Its a few years, but im back

ghenny440

Well-Known Member
Well its a while so i dont know whos on anymore, i left the GMT family and got a mitsu. But my son just bought an 03 TB ltz 4x4 for 600$ with 170k on it no rust.
well it needed the normal, idler pulley, belt, tuneup, exhaust manifold, o2 sensor, i did a new throttle body, got the fan clutch, getting the iat sensor and map sensor tomorrow.
well i am gettin the p0172 code(runs rich) and the fan speed sensor p1481 i believe it was.
So i guess my question is would these codes make this thing rev higher than normal to shift. Or should i also be lookin at fluid and filter for the tranny?
 

MRRSM

Lifetime VIP Supporter
Welcome Back to GMT Nation...

The Symptoms of the P0172 Code and the Higher RPM might indicate a Vacuum Leak along the limb of the Intake Manifold. There are Three "Figure 8" "O" Ring Style Gaskets that Seal the Black Plastic Intake Manifold Ports in Pairs to the Intake side of the Engine Head. The IM is held in place with Staggered Fasteners... some of which are a PITA to access and re-tighten near the Firewall.

Any "Un-Metered" Air that manages to get ingested in at these points an allow any unregulated "O2" to sneak within the ordinarily monitored Air Stream will prompt the PCM to Dump in More Fuel in an attempt to achieve a "Perfect Stoichiometry" of 14.7:1 Air to Fuel Ratio.

If you attempt to "Snug Up" the Intake Manifold "Trapped Fasteners" ...keep the Torque at NO MORE THAN 87-89 INCH Pounds... or you'll run the risk of Snapping Them Right Off!

Here are some other possible causes for the P0172 Code:


Some more Help from Youtube:

 
Last edited:

Mooseman

Moderator
The fan code, in itself, would not make the engine rev higher. However a rich running engine could.

For p0172, I would check fuel pressure, vacuum leaks and MAP sensor. Although counter-intuitive, did you replace the fuel filter? Another possibility is a leaky injector, which would require an injector balance test to confirm using a Tech 2 or other high-end scanner.

The p1481, what led you to replace the fan clutch in the first place? Did you have this code prior to replacing it? What brand clutch did you get? Does it seem to work anyway? It's possible that it's a wiring issue rather than a problem with the clutch itself.
 
OP
ghenny440

ghenny440

Well-Known Member
The fan code, in itself, would not make the engine rev higher. However a rich running engine could.

For p0172, I would check fuel pressure, vacuum leaks and MAP sensor. Although counter-intuitive, did you replace the fuel filter? Another possibility is a leaky injector, which would require an injector balance test to confirm using a Tech 2 or other high-end scanner.

The p1481, what led you to replace the fan clutch in the first place? Did you have this code prior to replacing it? What brand clutch did you get? Does it seem to work anyway? It's possible that it's a wiring issue rather than a problem with the clutch itself.
The p1481 code came up on its own. I havent replaced it yet. I did do the IAT sensor and MAP sensor today, deleted the codes and she rubs great now, and idles at 600. The fan code was pending after the sensor replace and code delete. My son drove it on the highway up to 75 mph and when he got home i re-scanned the codes and there arent ANY codes and NONE pending. Could the fan clutch be good and the run ritch code cause the fan code to be thrown?
 

Mooseman

Moderator
They are not related at all to each other so no. Something might have happened to the clutch's wiring. It often breaks at the bend in the harness.
 
OP
ghenny440

ghenny440

Well-Known Member
So i got it to my buddies shop and he did 2 tests he felt would tell him what was wrong. First a fuel preassure test incase fuel pump was either over preassurising the system and dumping too much gas. And the 2nd was disconnecting the exhaust and running a camera inside the catalytic converter to check if it was clogged if its clogged you leave the exhaust loose and drive it to see how she shifts.
Well the cat was EXTREMELY clogged and was the last issue for the p0172 code and the crappy shifting.
New catalytic converter, new muffler(cuz it was seperating at the seam) trans flush plus all the prts we replaced.
All in all he has an amazing running trailblazer LTZ 4x4 he only paid 600$ for. We put a lil over 1300 in parts in it
Parts list...
Exhaust manifold160$
O2 sensor... 100$
IAT sensor... 50$
MAP sensor... 50$
Throttle body... 160$
Coolant temp sensor... 60$
Fuel pump/filter/locking ring...130$
Catalytic converter/muffler/hangers/labor... 650$
 

zaid3ssaf

Well-Known Member
To add on what everyone said, make sure all the air intake ducts are free of holes and are fastened. My Bravada used to idle roughly until I replaced the duct between the resonator and the throttle body because it had a tiny hole.
 

gmcman

Well-Known Member
Welcome back :thumbsup:

Curious to what cat you went with. I'm going to have to replace mine soon enough. Works good under load, but won't light off at idle. Was thinking about the Magnaflow but IIRC, they run close to the trans lines.
 
OP
ghenny440

ghenny440

Well-Known Member
Welcome back :thumbsup:

Curious to what cat you went with. I'm going to have to replace mine soon enough. Works good under load, but won't light off at idle. Was thinking about the Magnaflow but IIRC, they run close to the trans lines.
My good buddy from highschool works at a tuffy muffler shop and he quotes me the walker dorect replacement for like 550 and did a crossreference on part numbers and the universal one for our trucks is the exact same walker one except it didnt have the extension pipes i believe, and it was like 229 so i went with that one
 

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