Hello,

My truck have 94k miles, F-150 4x4 Lariat 1999, yesterday the "service engine soon" turned on.

About 15 miles the light in the shifter stick started to blink.

This indicator lights an "OFF" signal when the driver turns off the overdrive. And by pressing the push-button again the "OFF" turns off and the overdrive is active.

So now I'm having two problems:
1.The "Service Engine Soon" is always "on".
2.The "OFF" signal is blinking at all the time.

Any Advice?

 

For the check engine light you can get the codes pulled at your local autozone. Write them down and post them back here.

The O/D light should be blinking in some sort of pattern...it will tell you what its problem is as well.

 

I also have the blinking O/D, it starts after a little while of driving you can park and shut down, start back up, its off, start driving then it starts after driving for a while, I have a OBD-II scan tool, does Auto-Zone and Advance have something that can tell what the blinking O/D light is meaning or do you have to go to a garage? Thanks.

 

The blinking O/D is most likely indicating something is wrong with the trans. Does it act weird when it starts blinking or anytime around then? My trans would overheat during the summer until I got it fixed. When it overheated, the O/D light started blinking. I went to a locla garage to have the codes pulled since my check eng light was on at the time also. It was about $25.

 

I took the truck to the garage, and this are the codes:

1. P0781
2. P0171

What are the codes related?

Thanks

 

P0781 = 1-2 Shift Malfunction
P0171 = System Too Lean

P0171 should be fairly simple. The passenger side of the engine is running lean because unmeasured air is entering the engine. Look for loose, cracked, disconnected hoses. The PCV valve is back there and that may be the problem.

P0781 is the transmission fault code. If the transmission is still shifting through 1-2 without any apparent problems, this is probably an electrical/sensor issue and not a mechanical problem. Do the RPMs rise higher than normal during the 1-2 shift and then cause the transmission to slam or bang into 2nd gear?

My method would be to solve P0171 first by finding the leak. When that is resolved, disconnect the battery's negative lead for a few minutes to reset the computer and see if the O/D light begins to blink again. If it continues, we can look a little deeper into this.

Check the vehicle certification label on the driver side door jam to see which transmission you have.

U=4R70W
E=4R100

 

Thanks, I fixed the problem, I used a hose and *** it trough every vacuum hose, finding the broken ones. It was the vacuum hoses from the PCV , I replaced every elbow and the valve either, They were broken and thin.