Have an 85 f250, 302. I got continous codes 21, 23, 24, and 31. Running codes 23, 44, 31, 34, and 25.

I know what they all mean according to my Haynes manual, but not sure where to go from here.

Code 21; ECT out of self test range, KOEO, does this mean the sensor is bad?
Code 23; TP sensor out of self test range, does this mean the sensor is bad, got this code both KOEO and KOER.
Code 24; ACT sensor out of self test range, KOEO, Bad sensor?
Code 31; PFE, EVP, or EVR circuit below minimum voltage, got this code both KOEO and KOER, what exactly does this mean?
Code 34; EVP voltage above closed limit, KOER, what does this mean?
Code 25; Knock not sensed during dynamic test, I assume this would indicate that my base timing is off?

Thanks for any help anyone can give me.

 

First I would check the ECM ground. It should be the small black wire going to the NEG post on the battery, if the ground is bad, the ECM will act very weird.
I have never seen these sensors all fail at the same time.
The ECT is located in the intake water jacket. It is the larger one with 2 wires going to it. The smaller single wire sensor is for the gauge in the dash.
The TP Sensor is slightly adjustable. If someone has turned in the throttle stop screw, the sensor will not home out and could be giving a code.
The ACT (Air Charge Sensor) located in one of the lower intake air ports, could be bad, but they rarely fail.
Codes 31 and 34 sounds like the EGR valve is sticking open. The sensor is bolted on top of the EGR valve. If you remove the EGR valve, I'll bet that the plunger is not closing which will cause a bad idle.
Code 25 means that during the self test, when you floored it for a second after the beep, the knock sensor did not detect a knock.
If the engine was not at operating temp, it may not knock.

Was the engine warm or cold when the test was run?

After checking the Ground, also check the 2 large wiring harness plugs near the rear of the intake. Could be a loose connection there too.

 

A cold engine could cause the ECT and ACT codes, even though the sensors themselves are fine. Break out the multimeter and start checking voltages and resistances of the sensors in question. The TPS should show just under 1V at closed throttle with the key on, engine off - measured between the green wire and the black wire on the tps, with the sensor plugged into the harness. The voltage should then smoothly increase until it gets to about 4.8V at full throttle.

 

the engine was cold when I did the KOEO test, I was trying to get the continous codes but didnt make it that far. However, it was at normal temp when I did the KOER test.
Not sure if they all went at the same time. before I bought the truck it sat for about a year. And before the guy I bought it from got it it sat for quite awhile, not sure how long. I work with all three of the previous owners.
Anyway, most of the time at idle, it hunts and misses, sometimes very bad to the point it will stall, sometimes it idles fine with just a hint of a miss. Usually when it gets to the point where it stalls out, it will start back up fine, but dies right back out. At any other driving condition it runs great, it is a constant miss, no matter how far I push the throttle down, but not so bad when I step on it, at cruising speeds it runs fine, only problem is at idle. I have noticed that when it is capable of holding an idle( if you could call it that) and starts missing so bad the idle jumps up and down, it runs rich, but if its not missing, it doesnt.

 

Check out the TPS first off, it could cause some of the symptoms you are experiencing. I would also check the MAP sensor electrically to see if it is sending the correct signal to the computer. The MAP will either be a voltage varying or frequency varying type, which are checked by a volt meter and a tachometer, respectively. If you don't have a Haynes manual, it might be a wise investment to pick up one. I'm not sure which one you should get though, since you have an '85 truck - the manual for those year trucks might not have a lot of info on EFI.

 

I do have a Haynes Manual, and it does tell alot as far as testing components and replacement. Its just not all the detailed as to what the codes mean and why the computer would be sending codes. So, I guess I need to invest in a vacuum pump to start testing things like the MAP sensor and the EGR valve.

 

Well, I did leanr today that the ECT and ACT will send a code if they are below 50 degrees F, so thats why I got those codes. So it looks like my problem is my TPS and EGR, I think....any ideas?

 

Check the TPS first off, it's probably what is causing the problems. Once you get it fixed, then you can start diagnosing the EGR code.

 

Still sounds like a bad EGR valve to me. With it stuck open, it will run real bad and run so lean that it smells rich. I have seen it many times on the truck EFI engines.

 

If the EGR is stuck open, it will idle like poo or not at all. If I run straight manifold vacuum to the EGR valve, the idle lopes like I have a big cam. With a TPS code and a hunting idle, I'd start there and get to the EGR after fixing the TPS.

 

well, finally replaced the EGR valve, the EVP sensor, and the TPS sensor, truck idles fine now, doesnt run rich, and barely a hint of a miss, you really have to listen to it to hear it miss. Next is a general tune up.
One other note, my Haynes manual says that the TPS will need to be adjusted to get one volt on the sig return wire after installation, but there were no provisions on my throttle body for adjustment. So....

 

the adjustment would actually be on the TPS if it is adjustable it would have elongated or oval shaped hole so you can spin it a little, not all of them have it though

 

one of the holes on the TPS was oval shaped, but not the direction that would let you turn it, it was elongated so you could move it side to side, but not more than about 1/16 of an inch, if that much.