P0126 repeatedly

[natjwest]

I guess this code has something to do with a/the thermostat. I get the code about a week after clearing it. The dashboard thermostat looks fine, i.e. it moves a bit off the left side under appropriate loads.

What's the best way to diagnose and repair so this code goes away? Or should I just do like I've been doing and clearing it when it shows up? I don't have an OBD reader so I've been making regular trips to Schucks. I also don't know too much about what I'm doing on the truck, so newbie instructions please. (I don't know where the t-stat is.)

Thanks guys.

 

[ak diesel driver]

If your dash guage is reading normally ie normal temp then you know that the CTS coolant temp sensor in the head is working ok. our trucks have 2 cts 1 in the head and a second 1 in the coolant crossover behind the waterpump on the top of the engine. this is the 1 that the ECM uses. the tsat is also right there too.

 

[natjwest]

Thanks Alaska, but where is the coolant crossover? Any more hints about where it is? Should I be replacing this thing asap?

 

[ak diesel driver]

start at the radiator next is the fan next is the fanclutch next is the waterpump above the waterpump is the tstat and coolant crossover in the crossover is a sensor with 2 wires. that's what your looking for. you never did say if your dash guage is reading normally?

 

[Paveltolz]

:nopics:

So here's one On a single T-Stat set up. Hope it helps.

 

[natjwest]

Dash gauge works well. I will take a look under the hood tomorrow and see if I can figure things out. Thanks gents.

 

[ak diesel driver]

if that sender in the coolant crossover is not working correctly it will have a large affect on how the engine runs/starts

 

[jmack91z28]

http://www.thetruckstop.us/forum/showthread.php?9494-Part-Locations

The sixth and seventh picture kinda show you where the CTS is. Couldn't find an actual picture of the t-stat, sorry.

 

[diesel65]

The code indicates that the engine is not meeting a minimum temperature within a fixed time upon a cold start.
I have always found the thermostats to be the culprit.
Replace the two thermostats and you should be good to go.
Newbie instruction, Follow the big black hose from the radiator back to the engine and it will end at the silver colored housing. The housing has a cover that the black hose is connected to, the cover is held by four bolts that require a 15mm wrench and or socket set to remove.

 

[natjwest]

...the cover is held by four bolts that require a 15mm wrench and or socket set to remove.

Okay with the cover off, what's the thermostat? The "Part Locations" thread doesn't have a picture of that, as far as I can tell. Thanks so much for helping this newbie. I'm enjoying learning how to fix my truck.

 

[diesel65]

http://www.napaonline.com/Search/Detail.aspx?A=THM385190_0293132446&An=599001+101999+50014+2014045
Hopefully the link works, this is what the thermostat should look like.
The black side goes into the housing and the silver side points torwards the hose.
If you are going to replace them, be aware that there is a groove for the stats to sit into before you put the cover (outlet) back on.

 

[natjwest]

... this is what the thermostat should look like...

Yes, I got the picture to come up. Thank you very much for taking the time to help me. I will report back when I get to the job, maybe tomorrow, maybe the weekend.

 

[natjwest]

...Follow the big black hose from the radiator back to the engine and it will end at the silver colored housing. The housing has a cover that the black hose is connected to, the cover is held by four bolts that require a 15mm wrench and or socket set to remove.

I'm guessing this silver housing with (in my case) the pink x is the water pump? Or is that called the coolant crossover? And the four bolts are on the back side, facing the cab, right? The bottom two bolts look kind of hard to reach.

 

[ak diesel driver]

that's the crossover and the temp sender should be just to your left. the tstats are sandwiched under the 4 bolts

 

[natjwest]

I just cannot get the bottom driver's side bolt. It's stuck. I lost a socket down underneath the PMD, still trying to figure out how to get it out.

Can I pull off the big hose coming into the crossover without losing too much coolant? Will the crossover have a lot of coolant in it too?

 

[Edzzed]

When I changed out my t-stats I also lost a bolt but fortunately I have a magnet tool for fishing stuff out of hard to reach places. Even has an LED light on it. When putting it back together tie a piece of thread to the bolt so you can hold it from falling out of the socket or dropping the bolt again. Ed

 

[natjwest]

that's the crossover and the temp sender should be just to your left. the tstats are sandwiched under the 4 bolts

Okay I got the four crossover bolts off, the sucker let loose a half-gallon of coolant, I put in two thermostats, put the cover back on. Right away, the in-dash temp gauge appears to show a higher reading than before. Didn't replace the lost coolant yet.

Do I need to replace either of the CTS sensors from these two images?

 

[ak diesel driver]

if your code doesn't go away try replacing the one in the crossover

 

[mgray]

Would this code also reduce boost? I have this code and I notice I’ve lost around half my boost

 

[MrMarty51]

Replace the coolant temp sensor, clear the codes then see how it performs.
If You are still running the vacuum pump system for the turbo, then one or more of the components in the vacuum system might have crapped out.