code 31 & 42
Thread Starter
|
Tuned
Joined: Jun 2006
Posts: 420
Likes: 4
code 31 & 42
hey guys, i have a 1990 f150 5L 5 speed that has a couple of codes (31 and 42) that i am having a hard time tracking down. for 31 i have a new erg valve and sensor, and its still telling me i have low voltage. can anyone suggest what my next thing to check would be? as far as 42 i am cluessless where to start. once and a while the truck will sudder in 1st and second (like its missing a lot), then the more i put my foot to the floor it reaches a certain spot and takes off REALLY good. could this be my tps or speed density sensor? or more likely something to do with the fuel system itself? thanks
Thread Starter
|
Tuned
Joined: Jun 2006
Posts: 420
Likes: 4
ok...well i'm not that clueless. i knew that it it meant system was rich (sorry i didn't post that). i meant i'm clueless on where to start diagnosing the problem. is there a way to test the O2 sensor? and if so what am i looking for (with a multimeter i presume). anyother things to look for/at?
Posting Guru
Joined: Jun 2004
Posts: 1,781
Likes: 1
From: Central NY
With your symptoms, I'd suspect a leaky injectors or bad plugs/wires.
When was the last tuneup and what plugs/wires did you use? Check the cap & rotor and replace as needed. Be sure the plug wires are routed correctly and not arcing.
Test your fuel pressure and bleed down rate and if they are ok, run a tankful or two with good injector cleaner. This never hurt anyways
If your o2 sensor had upwards of 60k on it the I would think its time to replace but I suspect it tuneup related.
When was the last tuneup and what plugs/wires did you use? Check the cap & rotor and replace as needed. Be sure the plug wires are routed correctly and not arcing.
Test your fuel pressure and bleed down rate and if they are ok, run a tankful or two with good injector cleaner. This never hurt anyways
If your o2 sensor had upwards of 60k on it the I would think its time to replace but I suspect it tuneup related.
Thread Starter
|
Tuned
Joined: Jun 2006
Posts: 420
Likes: 4
the plugs and wires are quite literaly brand new (my old ones were arcing so i replaced them thinking that was the problem, and all the plugs had good colour...not black and sooty), and my cap and rotor are only a year and a half old but i will check them. would it make sence for the injectors to leak only some of the time? i do have a true duel exhuast but i wouldn't think that would make any difference since it ran fine for many months after the intall. i did however cut and make the o2 sensor wires longer because of the headers...would this cause an negitive effect? i will dump injector cleaner in the tanks and give that a try. i am pretty good about all the regular maintenece stuff and i do all the work myself so it gets checked out on a regular basis. any thoughts about the 31 code? thanks for all the input so far.
Senior User
Joined: Apr 2006
Posts: 447
Likes: 0
From: youngstown ohio
Trending Topics
Lead Driver
Joined: Nov 2002
Posts: 9,557
Likes: 44
From: Concord, NC
People run the O2 sensor in one header all the time with no side effects like this. On the EGR sensor, is it white or black? Apparantly there is a difference between the two sensors and must be replaced with the same one. If you get a Haynes manual or Chiltons or your other favorite, there's some decent troubleshooting guides for EGR related codes as well as O2 sensor related codes.
FTE Stories
Ford Trucks for Ford Truck Enthusiasts
Top 10 Fords at 2026 Carlisle Ford Nationals
Joe Kucinski
3 Best / 3 Worst Parts of Modern Ford Ownership
Brett Foote
10 Amazing Upgrades That Solve Common Ford Truck Owner Headaches
Pouria Savadkouei
Every 2026 Ford Engine Explained
Brett Foote
10 Ugly Ford Trucks That We Still Kinda Love
Joe Kucinski
10 Things Every Truck Owner NEEDS (2026 Edition)
Michael S. Palmer
Rezvani's Latest Post-Apocalyptic Monster Is a Ford F-150 Raptor Underneath
Verdad Gallardo
Top 10 Most Expensive Ford Trucks Ever Sold on Bring a Trailer
Joe Kucinski
2027 Ford Super Duty Buyer's Guide (Every Model, Engine, & Package)
Brett Foote
Thread Starter
|
Tuned
Joined: Jun 2006
Posts: 420
Likes: 4
i replaced it with with a grey one (it was grey to begin with). i think the black ones are for the earlier EFI trucks. now they do talk about some control module for the egr, however in my code book it says its only related to cars. as far as the o2 sensor, is there any way to test it to see if it is working properly? i don't want to just start replacing random sensors because that would get pretty expensive and its just pissing in the wind. does anyone know if i can buy an o2 sensor with a longer lead insted of cutting the wires and makiing them longer? and if you know of one, would you happen to know the application or part number? thanks so far guys.
Lead Driver
Joined: Nov 2002
Posts: 9,557
Likes: 44
From: Concord, NC
I know bosch makes an O2 sensor with longer wiring, but I'm not sure if it is enough for what you need to do. As far as I can remember, the code 31 is for the EVP sensor voltage being too low (below .24V). This doesn't necessarily mean that the sensor itself is bad - it could be wiring or something else. This is where a good repair manual will help tremendously. My manual is at home so unfortunately, I can't relay that info to you.