B MACK Posted August 4 Share Posted August 4 My 1995 F150 had a check engine light on. I put my OBD1 reader on it, it showed some minor codes (brake lights, reverse light, etc.), the main code was 172.O2 sensor. I disconnected the battery and replaced the O2 sensor. The check engine light came back on with in 2 miles, maybe 10 minutes running. It is showing the same codes, 172 being one of them. Is there something else to do to reset codes on an OBD 1 system other than disconnecting the battery? Or does anyone have an idea why the 172, O2 code would keep coming up? Quote Link to comment https://www.bigmacktrucks.com/topic/74415-older-ford-issues/ Share on other sites More sharing options...
Joey Mack Posted August 4 Share Posted August 4 air/fuel ratio or mixture can cause this. was a basic tune up done? Quote Link to comment https://www.bigmacktrucks.com/topic/74415-older-ford-issues/#findComment-556424 Share on other sites More sharing options...
tjc transport Posted August 4 Share Posted August 4 sometimes you need to drive a "readyness" route to reset the computer to no codes. certain number of start/stops, varying speeds. Quote when you are up to your armpits in alligators, it is hard to remember you only came in to drain the swamp.. Link to comment https://www.bigmacktrucks.com/topic/74415-older-ford-issues/#findComment-556425 Share on other sites More sharing options...
BOBWhite Posted August 4 Share Posted August 4 My 91 Ford F250 has a similar problem, the check engine light is on all the time and it runs rough. It used a herculean amount of gas but I don't really care as it's just a fuel truck now. I've never really liked the 351 so I might swap it out someday. Haven't had as many issues with Chevys fuel injection system of that same era. Quote Link to comment https://www.bigmacktrucks.com/topic/74415-older-ford-issues/#findComment-556426 Share on other sites More sharing options...
JoeH Posted August 4 Share Posted August 4 Sounds like you need to do a Cummins swap! 🤠 1 Quote Link to comment https://www.bigmacktrucks.com/topic/74415-older-ford-issues/#findComment-556436 Share on other sites More sharing options...
B MACK Posted August 4 Author Share Posted August 4 It is a recently rebuilt 302 (5.0). Had them put a little different cam in it. All new plugs. It has less than 5 thousand miles on it. I've been told maybe a mass air flow sensor? Quote Link to comment https://www.bigmacktrucks.com/topic/74415-older-ford-issues/#findComment-556443 Share on other sites More sharing options...
mowerman Posted August 4 Share Posted August 4 I can’t really help you, but any reputable shop can get rid of the light if you can’t get it figured….:fuel pressure regulator switch went out on my 88 but the truck just completely quit and would not restart … bob Quote Link to comment https://www.bigmacktrucks.com/topic/74415-older-ford-issues/#findComment-556449 Share on other sites More sharing options...
B MACK Posted August 5 Author Share Posted August 5 Thanks for the info and ideas. Probably take it to the shop, but was trying to figure it out and do it myself. Quote Link to comment https://www.bigmacktrucks.com/topic/74415-older-ford-issues/#findComment-556463 Share on other sites More sharing options...
mowerman Posted August 5 Share Posted August 5 Yeah, that’s what I thought. I don’t blame you it. I probably would have tried the same thing first. I do know those lights come on a lotta times for absolutely no reason … bob Quote Link to comment https://www.bigmacktrucks.com/topic/74415-older-ford-issues/#findComment-556470 Share on other sites More sharing options...
tjc transport Posted August 5 Share Posted August 5 most of the time the check engine light comes on because the gas cap fails, or the person who puts it on leaves it loose or never puts it back on. 1 Quote when you are up to your armpits in alligators, it is hard to remember you only came in to drain the swamp.. Link to comment https://www.bigmacktrucks.com/topic/74415-older-ford-issues/#findComment-556471 Share on other sites More sharing options...
Freightrain Posted August 6 Share Posted August 6 My daily is a 95 F150, 302/auto. Absolutely love it. It has 177k miles on it now. Since you replaced the 02 sensor I would start looking at fuel issues. It was likely reading out of spec, but it may just be running rich due to too much fuel? Too little fuel? How many miles on injectors? I just replaced mine due to dripping. It was hard to restart after like 30 minutes of sitting. Friend has an injector cleaner, so I installed a fresh set and it runs/starts flawless and mileage actually increased about 1 mpg. 2 Quote Larry 1959 B61 Liv'n Large...................... Charter member of the "MACK PACK" Link to comment https://www.bigmacktrucks.com/topic/74415-older-ford-issues/#findComment-556538 Share on other sites More sharing options...
tjc transport Posted August 6 Share Posted August 6 check the fuel pressure too. ... the regulator may be bad. 1 Quote when you are up to your armpits in alligators, it is hard to remember you only came in to drain the swamp.. Link to comment https://www.bigmacktrucks.com/topic/74415-older-ford-issues/#findComment-556539 Share on other sites More sharing options...
Geoff Weeks Posted August 6 Share Posted August 6 All the code is telling you is the output to the "computer" is outside what is expected. It is up to you to determine the cause. Looking at the actual O2 sensor output might be of help, it would show if it is sensing rich or lean condition. The older the system, the less info it can provide. Depending on how "slightly different" the cam you put in is, it could even effect what the O2 sees and the computer is expecting to see. 1st place I'd look is for vacuum leaks and rich running do to fueling issues, 1st causes lean running 2nd rich. 1 Quote Link to comment https://www.bigmacktrucks.com/topic/74415-older-ford-issues/#findComment-556540 Share on other sites More sharing options...
B MACK Posted August 9 Author Share Posted August 9 Ok , thanks. That gives me a few more things to check. Quote Link to comment https://www.bigmacktrucks.com/topic/74415-older-ford-issues/#findComment-556740 Share on other sites More sharing options...
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