So just bought this truck about a month an a half ago. No problems but the other day the SES came on. It is showing P0171 and P0174. And P0000 (almost forgot that one) was told that's generic though. Haven't really noticed a difference in the way it's running. Has been extremely cold here in WV but the only thing I can notice (or think I notice) is the gas mileage has gone down a little. After reading some on this forum I'm looking for a vacuum leak correct? Any help would be appreciated, thanks!

 

I had a similar problem on my '02 5.4 i bought a month ago..had those two codes plus several H02 codes. It ended up being bad intake manifolds, it idled rough in colder weather, and would run smooth usually when fully warmed up. You need to look for vacuum leaks. I sprayed carb cleaner around the intake manifold till I heard the engine surge a little bit. plus the short term fuel trims went up at that time too..if you have access to a scanner with live data that will be extremely helpful.

 

Ahh sounds expensive. Hopefully on a nice day I can take a look. Too cold and snowy right now. You think any damage from still driving it?

 

the codes mean you have a vacuum leak. No problems driving it that way as long as it does not have excessive problems.. Could be manifold gaskets, but rubber vacuum hoses that are 14 years old setting next to HOT motor are suspect. Check the rubber elbow between intake manifold and firewall.... check the two small 1/4 inch hoses about 8 inches long on EGR above the drivers side valve cover. Pull off each hose one at a time, check for flexibility, cracks, burn spots... Replace any that are hard/ cracked.

 

Correction... Other code was P1000... And I just erased the codes and I will see if they come back up.

 

P1000 will show until the monitors have run successfully.

 

Actually, continued operation with a vacuum leak often damages the catalytic converters due to the excess unburned fuel hitting the cats.

Fix it quickly, converters are very expensive.

There are probably a thousand existing threads on this forum about this code combo. Many of them already have the correct diagnostic information and may of those were the result of leaks in the PCV system. Start there since that's what the odds say to do.

 

I just fixed this issue on my 03 SCrew. Mime ended up having an intake manifold gasket issue. These have been known to fail on the passenger side of the aluminum crossover tube at the front of the intake manifold. Mine had sprung a gasket leak and started to drip coolant and allow more air to be sucked in. You may want to take a look at the suspect corner and see if you notice any evidence of coolant outside the on the cylinder head. Hope you find it soon!

 

Since I have erased the codes I haven't seen anything pop up and I've driven about 8+hrs (400+ miles) and I was wondering if erasing a code how long would it take to pop back up?

 

It can vary. I would clear mine and then they would return after less than 50 miles. I noticed they would come back quick on cold mornings of less than 40 degrees.

 

However long it takes for the self-test to run while the fault is present and, depending on the internal diagnostic, it may take two consecutive self-test failures to turn on the MIL and post a DTC.

If/when it comes back on, make certain your retrieve and record the freeze frame data so the testing conditions can be identified.