My truck is putting out an intermittent P1247 code. It did not turn on the CEL lamp, but it was stored in the PCM. I cleared the code and drove the truck a few more times and the code did not reset.

After clearing, I took the truck out for a test drive with an OTC Genisys attached and in live data mode. At WOT throttle acceleration with no load on the truck, maximum manifold gauge pressure was at about 16-16.5 psi. With the wastegate disabled, manifold gauge pressure would max out a a bit more than 20 psi at WOT.

Do these numbers sound right to you? The 16-16.5 psi with the wastegate activated at WOT seems a bit low. I've searched Alldata and cannot find any specifications for boost pressure.

Thanks,

Nate

 

Shameless BTT looking for some help.

 

Did the genysis show any issues with the ICP pressure?

Low boost pressures are typically a result of loose boots on the IC tubes or intake plenums, or leaking up pipes. Have you checked those?

 

I am drawing a blank on the ICP abbreviation, can you remind me?

I've visually checked my up pipes for leaks, no soot marks around the joints that I can see. Not sure if there might be a leak I cannot see w/o a mirror. I will double check with a mirror. I built a boost leak check tool, pressurized the intake system to 20psi and soapy water tested all the boots/ listened for leaks. No leaks found.

The Genisys provides a wealth of live data, unfortunately I have no specifications to compare it too. I can't find any on Alldata either.

Thanks for the input!

 

What does the Genisys read with KOEO. My AE will read ambient air pressure with KOEO or at idle. I live at 5,000 ft and the AE reads 12.5 PSI KOEO or at idle. If the Genisys reads less than the ambient air pressure the MAP sensor may be bad.

 

Manifold absolute pressure was right about 14.5 PSIA at KOEO, right where it should have been. I live at about 800 ft above sea level.

 

ICP = Injection Control Pressure, but you can ignore that. I was trying to go from memory thinking 1247 was an ICP code. Turns out it's a turbo boost low pressure code. I really should look some of these up before I open my big mouth.

If you can't find a boost leak, check the MAP hose and sensor as Robin suggested.

Also, you might want to thumb around through this link 2001 PC/ED Manual

Section 4A has a listing for Diagnostic Trouble Codes and the troubleshooting chart associated with each code.

 

If you subtract the 14.5 from your max of 16.5 you are only getting 2 psi of boost. Like Chris suggested look for bosst leaks. If the MAP will read 14.5 it is probably working ok. Besides looking for loose clamp boots also check for a hole or tear in one of the boots. Inter coolers have also been known to leak.

Are you seeing alot of black smoke? If so that is a sign of a boost leak.

 

I have those charts available to me, ran through the chart on P1247 on Saturday. No avail.

Are my boost levels normal, or a tad low. The charts says that below 12psi could be a major leak, but doesn't spec a max. Does my 16-16.5/20 sound about right?

 

No black smoke. 14.5 PSIA (absolute) is equal to -.2 PSIG (Gauge). 14.7 PSIA (assumed average ambient atmospheric pressure) is equal to 0 PSIG. My 16-16.5/20 readings are in PSIG

 

What I see on live AE absolute manifold pressure is 12.5 higher than my boost gauge. When my boost gauge reads 15 the AE is reading 27.5. The ambient of 12.5 at 5,000 ft + the 15 of boost. So my AE reading is PSIA + PSIG. So I take it that the Genisys does not do this but subtracts PSIA to give a reading equivalent to PSIG. It must be able to read PSIA on its own to subtract it to come up with an equivalent of PSIG. The MAP sensor sends PSIA + boost to PCM. It would be nice if you had a boost gauge.

Please don't think that I am trying to correct you or teach you something. I am only stating my observations and trying to figure out how the Genisys works.

With all that said if you are getting 16.5 and 20 with WG disconnected that isn't all that bad. 22 to 24 for stock with WG disconnected would be good. Check the compressor wheel and see if the blades are in good shape, sharp clean edges and no chips. Also check it for play. No in and out play and just a very, very slight side to side or up and down. Of course the wheel should not come in contact with the housing.

By the way, how many miles on truck.

 

I apologize if it sounded like I was trying to teach you too. Doing the teaching thing is force of habit, I am an Industrial Technology teacher by trade and spend my days doing just that.

The Genisys reads ambient pressures in PSIA, and reads boost pressures in PSIG. It could throw someone for a loop if they weren't familiar with the difference between ambient and gauge pressures.

I can set the tool to display two gauges or graphs at the top of the list, one for Ambient Air Pressure in PSIA, and Manifold Gauge Pressure in PSIG. The ambient gauge/graph stays at a steady 14.5 PSIA as I drive while the Manifold Gauge Pressure fluctuates depending on boost conditions. I would hypothesize quite confidently that the Ambient Air Pressure reading is being derived for BARO sensor data, while the Manifold Gauge Pressure is coming off the MAP.

The Genisys is a very powerful tool, and I have yet to use even half of it's capabilities. I (my district) just picked it up for the school shop a few weeks back. Since OTC is closing them out, you can get the basic domestic, Asian, and ABS package for about $1250 with rebates if you get things right.

 

Thanks for the feedback. The Genisys takes some of the quess work out. Sounds like a great tool. I had to look up PSIA and PSIG to understand what we were talking about. Now I know.

One of the things I like so much about this sight is I learn something new almost every damn time I get on here.

Oh, and another place to look for a bosst leak is the plenum on each head. Only ever read about this happening once, but if I read it here once it has certainly happened more then once.

 

I retested for boost leaks today, and found a major one on the rear of the passenger side plenum. I betcha that's the culprit. Any ideas on how long it take to strip down the engine compartment and re-seal the plenums?

 

Unfortunately the passenger side plenum is the tougher of the two. The three bolts at the front and on the inside are the toughest to get back in. The plenum has a notch it it so the bolt at the front next to the fuel bowl only has to be loosened, NOT taken out. I am glad I noticed that on the new plenums I was putting in. If that bolt is removed it will be a real PITA to get back in. An offset box end 13mm made it easier to get to the two farthest forward bolts for tightening. It would have been much easier if I had removed the fuel bowl but I didn't want to cause any problems. As it was I did have to remove the two outlet fuel lines at the fuel bowl for enough room to get to these bolts. I had 2 parker sleeves to use to put them back on. I ran a small bead of black high temp RTV in the groove of the plenum and circled each bolt hole and let it set up for about 30 minutes before I put the plenum on.

Notice the notch at bottom left of plenum. This of course is the bolt you do not have to take out but just loosen. The two bolts to the right are the ones that are tough to get back in and tighten with fuel bowl in place. The offset wrench helped here. I couldn't find a torque spec so I just got them good and snug.

I can't give you a good time frame because I did both but I am real slow and it took me about an hour to remove the passenger side, clean the mating surface on the head and re-install. This is not counting getting everything out of the way first, like the IC tube and the GPR and its bracket or waiting for the RTV to set up. Figure close to three hours, working slowly. Be careful removing, it will bend easily.

I'm glad I mentioned checking the plenums. That never seems to come up when checking for boost leaks.