. Exactly in that same order. It's 96 GMC 1500 with 100K miles. The IP has been changed from the dealer last year. Fuel filter changed in the summer because the engine light came on and changing fuel filter seemed to have helped until the light came on again a week later but it would not shut off or hesitate it just kept running the same. In the last week it's been getting worst. It will stall while driving nowand when the light comes on it lacks power. In the past I have uplugged the batteries to get rid of the codes and it would run fine for a while but it did not seem to loose power or shut off like it does now. I also find the truck louder at start ups compared to before. I cleared the codes last night with scanner but did not use it today.
I had something similar to this happen on my dads blazer and it was the PMD. I didn't have a code reader then so I'm not sure what the codes were. I've read up on the codes but not to sure what they mean. Help!
DennisG01
10-11-2005, 10:06
I can only give you my experience with P0236. I had the same code come up (with loss of power and more black smoke) when my wastegate solenoid went bad. Do you have more smoke than usual? Is the wastegate itself sticking?
It will smoke under hard acceleration a little then ok but this is without a load.
The 251 and 370 codes pretty much condemn the pump. You can try removing the optic filter harness and plug the OE harness in direct to the encoder. The encoder is the large black plug in the top cover of the pump. I have yet to see any negatives from removing the filter harness, only positives.
I think your right it must be the pump. I just don't understand why. Since I bought this truck it never ran right. There's always something. My dads Blazer is a gem compared to this truck. When I purchased it in 2002 it only had 60K miles and shortly after they GM replaced the fuel pump under warranty because the ses light came on and there was a loss of power so they changed it. Two years later the pump was changed again for the same problem. Early this summer again the truck began acting up but the dealer replaced the fuel filter saying this was the problem. Two days later that bloody engine light back on. The truck seemed to running ok so I didn't bother going back even though the ses light would come and go. Last week my dad used it towing a utility trailer. On the way back home the ses light came back on again. This time when the light came on the truck would hesitate and then kept on going with a loss in power. I picked it up on Sunday and driving home with my wife and kids it just stalls while driving. I was able to restart it on the fly and came home with it. Yesterday I decided to check the codes because like I mentioned it before I invested in a code reader and got P0236, P0251 and P0370. Thinking maybe it's the PMD I swapped with my dad's SOL-D which I purchased for his Blazer. The truck started fine nice,smooth and quiet. I went for a ride and the acceleration was good and said to myself I found the problem. About 5 miles down the highway the ses light came on again! This time I said it can't be the PMD/FSD because it's running on the SOL-D which is good. I came back home and cleared the codes and did not use the truck. Tonight I decided to go for a ride and see what gives since I cleared the codes yesterday ....it made a weird start up sound like a bunch of marbles being dropped on the floor. It only lasted a few seconds. No ses light yet. I back out of my driveway and head down the street maybe a few hundred feet at the stop sign it shuts off. I started it up again and it would shut down right away. This went on for a few minutes. Then it finally started and felt like it was running without a cylinder it sort of placed itself a little after 20 or 30 seconds but still ran horrible again when I parked it.
I love this truck it looks great but it's just not reliable anymore. How could three fuel pumps within 100K miles be defective? I thought these fuel pumps were supposed to last over 200K miles. I'm at a lost. I think I will place everything back the way it was and bring it to the dealer and have them replace the pump again. It should be covered under warranty ...I hope. Unless it's something else?
Hi there,
Your dealer should have checked for this, but is your lift pump operating OK?
Can you clear the codes, run the truck and if any code lights come on again retest with the code reader to get some fresh readings.
Let us know what codes are showing on the scanner.
Good luck
Jim Twaddle
Biggar, Scotland
Barry Nave
10-12-2005, 00:17
Tonight I decided to go for a ride and see what gives since I cleared the codes yesterday ....it made a weird start up sound like a bunch of marbles being dropped on the floor. It only lasted a few seconds. No ses light yet. I back out of my driveway and head down the street maybe a few hundred feet at the stop sign it shuts off. I started it up again and it would shut down right away. This went on for a few minutes. Then it finally started and felt like it was running without a cylinder it sort of placed itself a little after 20 or 30 seconds but still ran horrible again when I parked it.
During this time did the SES come on?
If so,at first sign of the light,shut down or if it stalled before restarting check code again. May only have one or two codes set.
I also would do as JK said to do then test drive.
Sorry I forgot to post the codes when I rescanned last night after it stalled. I only got two codes this time. It was P0251 and P0370.
I'm not to sure what JK is talking about. Do I need to remove the aluminum intake manifold extension housing to get to the optic filter harness? I have not done much work on these engines so I'm not that familar with all the parts on the engine yet but getting there.
DennisG01
10-12-2005, 03:32
No, you can get to the plug w/o removing anything. It's a little bit of a bear the first time, but after you figure it out, it only takes a few seconds. Look in with a flashlight and you'll see a black plug with about 4 or 6 wires (don't remember off hand) that exit the plug towards the rear of the vehicle. There is a little white "clip" that keeps the black plug in place. You'll need to pull that out (from the driver's side) with needle nose pliers. Then, pry up the top part of the black plug a little bit and then start to pry the whole plug off - put a screwdriver where you see the green weather seal (it will slide off towards the rear of the vehicle)
I've found it's easiest to re-install it by stepping in the "holes" in the bumper and using both hands (one hand around each side of the intake).
By the way, I forgot to tell you that I once had the plug off and tried to start the vehicle (forgot to put the plug back in). It did start, but made that loud "marble" sound you talked about. It also set both codes you talked about.
Hope this helps!!!
[ 10-12-2005, 06:37 AM: Message edited by: Dennis Galligani ]
Take the upper intake casting off and it will be right there.
The clip will likely break off due to all the repeated baking from a non intercooed turbo. If the second clip breaks you can use a cable tie to secure the connection.
JK
If I remove the upper intake casting off will I need a new gasket or is there gasket between upper and lower intake?
If the truck runs well .....will this mean my IP needs replacing?
The gasket is a 50-50 proposition. They often crack so I'd have one on hand. I often glue the gasket to one surface and use a non stick coating (like spray dielectric grease) on the reverse of the gasket to facilitate re-use.
If the truck runs fine, enjoy, the optic filter was bad. The machine gun rattle is the timing going to lazy mode derfault.
Thanks for the info JK. I'll let you guys know what comes out of it when I get home tonight.
I had started to work on the truck last night but had to stop due to the rain. My garage is too small for the pickup.
One quick question for JK or anybody else....What does the optic filter do and is this part of the IP? Does GM change this part when they replace the IP? The reason I'm asking this because with 100K miles on the truck the pump has been changed three times with the same symptoms. I just find it hard to beleive that the IP was the culprit on all three prior occasions at the dealer.
The optic filter is part of the GM harness, not the pump. It's supposed to be a noise filter, but I've seen no negative to removing this part...
The latest update I tried JK suggesetion but much to my suprise there was no optic filter. The OE harness is connected directly to the encoder. Therefore eliminating this as a problem. I reseated the pmd connector and also the encoder. I put back the upper intake casting I also noticed alot soot in the upper intake casting. Is this normal?
Restarted the truck and no light it ran better than last time. I went for a run and shortly after the engine light came on and the truck shut off while driving. I shifted to neutral and restarted the truck and kept on going. When I got home I verified the codes again. The same two popped out P0251 and P0370. This fuel pump maybe has 20k miles or 25k at the most.
Any other ideas?
FYI
I brought my truck to the dealer on Monday to have it checked because I kept getting P0251 and P0370. The light kept coming on and off. After trying a few suggestion I thought it could be the pump again but somehow in the back of my mind I doubted it because like I mentioned it before the IP and PMD maybe has 20K miles on it and they insalled the latest model IP. Today the dealer called me since Monday when I droppped it off and 300 dollars later were unable to find the problem. They say it's not the IP or the PMD. They were pulling the same codes I got along with 1216 and 1270. They say it's electrical problem and reseated a few connectors and when reseating the onboard computer connector behind the glove box the light went off and hasn't come back yet. They wanted to do more tests but @ eighty dollars per hour I said forget it. The service guy suggested on changing the onboard computer but they can't guarantee this is the problem. So I still have this beautiful truck which could stall at anytime.
So far so good. Hope it keeps going like this. Could this be just by reseating the ECM connector?
I have also been getting a PO236 DTC on my 1996 chevrolet 6.5 usually
under a hard accleration. Got to checking and
the clip that holds the rod to the WG had fallen
out "anybody got a clip"
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