A friend of mine just got a 92 F150, 4x4, 5spd, 4.9l truck that needs a lot of TLC. It's got 290k miles on it.

So far we've given it a tune up with new plugs, wires, cap, rotor, air filter and we replaced the battery, master cylinder and Air Tube. The brake lines are rotted so the MC, while needing to be replaced is just the start of getting working brakes.

The truck runs but after scanning it for codes it has a laundry list of them. It's blowing black smoke and smells very rich. Here's the list of codes:

117 ECT sensor signal is less than the Self-Test minimum of 0.2 volts.
126 MAP/BP sensor out of self test range 1.4 to 1.6 volts.
122 TPS circuit below minimum 0.6 volts.
112 ACT sensor signal is less than the Self-Test minimum of 0.2 volts.
327 DPFE or EVP circuit below minimum voltage of 0.2 volts.
513 Failure in EEC processor internal voltage.
553 Air management 2 circuit failure (AM1/TAD)
552 Air management 1 circuit failure (AM1/TAB)
565 Canister purge circuit failure
556 Fuel Pump circuit failure
558 EGR Vacuum Regulator circuit failure

I'm thinking that with that many codes and with the 513 code the computer is cooked. We're going to look at the harness connectors but the wiring looks good itself, no broken, frayed, worn, etc wiring.

Thoughts?

Thanks,

 

Code 513 is a bad sign. Codes 112 and 117 are typically caused by not warming up the engine before running the KOEO tests. But then again if the PCM has an internal problem many codes may be false.

 

I'd agree. As I was reading down the list, I thought "how is this running at all".

If you do get a new PCM, this may help you identify one you can use - http://oldfuelinjection.com/?p=17

 

My cousin calls the EEC-IV "Flinstone Fuel Injection" because they can have tons wrong and still run...

It's running rich, shaking, etc. It moves under it's own power but we really haven't pushed it because of the lack of brakes.

Also, when we changed the AIR tube we also did the valve cover gasket and the inside looks really clean, no sludge whatsoever.

We're going to pull the computer later and order up a reman from Autozone most likely.

 

I have a 95 4.9L autotrans 2wd 140k miles. Mine is also throwing a ton of codes. (112,117,122,126,327,634,638). I just replaced a couple vacuum lines and changed the alternator (it was pulsing overvoltage and I expected the rough running would improve when all the reference voltage and square wave signals evened out. NOPE. Like the 92 4.9l in this thread, it blows black smoke, smells rich (really sooty tailpipe), shutters under throttle, shifts REAL hard and generally limps. I've disconnected the battery and drained any charge from capacitors on the ECM. After connecting the battery (with codes cleared) I'm not getting all the codes again but it still runs like it's real rich (or starved for air) and has virtually no power. The answer cannot be that all those sensors or circuits are faulty, in my estimation. And I don't get the dreaded 513 code but could it be as simple as a fouled up ECM? If so, I'd expect to get at least several of those codes as i drive the truck for a while but I've put a couple of hours on the truck and I've got no CEL and just a F150 that's not running worth a crap. I'd love constructive suggestions

 

Sounds like you've done a lot of troubleshooting. If you clear the codes and then drive the truck for a while, if after that you are still having issues and no codes, I'd suspect a bad ecu. Depending on the issue, you might be able to send it out for repair. Just make sure to match the 4 letter code on the ecu with one if you buy it

 

...or you could take a look inside the computer for damage.

7 year old thread resurrected from the dead on Halloween 👻

 

There are types of damage that can't be seen by just lookoling at the ecu. Some can be fixed and some can't

 

Going to resurrect this thread yet again.

I have a 91 F-150 4.9 L6 4x4 Manual with 2,400 miles on it and it's on it's 6th clutch. My grandfather bought it new during the blizzard of 91 to replace the old 1970's bronco that used to be our company plow truck but died.

Anyway, I've been trouble shooting it for the past few days because it's been running like crap the past 2 - 3 years and it's gotten bad enough that it's mostly unusable and the snow is here. Changed the 3 usual suspects, Idle Air Control valve, Ignition Control module, and Throttle position sensor. All that did was mostly fix the idle, so the truck is no longer surging, but it's still running very rough, very rich, and tries to stall out when you gas it too hard too fast.

I broke down and bought a OBD-I code reader for it and sure enough I pulled a slew of codes out of it. I pulled out almost every single code as the OP in the exact same order: 117, 126, 122, 112, 327, 513, 553, 552, 565 so I believe like the OP, my PCM is indeed shot, and that wouldn't surprise me since the PCM is constantly subject to severely fluctuating voltage from the plow. I've got a reman PCM coming in tomorrow, I'll be sure to post back and let the internet know if the replacement PCM is the solution.

Side Note since this is a Ford forum, I've also got a brand new 1996 Horizon Conversion VAN RV on an E250 chassis V8 gasser with 1200 original miles on it from when it was driven in from the manufacturer.

 

Certainly seems a new PCM is in order. Hope it clears up your other codes. Here is a link to your codes if you don't have one.

513 (O) Replace processor (PCM) (internal failure)

https://www.therangerstation.com/tec...gitcodes.shtml

 

The first 5 codes are all on the 5v sensor bus. So either the 5v wire got damaged, or the computer is not producing 5v any more. The 513 code says the ecc voltage is not reading correctly... Not too surprising since it doesn't have a 5 volt bus any more. The tab and tad circuits are 12v and controlled by the computer grounding the negative side of the solinoid coil. Dunno why that's coming up.
The ECC monitors the fuel pump circuit to ensure it's turning on and off when the ECU commands it. The fuel pump circuit obviously works because the truck runs, but the ECC doesn't see the 12v signal from the fuel pump.
You might try opening up your ECU and look for damaged/leaking capacitors. It could be a cheap fix with a little bit of labor. But these codes all point to a dying ECU.

 

New PCM fixed the truck. It still doesn't idle perfectly, but the CEL is off, the truck isn't running outrageously rich, and it doesn't try to stall the moment you gas it.

The imperfect idle could be a number of things, old gas, fouled plug from running crazy rich, or it could simply be that's just how the truck idles.

 

Thanks for reporting the fix. It's very helpful when someone else has a similar problem.

 

Yea, that's why I joined the forum, to post the solution incase anyone else stumbles across this thread through google like I did.

While I'm here though, I should see if there's any known alternator upgrades for this truck, the stock 75A we've got in it is really not up to the task of maintaining steady consistent voltage output while raising and manipulating the plow... Which probably contributed to the PCM failure.

 

Search for 3G alternator upgrade.