Got a CE on my 1997 F150, 5.4L engine. Took it to the dealer and he tells me that it is my gas cap, needs to be replaced. He never did tell me what the code was. He cleared the computer and I left. Light didn't come back for 3 months. This time, I needed to get the tranny serviced (power flush) and the tranny shop read the code and says it is P1450 first, P0171 and P0174 next. While tranny shop is performing service, I walk over to parts store and buy new gas cap. Tranny shop resets computer and I replace gas cap. Only got 10 miles from shop and CE comes back on.

So, can anyone give me some advice here? I searched forum and believe I understand what the codes are but did not find anything with the combination listed above. Any help greatly appreciated!

 

Mine had the P0171 and P0174 code before. My truck had a vacuum leak, the hose from the back of engine (IAC ?) that connects to the pcv valve has deteriorated and there's a big hole there causing the truck to idle hard.

 

You have to read the codes again to be sure what your dealing with.
After work or changes, you have to read again and trouble clear for the code indicated.
A gas cap won't clear codes 171 and 174.
Normally you don't just clear codes and hope they don't come back without some work.

 

Two separate problems:

1) P1450 has nothing to do with the fuel cap. Most likely, it's due to a plugged or restricted canister vent line, or other restrictive fault in or around the evap canister. Possibly a faulty FTP sensor.

2) P0171 & P0174 is likely the infamous PCV elbow. Most common reason so check it first.

Steve

 

Got a reread of the codes today. Same codes. Dealer swore the gas cap would solve the P1450 code. What is strange to me is my truck is running just fine. Smooth as can be at idle, all the power I ever remember it having when I get on it.

I understand the negative effect of the lean codes, something to not take lightly for sure. But what would be he negative effects of the P1450 code?

I did do a minor check under the hood, looking for a possible vacuum source but could find noone. I listen as well and everything sounds normal as far as I could tell. Have not had a change to dig deep into the back side of the engine to check the hoses but will in next day or two. Will also check out the canister vent line.

Any other things come to mind for me to check? Thanks.

 

The dealer is an idiot who can't even read his own service manuals.


You can't pass an emissions test for your license. No emission test, no problem except a yellow light on your dash.

Check that PCV hose elbow. Most common reason for the 171 and 174 codes.

Steve

 

Hope this gives you some help with the P1450 DTC.

Possible causes:

EVAP canister purge outlet tube (EVAP canister purge valve to EVAP canister) blockages or kinks.
EVAP canister tube (fuel tank to EVAP canister) blockages or kinks.
Fuel vapor elbow on EVAP canister contaminated.
Restricted EVAP canister.
Canister vent (CV) solenoid stuck closed (partially or fully).
Plugged or contaminated CV solenoid filter.
EVAP canister purge valve stuck open.
Fuel filler cap stuck closed (no vacuum relief).
VREF circuit open in fuel tank pressure (FTP) sensor.
Damaged FTP sensor.