I drive a 99 2500 Suburban 6.5T. THe SES light comes on Monday. So I take it to the local parts store to run test and they read P236 and P238. Take it to the dealer and they read only P236. They replaced the Wastegate Solenoids AND the vacuum pump. Drive it home Mon night and SES comes on again. Tuesday I take it back and dealer reads P606. They replaced the PCM and I drive home Tuesday night SES free. Today, Wednesday morning SES lit up again. Take it to a autoparts chain store and they find P238, P1631 and U1192. P238 is no problem. I have it on order and I will install new sensor when it arrives. My question is with the P1631 and U1192. Could these have been tripped when the new PCM was installed? What happens if I ignore it? Does it lock me out and keep me from starting the vehicle? As for the U1192, it is not even listed here in the FAQ OBDII section. Does anyone have a clue as to what I need to do to clear the P1631 and U1192? Any help would be GREATLY appreciated. I am a new diesel owner and quickly growing frustrated with my SES light.

I did't find either code. Reset them and see if the immediatly reappear. If they reappear they're hard codes.

Thanks Quantum. Im a newcomer and not very knowledgeable. How do you reset them and what do you mean by hard codes. Sorry for my lack of knowledge. But that's why I post here to learn.

On OBDII you must use a scantool. Autozone is reported to let you read and reset the DTC's for free.
Hard codes are always present, reset it and it reappears. Soft codes are secondary codes that may have been set due to a momentay condition that's no longer present and they do not reset.

1631 is a theft deterrent passcode mis match I suspect dealer did not do a theft learn, U1192 isn't in my 98 GM manual haven't a clue on that one, Take a minute to update your sig per welcome sticky will save some time/guesswork later on Check with your dealer see what led them to replace the vac pump, I doubt it was bad, see if they put on a gauge to check vac, if so what was the reading, few dealers now know 6.5s as well as we do, their techs mostly know Gassers or may have 1 DMAX tech in the crib, as this truck gets older it will only get worse, best advise I can give is do it yourself with the help of membership here. These aren't that difficult to work on, find a local mechanic with a Tech 2 or other OBDII bi-directional tool, snap on MT2500 does most functions but not all.

Get a GM manual pricey $150 new from www.helminc.com but well worth the money or ebay I think www.alldata.com has a lot of info you need also

Hey I found the U1192 code in my manual it is loss of vehicle theft deterrent Class 2 serial data Com, I think your dealer might have swapped PCMs on you troubleshooting or maybe did a update, if you want you can go to FAQ for theft deterrent learn info & do a relearn (lengthy procedure) and see if it clears the code, or according to the manual after 40 warm up cycles if a fault isn't present it will reset itself.

I went back and reread your initial post, you need to find a new Stealer I mean dealer, I doubt anything was wrong with either the vac pump or the PCM, It reset the codes when they replaced the PCM, but you need to get them to do the relearn procedure and demand they show you what EXACT steps they used to determine bad PCM and bad vac pump nothing in T2 would have told them to replace vac pump or PCM with these codes, did you see removed parts, I suspect original problem was about $40 worth of solenoid, or sensor I wish I wasn't on vacation when this one 1st came in could have saved you some coins.

Thanks Tim. I took the truck to Advance Auto to put the reader on it. They pulled a 236 and 238 code. Took it to the stealer to have it fixed (I am a newbie) and they replaced a solenoid to clear the 236. AND they replaced (claimed to anyway) replace the vacuum pump. I asked about the 238 code I got from Advance Auto and they said their reader was a piece of crap and couldnt be trusted. When SES light came on the next day I took it back and thats when they said ECM needed replaced. Next day SES light comes on again and went back to Advance. They pulled the 238 code again (I have part orderd and should be here tomorrow) and those 2 other odd codes. Problem is when I have to get on her to accelerate I am still getting sputtering when RPM's build. Hopefully the new Turbo Boost Sensor ( Code 238) will clear that up. If not what suggestions do you have? Also, I asked the stealer for a PSI reading on the turbo and it was 27. Sound about right??? Sorry for the questions posted that are addressed in FAQ's. I will do a little more researching nest time. THanks.

HELL NO, That ain't rite Dealer is full of crap code is a code regardless what tool is used to read it, GM T2 tool in proper hands is an awesome tool does tests Auto Zone tool can't do, but hell up until OBD II came out special tool was a paper clip and blinking light on the dash.

Still requires something between the ears to interpret what the code means, your dealers "Diesel expert" ain't got it at least when it comes to the 6.5. If you are going to keep this truck you need gauges and a full set of your own GM manuals, we will help you keep this truck running at it's peak regardless of your skill level, hang around here your newbie reservations won't last long

27 Psi boost measured where & with what, if that is what they saw there is your problem (bad sensor) code 236 & 238 can be caused by too high or too low a boost, it is a summary for out of range condition, Morons at your Stealership were thinking DMAX, they owe you some serious refunded coins Friggin part swappers. 16psi is about all a tweaked 6.5 will do with a GM-8 turbo your overboost indicated to PCM by the bad sensor is what is causing sputtering, PCM defuels on a uncontrollable high boost condition by making wastegate go full open to try and lower boost, then if high boost is still seen at PCM then it starts defueling.

Let me see if I understand you. All that needed replacing was the solenoid and the turbo sensor?? And by replacing the soelnoid and NOT also replacing the turbo sensor, they placed the blame on a ECM? And then I forked out $350 for the new ECM and I dont remember how much for the vacuum pump that I didnt need. After I replace the turbo sensor would it be right to ask them why they did what they did? I never saw the ECM code they said they pulled on any test we did at Advance Auto. Dadgummit. Boy, do i feel stupid now. Ill let you know what happens after I replace that sensor tomorrow. Thanks Tim.

I'm not even sure the solenoid was necessary, I think problem was boost sensor all along, I had a similar problem myself one giving a false high boost to PCM but it was hidden as I had a electronic fooler on it that lowered sensor output to PCM so I could make more boost by lying to the PCM; but on a hard dyno run at 9 psi by my pilar post mechanical gauge my boost kept clipping. electronically I was higher than boost level PCM factory program is happy with and did not know/realize it until later.

Following that run I went with a mechanical boost control for a while and pulled boost fooler and saw 35 psi boost on my Snap On scanner didn't think anything of it as reading was kPa (which is what dealer should also be reading not 27 psi I don't think T2 converts boost to non metric unit for boost, rest of them yes but not boost) and I thought I had converted wrong. (BTW mechanical fooling can code a OBD II truck if set for too much boost, which is why you need a electronic fooler to lower output of sensor to PCM )

I ran that way for a while until getting reflash PCM and removed the electronic fooler and ran the mechanical fooler only, without factory vacuum boost control only thing left was for PCM to defuel, swapped out for new boost sensor, readings went to normal level and then it also stopped defueling.

I'd get them to write out step by step the process they used to troubleshoot this thing, see if they mention hooking up a vacuum gauge or a mechanical boost gauge or did they just rely on Tech 2 data, if T2 only; it used same bad sensor input data as your PCM does, since your Stealer aparrently isn't familiar with 6.5s, they did what many do, trouble shoot by swapping out until they hit the right one which they still haven't done yet, and in swapping out PCMs they didn't even do that one correctly hence the PCM theft codes, I doubt they know theft deterrent relearn is required on 97-00 OBDII 6.5s which I'm reasonably sure are only ones equipped with this feature.

I replaced the turbo sensor and now runs like a scalded dog. No more sputtering or black smoke. All it took was a $75 part and I let the stealer take me for about $700. Thanks Tim.

When it hurts enough you'll stop taking it to them.