Hi! First post from a lurker. This is a short novella, so please be patient.

My 94 F250 460 4WD auto is in a no-start condition. When it first failed to start, I had never read out codes on a computer controlled vehicle, just ignoring the check engine light. I read the manual to find out how, and read codes 116 (coolant temp), 172 (lean bank), 452 (vehicle speed sensor), 556 (fuel pump relay), & 636 (trany temp). The truck had been hot back in the summer (radiator pluged with weed pollen in the pasture), which I assumed accounted for the coolant and trans temp codes. Also back in the summer I had found a harness on the transmission or transfer case, I don't remember which, unplugged after driving through several sand plum thickets. Plugging that back in resolved a problem which had arisen at the same time; not shifting until high rpm. I assumed that incident accounted for the vehicle speed sensor code. I didn't have an injection pressure tester, but I could hear both fuel pumps and I did have pressure at the schrader valve on the passenger side rail so I have no idea about the fuel pump relay code. I found and repaired a broken vacuum line which might have set the lean bank code. It still didn't start, and I called it a night.

Next morning I found I had left the key on after reading the codes, so the battery came out and went to the charger. That should have cleared all codes, according to my manual. With the battery back in, I tried to start it just for funnys, then read the codes again. This time I got 116, 114, & 636; fuel pump relay and lean bank codes gone, but coolant and trany temp codes reset and a new code for intake air temperature. Why would the coolant and trans temp codes reset without it even starting and warming up? And why the intake air temp code now but not before? The resitance across the air temp sensor terminals read about 20% below the room-temp spec in the manual and the element was very crudded up, so I changed it. Still no start. I cleared the codes and checked them again. Still throwing 114, 116, & 636. The only other hint I can find is that the voltage to the intake air sensor measures 4V whereas the book says it should be "approximately 5V". Is that much variation (20%) a problem? If so, the book says I should suspect a problem with the computer.

I sure hope some of you have some comments.

Thanks,
Floyd Pickering

 

Sorry, I've got nothing for you, but welcome to the site!

 

I think you are getting those codes because the engine has not ran since you cleared the codes. The computer has not seen the sensors go up to operating temp yet.
As for the others, I don't have a clue either.
Welcome.

 

Just an update to let you know what I finally found. Cleaning IAC finally got it started, but it still required constant feathering of the throttle to keep it runing until it warmed up. At this point I had gotten rid of ALL CODES, so I fell back on the basics I would have applied for an older non-computer vehicle. Spark plug tester showed no fire at the 1st 2 plug wires I pulled, so I checked at the coil wire. No fire there. Pulled it off and put the ohm-meter on it. Open circuit. Installed new coil wire and it fired up like a new truck. Guess it was arcing across an internal break just enough to start and then making better contact as it warmed up and materials expanded. Why it required constant throttle-feathering until it warmed up I have no idea.

Learned 4 things of value:
1 How to read codes.
2 Not to let codes pile up until I have half a dozen things to sort through.
3 Not everything sets a code.
4 It may be computerized, but the basics still apply.

 

Glad to hear it.....welcome to the site hope you enjoy....

JR

 

Glad it worked out for you, but it may not be done with you yet. Keep us up to date.

Welcome.