I posted a couple of weeks ago asking about a few trouble codes, but i'm not understanding what the codes mean, and how to remedy the problem(s) causing them...gassers are no problem, but the diesel side is new to me. From the previous post, I understand that bad elec. connections/wiring is often a culprit, so I have checked this, as well as the vacuum lines, and to be sure, even ran a new ground from engine block to the firewall. Aside from the codes, the boost seems to me to act unnatural. When going from cruising (50 mph) to passing, sometimes the boost guage will spike up to about 12-13 psi, but immediatly drop to 0, and level off at about 4-5 psi while still under the initial load with my foot on the floor. Others, it will only spike to 8 and drop...sometimes to 10 and drop...no apparent consistancy. Could this be related to the EGR faults listed??


DTC 29--Glow Plug Relay Fault--the glow plugs didn't work for about a day, but have worked for the last 3 weeks with no problems...i believe the relay is failing, which caused it to stick for that day.


DTC 32--EGR Circuit Error--Bad EGR valve??


DTC 33--EGR Control Pressure/Baro Sensor Circuit High--(High Vacuum)--what would cause the vacuum to exceed the parameters set in the system


DTC 74--Transmission Input Speed (TIS) Sensor Circuit--Replace the sensor?? All connections/wires appear to be good.

Bad map or baro sensor, PCM is probably clipping fuel/boost if it sees boost out of range, I'll 13 is pretty high boost, you need a fooler how are you getting 13 psi that is pretty high without a TM or a fooler installed. Not sure what is going on on the EGR side, ecxept that all of those solenoids are on common vac, if one solenoid were leaking could be affecting the others. I'll look in my manuals to see if I can make sense of it.

You can read your MAP and baro signal key on, with a dvm, ~1.50v=~15psi whatever barametric is where you're at.


The EGR truck has to have a good EGR and line to hold the vacuum pressure or a bolt in the hose because the baro at the other end of the "T" can sense the loss of vacuum and it affects the wg solenoid which may be sticking.Edited by: quantum mechanic

Thanks Turbine...


as for the boost, I dont know how i'm getting it that high...as far as I know, the truck is stock (the guy I bought it from said he was the 2nd owner, and he did nothing to it.) The boost, I think, should settle on a pressure though, and gradually decrease as the load decreases. At 55 mph, it sits on 0...increases as I accelerate, but immediately drops off, reguardless of when it peaks...spikes up again and back down. Say it reaches 10 PSI at WOT, it drops to 0, spikes up to 8, down to 0, up to 5, and levels off at about 2 at 65 mph. Is this normal??


I just had the 3rd engine put in the truck...it was replaced by a Reman at about 220,000 (had a "mysterious" disappearance of coolant...the heads were shot, bad when i bought it at 187,000, ad they finally gave out) and the new engine broke a timing chain after only 1200 miles. Now I'm on the 3rd with about 1500 on it with no problems so far. The SES light was flashing before the first reman, so I dont know how many of these codes were present before the install.

Quantum,


the only time i get a ses light is when the truck is at idle, or i'm coasting...never when I am into the throttle. as for the boost suddenly dropping, it doesn't even need to max out at 13...sometimes 8, 6, 10...just random times under acc.


DVM...digital volt meter??

Wastegate solenoid is faulty, hanging and under/over reacting, replace it.


32-33 EGR, circuit fault/voltage high indicates short to ground condition or hung open EGR solenoid. If it were hung open and your EGR system still live, you would have HEAVY black smoke and low power.


As for the Glowplugs, try clearing the code and testing glowplugs. If glowplugs test OK and code returns replace relay.

Thanks for the help guys.


There is some (I think Minor) black smoke at WOT, so that tells me the EGR valve is still OK? I will check the wiring closer.


As for the glow plugs, I just replaced the plugs about 20,000 miles ago.There were 1 or 2 days where they didn't cycle at all, and now they cycle every time I turn the key so I'm pretty sure its the relay.

Is there a chance that the Wastegate solenoid could be causing the EGR codes cause they are all on the same vacuumm line?

a break in any of the vacuum lines could conceivable set EGR codes but still operate WG at higher engine speed when EGR is off, but I can't see the WG solenoid causing the EGR faults.


Is it possible they're the wrong glowplugs or inferior aftermarket ones? I've seen whole new sets of 8 burn out in just days when cheaper ones are used. If they were burnt out you would have cold start difficulty for sure.

Vacuum Lines--I looked them all over, and replaced the one rubber line that looked dryrotted to no avail. All of the other lines are hard lines that broke when the engine was replaced...they were all spliced with short pieces of rubber hoses/black RTV...not by me, but the "mechanic" that I relied on to replace the engine.


Whatever the problem, the truck seems to me to run GREAT, much better than it did with badly cracked heads and the old motor. A lot more power than before, but I never had a good running 6.5 to compare it to


No problems with any cold starts...just let the plugs cycle, and she starts by touching the starter...as for INFERIOR, it's possible...but it was all advance auto carried at the time. I only ever had the problem for about a day or two, but the code still comes up (yes, i cleared the codes)


Maybe a short in the wiring that corrected itself, but why would the code still come up.


I'm really more concerned with the EGR and TIS codes right now, but want them all to disappearhttp://www.dieselplace.com/forum/smileys/smiley4.gif

Are you kidding me abunch of pieces of hard line spliced together with rubber hose. Spend the $5 for a new set of lines. I upgraded to thick soft rubber vac lines that fit the solenoid ports.





You could make the egr's function dissapear by blocking the EGR off.

As I said, I didn't do it, my so-called "mechanic" did. I've only had the truck back for a couple of weeks. I've heard of the rubber vac. lines "sucking closed" being the reason for the hard lines, and the "mechanic" said the hard lines had to be left in place because of the way they were routed.


Anyway, since he put a Reman engine in the truck, and the timing chain broke...BIG TROUBLE...and the hassle of getting it replaced, he's lost my business for sure...time to learn about the diesel side of mechanics myself.


Blocking off the EGRs function...wouldn't that send constant trouble codes?? I know I can cut a piece of steel and close off the ports. I have done it in older gassers but never with the newer, computerized crap. Also, to do this, what else would I need to bypass on the truck.

I've experienced thinner rubber lines sucking closed but the thicker ones are trouble free so far.


Somepeople on here advocate cutting out a thin piece of sheetmetal to place underthe EGR. That effectively blocks it off. You can also put "F" engine lower maifold gaskets to block the exhaust ports in the intake.

Thanks Quantum...I'll add thick vacuum hose and some new wire loom (all of mine is old/brittle, and I can't trace the wiring too well with it in the way) to my shopping list, and see what happens


I'll Let you guys know

Okay,


I took your guys' advice, and started with the vacuum lines. I went and bought the thick rubber vacuum hose from Auto Zone, and replaced all of them. In the process, I did find one hard line going to the Baro. Sensor that was cracked. Cleared the codes and drove it to the store and back.


Now the only codes coming up are


DTC 33--EGR Control Pressure/Baro Sensor Circuit High--(High Vacuum)--


DTC 74--Transmission Input Speed (TIS) Sensor Circuit


With the TDC 33--what does this mean...there's too much vacuum on this circuit?? What would controls the vacuum going into the EGR/BARO circuit?? The EGR Control Valve?

Just a wild guess are they plumbed correctly, vac & dump arean't cross connected, do you still have the sticker schematic one side os each solenoid is vac and other side is vent

http://www.dieselplace.com/forum/uploads/quantummechanic/2004-10-16_075714_egrsetup.jpgThis should help.


http://www.dieselplace.com/forum/uploads/quantummechanic/2004-10-16_073736_egr_solenoid.jpg


Sorry about it being blurry the scanner is down.

QuantumThanks for the info...just checked the lines, and no dice. Any other ideas as to why the system is reading too much vacuum? Maybe one of the solenoids is allowing there to be vacuum when there shouldn't be??


One question about the pics, though. In one of them, there is a "vent filter," but in the schematic and on my truck, there isn't one

Every trucks a little different. I have only the Turbo solenoid.

It's either the EGR or EGR vent solenoid , where's TDG or TD to say for sure?


I would still suspect turbo solenoid also. You check it by unplugging it and starting the truck and see if it passes vacuum. It should pass none. I'm not sure if you can check the other solenoids in a similiar manner.At $30 a pop for new ones check them first.

His code 33 reads 'Circuit High' indicating his problem is electrical, I'd say you have a faulty BARO sensor.

Is there a way to check the BARO sensor before I start "guessing" and this thing nickle and dimes me??

know anybody else with a chevy? Even a gasser? the baro sensor in yours is the same one they used for most of their vehicles for a long time. plug another one in and see what happens, its either the sensor itself or a wiring problem sounds like.

DVM. take a reading with the key on from the center pin on the baro.

In the manual I have, it says that a


"code 33--EGR control sensor circuit high" and in parenthesis (low vacuum)


what should my vacuum reading be coming into the BARO sensor--at idle--during operation??

25"hg at idle iirc

I've got to go in tonight, so I'll post my findings tomorrow. Goin' to pick up a volt meter/vacuum guage tonight.


I can't thank you guys enough...I really appreciate the help

I finally got a voltmeter and vacuum guage...been needing one for a while now. The voltage of the center wire coming out of the BARO sensor, with the key on (not running) was 4.98 V.


Vacuum at IDLE:The vacuum at the vac. pump was steady at 60"hg, 50" going into the BARO sensor, and what confuses me the most, only 15" going into the EGR valve. Shouldn't I get the same reading at the EGR valve as I do at the BARO sensor...they both get their vacuum from the same "T." I pulled the line off the BARO sensor, and got the reading with the other line hooked up to the EGR...same with the other reading, with the BARO sensor hooked up.


As soon as I push the ACC pedal, the vacuum at the BARO sensor dropped to 0.


Are these readings normal, and what do they tell me?? Quantum...you say the reading should be 25" at the baro sensor...Mine is reading 50" so is that solenoid bad??

are you sure your reading the gauge right? 30" is a perfect vacuum, you must be reading KPA or something. EGR should drop to 0 on APP movement so looks like your solenoid is good too.


5v reference, 4.98 is perfect, very low resistance from ground wire to ground and very high resistance on the feedback wire to ground is what you want.Edited by: Texas Diesel Guy

The center "B" wire from the baro is the baro signal, the "C" wire is the 5v reference "A" is ground. 4.98 on the signal means you're not resisting the 5v ref signal and the Baro is bad.


Vacuum pump makes 25" at idle. 60"hg is unheard of.

I assumed he was testing the wires unplugged, definitely yes, if there's 5v coming off the signal wire the sensor is bad.

Alright, I was reading the guage wrong...60 cm Hg vacuum...about 23-24"Hg from the pump...no, I did not plug any lines, what I did was remove the line from the pump that comes up behind the AC compressor, and got about 24". I then pulled the line off of the BARO sensor, and read the vacuum there (about 20") I hooked the line going to the BARO back up, and pulled the line off of the EGR, and got about 6". The lower pressure on the EGR side of the "T" caused me to look at the "T" a little closer...one side had a smaller hole than the others, so out of curiosity, I put a single sized "T" in its place, hooked it back up, and drove about 50 miles without the CHECK ENGINE light from coming on. Tonight, I have disconnected the batteries to see if the codes come back up tomorrow.


Again, THANKS. If the code comes back up, I'll take Quantum's advice and replace the BARO sensor. I will let you guys know tomorrow about the codes.

sounds like you got it.

You can clear DTC's by jumping pin A to B of the ALDL and stepping on the APP for 10 sec. key on engine off. it will flash 12 when all clear.

Thanks for everything guys. I have hooked the batteries up and it looks like my troubles are solved, at least with the EGR problems. The code 74 is still coming up. Should I start a new thread or just replace the trans. input speed sensor? Where is it?

Go ahead and start a new thread might help someone out later doing a search for tranny problems.


As for the where is it part, I can't help with that much, knock on wood tranny hasn't given me any problems to date for me tpo have to learn about it.